mar-apr 2008

Volume 25Volume 25Volume 25Volume 25Volume 25Number 2Number 2Number 2Number 2Number 2

March - April 2008March - April 2008March - April 2008March - April 2008March - April 2008

PRESIDENT

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VICE-PRESIDENTS

A K Agarwal P N Chopra Anita G Dandekar

PUBLICATIONS COMMITTEE

ChairmanM L Gupta

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Members

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Coopted

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Special Invitee

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EDITORIAL BOARD

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Dilip Sahay

Members

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IETE TECHNICAL REVIEW

The Institution of Electronics and Telecommunication Engineers

The IETE Technical Review invite articles preferably readable without mathematical expressions, state-of-the-art reviewpapers on current and futuristic technologies in the areas of electronics, telecommunication, computer science & engineering,information technology (IT) and related disciplines. In addition, informative and general interest articles describing innovativeproducts & applications, analysis of technical events, articles on technology assessment & comparison, new & emergingtopics of interest to professionals are also welcome. While all the papers submitted will go through the same detailed reviewprocess, short papers and Practical Designs will receive special attention to enable early publication. Manuscripts may pleasebe submitted in triplicate to the Managing Editor along with a soft copy on floppy/CD/e-mail. Detailed guidelines to authors maybe seen on IETE Website : http://www.iete.org under the heading ‘Publications.’Annual Subscription : Subscription and Advertising rates are available on request and also on website: iete.orgAddress for correspondence :Managing Editor, IETE, 2, Institutional Area, Lodi Road, New Delhi 110 003, Telephone : +91 (11) 43538842-44Fax : +91 (11) 24649429, email : [email protected]; [email protected], Website : http://www.iete.org; http://www.iete.info

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47

Vol. 25, No. 2, March-April’08 I E T E T E C H N I C A L R E V I E W

IETE TECHNICAL REVIEWPublished bimonthly by the Institution of Electronics and Telecommunication Engineers

March-April 2008 Vol 25 No 2

CONTENTS

Note : The Institution of Electronics and Telecommunication Engineers assumes no responsibility for the statements andopinions expressed by individual authors.

48 SCAN

Dilip Sahay

49 Telephone Caller-ID Signal SendingOver Internet

Aleksandar Lebl and •arko Markov

59 Issues in Mobile Ad hoc Networks forVehicular Communication

S S Manvi and M S Kakkasageri

INVITED ARTICLE

73 MediaFLO™ - The Ultimate MobileBroadcast Experience

Sachin Kalantri

IETE – R S KHANDPUR GOLD MEDALAWARD LECTURE

81 Binaural Dichotic Presentation ofSpeech Signal for Improving itsPerception to Sensorineural Hearing-Impaired using Auditory Filters

D S Chaudhari

91 Dielectric Parameters as DiagnosticTools and Indicatrix of Disease — AMicrowave Study

V Malleswara Rao, B Prabhakara Rao andD M Potukuchi

48


The second issue of Technical Review for the year 2008 contains five articles including aninvited paper and a lecture delivered during an IETE Award function.

First article by Aleksandar Lebl and Zarko Markov, describes calling subscriber numbertransmission over Internet to the called subscriber. The paper describes how real time protocolis used for this purpose. The paper discusses two ways of transmission of CLI over internet.According to the authors the two methods were developed for the telephony requirements ofTelecom Serbia.

In the second article, S S Manvi and M S Kakkasageri, explain “Vehicular Ad hocNetworks” (VANETs) for inter vehicle and vehicle to road side communication. The paperdescribes various characteristics and applications as well as a few issues that needs to betaken into consideration with VANETs. The paper broadly mentions the wireless technologiesthat can be utilized but misses the adaptation of available mobile access technologiesincluding PMRTS.

In the invited article, Shri Sachin Kalantri describes about multicast service on Mobile TV.The author has elaborated about MediaFLO platform to deliver quality content with roughly halfthe spectrum and less than half the infrastructure required. According to the author, Mobile TVservice is going to be quite popular and mobile broadcasting using mediaFLO would offer highquality service to the customers.

The fourth paper is an IETE-R S Khandpur Gold Medal Award lecture delivered by Prof DS Chaudhari on “Binaural Dichotic presentation of Speech Signal for improving its Perceptionto Sensor neural Hearing Impaired using Auditory Filters” on the theme “Connecting Personswith Disabilities: ICT opportunities for All” set by International Telecommunications Union(ITU) for this year’s theme.

In the last and fifth article, V Malleswara Rao, et all describe X-band microwave (9-10GHz) study on Dielectric Parameters as diagnostic tools and indicatrix of disease. This articledemonstrates the capability of MW dielectric Measurements.

I take this opportunity to convey to the readers about the sincere efforts that have goneto present these selected articles by the staff of the publication division of IETE. I also wouldlike to bring to your notice the sincere efforts to make some changes in the cover design of thisjournal by IETE Secretariat. I hope that this cover design gels with the serious and interestingreading of this journal and any suggestion in this regard is welcome.

I also take this opportunity to request and invite authors of article for state-of-the artreview papers on current and futuristic technologies and products in the areas of computerscience, engineering, Telecommunications, Information Technology etc and request them fortheir suggestions for improvement of the journal.

Dilip SahayChairman, Editorial Board

SCAN

49


Telephone Caller-ID Signal Sending Over InternetALEKSANDAR LEBL AND •ARKO MARKOV

ABSTRACT

This paper describes two methods of calling subscriber number sending over Internet to the called subscriber who isconnected to the classic telephone exchange by Internet. One, faster, method uses two event codes, while the othermethod uses only one event code, but it is significantly slower.

1. INTRODUCTION

In the process of integrating packet andtraditional telecommunication, different inter-working methods are developed. One interworkingmethod consists of connecting traditional userequipment (telephone, fax) and classic telephoneexchange, or interconnecting telephone exchanges,across Internet. The basis for this interconnectionis transmission of traditional telephone networksignals (dual tone multifrequency signals (DTMF),line signals, fax signals, interexchange signaling)using procedures adopted in Internet. Theseprocedures were standardized in RFC2833 [1], inyear 2000.

Considering its latitude, the authors separatedRFC2833 into three recommendations [2-4]. Inthese recommendations, possibilities for Internettransmission of almost all signals known in moderntelephone network are described. One of the rareexceptions, not presented in recommendations, isCaller Identification Signal (CIS), which localexchange (LE) sends to the called subscriber at theconnection beginning. This paper presents somesolutions for CIS signal transmission.

2. THE TRANSMISSION OF CISSIGNALS OVER INTERNET

The methods for CIS transmission over Internet,which are suggested in this paper, can be used inthe setup phase of connection, shown in Fig 1.

In the setup phase of connection, classic TE isconnected to the Local Exchange (LE) usingInternet. Gateways GW1 and GW2 are located atthe points of contact of telephone network and

Internet. These GWs make telephone speechsignals and signaling information suitable fortransmission over the Internet and enable theirregeneration in telephone format at the receivingend.

One of the Common Control Unit (CCU)functions in LE is to manage the operation of CISsignal generator (CISGEN). The generated CISsignal is sent from the LE towards GW1. Thedemodulator (DEM) in GW1 demodulates CISsignal, and the packetizer (PCK) forms packets ofCIS signal coded as telephony event in accordancewith the Internet standards. At the Internet egressport, depacketizer (DPC) in GW2 depacketizesmessages, and the modulator (MOD) modulatesCIS signal. In this way CIS signal is put back to itsoriginal shape, and sent towards TE.

3. METHODS FOR TELEPHONESIGNAL TRANSMISSION OVERINTERNET

Real Time Protocol (RTP) is used for telephonesignal transmission over Internet [5]. Two methodscan be used:

(1) Transmission of telephone signal parameters(TSP) (frequency, modulation frequency,level, duration) ([2], section 4. RTP PayloadFormat for Telephony Tones), This method oftransmission is shown in the Fig 1a;

(2) Transmission of event code (EC) ([2], section2. RTP Payload Format for Named TelephoneEvents), as it is shown in the Fig 1b. TheNamed Telephone Event means that it isnecessary to detect the type of the signal (for

50


Fig 1 The transmission of telephone signals over Internet

example: ring signal, DTMF digit, etc.), and tosend special code for the detected signal.

The characteristics of the first method arefaster transmission, simpler gateway, but also thepossibility to transmit invalid signal. For example, ifthe original signal is attenuated more than it isexpected, its level will be measured and theparameter expressing this attenuated level will besent across Internet.

The second method requires a more complexgateway. This gateway, standing at the point ofconnection between telephone and Internetnetwork, needs more time to recognize the type oftelephone signal at the Internet ingress port, but the(tone) signals are replayed in standard shape andlevel.

Figure 2 presents the RTP packet structurewhen signals are transmitted using event code andthe position of RTP packet in Internet packet.

After the usual RTP header, consisting of 12octets, RTP payload follows. In the example,represented by the figure, one event is defined. Thepayload format for each event consists of one 32-bit word, In this word, 8 bits at the beginning are theevent field for event code, E bit indicates if thepacket contains the end of the observed event, 6

bits are volume field describing the signal powerlevel, and 16 bits are the event duration field.

RTP packet, shown in the Fig 2, is the payloadof the UDP datagram.

4. ABOUT CIS SIGNAL AND ITSTRANSMISSION IN CLASSICTELEPHONE NETWORK

The procedures for CIS signal transmission inclassic telephone network are defined in [6].According to this recommendation, CIS signal issent associated with first ring (or ringing) signalusing two methods. In the first method, datatransmission occurs during the first long silentperiod between first two ring patterns. In the secondmethod, data transmission occurs prior to first ringpattern and in that case Terminal EquipmentAlerting Signal (TAS) is sent before data. TAS isused to signal to the Terminal Equipment (TE) thatdata transmission is to be expected. The TASshape and the characteristics are defined in [6].

Timing relations of CIS signal to ringing signal,or to TAS, are accurately defined. For example, ifthe CIS signal is transmitted during the first longsilent period between two ring patterns, itstransmission must start in the time interval between

(a)

(b)

51


Ether. Header IP Header UDP Header RTP Header RTP payload(14 bytes) (20 bytes) (8 bytes) (12 bytes)

0 PT 31

Event E R Volume duration

RTP header

RTP payload

)

Fig 2 RTF packet structure when signals are transmitted using event code

tdmin = 0.5s and tdmax = 2s after the first ringpattern, as it is shown in Fig 3.

The various timing parameters in Fig 3 are asfollows:

- R - ring signal;

- CIS - CIS signal;

- tRING - the duration of a ring signal;

- tm - the duration of a CIS signal;

- tdmax - maximum time delay between a ringsignal end and a CIS signal start;

- tdmin - minimum time delay between a ringsignal end and a CIS signal start;

CIS signal consists of sending Frequency-ShiftKeying (FSK) signal at the rate of 1200 baud [6,7].The signal of frequency 1300 Hz represents binary1 (mark bit) and the signal of frequency 2100 Hzrepresents binary 0 (space bit).

The parts of the CIS message are successive,without interruption in sending:

- Channel Seizure Signal: the block of 300continuous bits of alternating “0”s and “1”s;

- Mark Signal: the block of 180±25 or 80±25mark bits;

- Message type;

- Message length;

Fig 3 CIS signal transmission between two ring patterns

R CIS CIS R

tRING tdmin tm tm tRING

tdmax

52


- Presentation Layer Message (containsdifferent parameters: date and time of the call,calling line identity, etc.);

- Checksum, followed by 1 to 10 mark bits.

Every byte representing Message type,Message length, Presentation Layer Message andChecksum is enveloped by start bit (space) andstop bit (mark).

5. CIS SIGNAL TRANSMISSION USINGSIGNAL EVENTS

CIS signal presentation in the packet format, asthe one explained in Fig 2, is not mentioned in [2]and [3], but is possible. Such a coding is toocomplex and requires great number of bytes. Thiscoding will be realized by presenting every bit ofCIS information using 4 bytes, included in the RTPpayload shown in Fig 2. In order to avoid this, weformed the new format for telephone event coding.This format is presented in Fig 4. Some factssimplify the formation of a packet:

1) The CIS signal transmission level is defined in[6], and it can be known, a priori in GW2.That’s why it is not necessary to send it inRTP packet;

2) Each bit duration is also defined in [6], and it isnot necessary to send it in RTP packet;

3) The sequence of CIS message parts is definedand known in GW2, so must not be particularlycoded. For example, it is known a priori thatthe CIS message begins with channel seizuresignal consisting of alternating “0”s and “1”s,followed by the mark signal, consisting of ablock of mark bits.

There are two methods for CIS signaltransmission. In the first one, one telephony eventidentifies ring signal and CIS (ring signal & CIS).The second one uses transmission of differentcodes for ring and CIS.

5.1. The first method

The structure of RTP packet, which transmitsCIS signal coded as telephone event, is presentedin Fig 4. The payload type (PT) is included in RTPheader. For our application, we chose dynamic PT.

The use of dynamic PT is explained in [2]. Thestructure of the RTP payload in this case is asfollows:

- telephony event code: CIS signal transmissionafter ring (code CIS) - separated code, whichis not defined in [2] and [3] - 8 bits. Ourapplication only deals with CIS signaltransmission between two ring patterns, whilethe coding according to other scenarios,explained in [6], is planned for future;

- the length of the RTP content which codes CISsignal - 8 bits;

- the number of space-mark pairs in ChannelSeizure Signal of CIS - 8 bits;

- the number of mark bits in Mark Signal of CIS- 8 bits;

- the n bytes of CIS message content (fromMessage Type to Checksum) - nx8 bits.

This RTP payload has only 4 bytes more thanCIS message. According to recommendation [8],the maximum expected length of the PresentationLayer Message is 75 bytes (including MessageType, Message Length and Checksum, it is 78bytes). The Message Length in the CIS messagehas 8 bits, thus enabling the length of thePresentation Layer Message to be 255 bytes. Thevalue mentioned here and in [8] is significantlysmaller.

5.2. The second method

Alternatively, only CIS signal can berepresented by the telephony event code, and thering signal can be represented by the separatepacket and the separate telephony event code,mentioned in [2].

For sending CIS associated with TAS, asdefined in [6], the separate telephony event codescan be used for each scenario of sending. The RTPpayload format in this case may be the same as theone in Fig 4.

According to [1], the telephony event code 89 isreserved for ringing. After this code, the codes 90-95 are free for assignment. That’s why the codesare configured in the following way:

- 90 - the unique telephony event coderepresenting ring signal & CIS;

53


(n–1). byte in CIS mess. n. byte in CIS message

0 PT 31

event length 01 pairs num. is seizure bit 1 number in mark

1. byte in CIS message 2. byte in CIS message 3. byte in CIS message 4. byte in CIS message

RTP header

.

.

.

RTP payloadFig 4 RTP packet structure when the CIS signal is transmitted using telephone event code

- 91 - telephony event code representing onlyCIS, while the ring pattern is represented bythe code 89.

After this, codes 92 to 94 can be used for CISsignal transmission associated with TAS, accordingto scenarios defined in [6].

