doc.: ieee 802.22-05/0105r1 submission november 2005 carlos cordeiro, philipsslide 1 a cognitive...

November 2005

Carlos Cordeiro, Philips

Slide 1

doc.: IEEE 802.22-05/0105r1

Submission

A Cognitive PHY/MAC Proposal for IEEE 802.22 WRAN Systems

IEEE P802.22 Wireless RANs Date: 2005-11-07Authors:

Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22.

Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at [email protected].

Name Company Address Phone email

Carlos Cordeiro Philips 345 Scarborough Rd Briarcliff Manor, NY 10510 1-914-945-6091 [email protected]

Kiran Challapali Philips 345 Scarborough Rd Briarcliff Manor, NY 10510 1-914-945-6356 [email protected]

Dagnachew Birru Philips 345 Scarborough Rd Briarcliff Manor, NY 10510 1-914-945-6401 [email protected]

Vasanth Gaddam Philips 345 Scarborough Rd Briarcliff Manor, NY 10510 1-914-945-6424 [email protected]

Gene Turkenich Philips 345 Scarborough Rd Briarcliff Manor, NY 10510 1-914-945-6370 [email protected]

Martial Bellec France Telecom 4 rue du Clos Courtel 35512 Cesson-Sévigné - France 33 2 99 12 48 06 [email protected] Patrick Pirat France Telecom 4 rue du Clos Courtel 35512 Cesson-Sévigné - France 33 2 99 12 48 06 [email protected] Luis Escobar France Telecom 38-40 rue du Général Leclerc 92794 ISSY LES

MOULINEAUX France 33 245 29 46 22 [email protected]

Denis Callonnec France Telecom 28 Chemin du Vieux Chêne 38243 MEYLAN - France 33 4 76 76 44 12 [email protected] François Marx France Telecom 28 Chemin du Vieux Chêne 38243 MEYLAN - France 33 4 76 76 41 09 [email protected]

November 2005


Slide 2

doc.: IEEE 802.22-05/0105r1

Submission

PHY Abstract

Digital modulation systems presently make use of two basic modulation technologies: single carrier and multi-carrier. Their features are well-known since they have been deployed for several years around the world for broadcasting applications.

Wireless access applications differ from broadcasting since they require : flexibility on the downstream link : variable number of user, variable throughput

per user, variable level of protection, etc; multiple access on the upstream link.Single carrier modulation can tackle these objectives through time multiplexing

techniques. Multi-carrier modulation is however more flexible since it enables to control the signal in both time and frequency domains. This gives the opportunity to define two dimensional (time and frequency) slots and to map the services to be transmitted in both directions onto a subset of these slots.

Two types of multi-carrier modulation has been retained in IEEE 802.16 (WiMAX) standard: OFDM in the fixed MAN version and OFDMA in the mobile version.

In the continuity of IEEE 802.16, it is proposed here to consider OFDMA modulation for downstream and upstream links with two technological improvements:

• Spreading;• OQAM waveforming.To meet the tight link budget requirements of WRAN, duo binary turbo code is

proposed for service ranges up to 100 Km

November 2005


Slide 3

doc.: IEEE 802.22-05/0105r1

Submission

MAC Abstract

We propose the Cognitive MAC (CMAC) layer to be used as the basis for the future IEEE 802.22 WRAN standard operating in the TV bands. The proposed CMAC is in some respects inspired by the IEEE 802.16 standard, but it provides major extensions, improvements and also simplifications in order to meet the 802.22 functional requirements. CMAC is based on a superframe architecture which is general enough to allow multiple wireless systems to coexist in addition to support the flexibility to group multiple vacant TV channels and hence achieve greater capacity. To coexist with incumbent services, CMAC is able to efficiently manage distributed incumbent measurement, control, and recovery procedures, while also providing the necessary spectrum management features. To coexist amongst 802.22 systems, CMAC is the first of its kind to implement a novel coexistence beacon protocol (CBP) that allows BSs with overlapping coverage areas to coordinate and efficiently share the radio spectrum, hence minimizing interference. The efficiency of CBP is further improved by a new scheme that dynamically synchronizes overlapping BSs. Additional characteristics of CMAC include the support of various traffic types with different QoS requirements, flexible bandwidth management, and a combination of access mechanisms.

