4 wireless data networks

8/11/2019 4 Wireless Data Networks

1/30

12/23/2004 Wireless Data Networks 1

Wireless DataNetworks

with a special emphasis on

WLAN standards


2/30


Agenda

Why WLAN?

WMAN, WWAN, WLAN, WPAN...Bluetooth & 802.15

IEEE802.11xHiperLAN/2

HomeRFConclusions


3/30


Why emphasis on WLANs?

The market growth:From nearly zero to about 15 million customersduring 2001From about 10 to more than 180 WLAN productsduring 2001Impressive figures in a down market!

WLANs are the hottest topic in wireless worldthese days


4/30


WMAN

Wireless Metropolitan

Area NetworkVery high rate, point-to-point communicationsLMDS:

~30GHz carrier 155 Mbps data rate

IEEE802.16 WG

From www.lmdswireless.com


5/30


WWAN

Wireless Wide Area NetworkCoverage : few kilometersHigh power consumptionSlow Data Rates

GSM : 9.6 KbpsIS-95 : 14.4 KbpsGPRS : 115 Kbps (theoretical)

40-50 Kbps (realized)Licensed


6/30


WLAN

Wireles Local Area NetworkCoverage : few hundred metersData rate : tens of Mbps (depends on

distance to the Access Point)Medium to high power consumption802.11x , HiperLAN, HomeRF....

WLAN standards use unlicensed spectrumband


7/30


WLAN

WLAN configurations (from www.cisco.com)


8/30


WPAN

Wireless Personal Area NetworkReplace short-range cables in the offices and at

homeCoverage : ~10 meters

Very low power consumption Ad-hoc connectivity

Bluetooth, IrDA, HomeRF

IEEE802.15 WG set to make Bluetooth theWPAN standard


9/30


Bluetooth

Ericsson initiative, but has many backers (Nokia,IBM, Intel, etc.)

Technology developed by Bluetooth SIG, a not for-profit, free membership organization

Apple and Microsoft made Bluetooth future brightclear : They announced that Bluetooth will be

inherently supported by their OSs (early 2002)Microsoft presented first Bluetooth desktop peripherals(April, 2002)


10/30


Bluetooth

A BT chip is very cheap : ~ $5

Communication is quite securedNearly 1Mbps data rate

Supports voice and data

BT operates at unlicensed 2.4GHz spectrum

What else emits in this spectrum?Microwave ovens, light bulbs, HomeRF, 802.11b,etc.


11/30


IEEE 802.11b

The first (in market) and most widespread

wireless networking standardUp to 11 Mbps (depends on the

distance to the AP)

The Wireless EthernetGets cheaper every day

Two major drawbacks:Weak securityHigh power consumption


12/30


IEEE 802.11b

Security is a major issue:Most corporations wont implement WLAN in largescale if security is weak.

802.11b is protected with insufficient

WEP(Wired Equivalent Privacy) Protocol

Use of VPN and other security methods isstrongly encouraged!


13/30


IEEE 802.11b

WECA (Wireless Ethernet Compatibility

Alliance) certifies 802.11b products with

Most major technology companies are WECAmembers

Hundreds of products certified to date


14/30


InterferenceBluetooth and 802.11b operate at samefrequencies, do they interfere?

Yes and No. Due to different radio link accessmethods (DSSS vs. FHSS), most of the times they donot block each other.

However, no one can guarantee that interference willnot happen. This may affect real time audio/videostreams.

Solution: A Blue802

combo chip that supportsboth standards but prevents interference by notemitting at the same time! (demonstrated March,

2002)


15/30


IEEE802.11b vs. Bluetooth

Two standards operate in same frequencyband, do they compete?

This was the way they were seen until late 2001.Ex: Intel CEO announced that the Bluetooth is dead(July, 2001) and apologized (September, 2001)

Current trend: Bluetooth and 802.11bcomplement each other!

The current trend is welcomed by the productmanufacturer companies


16/30


IEEE 802.11b & Bluetooth

You wont build a Bluetooth only LANbecause:

It will be very expensive (remember the BTcoverage and think of how many access pointsyoull need)

Youll want to use Bluetooth for short-rangecommunications because:

802.11b is power hungry, not suitable for smallhandheld devices

BT is quite cheaper 802.11b doesnt support voice

802.11b and Bluetooth will coexist.