6. THE CHANNEL CAPACITY NEEDEDFOR CIS SIGNAL TRANSMISSION

The method, which is suggested in this paperfor CIS signal coding by telephony events, makesgreat saving in channel capacity. Let us supposethat Presentation Layer Message contains onlydate and time of call (8 bytes) and the calling lineidentity (6 bytes in our example, but more bytesmay be used). The message coded by this methodhas 25 bytes. This is significantly less than that inthe case of sample coding according to therecommendation G.711. The CIS message, withthe Presentation layer containing 8 bytes for dateand time of call and 6 bytes for calling line identity,will have 700 bits coded using FSK (the duration ofevery bit is 0.833 ms). For coding samples of thissignal, 4666 bytes are needed. The saving is greatalso compared to the case of coding each bit of FSKsignal by 4 bytes, as telephony events arepresented according to [2]. For this coding, 2800bytes must be used.

7. TIME RELATIONS IN THE RE-PRODUCED CIS SIGNAL

Important elements in CIS signal transmissionare the time relations between a CIS signal and aring signal. These relations in the reproduced signalon the receiving part of the connection GW2 → TEmust be the same as in the original signal on thesending part of the connection LE → GW1 (referFig 1).

If a CIS signal is transmitted using the firstmethod (section 5.1), by coding ring signal & CISwith the code 90, the ring signal reproduction willstart after a delay as shown in Fig 5. The timingparameters in Fig 5 are as follows:

- tp - the delay between a reproduced ring signalstart and an original CIS signal end;

- tD1 - the delay of a reproduced ring signal inrelation to an original ring signal. Otherabbreviations are adopted in Fig 3.

Signals in the direction LE → GW1 are calledoriginal signals. Signals in the direction GW2 → TEare called reproduced signals.

The original ring signal and CIS signal areshown in Fig 5a. The reproduced ring and CISsignal are shown in Fig 5b. The ring signalreproduction, according to Fig 5b, starts after the

54


Fig 5 (a) Original ring and CIS signal LE →GW1 (b) Reproduced ring and CIS signal GW2 → TE

original CIS signal is completely received. Thedelay of the reproduced ring signal after the end oforiginal CIS signal (tp) is the sum of the messagepropagation time over Internet and time for CISsignal end detection. Thus, the maximum delay ofring and CIS signal reproduction is:

tD1 = tRING + tdmax + tm + tp (1)

When the longest expected message, havingPresentation Layer Message of 75 bytes, is sent,its duration is tm ≈ 1080 ms. The ring signal durationis tRING = (1±0.1) s, and the delay in ring and CISsignal reproduction, neglecting tp, is:

tD1 ≤ 4180 ms (2)

As ring and CIS signals are sent using uniquetelephony event code, even in the case the CISsignal is not sent after ring pattern, it is necessaryto wait until the time tdmax, to see whether CISsignal succeeds ring pattern or not. If CIS signaldoes not succeed ring pattern, GW1 sends thetelephony event code 89 - “only ring signal”. In thisway, the ring signal delay in reproduction, whenonly ring signal is sent, is:

tD ≥ tRING + tdmax ≈ 3s (3)

If CIS signal follows ring pattern, after CISmessage reception and its decipherment, thetelephony event code 90, which defines ring signal& CIS, is sent.

The second method (section 5.2) can be usedfor CIS signal transmission, whereby separatepackets are used for telephony event ring (packetwith event code 89), and for telephony event CIS(packet with event code 91). In this case, the delayin reproduction is shorter than in previous case(given in section 5.1) when ring and CIS are sent byunique event code (packet with the event code 90).The delay can be explained using Fig 6.

Original ring and CIS signal are presented inFig 6a. Reproduced ring and CIS signal on the GW2side of connection are presented in Fig 6b only forthe case of maximum CIS signal start delay. First,the ring signal, which is sent as the event code 89,is reproduced. It starts with the delay tp after theoriginal ring signal end.

The reproduced CIS signal starts with the delaytp after the original CIS signal message end. Thistime is the sum of message propagation time overInternet and the time needed for CIS signal enddetection.

Due to this, the maximum delay between thestart of reproduced CIS message and reproduced

tRING tm

R CIS

tdmax

a)

b)R CIS

tD1

tRINGtp

55


Fig 6 (a) Original ring and CIS signal LE → GW1 (b) Reproduced ring and CIS signalGW2 → TE (c) Required implemented delay of ring signal

ring signal is:

tD2 = tdmax + tm – tRING (4)

Considering the requirement defined in [6], tosatisfy the condition tD2 ≤ tdmax, we need to havetRING ≥ tm.

If this condition is not satisfied, the start of thereproduced CIS signal could be delayed by morethan tdmax: = 2s. The most unfavourable situation iswhen the longest message is sent and thereproduced ring signal has the shortest duration.The Presentation Layer Message of this CIS signalhas 75 bytes, and the message duration is tm ≈1080 ms. For the shortest ring pattern of tRING ≈

900 ms, we have:

tD2 ≈ 2180 ms (5)

In order to prevent this situation, the delay mustbe introduced in the start of ring signal reproduction,represented in Fig 6b. The delay of the ring signalstart in this case can be seen in Fig 6c. Its valueis:

tDRING > tm – tRING (6)

and with concrete values tm ≈ 1080 ms and tRING ≈900 ms, we obtain:

tDRING > 180 ms (7)

tRING tm

R CIS

tdmax

tRING

R CIS

R CIS

b)

c)

tD2

tP tP

tDRING tRING tD3=tD2–tDRING

a)

56


8. THE ERROR PROBABILITY IN CISSIGNAL TRANSMISSION

When CIS signal is transmitted using telephonyevent code, the wrong identification may happen asthe result of error in transmission over Internet. As

Fig 7 Probability error in CIS signal transmission

CIS signals are sent using RTP, they are sentwithout checking and retransmission and may becorrupted.

The message will be wrong in the case of erroron the part of message whose accuracy is verified

Perror CIS

10-1

10-2

10-3

10-4

10-5

10-6

10-8 10-7 10-6 10-5BER

57


by the part of message called frame checksequence (FCS). This part of message, exceptRTP payload, includes Ethernet Header, IP Header,UDP Header and RTP Header and its length is,according to Fig 2, LNHeader = 54 bytes (or LHeader= 432 bits), where LNHeader and LHeader are thelengths in bytes and bits of all headers which arechecked by the FCS. RTP payload can be at mostLNRTPpay = 82 bytes (or LRTPpay = 656 bits) for CISsignal transmission in our case. The packet errorprobability (i.e. probability of packet loss) can becalculated as:

PerrorCIS = (LHeader + LRTPpay) . BER (8)

where BER is Bit Error Rate, i.e. the probability thata bit is corrupted.

The result of this calculation is shown in Fig 7.

9. CONCLUSION

The paper presents two methods of callingsubscriber number transmission over Internet tothe called subscriber. These methods aredeveloped for the telephone network requirementsof Telekom Serbia. The first method uses only onetelephony event code from the group of codes,but, unfortunately, produces great delay of ringsignal.

The other method is efficient, because ringsignal delay is small, but the method uses twotelephony event codes and the more complicatedGW on the user side.

ACKNOWLEDGEMENT

This paper is the result of research supported byMinistry of Science of Republic of Serbia.

REFERENCES

1. H Schulzrinne & S Petrack, RFC2833: RTP Payloadfor DTMF Digits, Telephony Tones and TelephonySignals, May 2000.

2. H Schulzrinne & T Taylor, RFC 4733: RTF Payloadfor DTMF Digits, Telephony Tones, and TelephonySignals, December 2006.

3. H Schulzrinne & T Taylor, RFC 4734: Definition ofEvents for Modem, Fax, and Text Telephony Signals,December 2006.

4. H Schulzrinne & T Taylor, Definition of Events ForChannel-Oriented Telephony Signalling draft-ietf-avt-rfc2833biscas-05, June 2007.

5. H Schulzrinne, S Casner, R Frederick & V Jacobson,RFC 3550: RTP: A Transport Protocol for Real-TimeApplications, July 2003.

6. ETSI EN 300 659-1 Vl.3.1, Access and Terminals(AT); Analogue access to the Public SwitchedTelephone Network (PSTN); Subscriber line protocolover the local loop for display (and related) services;Part 1: On hook data transmission, 2001-01.

7. ITU-T Rec. V.23, Data Communication over theTelephone Network: 600/1200-baud modemstandardized for use in the general switchedtelephone network, Fascicle VIII. 1, November 1988.

8. ETSI ETS 300 778-1, Public Switched TelephoneNetwork (PSTN); Protocol over the local loop fordisplay services; Caller Display Service - TerminalEquipment Requirements; Part 1: Off-line datatransmission, July 1996.

58


AuthorsAleksandar Lebl, born 1957, BSc 1981, MSc 1986 is employed from 1981 in the SwitchingDepartment of Research and Development Institute IRITEL in Belgrade, Republic of Serbia.During years he worked on the project of Digital Switching System for SerbianTelecommunication Industry.

Address: Aleksandar Lebl, IRITEL d.d, Batajnicki put 23, 11080 Zemun, Serbia, Europe.E-mail: <[email protected]>

•arko M Markov, born 1946, BSc 1969, MSc 1975, PhD 1976 is a scientific counsellor inIRITEL, Institute for Electronics and Telecommunications, Belgrade, Serbia. Area of work:Switching technics, Teletraffic theory, Network signalling. Author or co-author of hundredpapers and six books. At the University of Belgrade, School of Electrical Engineering, DrMarkov is a professor at the course of Switching technics and Network signalling.

Address: • arko Markov, IRITEL d.d, Batajnicki put 23, 11080 Zemun, Serbia, Europe.

Paper No 143-B; Copyright © 2008 by the IETE.

^

^

59


Issues in Mobile Ad hoc Networks forVehicular Communication

S S MANVI AND M S KAKKASAGERI

ABSTRACT

Vehicular ad hoc networks (VANETs) are a specific type of Mobile Ad hoc Networks (MANETs) that are currentlyattracting the attention of researchers around the world. With pervasiveness of mobile computing technology andwireless communications, VANETs could be a key networking technology of the future vehicle communications.VANETs can make a possible wide-range of interesting applications focusing on vehicle traffic safety, entertainmentin vehicles, cooperative driver assistance, sharing traffic and road conditions for smooth traffic flow, user interactions,information services, etc. Key characteristics that distinguish VANETs from other networks are time-varying natureof vehicle density, high mobility, and time-critical safety applications. Hence, devising protocols for VANETs may notbe successfully accomplished by simple adaptation of protocols designed for wired networks and MANETs. Thispaper outlines the current research issues in VANETs, which may benefit the researchers to design and developprotocols for VANETs.

1. INTRODUCTION

Vehicular Ad hoc Networks (VANETs) are anenvision of the Intelligent Transportation System(ITS). Vehicles communicate with each other in twoways: (1) Intervehicle communication and (2)Vehicle to roadside infrastructure communication.VANETs are based on short-range wirelesscommunication between vehicles. Unlikeinfrastructure-based networks such as cellularnetworks, these networks are constructed on thefly (self organizing).

VANETs are special case of Mobile Ad hocNetworks (MANETs). The key differences ascompared to MANETs are following: componentsbuilding the network are vehicles, restricted vehiclemovements, high mobility and time-varying vehicledensity [1]. One advantage of VANETs overMANETs is that most of the vehicles providesufficient computational and power resources, thuseliminating the need for introducing complicatedenergy-aware algorithms [2].

The optimal goal of VANETs is to provide saferand more efficient roads in future by communicatingtimely information to drivers and concernedauthorities. The prominent evolution of wirelesscommunication witnessed recently has sparkledthe interest of the automotive industry. Many

manufacturers have already developed systemprototypes, allowing vehicles to communicate withtheir surroundings using wireless media [3]. Thishas motivated the research community to designand develop protocols and standards for VANETs.

A typical VANETs scenario is as shown inFig 1. Vehicle to vehicle and vehicle to roadsidebase station/gateway communication is possiblefor providing safety and other information servicesto vehicle users. Group of vehicles together mayform a cluster to disseminate information amongthemselves as well as to other clusters and basestations.

VANET may integrate networking technologiessuch as WiFi (Wireless Fidelity Standard IEEE802.11 b/g), WiMAX (Wireless Metropolitan AccessStandard IEEE 802.16) and Bluetooth (IEEE802.15). WiFi can be used for vehicle to vehicle aswell as vehicle to base station communication.WiMAX can be used for forming wireless backboneconnecting different base stations. Bluetooth canbe used for intra-vehicle communication as well ascommunicating with nearest neighbors.

In a VANET, each vehicle in the system isequipped with a computing device, a short-rangewireless interface and a GPS (Global PositioningSystem) receiver. GPS receiver provides location,speed, current time and direction of the vehicle.

60


Fig 1 A typical VANET scenario

Manufacturers are already enhancing cars withsensors that help drivers to park and provide GPScompasses as standard equipment on luxury cars.Within a decade, full integration of on-boardsoftware and hardware computing facilities withwireless communications and environmentalsensors can be achieved.

Each vehicle stores information about itself andother vehicles in a local database. The records inthis database are periodically broadcasted. Arecord consists of the vehicle identification, positionin the form of latitude and longitude, current speedof the vehicle, direction, and timestampscorresponding to when this record was first createdand when this record was received.

The vision for VANETs includes applicationssuch as route planning, road safety, e-commerce,entertainment in vehicles, cooperative driverassistance, sharing traffic and road conditions forsmooth traffic flow, user interactions, informationservices, etc. [4-9]. VANETs have uniquerequirements with respect to applications, types ofcommunication, self-organization and other issues

such as media access, security and routing. Inorder to meet these requirements, the structuringof functionalities into protocols and their interactionmust be re-thought.

A number of research projects show greatinterest in VANET, which aim at development ofVANET protocol architecture, connectivity for inter-vehicle communications using roadsideinfrastructure and secured routing of critical events[10-12]. This paper briefly outlines research issuesin a VANET and also focuses on the adoptablewireless technologies for deployment of VANETs.

2. UNIQUE CHARACTERISTICS OFVANETs

In order to suggest a protocol stack suitable forVANETs, we should pinpoint the fundamentalcharacteristics that differentiate VANETs fromother networks.

• Geographically constrained topology:Roads limit the network topology to actually

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one dimension; the road direction. Except forcrossroads or overlay bridges, roads aregenerally located far apart. Even in urbanareas, where they are located close to eachother, there exist obstacles, such as buildingsand advertisement walls, which preventwireless signals from traveling between roads.This implies that vehicles can be consideredas points of the same line; a road can beapproximated as a straight line, or a small-angled curve. This observation is quiteimportant, because it affects the wirelesstechnologies that can be considered. Forexample, since the packet relays are almostall in the same one-directional deploymentregion, the use of directional antennas couldbe of great advantage.

• Partitioning and large-scale: The probabilityof end-to-end connectivity decreases withdistance; this is true for one-dimensionalnetwork topologies. In contrast, connectivityis often explicitly assumed in research fortraditional ad hoc networks, sometimes evenfor the evaluation of routing protocols. Inaddition, VANETs can extend in large areas,as far as the road is available. This artifacttogether with the one-dimensional deploymentincreases the above probability.

• Self-organization: The nodes in the networkmust be capable to detect each other andtransmit packets with or without the need of abase station.