November 2005


Slide 4

doc.: IEEE 802.22-05/0105r1

Submission

Presentation Outline

• Introduction– A Glimpse of IEEE 802.22

• The Cognitive PHY Proposal

• The Cognitive MAC Proposal

• Conclusions

November 2005


Slide 5

doc.: IEEE 802.22-05/0105r1

Submission





• Conclusions

November 2005


Slide 6

doc.: IEEE 802.22-05/0105r1

Submission

November 2005


Slide 7

doc.: IEEE 802.22-05/0105r1

Submission

PAN< 10 m

802.15.1 (Bluetooth) – 1 Mbps802.15.3 > 20 Mbps

802.15.3a (UWB) < 480 Mbps802.15.4 (Zigbee) < 250 kbps

LAN< 150 m

11 – 54 Mbps

802.11a/b/e/gHiperLAN/2

802.11n (proposed) > 100 Mbps

MAN< 5 km

802.16a/d/e - 70 MbpsLMDS - 38 Mbps

WAN< 15 km

802.20 (proposed)GSM, GPRS, CDMA, 2.5G, 3G – 10

kbps to 2.4 Mbps

RAN< 100 km

802.22 (proposed) - 18 to 24 Mbps

The IEEE 802.22

• From 18 Mbps to 24 Mbps

• Propagation delays in excess of 300 µs

• Operates in TV bands– 54 to 862 MHz

– 6 MHz, 7 MHz and 8 MHz channel bandwidth

November 2005


Slide 8

doc.: IEEE 802.22-05/0105r1

Submission

Deployment Scenario

• Master/Slave relationship

• Entities– Base Station (BS)

– Consumer Premise Equipment (CPE)

• 4W CPE transmit power

BS

BS

CPE

CPECPE

CPE

CPE

CPECPE

33 - 100 Km

Backbone Network

BS

CPE

CPE

BS

CPE

CPE

CPE

November 2005


Slide 9

doc.: IEEE 802.22-05/0105r1

Submission





• Conclusions

November 2005


Slide 10

doc.: IEEE 802.22-05/0105r1

Submission

PHY Presentation Outline

• Background

• Top-level description of modulation/coding

• Channel bonding

• Modulation Parameters

• Spreading OFDMA

• Sensing techniques

• OQAM/OFDMA

• Duo-binary CTC

November 2005


Slide 11

doc.: IEEE 802.22-05/0105r1

Submission

802.22 requirements consideration

• Regional Area Network (up to 30Km)– Operate in vacant TV bands– Detect vacant TV bands

• Large delay spread and roundtrip time• Data rate: from 1.5 Mbps DS and ~300 Kbps US• Should not cause harmful interference to other devices

– -70dB OOB emission– detect and avoid

• Flexibility– Bandwidth, bit rate, TX power, access mechanism, etc

• Spectral efficiency • 4 watt transmission power

November 2005


Slide 12

doc.: IEEE 802.22-05/0105r1

Submission

PHY Overview

• OFDMA both in uplink and downlink

• QPSK, 16-QAM, and 64-QAM, spreaded-QPSK

• More than 32 sub channels

• Contiguous channel bonding upto 3 TV channels ( and beyond in a stack manner)

• Data rate range from 5Mbps to 60Mbps

• Option of OQAM/OFDMA and turbo code

RandomizerModulation

(constellationmapping)

InterleaverFEC

November 2005


Slide 13

doc.: IEEE 802.22-05/0105r1

Submission

Why OFDMA ? • Single carrier and multi-carrier have been used for broadcasting, wireless

access, etc– Their behavior is well understood (capacity, filtering requirements, PAPR,

equalization, flexibility, efficiency)

• 802.22 Wireless access differ from broadcasting and most other system– flexibility in downstream and upstream link– variable # of users, variable throughput, – large round-trip signal delay– multiple access