17/30


IEEE802.11a

Operates at 5 GHz unlicensed spectrum

54 Mbps

MAC layer same as 802.11bPhysical layer different (OFDM)

Lower range compared to 802.11b, but experimentsshow that superior data rates are observed at alldistances

WECA will certify compatible devices with Wi-Fi5logo


18/30


IEEE 802.11a

Power consumption three times less than802.11bFaces much less interference compared to802.11b

Not compatible with 802.11b!Mixed 802.11a&b networks possible:

Cisco Aironet 1200 - Mixed 802.11a&b access point(April, 2002)Mixed mode NICs on the way!


19/30


IEEE 802.11x

Other Work Groups also formed:802.11i

Solve the prolonged security issues with 802.11xs

WG operations almost completed

802.11g Above 20 Mbps

Operates in 2.4GHz band

Differs from 802.11b in PHY layer : 802.11g deploysOFDM

Products expected late 2002


20/30


HiperLAN/2

ETSI didnt approve 802.11a:

Unlicensed 5GHz spectrum is being used bysatellite operators and military, therefore, Europe

would allow a standard that has

1: Dynamic Frequency Selection

2: Transmit Power Control

None of these exist in 802.11a!

ETSIs alternative : HiperLAN


21/30


HiperLAN/2

Same PHY layer and data rate capabilities as802.11a

Advantages of HiperLAN/2 over 802.11a:QoS

ATM based protocol not just an EthernetGreater spectrum efficiency and lower interference

Almost everyone was sure that HiperLAN/2 willprevail in Europe, but..


22/30


HiperLAN/2HiperLAN/2 was late...

Philips announced that it wont produce HiperLAN chips

(October, 2001)Not a big surprise, maybe, as the chairman of 802.11 WG is aPhilips employee...

Intel declared that two coexisting 5GHz LAN standardswill harm both parties...

Ericsson (the main supporter) says theyre notinterested in HiperLAN anymore (December, 2001)HiperLAN is over.....


23/30


802.11 again..

Which fast wireless standard is going to be

implemented in Europe?Not 802.11a, it lacks the two criticalrequirements....

It is 802.11h!This is simply 802.11a with Dynamic FrequencySelection and Transmit Power Control

WG specs completed already...


24/30


HomeRF

An alternative standard that competed both

with Bluetooth and 802.11bIncorporates DECT for voice and 802.11bsCSMA/CA protocol for data

Operates in 2.4 GHz unlicensed band

Due to its physical layer, HomeRF is less

vulnerable to interference compared to 802.11bHomeRF : 2 Mbps

HomeRF2.0: 10 Mbps


25/30


HomeRF

Some strengths of HomeRF over 802.11b:Better security

Lower power consumptionVoice capabilitesEasier setup

QoSHowever, HomeRF2.0 was late:

10 Mbps 802.11b products have already entered the

market and benefiting from economies of scale802.11b soon became cheaper than HomeRFIntel abandoned HomeRF group (March 2001) in favor of802.11b


26/30


HomeRF

Apparent success of 802.11b and Bluetooth causedHomeRF to change strategy:

None of these standards compete, they complement each other:


27/30


HomeRF

HomeRF still striving for market share

Currently working on a new, morecompetitive standard : HomeRF3.0Main supporter : Siemens

Currently HomeRF future doesnt look very

bright...


28/30


Current Trends

All-in-one cellular phone chips (GSM/GPRS,Bluetooth, GPS)

WLAN-TDMA or WLAN-CDMA combo NICs

Deutsche Telecom announces plans tointegrate WLAN with WWAN (GSM, GPRS...)services

Telcos are entering the market! Be prepared fororganised, proprietary WLAN networks andcombo phone bills!


29/30


Conclusions

IEEE sets the wireless data

standards!802.11x : Wireless LAN802.15 : Wireless PAN

802.16 : Wireless MAN


30/30


Conclusions

Wireless data market will continue to

grow very fast

802.11x doesnt explicitly supportvoice, but there is need for it:

VoIP standards are the next hot topic

4 wireless data networks

Documents