• Unpredictability: The nodes (or vehicles)constituting the network are highly mobile.Because of this reason, there is also a highdegree of change in the number anddistribution of the nodes in the network atgiven time instant. The nodes must beconstantly aware of the network status, keeptrack of the hosts associated with the network,detect broken links and update their routingtables whenever necessary.

Since vehicle mobility depends on thedeployment scenario, the movement direction ispredictable to some extent. In highways, vehiclesoften move at high speeds, while in urban areasthey are slow. In addition, mobility is restricted bythe road directions as well as by traffic regulations.Assuming that these regulations are obeyed, thereare lower and upper speed bounds, and restriction

signs that obligate drivers to move on specificroads and directions. Hence, mobility models cannow include some level of predictability inmovement patterns. Car manufacturing companieshave already implemented such models for testingmechanical parts.

• Power consumption: In traditional wirelessnetworks, nodes are power limited and theirlife depends on their batteries - this isespecially true for ad hoc networks. Vehicleshowever can provide continuous power to theircomputing and communication devices. As aresult, routing protocols do not have to accountfor methodologies that try to prolong thebattery life. Older network protocols includemechanisms such as battery-life reports forenergy-efficient path selection, sleep-awakeintervals, as well as advanced network cross-layer coordination algorithms. These schemescannot offer any additional advantages tovehicular networks.

• Node reliability: Vehicles may join and leavethe network at any time and much morefrequently than in other wireless networks.The arrival/departure rate of vehicles dependson their speed, the environment, as well as onthe driver needs to be connected to thenetwork. In case of ad hoc deployments, thecommunication does not easily depend on asingle vehicle for packet forwarding. Thisoccurs because of non-coverage ofcommunication range between communicatingvehicles. Thus there is a need to take help ofintermediate nodes for packet forwarding todestination vehicle. Intermediate nodes mustbe reliable to forward the packets efficiently.

• Channel capacity: The channels in VANETsover which the terminals communicate aresubjected to noise, fading, interference,multipath propagation, path loss, and haveless bandwidth. So high bit-error rates arecommon in VANETs. One end-to-end path canbe shared by several sessions. In somescenarios, the path between any pair of userscan traverse multiple wireless links and thelink themselves can be heterogeneous. Sosmart algorithms are needed to overcome offluctuating link capacity in networks.

• Vehicle density: Multi-hop data deliverythrough vehicular ad hoc networks is

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complicated by the fact that vehicularnetworks are highly mobile and sometimessparse. The network density is related to thetraffic density, which is affected by thelocation and time. Although it is very difficultto find an end-to-end connection for a sparselyconnected network, the high mobility ofvehicular networks introduces opportunitiesfor mobile vehicles to connect with each otherintermittently during moving.

To deal with disconnections in sparse ad hocnetworks, carry and forward, (where nodes carrythe packet when routes do not exist, and forwardthe packet to the new receiver that moves into itsvicinity) method may be applied. Work given in [13]explains that there is a high chance for movingvehicles to set up a short path with few hops in ahighway model.

• Vehicle mobility: Since the nodes are mobile,the network topology may change rapidly andunpredictably and the connectivity among theterminals may vary with time. VANET shouldadapt to the traffic and propagation conditionsas well as the mobility patterns of the mobilenetwork nodes. The mobile nodes in thenetwork dynamically establish routing amongthemselves as they move about, forming theirown network on the fly. Moreover, a user in aVANET may not only operate within thenetwork, but may also require access to aroadside infrastructure. Hence there is a needof strong mobility patterns in VANETs.

3. APPLICATIONS OF VANETs

Some of the important applications of VANETsare as follows:

• Message and file delivery: This applicationfocuses on enabling the delivery of messagesand files in a vehicular network to the targetreceivers (group communication) withacceptable performance.

• Internet connectivity: This applicationfocuses on connecting the vehicles to theInternet using roadside infrastructure andintervehicle communications to facilitatebrowsing, send/read e-mails, chatting, etc.

• Communication-based longitudinalcontrol: Exploiting the look- through capabilityof VANETs to help avoiding accidents. For

example, a vehicle can check the status of upfront vehicles status (speed, brake applied,road blocks, etc.).

• Co-operative assistance systems:Coordinating vehicles at critical points suchas blind crossings (a crossing without lightcontrol) and highway entries.

• Safety services: Safety applications includeemergency breaking, accidents, passingassistance, security distance warning, andcoordination of cars entering a lane.Furthermore, sensors embedded in the carengine and elsewhere could be used forexchanging information, either with theonboard computer of the vehicle itself orvehicles with sophisticated computing andcommunication abilities, for diagnosticpurposes. Also, safety applications are timesensitive and should be given priority overnon-safety applications. This could facilitatepreventive maintenance and minimizes roadbreakdowns.

• Traffic monitoring and managementservices: In such type of services, all vehiclesare part of a ubiquitous sensor system. Eachvehicle monitors the locally observed trafficsituation such as density and average speedusing an onboard sensor and the results aretransferred to other vehicles via wireless data-link through the network.

Other applications are more related tomultimedia communications like entertainment andnon-safety information for example informationdownload at gas stations or public hotspots, andcar-to-car information exchange, etc. Some ofthese applications will be free, while others wouldrequire a service subscription or a one-timepayment.

4. ISSUES IN VANETs

VANET raises several interesting issues inregard to media access control, mobilitymanagement, data aggregation, data validation,data dissemination, routing, network congestion,performance analysis, privacy and security.

4.1. Media access control (MAC)

Design of VANET MAC protocols should give

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more significance to fast topology changes andtypes of services rather than power constraints ortime synchronization problems. Moreover, VANETMAC protocols have to reduce the medium accessdelay and increase the reliability, which is importantin case of safety applications.

An IEEE working group is investigating a newPHY/MAC amendment of the 802.11 standarddesigned for VANETs, which is known as WirelessAccess in Vehicular Environments (WAVE), alsoreferred as IEEE 802.11p [14]. In terms of MACoperations, WAVE uses CSMA/CA (Carrier SenseMultiple Access / Collision Avoidance) as the basicmedium access scheme for link sharing and shouldprobably use one control channel to set uptransmissions.

ADHOC MAC [15] is a MAC protocol conceivedwithin the European project CarTALK2000 with thepurpose to design novel solutions for VANETs.ADHOC MAC works in slotted frame structure,where each channel is divided into time slots. TheADHOC-MAC protocol is devised for anenvironment in which the terminals can be groupedinto clusters in such a way that all the terminals ofa cluster are interconnected by broadcast radiocommunication through slotted channel. Such acluster is defined as One-Hop (OH). The accessmechanism of ADHOC-MAC is Dynamic TDMA(Time Division Multiple Access) and channels areassigned to the terminals according to terminalneeds.

Directional antenna transmission has apromising place in VANETs, in particular for MACissues. In VANETs, node’s movement is limited byroads and driving rules (e.g. opposite drivingdirections on the same road). Hence, directionalantennas would surely help in reducing interferenceand collisions with ongoing transmissions overparallel neighboring vehicular traffic.

A MAC protocol that uses directional antennasin an ad hoc network where the mobile nodes do nothave any location information is proposed in [16].The protocol uses RTS/CTS (Request to send /Clear to send) exchange similar to that in 802.11 forenabling the source and destination nodes toidentify each other’s directions. The nodes transmitas well as receive data packets using directionalantennas, thereby reducing the level of interferenceto other nodes as well as to themselves.

A MAC protocol that adapts Dual Busy ToneMultiple Access (DBTMA) for use with directionalantennas is discussed in [17]. By transmitting busytones directionally, in addition to the directionaltransmission of RTS/CTS and data frames, protocolavoids collisions in a much finer grain in terms ofspatial reuse and thus increases the channelcapacity significantly.

4.2. Mobility management

Since vehicles are highly mobile and changetheir point of network attachment frequently whileaccessing Internet services through gateways, it isadvisable to have some mobility managementschemes that take care of vehicle mobility andprovide seamless communication. Mobilitymanagement has to meet the followingrequirements: seamless mobility (communicationmust be possible irrespective of vehicle position),low handoff latency, support IP V6, scalable interms overheads. Ad hoc routing protocolextensions are unsuitable for the mobilitymanagement of VANETs. They highly depend onthe routing protocol deployed in the ad hoc network,and they do not support Mobile IPv6. Application-specific enhancements are an interesting approachfor the mobility management of VANETs. Theysupport the mobility of nodes and they areindependent of the ad hoc routing protocol.

A mobility management protocol called MMIP6is based on the principles of Mobile IPv4, but isdesigned to support IPv6-based mobile nodesorganized in ad hoc networks [18]. MMIP6 usesforeign agents (FAs) like in Mobile IPv4, which arelocated at the Internet Gateways (IGWs). The FA(Foreign agents) represents the vehicle located inthe VANET; this way, it hides the multihop capabilityof the VANET and the vehicles appear as commonmobile nodes. A very important feature is thatMMIP6 relies on globally routable and permanentIPv6 addresses to identify the vehicles. With theuse of FAs, all vehicles participating in the VANETform one logical IPv6 subnet, where the IGWs actas transition points between the VANET and theInternet. The IPv6 addresses can be assignedstatically to each vehicle, i.e. they arepreconfigured in the communication hardwareshipped with the vehicles. In contrast to MobileIPv6, a vehicle does not receive a valid IPv6 care-of address when entering a foreign network. MMIP6

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avoids link local addresses when a vehicle islocated in a foreign network.

4.3. Data aggregation

The vehicles have to pass on the data sent bythe neighbors to other neighbors of its coveragearea. This increases the number of packets to besent by a vehicle. Therefore, data aggregationtechniques are applied to reduce such overheads.Data aggregation is an interesting approach, whichreduces the number of packets transmitteddrastically by combining several messages relatedto the same event into one aggregate message. Forexample, the records about two vehicles can bereplaced by a single record with little error, if thevehicles are very close to each other and movewith relatively the same speed.

The CARISMA road traffic simulator served asa means for modeling the mobility of the networknodes and tests the data aggregation [19]. Insimulations, a rain area was placed randomly withinthe scenario and all vehicles start to send a warningmessage if they detect it. After the aggregation, theaggregate is not broadcasted directly, however, atimer is started to wait for further messages. Arevocation message will be generated if a vehicledetects no rain. This revocation message isincluded in the aggregate to adapt the hazard areainformation.

4.4. Data validation

A vehicle may send the data it has observeddirectly (assuming that a vehicle always trusts thedata it has gathered itself) to its neighbors.Sometimes, malicious vehicles may send theincorrect information to confuse the users. Forexample, a malicious node may send the falseaccident information and divert all the vehicles onother roads, which may some times lead to trafficcongestion. In such situation, data validationtechniques must be applied before passing on thereceived information to other nodes.

The vehicles test the validity of data receivedfrom other vehicles. This is done by correlating thedata from different vehicles and cross-validate itagainst a pre-defined set of rules. A formal model ofdata validation and dissemination in VANETs andstudy of how VANET characteristics, specificallythe bi-directional mobility on well defined paths,

affects the performance of data dissemination isgiven in [20].

A probabilistic validation of aggregated data inVANETs is given in [21]. An aggregated recordcomprises of following: individual records fromvehicles, random number, time stamp, signature;regular record (one of the individual record selectedby using “random-number mod number-of-individual-records”), time stamp and signature.When a vehicle receives an aggregated record, itfirst verifies the signature and certificate of thesender and then verifies individual records. Vehicleuses random number to generate an index for set ofrecords. Later, it checks for regular record matchingwith the record in set of records as per the index. Ifthere is a match, then the record is valid.

4.5. Data dissemination

Data dissemination can be defined asbroadcasting information about itself and the othervehicles it knows about. Each time a vehiclereceives information broadcast by another vehicle,it updates its stored information accordingly, anddefers forwarding the information to the nextbroadcast period, at which time it broadcasts itsupdated information. The dissemination mechanismshould be scalable, since the number of broadcastmessages is limited, and they do not flood thenetwork. VANET characteristics like high-speednode movement, frequent topology change, andshort connection lifetime especially with multi-hoppaths needs some typical data disseminationmodels for VANETs. This is because topologicaltransmission range needs to maintain a path fromthe source to the destination, but the path expiresquickly due to frequent topology changes.

A successful VANET data dissemination modelneeds to handle issues such as sparse networkdensity, interfering environment, long path length,latency, etc. The transmission power signal level ofa vehicle may be too strong or too weak duringcertain times of the day and in certain cityenvironments. When the transmission range is toostrong, it creates interference and lowers thesystem throughput. When transmission powersignal level is too low, the vehicle cannot reachother vehicles. Smart algorithms for datadissemination that adjusts according to thetransmission power signal level are needed.

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The dissemination mechanism can eitherbroadcast information to vehicles in all directions,or perform a directed broadcast restrictinginformation about a vehicle to vehicles behind it.Further, the communication could be relayed usingonly vehicles traveling in the same direction,vehicles traveling in the opposite direction, orvehicles traveling in both directions.

In order to design a data dissemination model,we have to consider some of the following issues:

• For one way, and two way in the context oftraffic, a system for scalable traffic datadissemination and visualization in VANETs isneeded. Vehicles moving in both directionsmay yield the best performance. But vehiclesin the opposite direction needed better modelto increase the data disseminationperformance.

• How to make efficient usage of availablebandwidth consumed by each vehicle?

• To limit the number of re-transmissions due tocollisions.

• In dense networks, such as cities or majorhighways with a large portion of equippedvehicles, the data load on the channel shouldbe controlled in order not to exceed the limitedwireless bandwidth. In contrast, in sparsenetworks, channel saturation is not a criticalissue. Moreover, messages should berepeated since equipped vehicles are mostlikely out of wireless radio range of eachother; vehicles inside the area of influence ofa hazard, but not reachable at the time theyare detected, should also be notified. Notethat in case of experiencing a dense network,the forwarding strategy is required to be veryefficient in terms of overhead while ensuringhigh reliability to priority messages with themost important payload, i.e., safety-of-life.

• Safety information must be kept alive: Safetyhazards can be associated with a time durationand geographical area while/where they canpotentially affect vehicles safety state. Thedistribution of some state information will berepeated (e.g., periodically or at detection of anew neighboring vehicle) for a defined durationof time while being inside a specificgeographical area. The specific strategy to

optimize this repetition process is to bedeveloped.

A multihop information dissemination schemein inter-vehicle networks is discussed in [22]. Modelfor information Dissemination in mobile ad hocgeosensor networks is given in [23].

4.6. Routing

Since the topology of the network is constantlychanging, the issue of routing packets between anypair of nodes becomes a challenging task. Mostprotocols should be based on reactive routinginstead of proactive routing. Multicast routing isanother challenge because the multicast tree is nolonger static due to the random movement of nodeswithin the network. Routes between nodes maypotentially contain multiple hops, which situation ismore complex than the single hop communication.

Improving proactive routing in that of VANETswith the movement prediction framework is given in[24]. A route is composed of several communicationlinks (pair of vehicles) connected to each otherfrom the source to the destination. By knowing themovement information of vehicles involved in theroutes (including source and destination), we canpredict their positions in the near future in order topredict the lifetime of the link between each pair ofvehicles in the path.