• Multi-carrier system more suitable to meet these objectives– It enables to control the signal in time and frequency– Results in a two dimensional grid to assign resources to a user OFDMA– Resources can be allocated on a per user basis

• OFDM used in standards such as – WiMedia UWB, WiMAX (Fixed MAN), DAB, DMB, DVB-T, DVB-H, ISDB-T

• OFDMA used in WiMax, DVB-RCT

November 2005


Slide 14

doc.: IEEE 802.22-05/0105r1

Submission

OFDMA

• Based on OFDMA (sub-channels per user)– US/DS

– Reduces overhead for short messages

– Flexibility in choosing modulation/coding for CPE

– Reduced PAPR for CPEs

frequency

Sub chan. 1 Sub chan. 2 Sub chan. 3 Sub chan. 4

November 2005


Slide 15

doc.: IEEE 802.22-05/0105r1

Submission

Coding

PuncturerRate - ½

convolutionalcoder

PuncturerDuo-binary

CTC

CTC mode

CC mode

November 2005


Slide 16

doc.: IEEE 802.22-05/0105r1

Submission

Modulation

S/PConstelation

mappingIFFT S/P

AddGI

OFDMA

OQAM/OFDMA

1:NReal QAMmodulator

OFDM/IOTA symbol rate =N/0 symbols/sec

N symbolstreams1/0symbol/sec

IFFT

OFDM/IOTAsymbols1/0symbol/sec

N/2 :1 OFDM/IOTAsymbols

IOTAPolyphaseFiltering

November 2005


Slide 17

doc.: IEEE 802.22-05/0105r1

Submission

Channel Bonding

• More data rate

• Multi-path Diversity– Small BW signal can have deep fade or flat fade

– Wider-bandwidth signal provides more frequency/multipath diversity

• Interference– Wider-band reduces the amount of interference

November 2005


Slide 18

doc.: IEEE 802.22-05/0105r1

Submission

Channel Bonding/capacity

• Aggregate TV channels to get more capacity– Shannon: C = B.log2(1+S/N)

– Capacity proportional to BW, but logarithmic with SNR or signal power

• If S/N is fixed, then capacity increases linearly with bandwidth

• If signal power is fixed, but bandwidth is increased– C = B.log2(1+S/(BNo))

– Capacity still increases as bandwidth is increased

November 2005


Slide 19

doc.: IEEE 802.22-05/0105r1

Submission

Capacity of aggregated channels as a given signal power is spread over more channels

November 2005


Slide 20

doc.: IEEE 802.22-05/0105r1

Submission

Channel bonding

• 6, 12, 18 MHz channels

• Depends on availability

• Several receiver techniques to deal with flexible BW– Selectable analog filters

– Up sampling digital filters

TVTV

WRAN

N N+1 N+2N-1N-2 N+4N+3N-3

TVTV

WRAN

N N+1 N+2N-1N-2 N+4N+3N-3

TVTV

WAN

N N+1 N+2N-1N-2 N+4N+3N-3

November 2005


Slide 21

doc.: IEEE 802.22-05/0105r1

Submission

Channel bonding structure

• 6K FFT over 3 TV channels– 2K per TV channel

– Null out the outer carriers for 1 or 2 TV channels

• Fixed inter-carrier spacing– Several implementation

possibilities

DataSub-carrier

PilotSub-carrier

Guard/NullSub-carrier

6 MHz

18 MHz

12 MHz

DC

DC

DC

12 MHz

6 MHz

18 MHz

November 2005


Slide 22

doc.: IEEE 802.22-05/0105r1

Submission

Frame structure: Superframe

Superframe n-1 Superframe n Superframe n+1 ...Time

...

Preamble SCH frame 0 frame 1 frame m...

TV Channelt-1

TV Channelt

TV Channelt+1

Time

Preamble SCH

Preamble SCH

Fre

qu

en

cy

Preamble SCHFrame

0Frame

1

Framem-2

(Quiet)...

... Frame0

Frame1

Preamble SCH

Preamble SCH

Occupied by Incumbent


Framen


Framem

Framem-1

November 2005


Slide 23

doc.: IEEE 802.22-05/0105r1

Submission

Spectrum of the signal (before further filtering)

Produced using a 6K FFT

for a single TV channel

November 2005


Slide 25

doc.: IEEE 802.22-05/0105r1

Submission

Inter-carrier spacing and FFT/IFFT period values for different bandwidth options

Table 2: Inter-carrier spacing and FFT/IFFT period values for different bandwidth options

6 MHz based channels

(6, 12 and 18 MHz)


(7, 14 and 21 MHz)


(8, 16 and 24 MHz)

Inter-carrier spacing, F (Hz)

3348.214 3906.625 4464.286

FFT/IFFT period, TFFT (s)

298.666 256.000 224.000

November 2005


Slide 26

doc.: IEEE 802.22-05/0105r1

Submission

OFDMA parameters

3 TV bands 2 TV bands 1 TV band Parameter

18 21 24 12 14 16 6 7 8 Inter-carrier spacing,

F (Hz) 3348 3906 4464 3348 3906 4464 3348 3906 4464

FFT period, TFFT (s) 298.66 256.00 224.00 298.66 256.00 224.00 298.66 256.00 224.00

Total no. of sub-carriers,

NFFT 6144 4096 2048

No. of guard sub-carriers,

NG (L, DC, R) 960 (480, 1, 479) 640 (320, 1, 319) 320 (160, 1, 159)

No. of used sub-carriers,

NT = ND+ NP 5184 3456 1728

No. of data sub-carriers,

ND 4608 3072 1536

No. of pilot sub-carriers, NP 576 384 192

Signal bandwidth (MHz)

17.356 20.249 23.141 11.571 13.500 15.428 5.785 6.750 7.714

November 2005


Slide 27

doc.: IEEE 802.22-05/0105r1

Submission

Modulation/coding modes and corresponding rates

PHY Mode Modulation Coding Rate Spreading

Factor Spreading Matrix

Data rate (Mb/s)

0 QPSK ½ 4 SCH 1 QPSK ½ 1 Hadamard 4.84 2 QPSK ½ 1 Identity 4.84 3 QPSK ¾ 1 Hadamard 7.26 4 QPSK ¾ 1 Identity 7.26 5 16-QAM ½ 1 Identity 9.68 6 16-QAM ¾ 1 Identity 14.52 7 64-QAM ½ 1 Identity 14.52 8 64-QAM 2/3 1 Identity 19.36 9 64-QAM ¾ 1 Identity 21.78

10 64-QAM 5/6 1 Identity 24.20 11 OQPSK ½ tbd tbd 5.14 12 OQPSK 2/3 tbd tbd 6.86 13 OQPSK ¾ tbd tbd 7.71 14 16-OQAM ½ tbd tbd 10.29 15 16-OQAM 2/3 tbd tbd 13.71 16 16-OQAM 3/4 tbd tbd 15.43 17 64-OQAM ½ tbd tbd 15.43 18 64-OQAM 2/3 tbd tbd 20.57

November 2005


Slide 28

doc.: IEEE 802.22-05/0105r1

Submission

Preamble

• Superframe preamble – Over 1512 sub-carriers (every fourth or second non-zero),

– 5 MHz BW

– Simply duplicate for additional TV channels

– 1 MHz gap between adjacent channels to relax filtering

– 2 symbol duration (1 more for data)

• Frame preamble: 1-3 TV channels – 1728*N sub-carriers

– Short preamble is optional

ST1 ST5ST4ST3ST2 LT1 LT2GI

TSYMTSYM (short) (long)

November 2005


Slide 29

doc.: IEEE 802.22-05/0105r1

Submission

Spreaded QPSK/OFDMA

• Spread data over some sub-carriers (Hadamard)

• Increases capturing of multipath diversity

• Increases resiliency to interferers

• Simple receiver structure (MMSE)

dev 1(64QAM)

dev3

dev5 (16QAM)

Dev4 (S-QPSK)

Dev2 (16QAM)

Dev7 (S-QPSK)dev6 (64QAM)

Dev8(64QAM)

1234

Time (in OFDM symbol unit)

subchannels

HxY

November 2005


Slide 30

doc.: IEEE 802.22-05/0105r1

Submission

Simulation results for QPSK, rate 3/4

S-OFDMA gives 2-4dB

gain!