4.7. Network Congestion

Congestion control in VANETs is a challengingissue. The Internet is based on an end-to-endparadigm, where the transport protocol (e.g. TCP)instances at the endpoints detect overloadconditions at intermediate nodes. In case ofcongestion, the source reduces its data rate.However, in VANETs, the topology changes withinseconds and a congested node used for forwardinga few seconds ago might not be used at all at thepoint in time when the source reacts to thecongestion.

Due to the mainly broadcast/geocast orientedcommunication and the highly dynamic networktopology, conventional mechanisms such as per-flow fair queuing are difficult to apply. So anappropriate model is needed for VANET where eachnode locally adapts to the available bandwidth.Congestion control for VANETs has not been

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studied thoroughly so far but this feature will beextremely necessary for VANET applications andnetwork performance. The work given in [25]performs congestion control by using clustersdepending upon the vehicle density. The clustersize is reduced as the vehicle density increases.Due to the high mobility and the resulting highlydynamic network topology, congestion control hasto be performed in a decentralized and self-organized way, locally in each VANET node.

4.8. Performance analysis

The cost of deploying and implementingdesigned schemes for VANETs in the real world ishigh. Hence there is a need for development ofeffective simulators to evaluate the performance ofprotocols for VANETs before deployment. Mostresearch in this area relies on simulation forevaluation. Key component of simulations is arealistic vehicular mobility model that ensuresconclusions drawn from experiments will carrythrough to real deployments. A VANET simulationplatform should provide support to vehicle to vehicleas well as vehicle to base station communicationsin various road conditions, traffic conditions andmobility patterns. Simulation may also usecollection of mobility traces and network statisticsto experiment on a real vehicular network.

To facilitate users to rapidly generate realisticmobility models for VANET simulations followingmobility models may be considered [26]: Straightfreeway model or Highway mobility model, RandomWaypoint (RWP), and Real-Track model (RT).

In Straight freeway model or Highway modelnodes move following a certain path in certaindirection. Nodes are not supposed to change theirdirection. The velocity in case of Highway mobilitymodel is very high in three lanes (slow, medium andfast lane). Vehicle can change lanes as they do inreal life situation i.e. from slow to medium lane butnot to fast lane directly. Nodes can overtake eachother.

The Random Waypoint model implementationis as follows: At every instant, a node randomlychooses a destination and moves towards it with avelocity chosen randomly from minimum tomaximum allowable velocity for every mobile node.After reaching the destination, the node stops for a

duration defined by the ‘pause time’ parameter.After this duration, it again chooses a randomdestination and repeats the whole process againuntil the simulation ends.

Real- track model are derived from the streetsof the actual maps. The grouped nodes must movefollowing the constraint of the tracks. At the switchstations, which are the intersections of tracks/streets, a group can then be split into multiplesmaller groups; some groups may be even mergedinto a bigger group. Such group dynamics happenrandomly under the control of configured split andmerge probabilities. Nodes in the same group movealong the same track. They also share the samegroup movement towards the next switch station. Inaddition, each group member will also have aninternal random mobility within the scope of a group.The mobility speeds of these groups are randomlyselected between the configured minimum andmaximum mobility speeds. One can also definemultiple classes of mobile nodes, such aspedestrians, and cars, etc. Each class of nodeshas different requirements: such as moving speedetc. In such cases, only nodes belonging to thesame class can merge into a group.

The random trip model is a generic mobilitymodel that generalizes random waypoint andrandom walk to realistic scenarios, which gives arealistic flavor to simulations [27].

Some of the simulators used for evaluation ofVANETs are as follows. VanetMobiSim, Glomosim,CORSIM, QualNet, NS-2, OPNET, PARAMICS,CORSIM and VISSIM [28-32]. But none of them arestandard simulators. Thus there is a scope fordesigning VANET simulators.

4.9. Privacy and Security

VANETs demand a thorough investigation ofprivacy related issues. On one hand, users of suchnetworks have to be prevented from misuse of theirprivate data by authorities, from location profilingand from other attacks on their privacy. On theother hand, system operators and carmanufacturers have to be able to identifymalfunctioning units for sake of system availabilityand security. Further, wireless link characteristicsintroduce also reliability problems because of thelimited wireless transmission range, the broadcastnature of the wireless medium (e.g. hidden terminal

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problem), mobility-induced packet losses, and datatransmission errors.

In the automotive market, customers canchoose among a large variety of products and thereis a strong competition among automakers.Customers concerned about a new technologywould probably pick products that reflect theirconcerns. It is therefore a vital interest of all carmanufacturers promoting vehicle to vehiclecommunication technology, to pay close attentionto security and privacy of such systems. The hugenumber of vehicles registered in different countriesand traveling long distances, well beyond theirregistration regions, requires a robust and scalableprivacy and security management scheme.

Some of the security and privacy related issuesare as follows.

• Secure Positioning: Position is one of themost important data for vehicles. Each vehicleneeds to know not only its own position butalso those of other vehicles in itsneighborhood. GPS signals are weak, can bespoofed, and are prone to jamming. Moreover,vehicles can intentionally lie about theirpositions. Hence there is a need for a securepositioning system that will also support theaccountability and authorization properties,frequently related to a vehicle’s position.

• A very dangerous and often ignored fact aboutprivacy is that innocent looking data fromvarious sources can be accumulated over along period and evaluated automatically. Evensmall correlations of the data may revealuseful information. And once privacy is lost, itis very hard to re-establish that state ofpersonal rights.

A data verification system, which helps toprevent the forging attacks, has to be developed.This can be achieved by a data correlationmechanism that compares all collected dataregarding a given event.

• Existing solutions such as frequency hoppingdo not completely solve the problem ofjamming. The use of multiple radiotransceivers, operating in disjoint frequencybands, can be a feasible approach.

• In scenarios where a vehicle communicateswith a dedicated partner, we assume that in

some cases the vehicle real identity will berequired for service usage. In such a case, itis obvious that the communication partner hasthe identity anyway, so the identity must onlybe protected from neighbors overhearing thecommunication. A communication protocolthat keeps the identity of the vehicle hiddenfrom third party observers is needed.

• A good thing about mobility is that real(communication) traffic analysis wouldprobably be hard to do, since nodes usuallymove at high speed and in large geographicareas. But nevertheless, an attacker mightuse the properties of communicating vehiclesas an aid for tracking a specific car. A strongsolution is needed to overcome this problem.

• Vehicular networks lack the relatively long-lived context. Hence password-basedestablishment of secure channels, gradualdevelopment of trust by enlarging a circle oftrusted acquaintances, or securecommunication only with a handful ofendpoints may be impractical for securingvehicular communication. Particularly forVANETs security concerns, the issues foridentification and addressing have to beresolved.

Some of the efficient architectures that canreally manage above mentioned privacy andsecurity related issues are discussed in [33-36].

A group signature based secure and privacypreserving vehicular communication framework isgiven in [37]. This scheme achieves authenticity,data integrity, anonymity, and accountabilitysimultaneously. It utilizes a group signaturescheme, in which members maintain only a smallnumber of secret key/group public key pairs.Privacy is provided due to the fact that signers areanonymous within the group from which they sign.Additionally, not only are signers anonymous withintheir group, but two messages signed by the sameindividual are not linkable, that is to say, one cannotdetermine if two messages came from the samemember of the group, or two different members ofthe group.

Digital signatures are a good choice becausesafety messages are normally standalone inVANETs [38]. Because of the large number ofnetwork members and variable connectivity to

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authentication servers, a Public Key Infrastructure(PKI) is a good way to implement authentication.Under the PKI solution, each vehicle would begiven a public/private key pair. Before sending asafety message, it signs it with its private key andincludes the Certification Authority (CA) certificate.Because of the use of private keys, a tamper-proofdevice is needed in each vehicle. This is where thesecret information will be stored and the outgoingmessages will be signed. To lower the risk ofcompromise by attackers, the device should haveits own battery and clock. The clock should becapable of being resynchronized when passing by atrusted base station on the side of a road.

5. WIRELESS TECHNOLOGIES FORVANETs

Wireless technologies suitable for VANETs areWireless Metropolitan Area Networks (WMANs),Wireless Local Area Networks (Wireless LANs/WiFi) and Wireless Personal Area Networks(Wireless PANs), Dedicated Short RangeCommunications (DSRC)/WAVE (Wireless Accessin Vehicular Environments) together with their adhoc mode of operation [39,40].

5.1. WMANs

A WMAN (Wireless Metropolitan Area Network)can interconnect distant locations. Two kinds ofWMANs exist: back haul and last mile. Back haul isfor enterprise networks, cellular base stationcommunications and Wi-Fi hotspots. Last mile set-ups can establish wireless as an alternative toresidential broadband modems. WMANconnections can be PTP (Point-to-Point) or PMP(Point-to-Multipoint).

One of the most interesting recentdevelopments is the standardization of WMANs inthe form of WiMAX IEEE 802.16. Finally, the WMANcategory also includes the GSM/GPRS (GlobalSystem for Mobile communications/ GeneralPacket Radio Service) Cellular infrastructurenetworks. The WMAN type of technology could beemployed in infrastructure - based vehicularnetworks alone, or in coordination with WirelessLANs or Wireless PANs (and their ad hoc multihoptypes) as last-hops. It provides a high-potentialsolution for vehicular networks, even for distanthighway environments. Another possibility is to

maintain permanent direct links from vehicles tocellular base stations, without the directcommunication among vehicles. However, from thecellular network perspective this will probably resultin a relatively low throughput. Features of WiMaxare given in Table 1.

5.2. WLAN/WiFi

WiFi is another possibility for vehicularnetworks. An IEEE 802.11 transmitter has a 250mts omni directional coverage range, which ispotentially sufficient enough to maintain a level ofmultihop connectivity in both highway and urbanregions. In addition, extended-vicinity antennas(umbrellas) could be employed in base stations, forcovering larger distances. A lot of research hasbeen done for the popular IEEE 802.11 wirelessprotocol, mostly for the MAC (CSMA/CA) andnetwork layers. However, this research cannot betaken off the shelf for use in vehicular networks.This is because of the unique characteristics ofVANETs that we have described in section 2.Features of WiFi standards are given in Table 2.

5.3. WPAN

Wireless Personal Area Networks are used forshort-range wireless communications (IEEE 802.15or Bluetooth). Even though the data rates offered byWPAN are tempting, the short transmission range(maximum 10-20m) restricts the applicability ofthis technology to only dense urban-areavehicular networks. Features of Bluetooth are givenin Table 3.

5.4. DSRC/WAVE

Dedicated Short Range Communications(DSRC) was conceived to provide architecture fornodes within a vehicular network to communicatewith each other and with the infrastructure. InDSRC, subsequently specialized as WAVE(Wireless Access in Vehicular Environments, alsoreferred as IEEE 802.11p), GPS-enabled vehiclesare equipped with on board units, which cancommunicate with each other to propagateinformation through Vehicle-to-Vehiclecommunications.

DSRC/WAVE operates in the 5.9 GHz band(U.S.) or 5.8 GHz band (Japan, Europe) and has 75

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TABLE 1: WMAN standards

802.x Characteristics Advantages Applications

16 a Operates in 2 to 11 GHz range. Very long range. Broad bandWiMAX, Range up to 50 Kms. High data throughput. wireless accessData rate per sector is between 60 Thousands of users per site. for rural andand 70 Mbits/s. MIMO (multiple-input and multiple- metropolitanSupport modulation methods from output) support and turbo code areas.BPSK (binary phase shift keying) support. Backhaul forup to 64 QAM (Quadrature WLANamplitude modulation). hotspots/hubs.

16 e Operates in 2 to 6 GHz range. Support of low latency Offers regionalMobile WiMAX, typical range is data, video, and real time voice roaminglikely to be between one and three services for mobile users at uptomiles. pedestrian speed.Data rate is up to 15 Mbits/s. Backward compatible withSupport for adaptive modulation. 16 a base stations.

MIMO and EnhancedLDPC (low-density parity-check)coding support.

20 Operates in licensed bands Support for mobile Mobile users inbetween 500 MHz and 3.5 GHz. users at very high motor vehiclesMobile broadband wireless access, speeds of up to 250 Kmph. and trains.range up to 15 Kms. Also supports voice over internetData rates of 1 Mbit/s per user. protocol.Modulation rates from BPSK to Global mobility and roaming.64QAM. Supports both convolutional and

turbo coding.

TABLE 2: WLAN/WiFi standards


11 a Operates in unlicensed 5.725-to-5.850 No interference. MultimediaGHz. applications likeOptimum range is 50 feet. home and business.High average throughputspeed 6 to 54 Mbps.OFDM (Orthogonal frequency-division multiplexing) modulationtechnique.

11 b Three channels in the 2.4 GHz Low hardware price. Home, campus, factoryunlicensed frequency. Compatible with 11 g. and office networking.Range up to 150 feet.Throughput speeds of 2 to 11 Mbits/s.DSSS (Direct sequence spreadspectrum) modulation technique.

11 g Three channels in the 3.4 GHz High average throughput Multimediaunlicensed frequency. speeds. applications likeRange upto 150 feet. Backward compatible with Home andThroughput speeds 11 b. office networks.of 6 to 54 Mbits/s.OFDM modulation technique.

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TABLE 3: WPAN standards


15.3 Operates in 2.4 – 2.4835 GHz frequency. Can penetrate High speedUWB Data throughput speed of 110 Mbits/s at a range walls. home and office(Ultra of 10 mts and 480 Mbits/s over 1 mt. Uses less power. networking.wideband) OFDM, optional TDD (Time division duplex) Specialized imaging.

modulation.

15.4 Operates 27 channels in three unlicensed Uses very Personal-area-ZigBee frequency bands: 2.4 GHz, 902 to 928 MHz low power. network (PAN) for

and 868 to 870 MHz. monitoring andCovers up to 30 mts range. controlling devicesPeak data rate is 250 Kbps. in home networks.CSMA-CA (Carrier Sense MultipleAccess/Collision Avoidance), optional TDD.

MHz of bandwidth allocated for vehiclecommunications, which are based on line of sightwith a range of up to 1 km and vehicle speeds of upto 140 km/h.

6. CONCLUSIONS

VANETs combine short-range communica-tions, with the scalability and mobility of classic adhoc networks, in order to support a number ofapplications aiding in the safety, entertainment andsimplification of everyday driving. Emergingwireless technologies are expected to enhance thebetter models in vehicular networks, if both theautomotive manufacturers and the researchcommunity show great interest in creating efficient,interoperable standards.

This article described the characteristics ofVANETs and raised several issues such as mediaaccess, routing, congestion, performance analysis,security, etc., for implementing intelligenttransportation system and services. The articlehas also reviewed the ongoing progress in the areaof VANETs and the technologies to be adopted forVANET deployment. The article has given enoughcoverage to understand the research problems inVANETs.

REFERENCES

1. M Rydstrom, A Toyserkani, E Strom & A Svensson,Towards a Wireless Network for Traffic safety

Applications, Proc. Radio and Communication,Linkoping, Sweden, pp 375-380, 2005.