Channels: •ATSC Brazil D•802.22 Profile A •All with Doppler

November 2005


Slide 31

doc.: IEEE 802.22-05/0105r1

Submission

Preliminary Link Budget(LOS)Throughput/channel 5 19 Mb/scenter frequency 0.7 0.7 GHzbandwidth 6 6 MHzDistance 30000 30000 mTx power 4 4 WTx averg power 36.0 36.0 dBmTX antenna gain 18.0 18.0 dBiRx powerfree space path loss 119 119 dBRx antenna gain 12 12 dBicable and other losses 3 3 dBTotal received avrg power -56 -56 dBmReceiver noise figure 4 4 dBNoise power -106 -106 dBmInterference allowance 3 3 dBReceived SNR 43 43 dBRequired SNR 4 25 dBImplementation/OFDM loss 6.0 6.0 dBLink Margin 33.4 12.4 dB

November 2005


Slide 32

doc.: IEEE 802.22-05/0105r1

Submission

Other Features

• Ranging

• Transmitter Power Control (TPC)

• Consideration of multiple antenna

November 2005


Slide 33

doc.: IEEE 802.22-05/0105r1

Submission

Channel Measurement

• Received signal strength– Quality measurement of its own signal (TPC, modulation/coding)

– Fast channel ‘busy’ detection

• Signal feature detection– Detection of the type of the signal

• ATSC, DVB-T, Part 74, .22, etc

– Should be robust to receiver imperfections

November 2005


Slide 34

doc.: IEEE 802.22-05/0105r1

Submission

Received Signal Strength

• Several implementation techniques– FFT, IOTA/FFT, simple low-pass filter etc

– Possibility to measure a part of the spectrum

• Various degrees of performance

• Integration time and threshold is very important

• BS sets essential parameters (constant)

• Either the BS makes the detection decision based on the collective measurement results or CPE’s can make the decision – distributed measurement

November 2005


Slide 35

doc.: IEEE 802.22-05/0105r1

Submission

Simulated performances of OFDM and OQAM: detecting ATSC pilot

5ms integration time

November 2005


Slide 36

doc.: IEEE 802.22-05/0105r1

Submission

DTV signal feature detection

• Should not be sensitive to frequency selective fading, and receiver impairments (e.g., frequency error)

• Use field sync correlation detection for ATSC, similar correlation for other standards– Compare correlation peak to the mean of the standard deviation of

the correlation

– Characterized the theoretical performance

– Experimental tests

November 2005


Slide 37

doc.: IEEE 802.22-05/0105r1

Submission

MULTIPATH SIMULATOR

ATTENUATOR

RECEIVER

8VSB_SOURCE

Experimental setup for DTV detection

November 2005


Slide 40

doc.: IEEE 802.22-05/0105r1

Submission

ENERGY SENSOR, DETECTION RATE, %

VSB SENSOR, DETECTION RATE, %

PATH 1 POWER, dBm PATH 1 POWER, dBm

DELAY, usec

DOPPLER, Hz

ATTEN, dB

-107 -100 -90 -107 -100 -90 PATH 1 0 0 0

PATH 2 3.0 0.1 7.0

PATH 3 8.0 2.5 15.0 100 100 100 100 100 100 PATH 4 11.0 0.13 22.0

PATH 5 13.0 0.17 24.0

PATH 6 21.0 0.37 19.0

Based on Doc.: IEEE802.22-05/0055r7.

Profile A.

November 2005


Slide 42

doc.: IEEE 802.22-05/0105r1

Submission

Part 74 detection

• Part 74 devices occupy a small portion of the spectrum• Thus, use spectral estimation and statistics of the estimated

signal– Spectral estimation using FFTs (windowing techniques can also be

employed to better localize the spectrum)• Perform FFT • Average each freq bin

• Average across freq bin

– Compute mean and “variance”

1

0

2),(

1),(

K

i

mikYK

mkP

1

0

1

0

),(

),(

N

mkk

N

mk

mkP

mkP

FFT

avg

W.F.