2. Emanuel Fonseca & Andreas Festag, A Survey ofExisting Approaches for Secure Ad Hoc Routing andTheir Applicability to VANETS, NEC Technical ReportNLE-PR-2006-19, NEC Network Laboratories, March2006.

3. Jun Luo & J. P. Hubaux, A Survey of Inter-VehicleCommunication, Proc. Embedded security in Cars-Securing current and Future Automotive ITapplications, pp 164-179, Springer-Verlag, October2005.

4. Murat Caliskan, Martin Mauve, Bernd Rech &Andreas Luebke, Collection of dedicated Informationin Vehicular Ad Hoc Networks, Proc. 12th WorldCongress on Intelligent Transport Systems 2005,San Francisco, U.S.A., November 2005.

5. HolgerFler, MarcTorrent-Moreno, MatthiasTransier,RolandKrger, HannesHartenstein & WolfgangEffelsberg, Studying Vehicle Movements onHighways and their Impact on Ad Hoc Connectivity,Proc. ACM MobiCom 2005, Cologne, Germany,August 2005.

6. SaschaSchnaufer, HolgerFler, MatthiasTransier &WolfgangEffelsberg, Vehicular Ad Hoc Networks:Single-Hop Broadcast is not enough, Proc. 3rdInternational Workshop on Intelligent Transportation(WIT 2006), Hamburg, Germany, pp 49-54, March2006.

7. SaschaSchnaufer, HolgerFler, MatthiasTransier &WolfgangEffelsberg, TrafûcView: Trafûc DataDissemination using Car-to-Car Communication,ACM Mobile Computing and Communications Review(MC2R), vol 8, no 3, pp 6-19, July 2004.

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8. S S Manvi, M S Kakkasageri, Jeremy Pitt & AlexRathmell, Multi Agent Systems as a Platform forVANETs, Proc. Autonomous Agents and Multi AgentSystems (AAMAS), ATT, pp 35-42, Hakodate, Japan,May, 2006.

9. S. S. Manvi, M. S. Kakkasageri & Jeremy PittInformation Search and Access in Vehicular Ad hocNetworks (VANETs): An Agent Based Approach,Proc. International conference on Communication inComputing (CIC-2007), The 2007 World Congress incomputer Science, Computer Engineering andApplied Computing, Las Vegas, Nevada, USA, pp23-29, June, 2007.

10. H Fubler, M Moreno, M Transier, A Festag & HHartenstein, Thoughts on a protocol Architecture forVehicular Ad hoc Networks, Proc. 2nd InternationalWorkshop in Intelligent Transportation (WIT 2005),Hamburg, Germany, pp 41-45, March 2005.

11. M M Artimy, W Robertson & W J Phillips. Connectivityin inter-vehicle ad-hoc networks, Proc. EngineeringCanadian Conference on Electrical and Computer,vol 1, pp 293-298, May 2004.

12. Stephan Eichler, Florian Dtzer, ChristianSchwingenschlgl, Javier Fabra & Jrg Eberspcher,Secure Routing in a Vehicular Ad Hoc Network, IEEEVTC 2004 Fall, Los Angeles, USA, September, 2004.

13. Vinod Namboodiri, Manish Agarwal & Lixin Gao, Astudy on the feasibility of mobile gateways forvehicular ad-hoc networks, Proc First InternationalWorkshop on Vehicular Ad-hoc Networks,Philadelphia, USA, Oct 2004.

14. Stephan Eichler et al., Performance Evaluation of theIEEE 802.11p WAVE Communication Standard, Proc.1st IEEE International Symposium on WirelessVehicular Communications (WiVeC), Baltimore, USA,September 2007

15. F Borgonovo, A Capone, M Cesana & L Fratta,ADHOC MAC: a new MAC architecture for ad hocnetworks providing efficient and reliable point-to-pointand broadcast services, ACM Wireless Networks(WINET) Journal, July 2004.

16. A Nasipuri et al., A MAC Protocol for Mobile Ad HocNetworks Using Directional Antennas, Proc. IEEEWCNC 2000, Chicago, vol 1, pp 1214-1219,September 2000.

17. Z Huang et al., A Busy Tone-Based Directional MACProtocol for Ad Hoc Networks, Proc IEEE MILCOM2002, Anaheim, CA, October 2002.

18. Bechler, M & Wolf, L, Mobility Management forVehicular Ad hoc Networks, Proc. Vehiculartechnology conference, vol 4, pp 2294-2298, 2005.

19. Stephan Eichler, Christian Merkle & MarkusStrassberger, Data Aggregation System for

Distributing Inter-Vehicle Warning Messages, ProcIEEE conference on local computer networks (LCN),Florida, USA, 2006.

20. Tamer Nadeem, Pravin, Shankar & Liviu Iftode, AComparative Study of Data Dissemination Modelsfor VANETs, Proc. The 3rd ACM/IEEE AnnualInternational Conference on Mobile and UbiquitousSystems: Networks and Services (MOBIQUITOUS2006), San Jose, California, July 17- 21, 2006.

21. Fabio Picconi, Nishkam Ravi, Marco Gruteser & LiviuIftode, Probabilistic Validation of Aggregated Data inVehicular Ad-hoc Networks, Proc 3rd internationalworkshop on Vehicular ad hoc networks, pp 76 - 85,2006.

22. Timo Kosch, Christian Schwingenschlgl & Li Ai,Information Dissemination in Multihop Inter VehicleNetworks - Adapting the Ad-hoc On-demandDistance Vector Routing Protocol (AODV), ProcIEEE 5th International Conference on IntelligentTransportation Systems, Singapore, 2002.

23. S Nittel, M Duckham & L Kulik, InformationDissemination in Mobile Ad-hoc GeosensorNetworks, Proc. Third International Conference onGeographic Information Science (GIScience 2004),College Park, Maryland, October 2004.

24. Menouar, Hamid Lenardi, Massimiliano Filali & Fethi,Improving Proactive Routing in VANETs with theMOPR Movement Prediction Framework, Proc. 7thInternational conference on ITS, Sophia Antipolis,France, pp 1-6, 2007.

25. M Al-kahtani & H Mouftah, Congestion control andclustering stability in wireless ad hoc networks:Enhancements for clustering stability in mobile adhoc networks, Proc 1st ACM Workshop on Qualityof service and security in wireless and mobilenetworks, 2005.

26. Niranjan Potnis, Atulya Mahajan, Mobility models forvehicular ad hoc network simulations, Proc. 44thannual Southeast regional conference, Florida, pp746-747, 2006.

27. J Y Le Boudec & M Vojnovic, Perfect Simulation andStationarity of a Class of Mobility Models, IEEEInfocom 2005, Miami, Florida, 2005.

28. Fiore, Harri, Filali & Bonnet, Vehicular MobilitySimulation for VANETs, Proc 40th Annual SimulationSymposium (ANSS’07), Norfolk, USA, pp 301-309,2007.

29. h t tp : / /www.webs1.u idaho.edu/n ia t tp ro jec t /corsim.html

30. http://www.paramics-online.com

31. http://www.csie.ncku.edu.tw/ klan/move/

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AuthorsSunilkumar S Manvi completed his PhD from Indian Institute of Science, Bangalore.Presently he is serving as a Professor of Department of Computer science andEngineering, REVA Institute of Technology and Management, Bangalore. His areas ofresearch include wireless/wired networks, AI applications in network management, E-commerce, Grid Computing and multimedia communications. He has published over 25papers in referred national/international Journals and 60 papers in referred national/international conferences. He has coauthored books “Communication ProtocolEngineering” and “Computer Concepts and C Programming” published by PHI. He is areviewer of several reputed international/national Journals. He is a member of IEEEUSA, Fellow of IETE, India, Fellow of IE, India and member of ISTE, India. He has beenincluded in Marqui’s Who’s Who in World and International Biographies of Cambridge,London in the year 2006.

Address: Department of Electronics and Communication Engineering, Basaveshwar EngineeringCollege, Bagalkot 587 102, India.

Email: <[email protected]>

Mahabaleshwar S Kakkasageri completed his MTech from VisvesvarayaTechnological University Belgaum, Karnataka. He is pursuing his PhD in the area ofVehicular Ad hoc Networks (VANETs). Presently he is serving as a Lecturer ofDepartment of Electronics and Communication Engineering, Basaveshwar EngineeringCollege, Bagalkot, Karnataka. He has published 03 papers in referred national/international Journals and 06 papers in referred national/international conferences

Address: Department of Electronics and Communication Engineering, Basaveshwar EngineeringCollege, Bagalkot 587 102, India.

Email: [email protected]>

Paper No 146-A; Copyright © 2008 by the IETE.

32. Owen, L E, Yunlong Zhang, Lei Rao & McHale, G,Trafûc Flow Simulation Using CORSIM, Proc.Simulation Conference, Orlando, USA, pp 1143-1147,2000.

33. Jong Youl Choi, Markus Jakobsson & SusanneWetzel, Balancing Auditability and Privacy inVehicular Networks, Proc. 1st ACM internationalworkshop on Quality of service and security inwireless and mobile networks (Q2SWinet ’05),October 2005.

34. Klaus Pll, Thomas Nowey & Christian Mletzko,Towards a Security Architecture for Vehicular AdHoc Networks, Proc. The First InternationalConference on Availability, Reliability and Security(ARES 2006, IEEE Computer Society ConferencePublishing Services, pp 374-381, Los Alamitos, 2006.

35. Amer Aijaz, Bernd Bochow, Florian Dtzer, AndreasFestag, Matthias Gerlach, Rainer Kroh & TimLeinmller, Attacks on Inter-Vehicle CommunicationSystems Analysis IT 2006, Proc 3rd InternationalWorkshop on Intelligent Transportation, Hamburg,Germany, March 14-15, 2006.

36. M Jakobsson, Xiao Feng Wang & S Wetzel, StealthAttacks in Vehicular Technologies, Proc. FirstInternational Workshop on Vehicular Ad-hocNetworks, Philadelphia, USA, Oct. 2004.

37. J Guo, J P Baugh & S Wang, A Group SignatureBased Secure and Privacy Preserving VehicularCommunication Framework, Proc Mobile Networkingfor Vehicular Environments (MOVE) workshop inconjunction with IEEE INFOCOM, Anchorage,Alaska, 2007.

38. M Raya & J P Hubaux, The Security of Vehicular AdHoc Networks, Proc Third ACM Workshop onSecurity of Ad Hoc and Sensor Networks (SASN),New York, USA, 2005.

39. Y F Ko, M L Sim & M Nekovee, Wi-Fi basedbroadband wireless access for users on the road,BT Technology Journal, vol 24, no 2, pp 123-129,April, 2006.

40. C Laurendeau & M Barbeau, Threats to Security inDSRC/WAVE, Proc 5th International Conference onAd-hoc Networks, Ottawa, Canada, pp 266-279,2006.

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MediaFLO™ - The Ultimate MobileBroadcast Experience

SACHIN KALANTRI

ABSTRACT

The exponential growth in wireless penetration and advancement in technology has accelerated the development ofnew and exciting wireless services. Given the mass appeal for video and multimedia content, technology providershave debated the feasibility and economical viability of large scale delivery of high-quality multimedia content to awide range of wireless subscribers.

Although delivery of this type of content is technically feasible over today’s existing unicast networks such as 3G,these networks cannot support the volume and type of traffic required for a fully realized multimedia delivery service(many channels delivered on a mass market scale). Offloading multicast (one-to-many) multimedia traffic to adedicated broadcast network is more efficient and less costly than deploying similar services over 3G networks.

Multicast services, such as the FLO mobile broadcast platform, are built ground up to address the market demand formobile media and provide the critical link between technical feasibility and economic viability. Designed to work inconcert with existing cellular data networks, FLO effectively addresses the issues in delivering multimedia content toa mass consumer audience. Unencumbered by legacy terrestrial or satellite delivery formats, this technology offersbetter performance for mobility and spectral efficiency than other mobile broadcast technologies, offering twice thechannel capacity.

FLO is a globally-recognized, open technology standard with a broad-based licensing program. The FLO Forum, with90+ active members, including Huawei, LG Electronics, Motorola, Samsung and Sony Sharp, is driving the globalstandardization of MediaFLO Technology.

MOUNTING DEMAND FOR MOBILE TV

In 2007, worldwide mobile telephonesubscriptions reached 3.2 billion – equivalent tohalf the global population. India’s mobile subscriberbase totaled 281.62 million at the end of January2008 [1]. The exponential growth in wirelesspenetration and advancement in technology hasaccelerated the development of new and excitingwireless services. The mobile phone has becomeindispensable in India today, increasingly providingconsumers with access to targeted andpersonalized content.

The advent of mobile TV is one of the mostexciting of all the latest capabilities transformingthe mobile phone today. Research suggests thatmobile TV service is around four times moreappealing than mobile gaming [2,3]. That revelation,coupled with the fact that there was a 15 percentincrease in the worldwide sale of mobile handsetslast year [4], highlights the potential for a truly amass-market technology. Spurred by the strongappeal for video and multimedia content, technology

providers have constantly debated the feasibilityand economical viability of large scale delivery ofhigh-quality multimedia content to a wide range ofwireless subscribers.

ADVANTAGES OF A DEDICATEDBROADCAST NETWORK

Although delivery of multimedia content istechnically achievable over today’s existing cellularnetworks, these networks cannot support thevolume and type of content traffic required for afully realized multimedia delivery service (manychannels delivered on a mass market scale). Thebest mobile TV experience is delivered over adedicated mobile broadcast network, whichaggregates programming and prepares it fortransmission to handsets. 2.5 G or 3G telephony isconfigured for one-to-one or “unicast” networkconnectivity – this enables streaming of livecontent to mobile handsets but the quality of thebroadcast will deteriorate as the number of viewersincrease.

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Fig 1 Forecast showing significant growth for mobile TV [2]

Note: Based on server cost for 1,000 to 3,000 simultaneous users is $40,000 (Source:Bakhizen & Horn, 2005, and Interview with Wireless Carrier by Robert Hale & Associates).

Fig 2

By establishing a dedicated broadcast networkfor mobile TV, operators can prevent anydegradation to existing voice and data services. Adedicated mobile broadcast network allows pay TVproviders to deliver a range of different channels

and services, while maintaining a very high qualityuser experience. In other words, they can provide acompelling mobile viewing experience that mimicswhat consumers have become accustomed to aftermore than 70 years of conventional television.

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Figures 2 & 3 show how content server costsvia unicast technology rise based on the number ofusers; however, mobile broadcast technology costsremain fixed for unlimited users.

MediaFLO - The Technology with anEdge

The MediaFLO mobile broadcast platformenables the delivery of high-quality media tocountless mobile subscribers, with more efficientcoverage and higher channel capacity thanalternative technologies. A key component of theMediaFLO mobile broadcast platform is the FLO airinterface, a globally-recognized, open technologystandard which is purpose-built to efficientlybroadcast rich multimedia content over both single-frequency and multiple frequency networks with noimpact on the capacity of the cellular network. Thisallows for the efficient distribution of mobiletelevision in the most cost–effective manner. As aresult, existing cellular networks can be preservedfor core voice, SMS, data, and other value-addedservices.