V>k*avg

November 2005


Slide 43

doc.: IEEE 802.22-05/0105r1

Submission

Part 74 detection (cont.)

• Detection

• Theoretical performance

N

M

M

KKalarmfalseob

KKectionob

KKmissob

),(1.__Pr

),(1det_Pr

),(_Pr

kk kkmkP 21)),(max(

November 2005


Slide 44

doc.: IEEE 802.22-05/0105r1

Submission

Narrow-band detection (Part 74): Theoretical and simulated performance

November 2005


Slide 45

doc.: IEEE 802.22-05/0105r1

Submission

Probability of miss detection and false alarm

November 2005


Slide 46

doc.: IEEE 802.22-05/0105r1

Submission

Detector Link Margin

center frequency 0.7 0.7 GHzbandwidth 200 200 KHzDistance 500 1500 mTx power 10 10 mWTx averg power 10.0 10.0 dBmTX antenna gain 0.0 0.0 dBiRx powerfree space path loss 83 93 dBRx antenna gain 0 0 dBicable and other losses 3 3 dBTotal received avrg power -76 -86 dBmReceiver noise figure 4 4 dBNoise power -121 -121 dBmInterference allowance 3 3 dBFading allowance 10 20 dBBody absorption 10 10 dBReceived SNR 18 -2 dB

Required SNR -6 -6 dBImplementation loss 3.0 3.0 dBLink Margin 20.7 1.1 dB

November 2005


Slide 47

doc.: IEEE 802.22-05/0105r1

Submission


• Background


• Channel bonding


• Spreading OFDMA


• OQAM/OFDMA

• Duo-binary CTC

November 2005


doc.: IEEE 802.22-05/0105r1

Submission

OFDM/OQAM Outline

• Principles of OFDM/OQAM

• The IOTA Waveform

• Advantages of OFDM/OQAM

• Simulation results

November 2005


doc.: IEEE 802.22-05/0105r1

Submission

OFDM/OQAM principles (1)

• Aim: to increase OFDM spectral efficiency by :– Removing the guard interval (cyclic prefix);

– Delivering a sharper spectral signal than OFDM.

• How: The waveform that modulates OFDM sub-carriers should be as much as possible localized in time and frequency domains to minimize inter-symbol and inter-carrier interferences.

November 2005


doc.: IEEE 802.22-05/0105r1

Submission


• However, the waveform must guarantee orthogonality between sub-carriers and multi-carrier symbols.– Appropriate waveform exist but guarantee orthogonality in the real

domain OffsetQAM modulation should be considered on each sub-carrier.

• Example: IOTA waveform (optimally localized in time and frequency).

November 2005


doc.: IEEE 802.22-05/0105r1

Submission


• OFDM/QAMTransmitted signal:

• takes the complex value representing the transmitted encoded data sent on the mth sub-carrier at the nth symbol;

• and the basic functions are obtained by translation in time and frequency of a prototype function such as:

• With• Rectangular function x used in OFDM has weak frequency

localization.

• OFDM/OQAM• Introduces a time offset between real and imaginary parts of

symbols• takes real values;• And with

nm

nm txts,

,nm,a)(

nma ,

tx nm,

02

,0 ntxetx tmi

nm 100

nma ,

02

,0 ntxeitx tminm

nm 2/100

November 2005


Slide 52

doc.: IEEE 802.22-05/0105r1

Submission


• Time-frequency lattice

November 2005


doc.: IEEE 802.22-05/0105r1

Submission

The IOTA function (1)

IOTA = Isotropic Orthogonal Transform Algorithm

• IOTA is a prototype function obtained by the orthogonalization of the Gaussian function

• Its particularity: the IOTA waveform modulating each sub-carrier is:

– Quasi-optimally localized in both time and frequency

– Isotropic: it has the same shape as its Fourier transform => delay spread and Doppler are both equally managed