The MediaFLO platform supports layeredmodulation and source coding which extends thegeographic coverage area while providing agraceful degradation of service. Consumers canreceive signals where reception would nototherwise be possible, and this efficiency providesbetter coverage along with higher quality services.Network coverage is more predictable, and thatadds up to a better quality of service.

MediaFLO technology can deliver superiorservice with roughly half the infrastructure ascompared to legacy broadcast technologies.Alternatively, it supports twice as much capacityfor content programming within the same amount ofspectrum and geographic coverage area. Greatercapacity equates to a dramatic increase in revenue-generating services and optimizes operationalcosts while delivering a compelling end-userexperience. This clearly differentiates theMediaFLO platform from alternative technologies.

Eliminating wait times associated withdownloading and buffering content, MediaFLOtechnology provides a more immediate, immersive,interactive experience. Channel switching takesapproximately two seconds, replicating the channelsurfing experience that consumers have grownaccustomed to while watching TV at home.

Invented for the mobile environment, theMediaFLO platform optimizes power consumptionon the mobile device (4 hours of view time on astandard battery). This technology providessuperior carrier to noise performance that veryfavorably impacts a network’s infrastructure cost.A factor of two reductions in transmitter costs is areasonable outcome for similar bit per second Hzcapacity modes – based on current independentfield test results using typical log 30 propagation.MediaFLO achieves superior throughput andspectral efficiency in 5, 6, 7 and 8MHz channels.For example, in a single 8 MHz RF channel,MediaFLO can support up to 30+ streamingchannels of QVGA-quality video and AAC+ stereoaudio as well as multiple Clipcasting™ downloadsper day.

Live mobile TV for the masses

MediaFLO provides the delivery platform for acompelling mix of content and services, includingbroadcast TV, which help reach a mass viewingaudience in the millions. Wherever they go,subscribers can watch their favorite sports, ‘must-see’ shows, and live newscasts. By multiplexingchannels, MediaFLO technology can pack morethan twice as many services into availablespectrum than competitive technologies at the samelevel of quality. And because it uses an efficienttransport mechanism with less overhead, there isadditional capacity for more tailored content suchas short-format video clips and streaming dataservices.

Clipcasting™ Media

Consumers have a nearly insatiable demandfor personalized, timely, and informative content.The MediaFLO system allows them to tap newrevenue with Clipcasting media – short-formatvideo clips delivered on a scheduled basis. Fromnews and individual sports highlights to moviemoments and comedy clips, consumers cansubscribe to a wide variety of Clipcasting mediathat is broadcast and stored on their devices.

IP Datacasting Applications

The mobile lifestyle is all about staying informedand connected, and the MediaFLO system can helpby instantly delivering a large number of data and

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services. This persistent stream of information canprovide constant real-time updates to applicationssuch as news tickers, sports scores, financialreports, weather, and traffic. By combining thedelivery of live TV with value-added services suchas Clipcasting and IP datacasting, MediaFLO isproviding the most compelling mobile mediasolution available with no compromise to the userexperience (Table 1).

Media FLO vs Competitive Techno-logies

A number of technologies address, at leastpartially, the requirements of mobile multimedia.These technologies are mostly variants orderivatives of an existing digital televisionbroadcast format. The Table 1 lists a number ofsignificant features of the individual formats andthe implications for the user.

By providing an ideal balance of technicalperformance parameters, MediaFLO provides asuperior user experience. The ability to change

channels quickly is always important to the user.Watch time should be comparable to talk time, if notlonger, so as to not compromise the functionality ofthe device. The capacity of the system is optimizedwhen per application QoS is available in a network.

A combination of both real-time and non-real-time media provides the best overall content mix.The delivery of non-real-time content allowsimmediate access to content such as weather ornews summaries by topic, while real-timestreaming services support live events such assports. The ability to support both wide-area andlocal content within a single RF carrier allows anoperator to maximize the value of the availablespectrum through the flexible allocation ofchannels.

Why Service Provider Should ChooseMedia FLO

The selection of a mobile broadcast technologycan have a strong influence on network deploymentcosts. Several factors help determine the cost:

TABLE 1: Service experience and features

Format Average Time Video Watch Per File Download Local- andChannels Time With 850 Channel Wide-AreaSwitching mAhr Battery QoS [4] in Single

RF Channel

ISDB-T ~1.5 sec unknown Yes No No

T-DMB ~1.5 sec ~2 hours Possibly Possibly No

S-DMB ~5.0 sec ~1.2 hours No No No

DVB-H ~5.0 sec Goal ~4 hours No Possibly NoDemo ~2 hourswith 1600 mAhrbettery

MediaFLO 1.5 sec ~4 hrs with Yes Yes + integrated Yesstandard 850 ClipcastingmAhr battery solution with

memorymanagement,conditionalaccess andsubscriptionmodel

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• Number of infrastructure sites that arerequired.

• Total spectrum required to support a definedchannel line up.

• Total number of transmitter assembliesrequired to achieve a service line up.

The table below shows the relative costs ofutilizing the various technologies (Table 2).

This comparison assumes that each systemhas the same link margin, which forces the capacityconstraints. The table attempts to target 20 real-time services at 300kb/sec per service; however,due to structural limitation, some formats cannotachieve the desired link margin at the specified bitrate. In those cases, the product of average bit rateand number of services is held constant.

This analysis shows that, due to the superiorefficiency of the FLO air interface in the areas ofPacket Error Rate (PER) performance, protocolefficiency, and the application of layered serviceand modulation, MediaFLO technology can deliverequivalent or superior service with roughly half thespectrum and less than half the infrastructurerequired. The implications for the user and serviceoperator are significant relative to the cost andbreadth of services that can be delivered.

A GLOBAL ECOSYSTEM

The introduction of mobile television servicesin India presents a major opportunity for the entiremobile TV value chain including: service providers,wireless operators, broadcasters, handsetmanufacturers, infrastructure providers,technology enablers, and content providers(Fig 3).

Wireless Operators

For wireless operators, new revenue streamsare possible through subscriptions and mobileadvertising. Wireless operators can also benefitfrom exclusive access to popular content,programming, or value-added services – such asClipcasting, IP datacasting, interactive services –or by exclusive rights to sell certain handsets.

Content Providers and Programmers

For content providers, mobile TV presents anexciting opportunity to increase revenue and extendtheir services into the mobile space by leveragingexisting content assets and developing new mobilecontent. Content providers and programmers mayalso be able to negotiate for a share of advertisingrevenues.

TABLE 2: Required infrastructure for comparable service

Format Channels Per Infrastructure Costs Channels RequiredTransmitter for 20 Channels per MHz Spectrum for

20 Channels

ISDB-T 13 channels, 6 ~2X ~2 12 MHz (26MHz lower quality~ 230kbps each channels)

T-DMB 3 channels, 1.5 ~4-6X ~2 10.5 MHzMHz~ 250kbps each

S-DMB ~20 channels, Broadcast satellite <1 25MHz25 MHz plus terrestrial

repeaters

DVB-H 9 channels, 6 MHz ~2X 1.5 12MHz~ 300kpbs each

MediaFLO 20 channels, 6 Reference (1X) >3 6MHzMHz~ 300kbps each

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Handset manufactures

Handset manufacturers are able to selladvanced products to wireless operators whichmay exportable to other countries that have alsochosen MediaFLO as their preferred mobile TVtechnology platform.

Other stakeholders

There are many other key players in theMediaFLO ecosystem For example, infrastructurevendors are very critical to the success of theMediaFLO platform. They fall in a variety ofbusiness categories including transmitters,encoders, and Conditional Access Systems (CAS).There are numerous opportunities for companies tosupply their mobile TV infrastructure in support ofthe MediaFLO ecosystem.

CONCLUSION

While the mobile TV market is still in its infancy,it is expected to be a key driver in the sale of mobile

devices and the creation of new multimediaservices. Currently, India is fourth in global wirelesspenetration and the consumers here areincreasingly looking at their mobile phones as ‘all-purpose’ devices. This trend, coupled with our hugeappetite for entertainment on the television hints atthe future success of mobile TV in the country.MediaFLO technology was designed specifically toaddress the global market demand for mobilemultimedia services, making them moreeconomical, efficient, and accessible than everbefore.

REFERENCES

1. TRAI January 2008.

2. Informa – August, 2007, Juniper – September, 2007,TeleAnalytics – November, 2007(this compilationshows that Mobile media subscribers are expectedto grow significantly across the globe).

3. FICCI-PWC report 2006- 2007.

4. Q3 mobile handset sales: Gartner (source: http://www.thehindubusinessline.com/2007/11/28/stories/2007112851720400.htm)

Fig 3 The mediaFLO ecosystem bringing all players in the value chain together

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Author

Sachin Kalantri is a senior staff engineer, Qualcomm, India. Sachin is responsible forpromoting MediaFLO Technology in the South Asia region and is actively involved in field trialsand product deployment for MediaFLO. In the past, Sachin has been the Chair of the Test andCertification Committee under the FLO Forum, a US based organization that is responsible forthe standardization of FLO Technology and has worked extensively on QSEC 800, BREWChat,QChat, MediaFLO and Digital Cinema.

Prior to joining Qualcomm, Sachin has worked with leading companies such as IBM,Bellcore, TATA Consultancy Services and P&O NedLloyd. He has been associated with MTNL,Indian Air Force, and DRDO on various projects. Sachin has experience of more than 17 yearsin the telecom industry, in areas spanning wireless systems, residential broadband, mobilebroadcast, video on demand, VoIP and push-to-talk systems.

Sachin holds a Bachelors degree in Electronics and Telecommunications Engineering fromthe Government College of Engineering, Pune and a Masters degree in Electrical ControlSystems from the Indian Institute of Information Technology, Kharagpur.



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Binaural Dichotic Presentation of Speech Signalfor Improving its Perception to SensorineuralHearing-Impaired using Auditory Filters

D S CHAUDHARI

ABSTRACT

Sensorineural hearing loss relates to spread of spectral masking resulting in reduction in frequency resolvingcapacity. Such hearing-impaired persons find difficulties while identifying consonantal ‘place’ feature cued byspectral differences. In binaural dichotic presentation scheme splitting of speech signal in real-time into two signalswith complementary short-time spectra using filters with magnitude response based on two auditory filter bankswith linear phase was implemented and evaluated. Filter banks corresponding to eighteen critical bands over 5 kHzfrequency range were used. Listening tests were performed on subjects with ‘mild’ to ‘very severe’ bilateralsensorineural hearing loss. The usefulness of the scheme for better reception of spectral characteristics was evidentas the results indicated improvement in speech quality, response time, recognition scores and transmission of‘place’ feature particularly.

INTRODUCTION

Sensorineural hearing loss entails increase inhearing threshold, dynamic range reduction, andincrease in temporal masking and hencedegradation of temporal resolution and increase inspectral masking due to degraded frequencyresolution. Amplitude compression and frequencycompensation are incorporated in many hearingaids. Signal processing schemes such as spectraltransposition and speech enhancement using theproperties of ‘clear’ speech form the basis forseveral techniques that have been investigated.These techniques are supposed to enhance theperformance of hearing aids for the persons withresidual hearing. Besides, they are also likely toenhance the performance of other sensory aids likecochlear prostheses and vibro-tactile aids used byprofoundly hearing-impaired.

Widening of auditory filters along the cochlearpartition characterise the increase in hearingloss [1]. The problem of degradation in speechperception due to broadening of critical bandscorresponding to auditory filters is not adequatelydealt with by above-mentioned processingschemes. Due to spectral masking, recognition oftransition of formants and frequency bands of thenoise bursts becomes difficult for a person.

Binaural dichotic presentation, in which speechsignal is split into two complementary spectra,would solve above problem. In this, the signalscorresponding to two neighbouring bands that arelikely to mask each other get presented to differentears. Humans have ability to perceptually combinethe binaurally received signals from the two earsfor improving speech perception under adverselistening conditions [2].

Among several schemes used for binauraldichotic presentation, one employed synthesis ofvowels with the alternate formants presented to thetwo ears. Possible fusion of the information at thehigher levels in the auditory system resulted inproper perception of vowels. Some researcherstested the scheme of splitting speech using 8-channel constant bandwidth of 700 Hz for binauraldichotic presentation. The scheme wasexperimentally evaluated by finding the signal-to-noise ratio (SNR) that satisfied 50% correct speech(word) recognition. An overall improvement of about2 dB in SNR for the dichotic condition over dioticwas indicated [3].

The proposed scheme used critical bandscorresponding to auditory filters based onpsychophysical tuning curves as described by oneof the researchers [4]. Eighteen critical bands over

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5 kHz frequency range were used. The magnituderesponse of each band is an approximation of anideal filter with the bandwidth of critical band havinglinear phase response. The implementation wasdone using the off-line processing of speech signalon five normal hearing subjects with simulatedsensorineural hearing loss of varying degrees inthe age group of 21 to 40 years and ten hearing-impaired subjects in the age group of 18 to 58 yearswith ‘mild’-to-‘very severe’ bilateral sensorineuralhearing loss [5,6]. The usefulness of the schemewas indicated by improvement in speech quality,response time decrease, enhancement inrecognition scores. The better reception ofconsonantal ‘place’ feature without affecting theother features was realised by noting transmissionof various speech features.

Based on the above encouraging results, thescheme was implemented for real-time processingof speech signal. For comparison of the dichoticpresentation of the processed signal with dioticpresentation of the unprocessed ones, listeningtests were carried out on subjects with bilateralsensorineural hearing loss.

1. METHOD

1.1. Subjects

The bilateral sensorineural hearing-impairedsubjects who participated in test were from differentparts of India and had no difficulty in clearlyrecognising the test stimuli. The six right-handedhearing-impaired subjects were familiar withEnglish and they had ‘mild’ to ‘very severe’ bilateralsensorineural hearing loss. The pure tone thresholdaverages (PTAs) are given in Appendix - A.Subjects’ PTA difference between right and left earwas from 4 to 30 dB.

1.2. Stimuli

Nonsense syllables were used for stimuli forminimising the contribution of linguistic factors andmaximising the acoustic factors. The twelveconsonants /p, b, t, d, k, g, m, n, s, z, f, v / wereused with vowel /a:/ as in father in vowel-consonant-vowel (VCV) and consonant-vowel (CV)contexts. In order to conveniently accommodatethem on subjects’ screen in computerised testadministration system, the number of stimuli was

restricted to twelve.

Speech stimuli were acquired and analysedusing a PC based set-up. The signal frommicrophone goes to an amplifier, low pass filter(fp = 4.6 kHz, fs = 5.0 kHz, pass band ripple < 0.3dB, stop band attenuation > 40 dB) and then throughADC of data acquisition board interfaced to a PC.DAC of data acquisition board was used for testingthe stimuli.

Syllables were spoken by a male speaker andeach syllable was recorded a number of times.They were played back after spectrographicanalysis. Out of these recordings, the syllableswith most normal sounding were chosen to bestimuli.

1.3. Procedures

Two DSP boards based on 16 bit fixed-pointprocessor TI/TMS320C50 were used for real-timespeech processing [7]. Each board comprises aprocessor along with analogue interfacing circuit(AIC) with 14-bit ADC, DAC with low pass filter anda programmable timer used for setting samplingrate. The processing set-up consisted of an inputlow pass filter, two DSP boards operating withsampling rate of 10 k samples/s and two audioamplifiers.

In the off-line processing implementationcascade combination of band-reject filters [5] wasused. Being computationally intensive it was foundunsuitable for real-time implementation. An FIRfilter with comb filter magnitude response was usedfor real-time implementation as shown in Fig 1. Thefrequency sampling technique of an FIR filter designwas used and magnitude response wasapproximated with 128 coefficients. The filterprogram and coefficients were loaded into theprogram RAM on the DSP chip using serial portinterface. After loading, the serial port wasdisconnected while keeping DSP boards powered.However, there was no data transfer between thetwo DSP boards.

The magnitude of all filter bands was keptconstant in real-time processing of speech stimuli.The magnitude response of each filter bank wasobtained by applying sine waves of constantamplitude from 100 Hz to 5 kHz (∆f = 20 Hz) andplotted as shown in Fig 2 (pass band ripple < 2 dB,sideband attenuation > 28 dB, transition bands < 90


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Band Passband Band Passbandfrequency frequency

1 -- – 0.20 2 020–0.30

3 0.30–0.40 4 0.40–0.51

5 0.51–0.63 6 0.63–0.77

7 0.77–0.92 8 0.92–1.08

9 1.08–1.27 10 1.27–1.48

11 1.48–1.72 12 1.72–2.00

13 2.00–2.32 14 2.32–2.70

15 2.70–3.15 16 3.15–3.70

17 3.70–4.40 18 4.40

Fig 1 Schematic representation for splitting of speech signal using two combfilters. The filter magnitude response is shown in each block (tableshows 3-dB cut-off frequencies)

Filter 1 1 3 17.........

Filter 2 2 4 18.........

s1(n)

s2(n)

s(n)

Hz). The magnitude response was verified byobtaining spectrograms using a spectrographicanalysis set-up [8].

1.4. Listening tests

Experimental investigation aimed at evaluatingthe effectiveness of the scheme in reducing theeffects of spectral masking. The implementationhad constant gain for all filter bands and listeningtests were conducted on bilateral sensorineuralhearing-impaired subjects. The stimuli werepresented at the most comfortable listening level ofan individual subject [9]. For each listeningcondition, subject did presentation level selectionsand it was kept constant for all the tests under aparticular listening condition.

To find confusion among the set of 12 Englishconsonants, listening tests were performed.Automated computerised test administrationsystem was resorted to avoid the repetitivenessand time consuming nature of the tests [8]. Thetests were administered for (a) an unprocessedspeech diotically presented and (b) processedspeech dichotically presented. The subjects werebriefed about the test procedure.

1.5. Evaluation schemes

Various researchers used different methods forperformance evaluation of speech processingschemes. Intelligibility test and perceived soundquality judgement have been generally employed.In intelligibility test subject listened to a list of


84


Fig 2 Magnitude response of the filters used in real-time processing ofspeech signal: (a) left ear (b) right ear

(b)

(a)

standard words (e.g. spondees, phoneticallybalanced words, central institute for the deafwordlist) and the correct responses were noted.The parameters like clarity, loudness, etc. wereconsidered for perceived sound quality judgement.Though speech intelligibility test is well established,judgement of sound quality has been used forcomparing hearing aids [10]. The recognition scoreversus SNR (15, 20, 25 and ∞ dB) for both types ofhearing aids were plotted for comparing theperformance. The evaluation scheme in which theprocessed speech is mixed with noise andlistening tests were carried out to find the SNRs

for 50% correct word recognition was alsoemployed in some studies [10,11]. Someresearches used this method with a variation ofSNR in 3 dB steps [3].

The features responsible for the relativeimprovement cannot be assessed from intelligibilityscores. Earlier subject responses were noted for16 syllables in consonant-vowel context to thestimuli and scores were recorded in the form ofconfusion matrix. For studying the various featuresthe stimulus-response cell entries were convertedto stimulus-response confusion probabilities that


85


were then subjected to information transmissionanalysis. The probability of correct responses iscalled recognition or articulation score. It can beobtained as the sum of probabilities in the diagonalcells. Recognition scores may have influence ofthe subjects’ response bias. A measure ofcovariance between stimuli and responses,employing mean logarithmic probability (MLP)measure of information was furnished in informationtransmission analysis [12].

The response time statistics shall help incomparing the speech processing and presentationschemes besides the information available fromstimulus-response confusion matrices. In case ofsame recognition score or information transmittedas a result of two schemes, one with less responsetime can be considered as superior.

In present study for evaluating the benefits ofspeech processing for dichotic presentation, thestimulus-response confusion matrix for the closeset of speech stimuli was used and the responsetime statistics was obtained. For obtainingrecognition scores and information transmissionmatrices were analysed. In order to study thecontribution of various speech features, the cellentries in the matrix were used to obtain matricesby grouping stimuli with the same feature. The aim

of the scheme was to study the effect of spectralsmearing due to the loss of spectral resolution.Hence improvement in the reception of placefeature without adversely affecting the reception ofother features was desirable. This requiredappropriate selection of set of stimuli. Thenonsense syllable stimuli with 12 consonantsformed two stimuli sets in VCV and CV contextswith vowel /a:/ were used for studying the receptionof consonantal features of voicing, place, manner,nasality, frication and duration [9].

2. RESULTS AND DISCUSSION

Listening tests were carried out on six hearing-impaired subjects in order to evaluate the schemefor dichotic presentation. The evaluation was doneby qualitative assessment of the stimuli followed byassessment based on response times, recognitionscores and information transmission for variousfeatures.

The results from listening tests conducted withsix hearing-impaired subjects in VCV and CVcontexts are presented here. The speech stimuliwere presented for comparing diotic presentationof an unprocessed speech with the dichoticpresentation of processed speech with constant

Fig 3 Recognition scores in VCV and CV contexts : (a) for subject SG(b) averaged for the six subjects. US: unprocessed speech, PS:processed speech


86


Speech Features(a)

Fig 4 Percentage relative information transmitted for subject SG: (a) VCV and (b) CV contexts.OV: overall, DU: duration, FR: frication, NA: nasality, MA: manner, VO: voicing, PL: place

Speech Features(b)

gain filter implementation. A compilation ofsubjects’ qualitative assessment about the teststimuli for ascertaining the improvements in speechquality was carried out. Subjects indicated definitepreference for processed speech overunprocessed.

In order to compare the effectiveness ofprocessing scheme in terms of load on perceptionprocess, average response time was used. Forobtaining recognition scores stimulus-responseconfusion matrices were used, which weresubjected to information transmission analysis in


87


Speech Features(a)

Fig 5 Percentage relative information transmitted averaged for the six subjects: (a) VCV and (b) CVcontexts. OV: overall, DU: duration, FR: friction, NA+ nasality, MA: manner, VO: voicing, PL:place

Speech Features(b)

order to obtain a measure that is not affected bysubjects’ response bias. The matrices resultingafter combining the twelve stimuli in-groups wereanalyzed for reception of the consonantal featuresof duration, frication, nasality, manner, place andvoicing.

In response time analysis, decrease inresponse time was observed due to processing forall the subjects. As seen by t-test, decrease inresponse time was statistically significant for mostof the subjects. Highly significant decrease(p < 0.005) in both the contexts were indicated from


88


paired t-tests across the subjects. Most of thehearing-impaired subjects showed significantdecrease in response time for processed speech.This indicated an improvement in listening conditionwith processing.

The recognition scores for a subject andaveraged across the subjects for both the contextsare plotted in Fig 3. The scores for processedspeech (PS) implementation were higher thanunprocessed speech (US) for all the subjects. Therelative improvement in recognition score (R.S.)was calculated by following formula.

[(R.S.)PS – (R.S.)US]/(R.S.)US

Percentage scores ranged from 9.2 to 23.6 inVCV and 14.4 to 19.2 in CV contexts. Averagedacross the subjects, the percentage improvementin the scores was 14 in VCV and 16.3 in CVcontexts. For testing the statistical significance ofimprovements in scores due to processing, therecognition scores were subjected to t-test. Highlysignificant (p < 0.005) improvement in both contextswas observed for all the subjects. For testing thesignificance of the improvement due to processingpaired t-test was also carried out across thesubjects. And the improvements were highlysignificant (p < 0.0005) for both the contexts. Theusefulness of the scheme was evident as all thesubjects showed highly significant improvement inrecognition score due to processing.

The confusion matrices were subjected toinformation transmission analysis. The overallinformation transmitted as well as informationtransmitted for specific features were obtained forall the subjects. Figures 4 and 5 show informationtransmitted for a subject and averaged across thesix subjects for VCV and CV contexts. Betterreception of almost all the six features of duration,frication, nasality, manner, place and voicingcontributed to overall improvements in speechreception. These improvements were observed tobe higher for the features of manner, voicing, andplace in both the contexts. Maximum improvementin place feature was observed for all subjects aswell as averaged across the subjects. Averagedacross the six subjects, the relative improvementfor place feature was 34 and 41 % in VCV and CVcontexts respectively.

The contribution of all the six features ofduration, frication, nasality, manner, place and

voicing to overall improvement was indicated byinformation transmission analysis of the stimulus-response confusion matrices. Maximumimprovement was observed for place feature foralmost all the subjects. Since the place informationis linked to frequency resolving capacity of theauditory process, it can be said that theimplemented scheme has reduced the effect ofspectral masking without adversely affecting thereception of the features cued by amplitude andduration.

3. CONCLUSIONS

The promising strategy for improving speechintelligibility for hearing-impaired listeners wasimplemented in which speech signal was split intotwo signals with complementary spectra employingcritical bandwidth corresponding to auditory filters.The use of signal processing strategy resulted inimprovement in overall speech reception quality inthe listening test carried out on sensorineuralhearing-impaired listeners with real-timeprocessing of speech for dichotic presentation. Thetests recorded remarkable fall in average responsetime for most of the subjects indicating reduction inload on perception process. Significantimprovement was recorded in recognition scoresuggesting the corresponding enhancement inlistening condition. Results indicated reduced effectof spectral masking since better reception ofconsonantal ‘place’ feature was observedimplicating possibility of implementing the strategyin binaural hearing aids for persons with ‘mild’ to‘very severe’ levels of binaural sensorineuralhearing impairment.

ACKNOWLEDGEMENT

The author wishes to the authorities ofDepartment of Science and Technology, New Delhifor providing supports.

REFERENCES

1. J R Dubno & D D Dirks, Auditory filter characteristicsand consonant recognition for hearing impairedlisteners, Journal of the Acoustical Society ofAmerica, vol 85, pp 1666-1675, 1989.

2. B C J Moore, An Introduction to the Psychology ofHearing, Academic, London, 1997.

3. T Lunner, S Arlinger & J Hellgren, 8-channel digitalfilter bank for hearing aid use: preliminary results in


89


monaural, diotic and dichotic modes, ScandinavianAudiology Journal, S 38, pp 75-81, 1993.

4. E Zwicker, Subdivision of audible frequency rangeinto critical bands. (Frequenzgruppen), Journal ofthe Acoustical Society of America, vol 33, p 248,1961.

5. D S Chaudhari & P C Pandey, Dichotic Presentationof Speech Signal with Critical Band Filtering forImproving Speech Perception, Proceedings of IEEEInternational Conference on Acoustics Speech andSignal Processing, Seattle, Washington, paper AE3.1,1998.

6. D S Chaudhari & P C Pandey, Dichotic Presentationof Speech Signal using Critical Filter Bank for BilateralSensorineural Hearing Impairment, Proceedings of16th International Congress on Acoustics (ICA),Seattle, Washington, 1998.

7. Texas Instruments, User’s Guide, TI-TM320C5XDigital Signal Processor Products, TexasInstruments, USA, 1993.

8. D S Chaudhari, Dichotic presentation for improvingspeech perception by persons with bilateralsensorineural hearing impairment, PhD thesis, IITB,Mumbai, 2000.

9. C Simon, On the use of comfortable listening levelsin speech experiments, Journal of the AcousticalSociety of America, vol 64, pp 744-751, 1979.

10. A Gabrielsson, B N Schenkman & B Hagerman, Theeffects of different frequency response on soundquality judgments and speech intelligibility, Journalof Speech and Hearing Research, vol 31,pp 166–177, 1988.

11. D B Hawkins & W S Yacullo, Signal-to-noise ratioadvantage of binaural hearing aids and directionalmicrophones under different levels of reverberation,Journal Speech and Hearing Disorder, vol 49,pp 278-286, 1984.

12. G A Miller, P E Nicely, An analysis of perceptualconfusions among some English consonants, Journalof the Acoustical Society of America, vol 27(2),pp 338-352, 1955.

APPENDIX – A

Hearing thresholds for the hearing impaired subjects

Subject Code Ear Hearing thresholds (dB HL) PTA(Sex, Age) L: left

R:right Frequency (kHz)

0.25 0.50 1.0 2.0 4.0 6.0

SG (M, 27) L 25 45 75 100 120 120 73

R 25 60 70 100 120 120 77

SSN (M, 31) L 80 70 80 75 75 75 75

R 65 60 70 65 85 85 65

KRV (M, 49) L 50 60 60 60 60 65 60

R 40 45 50 60 65 75 52

BAS (M, 58) L 50 40 30 30 40 40 33

R 45 50 35 30 30 30 38

SAV (M, 46) L 50 45 45 45 35 40 45

R 60 70 65 65 85 95 67

LDM (M, 52) L 65 65 50 40 40 75 52

R 70 80 85 80 80 95 82

PTA: pure tone average hearing threshold level (dB HL), test frequencies: 0.5, 1 and 2 kHz.


90


Author

Devendra Chaudhari, obtained BE, ME from Marathwada University, Aurangabad and PhDfrom Indian Institute of Technology, Bombay, Mumbai. He has been engaged in teaching,research for period of about 21 years and worked on DST-SERC sponsored Fast Track Projectfor Young Scientists. Presently he is working as faculty member in Department of Electronicsand Telecommunication Engineering at Government College of Engineering, Amravati.

Dr Chaudhari published research papers and presented papers in international conferencesabroad at Seattle, USA and Austria, Europe. He worked as Chairman / Expert Member ondifferent committees of All India Council for Technical Education, Directorate of TechnicalEducation for Approval, Gradation, Inspection, Variation of Intake of diploma and degreeEngineering Institutions. As a university recognised PhD research supervisor in Electronicsand Computer Science Engineering he has been supervising research work since 2001.

He has worked as Chairman / Member on different university and college level committees likeExamination, Academic, Senate, Board of Studies, etc. He held chair position for one of thetechnical sessions of International Conference held at Nagpur. He is fellow and life member ofvarious national, international professional bodies. He is recipient of Best Engineering CollegeTeacher Award of ISTE, New Delhi. He has organized various Continuing EducationProgrammes and delivered Expert Lectures on research at different places. His presentresearch and teaching interests are in the field of Biomedical Engineering, Digital SignalProcessing and Analogue Integrated Circuits.

Address: Department of Electronics and Telecommunication, Government College ofEngineering, Amrarali 111604.