November 2005


doc.: IEEE 802.22-05/0105r1

Submission


0 0 2*0 30

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

symbol duration

Am

plit

ude

IOTA

-2*0 0- 30

0 0 2*0 30

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Inter-carrier spacing

Am

plitu

de

IOTA Fourier Transform

-2*0 0- 30

November 2005


doc.: IEEE 802.22-05/0105r1

Submission


• The IOTA function can be denoted by:

Where:

• The transmitted signal is:

22

,, ntIeetI mtii

nmnm

2/)(, nmnm

2

2,

, ntIeeats mtiinm

nm

November 2005


Slide 56

doc.: IEEE 802.22-05/0105r1

Submission

Advantages of OFDM/OQAM (1)• Spectrum is sharper : 70 dB instead of 30 dB

• This feature helps to protect the adjacent channels

November 2005


Slide 57

doc.: IEEE 802.22-05/0105r1

Submission

Advantage of OFDM/OQAM (2)

• Cyclic prefix not mandatory more useful bit-rate

• This extra bit-rate may be used to:–Increase the global net bit-rate of the system;

–Increase the robustness and therefore the range, or decrease the power.

Cyclic prefix 1/4 1/8 1/16 1/32

Bit-rate OFDM/QAM 1/2 11.57 Mbits/s 13.5 Mbits/s 14.47 Mbits/s 14.95 Mbits/s

Bit-rate OFDM/OQAM 1/2 15.43 Mbits/s 15.43 Mbits/s 15.43 Mbits/s 15.43 Mbits/s

November 2005


Slide 58

doc.: IEEE 802.22-05/0105r1

Submission

Simulation resultsSimulation parameters:

– Constellation : 64 QAM

– Coding rate : ½

– Bandwidth : 7 MHZ

– Channel: 641 MHz

– Channel model: Profile A of WRANProfile A

-30

-25

-20

-15

-10

-5

0

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60

Excess delay (usec)

Re

lati

ve

att

en

ua

tio

n (

dB

)

November 2005


Slide 59

doc.: IEEE 802.22-05/0105r1

Submission

OFDM/OQAM vs OFDM/QAMwith Convolutional FEC

Convolutional rate 1/2

-6

-5

-4

-3

-2

-1

0

13 14 15 16 17 18 19 20 21

C/N

BE

R (

log

)

OFDM

OQAM

November 2005


Slide 60

doc.: IEEE 802.22-05/0105r1

Submission

OFDM/OQAM vs OFDM/QAMwith Duo-binary Turbo-codes

Duo-binary Turbo-code rate 1/2

-6

-5

-4

-3

-2

-1

0

13 14 15 16 17 18 19 20 21

C/N

BE

R (

log

)

OFDM

OQAM

November 2005


Slide 61

doc.: IEEE 802.22-05/0105r1

Submission

State of the art

• OQAM waveform has been standardized by TIA committee TR8 for Private Land Mobile applications

November 2005


Slide 62

doc.: IEEE 802.22-05/0105r1

Submission


• Background


• Channel bonding


• Spreading OFDMA


• OQAM/OFDMA

• Duo-binary CTC

November 2005


Slide 63

doc.: IEEE 802.22-05/0105r1

Submission

Duo-binary Turbo-codes Outline

• Duo-Binary Turbo Codes

• Internal interleaver

• Flexibility

• Performance

• Simulations

November 2005


Slide 64

doc.: IEEE 802.22-05/0105r1

Submission

Duo-Binary Turbo-codes

Information bits are encoded by

couples

November 2005


Slide 65

doc.: IEEE 802.22-05/0105r1

Submission

Duo-Binary Turbo-code

• Duo-Binary input: two decoded bit output at a time – Reduction of latency and complexity per decoded bit (compared to

Binary TC)

– Better convergence

• Circular (tail-biting) encoding– No trellis termination overhead

• Original interleaving scheme– Larger minimum distances

– Improved asymptotic performances

November 2005


Slide 66

doc.: IEEE 802.22-05/0105r1

Submission

Internal Interleaver

• Algorithmic permutation–One equation, 4 parameters (P0, P1, P2, P3)