91


Dielectric Parameters as Diagnostic Tools andIndicatrix of Disease — A Microwave Study

V MALLESWARA RAO, B PRABHAKARA RAO AND D M POTUKUCHI

ABSTRACT

An X-band microwave, (9-10 GHz) technique to determine the dielectric blood parameters as an indicatrix for theseverity of disease is reported. Relevance of dielectric parameters as the main indicators in the area of diagnostictools is discussed. An experimental set-up and the relevant procedural details for the measurement of microwaveblood parameters for the typhoid and diabetic disease is presented. Microwave (MW) dielectric parameters viz,dielectric constant εεεεεr*(ωωωωω), wave velocity ννννν (ωωωωω) and the impedance z(ωωωωω) are measured for collected blood samples (fromhospitals) and compared to the clinical values reflecting the disease severity. The dielectric parameters are identifiedto exhibit similar trends as exhibited by clinical parameters for disease severity. Parametric relations are obtained toaddress the correlation between dielectric and clinical parameters reflecting the severity. The capability of MWdielectric measurements as the diagnostic tools and severity indicators is demonstrated.

INTRODUCTION

At MW frequencies, the changes in the dielectricproperties of tissues are closely related tofrequency and to the amount of water present. TheMW method of determining the lung water contentis known [1] to utilise the changes in dielectricproperties. The method is based on a continuousmonitoring of the reflection / transmissioncoefficient to indicate changes in the permittivity ofthe lung tissue. This method has the advantage ofusing highly penetrating MW signals rather thanultrasonic signals, the later being highly attenuatedand dispersed in the lung. Radiometry techniqueoriginates [2] from the fact that all bodies aboveabsolute zero temperature emit energy in the formof electromagnetic radiation. The use of energy inthe MW spectrum provides a method of controllingthe rate and uniformity of heating of deep-frozenmaterials. MW thawing [3] techniques are known torecover the deep frozen organs from lowtemperature storage banks. In MW biology studies,waveguide systems are preferable as the fields areknown. Recent investigations [4-6] have revealedthat effect of non-ionising EM radiation on humanbody may not be restricted to thermal effects only,but it may help to explain some of the unsolvedimportant biological activity.

The propagation of electromagnetic (EM)radiation in a fluid needs to be characterised in

terms of characteristic constants of the media,viz., the propagation constant γ ( i.e expressed interms of attenuation constant α, and phase shiftconstant β). Needless to say that depend upon thenature of the media, one can estimate the mediaconstants by measuring these parameters bypropagating the EM radiation in the fluid.Measurements of MW region parameters [7,8] viz.,complex dielectric constant εr*(ω), attenuationconstant α, Phase shift constant β, electron (or ion)density ηe and collision frequency ‘ρ'’ provide thenecessary information to estimate thecharacteristic constants of the components of thefluid under test. Finally, these measurementsrepresents a family of diagnostic tools in the field ofMW EM radiation.

In the present research work, it is proposed toperform diagnosis by propagating EM radiation inblood plasma. An attempt is made to study thediversity of the blood parameters using MW EMradiation. The present work is based on the fact thatthe changes in electrical properties are caused bythe prevalence of disease at varied severity in thehuman anatomy.

EXPERIMENTAL SET UP FOR MEASUR-ING THE BLOOD PARAMETERS

The block diagram of the experimental set-up[9] consisting of a MW bench used for measuring

92


the blood parameters during the presentinvestigation is presented in Fig 1. The dielectricconstant of the collected blood sample is determined[10,11] with the experimental set up shown in Fig 1.

The MW bench is operated at a frequency of 10GHz.

RESULTS AND DISCUSSION

The blood sample (collected from the patient) isdivided into two equal parts. While the clinical testis administered ( by the hospital clinics) over thefirst part, the second part of the sample is exposedto microwave radiation as to further determine thedielectric parameters, i.e., that the sample istreated as the media of propagation. The clinicaltest on the first sample is known to come out with aparameter value, whose magnitude reflects uponthe severity of the disease. As such, more is theclinical parameter, the severe is the diseaseattributed (or the blood sample of the patient isseverely inflicted). The dielectric parameters of theblood samples (of patients with diversity of disease

collected from hospitals) is presented for thefollowing case studies.

1) Typhoid

2) Diabetes

The observed variation of MW blood parameters(collected from patients of different diseases) arepresented in Fig 2 and 3 for typhoid and diabetesrespectively.

1. Typhoid

It is observed that for values obtained for

Dielectric constant εr*(ω):

(a) The dielectric constant εr*(ω) is found to beslightly greater than 2.95 for normal bloodsample, the sample not affected by thetyphoid disease. The corresponding valueof clinical parameter is less than 80.

(b) The dielectric constant εr*(ω) is found tovary between values 2 and 2.9, for the caseof marginally affected typhoid sample.

KlystronPowerSupply

KlystronOscillator

Isolator AttenuatorSlotted

WaveguideSection

Load

CrystalDetector

VSWRmeter

Fig 1 Experimental set up for the measurement of dielectric parameters of blood sample

93


However, the corresponding value of theclinical parameter is found to be 80 for thatmarginally effected case.

(c) The dielectric constant εr* (ω) is found to beless than 2, for the affected blood sample,while the corresponding value of the clinicalparameter is found to be more than 80.

2. Diabetes

It is observed that for values obtained forDielectric constant εr*(ω):

(a) found to be a value between 1.915 and 4.9for the normal blood sample, the sample notaffected diabetes. While correspondingvalue of the random sugar is found to be inbetween 60-160.

(b) found to be greater than 5 for the diabeticaffected blood sample. While thecorresponding value of the clinicalparameter (random sugar) is greater than160 (mg/dL)

Statistical Analysis for parametricrelations and correlation between MWdielectric and clinical parameters

An overview of the collected data of clinicalparameters and the observed dielectric parameters(at the various levels of disease severity) seems tomaintain a strong correlation between them toaddress the problem of severity of disease and its

determination by MW dielectric method. Theobserved variation of MW dielectric parametervalues with severity of disease is found to beanalogous to the variation of clinical parameters(supplied by clinics) with severity of disease. Assuch, the possible correlation between them areestimated for different samples. The value of thecorrelation coefficient [12] between MWmeasurement and clinical measurement isestimated. The values of these coefficients arefound to be in between 0.96 6 to 0.996 to imply thatthere is a strong correspondence between the twomethods used to estimate the severity of disease.

Further a meticulous and in depth analysis iscarried out for a possible parametric dependencebetween the clinical measurement and MWmeasurement of blood parameters. An overview ofvariation of observed dielectric parameters (Tables1 and 2) with clinical parameters (reflecting theseverity of disease) seems to follow a third orderpolynomial dependence.

A non linear least square method is used to fitthe data to the equation

f(x) = a + bx + cx2 + dx3 (1)

Where x is dielectric value

The data in Tables 1 and 2 is fitted to theequation (1). The goodness of the fit [13] isdemonstrated through the corresponding t-test andthe p values ≥ 0.995. The back estimated valuesare superposed as solid lines in the Figs 2 and 3 for

TABLE 1: The values of clinical parameters and dielectric parameters for typhoid disease

S.No. Clinical lab Dielectric Velocity Impedance ConfirmationParameter Constant (108)m/s (Ω)

1 640 0.7486 3.4673 435.73 Positive

2 620 0.917 3.1328 393.69 Positive

3 160 1.315 2.6161 ;328.76 Positive

4 88 1.495 2.4536 308.33 Positive

5 80 2.065 2.0877 262.35 Marginally effected

6 80 2.864 1.7727 222.77 Marginally effected

7 20 7.005 1.1335 142.44 Negative

8 10 9.905 0.9532 119.79 Negative

94


TABLE 2 : The values of random sugar and dielectric parameters for diabetes

S.No. Random Dielectric Velocity Impedance ConfirmationSugar Constant (108)m/s (Ω)

(mg/dL)

1 63 1.915 2.1678 272.43 Negative

2 68 2.065 2.0876 262.35 Negative

3 71 3.155 1.6889 212.25 Negative

4 77 3.275 1.6577 208.32 Negative

5 152 4.965 1.3463 169.19 Positive

6 177 6.225 1.2024 156.10 Positive

7 231 7.255 1.1137 139.97 Positive

8 240 7.705 1.0807 135.82 Positive

9 292 8.625 1.0215 128.37 Positive

10 307 10.285 0.9354 117.55 Positive

11 328 10.675 0.9182 115.39 Positive

Fig 2 Variation of the clinical parameter with dielectric constant of the bloodsample for typhoid disease for both in normal and abnormal range of disease

Fig 3 Variation of the random sugar with dielectric constant of the blood sample fordiabetes disease for both in normal and abnormal range of disease

150

100

50

0

NORMAL

Clin

ical

Par

amet

ers

Clin

ical

Par

amet

ers

Dielectric Constant Dielectric Constant

—— Polynormial x Experimental

800600400

200

0–200

ABNORMAL


0 0.5 1 0.2 0.4 0.6 0.8 1

xx

xx

x x

xx x

200

150

100

50

NORMAL

Ran

dom

Sug

ar

Dielectric Constant


0.2 0.4 0.6 0.8 1

Ran

dom

Sug

ar

Dielectric Constant0.4 0.6 0.8 1


ABNORMAL350

300

250

200

150

100x x x x

x

x

xx

xx x

95


different diseases. An overall study of relativemagnitude of the polynomial coefficients reflectsupon highest value adopted by the linear coefficientterm and its predominance for the strongcorrespondence (or correlation) between dielectricparameters and clinical parameters. Thisobservation is suggestive of using MW dielectricparameters as an equivalent and potential tool ofmedical diagnostics.

CONCLUSIONS

In this paper, the estimation of severity ofailment of typhoid and diabetes diseases areconsidered by measuring the dielectric constant,velocity and impedance of the blood sample. This iscarried out by propagating electromagnetic wavesthrough the blood sample. The trends of results andinvestigations are fruitful as the meticulousstatistical analysis presented in the paper supportsthe claim that the microwave dielectric parametercan be used as a powerful tool to estimate theseverity of disease. The above discussion for theobserved trends in clinical and dielectricparameters followed by the meticulous statisticalanalysis is suggestive of

• Subtle and strong implied relationshipbetween the MW dielectric and the clinicalparameters.

• MW dielectric parameters can also betreated as bench markers to diagnosemedical diagnostics.

• Representing a reliable estimate of theseverity of disease (affecting the biologicalsystem under consideration).

REFERENCE

1. Magdy F Iskander & Carbh Durney, ElectromagneticTechniques for Medical Diagnosis: A Report, ProcIEEE, vol 68, no 1, Jan 1980.

2. Om P Gandhi, Medical applications ofElectromagnetic fields-Part V, IEEE Trans MicrowaveTheory Tech, July, 15, 1981.

3. R Paglione and et al, 27 MHz Ridged WaveguideApplications for Localized Hyperthermia Treatmentof Deep-seated Malignant Turners, MicrowaveJournal, vol 24, Feb 1981.

4. S Gabriel, R W Lau & C Gabriel, The dielectricproperties of biological tissues: III parametric modelsfor the dielectric spectrum of tissues, Phy Mod Biol,vol 41, 1996, pp 227-2293.

5. Yuri Feldman & Irina Ermolina, Time domain dielectricspectroscopy study of biological systems, IEEETransactions on Dielectrics and Electrical Insulators,vol 10, no 5, 2003, pp 728-748.

6. Liquid dielectric property determination using monopole probes operating at microwaves frequencies,IEEE Instrumentation and Measurement TechnologyConference 2006, Sorrent, Itley.

7. Edward C Jordan & Keith G Balmain,Electromagnetic Waves and Radiating Systems, PHI,New Delhi, 2004.

8. Rajeswari Chatterjee, Microwave Engineeringspecial topics (A post graduate text book), AffiliatedEast West Press, New Delhi 1988.

9. V Malleswara Rao & B Prabhakara Rao, The Role ofMicrowaves in the measurement of BloodParameters, Journal Institute of Engineers India, pp61-63, Jan 2006.

10. V Malleswara Rao, B Prabhakara Rao, Blood SugarEstimation Through Measurement of DielectricConstant By Using Microwaves, 62nd ARFTG IEEEMicrowave Measurements Conference DifferentialMeasurements, Dec 2-5, 2003, Hotel BoulderadoDowntown Colorado USA, pp 301-305.

11. M L Sisodia & G S Raghuvamshi, Basic MicrowaveTechniques and Laboratory-Manual, New ageInternational Pvt Ltd, New Delhi, 2000.

12. K Park, Preventive and Social Medicine, M/sBanarsidas Bhanot publishers, Jabalpur, 2002.

13. Suranjan Saha, Mathematics and Statistics Centre’sC.A. Foundation course series 2002, New centralbook agency (P) Ltd, Calcutta (India).

96


Authors

V Malleswara Rao

Email: <[email protected]>Address: Department of Electronics and Communication Engineering, GITAM College of Engineering,Visakhapatnam 530 045, India.

* * *

B Prabhakara Rao

Address: Depepartment of Electronics and Communication Engineering, Jawaharlal Nehru TechnologicalUniversity College of Engineering, Kakinada 533 003, India.

* * *

D M Potukuchi

Email: <[email protected]>Address: Depepartment of Physics, Jawaharlal Nehru Technological University College of Engineering,

Kakinada 533 003, India.

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Subject of on-line submission & review of articles for IETE Journals has been underconsideration for a long time. Keeping the present trend of Internet, automation andcomputerization at different levels, it was considered prudent and necessary to movefrom manual hard copy submission and review system to on-line system. The proposedsoftware is expected to help authors, Honorary Editors, Reviewers, Editors-in-Chief andIETE HQs to streamline submission and reviewing process for timely publication of journals.The procurement of software system has been approved by the Council of IETE and willbe operationalized in the near future. Effective date for system will be publicised in IETEJournals and website.

The salient features of the proposed system are as follows:-

a) The software system will create the website and a radio button to choose the journalfrom drop-down list. All the three journals will appear in the list. The authors willchoose one of the journal and upload the manuscript.

b) Resource templates based on approved standard would be hosted on IETE websitethe software as guidelines to authors for submission of articles on line.

c) The chairpersons of the editorial boards would be the Editors-in-Chief for the threejournals, i.e. IETE Journal of Education (JE), IETE Journal of Research (JR) andIETE Technical Review (TR).

d) Each journal will have area editors from across the world as empanelled by therespective editor-in-chief. Those panels would be periodically reviewed taking intoconsideration the performance of the panelists.

e) The concerned Editor-in-Chief will carry out on-line preliminary review for furtherprocessing or out-right rejection with intimation to author. The IETE HQ will keep therecord of entire submission, revision, rejection and acceptance details.

f) After final acceptance by the Editor-in-Chief, an e-mail will be generated automaticallyto the Administrator, Publication Section at IETE HQs who will have the access tothe word / pdf document of the final accepted manuscript. The administrator willdownload it and carry out all editorial changes before it is given to Press for printingof the journals.

g) The printed journals will be hosted on IETE website for free downloading by readers/ authors and will be available for six months on IETE website & thereafter in ourarchive.

Any suggestions and feedback are most welcome. Please email to [email protected]

mar-apr 2008

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