–Parameters selected such that interleaver is contention-free

• Adjusting the TC to a blocksize only requires modification of the 4 parameters

• Quasi-regular permutation (easy connectivity)

• Inherent parallelism

i = 0, …, N-1, j = 0, ...N-1

level 1: if j mod. 2 = 0, let (A,B) = (B,A) (invert the couple)

level 2:

- if j mod. 4 = 0, then P = 0;

- if j mod. 4 = 1, then P = N/2 + P1;

- if j mod. 4 = 2, then P = P2;

- if j mod. 4 = 3, then P = N/2 + P3.

i = P0*j + P +1 mod. N

November 2005


Slide 67

doc.: IEEE 802.22-05/0105r1

Submission

Flexibility

• Can be easily adjusted to any blocksize–Storage of the 4 parameters for all blocksizes considered–Possibility of a generic approach (default parameters)

• All coding rates are possible–Through puncturing patterns–Natural coding rate is ½: increased robustness to puncturing

• Performance vs complexity: several adjustments are possible

–Number of iterations, Decoding algorithm, …

• Implementation: interleaver enables different degrees of parallelism

–Can be adjusted to meet complexity/throughput requirements

November 2005


Slide 68

doc.: IEEE 802.22-05/0105r1

Submission

Flexibility

• The number of iterations can be adjusted for a better performance-complexity trade-off

November 2005


Slide 69

doc.: IEEE 802.22-05/0105r1

Submission

Performance

• Duo-Binary TC, 8 iterations, Max-Log-MAP decoding

• IEEE 802.16e structured LDPC, BP decoding, 50 iterations

• AWGN, R=1/2, QPSK

• N=576 and 2304 (coded blocksize)

November 2005


Slide 70

doc.: IEEE 802.22-05/0105r1

Submission

Short blocksize performance

• Hardware measurements

• Low BER (down to 10-11) are achievable without error floor

November 2005


Slide 71

doc.: IEEE 802.22-05/0105r1

Submission

Simulation results• Simulation parameters

– Constellation : 64 QAM

– Coding rate : ½

– Bandwidth : 7 MHZ

– Channel: 641 MHz

– Channel model: Profile A of WRANProfile A

-30

-25

-20

-15

-10

-5

0

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60

Excess delay (usec)

Re

lati

ve

att

en

ua

tio

n (

dB

)

November 2005


Slide 72

doc.: IEEE 802.22-05/0105r1

Submission

Duo-binary Turbo-codes vs Convolutionalwith OFDM/QAM modulation

OFDM 64 QAM rate 1/2

-6

-5

-4

-3

-2

-1

0

13 14 15 16 17 18 19 20 21

C/N

BE

R (

log

)

Convolutional

DTC

November 2005


Slide 73

doc.: IEEE 802.22-05/0105r1

Submission

Duo-binary Turbo-codes vs Convolutionalwith OFDM/OQAM modulation

OQAM 64 QAM rate 1/2

-6

-5

-4

-3

-2

-1

0

13 14 15 16 17 18 19 20 21

C/N

BE

R (

log

)

Convolutional

DTC

November 2005


Slide 74

doc.: IEEE 802.22-05/0105r1

Submission

Advantages of Duo-binary Turbo-codes

• Good performance for a very wide range of blocksizes

• Highly flexible scheme, enabling a very fine granularity– Same encoder/decoder for all blocksizes/coding rates.

– Several trade-off in performance (number of iterations, decoding algorithm), implementation complexity (degrees of parallelism).

• Reasonable complexity– Approximately 35% decrease in complexity per decoded bit

compared to Binary TC.

November 2005


Slide 75

doc.: IEEE 802.22-05/0105r1

Submission

State of the art

• Duo-binary Turbo-code is a mature technology

• This technology has already been selected by several standardization groups– IEEE 802.16 / WiMAX;

– DVB-RCS;

– DVB-RCT;

– ETSI HIPERMAN

November 2005


Slide 76

doc.: IEEE 802.22-05/0105r1

Submission

Summary:Gains brought by OQAM and DTC

• OFDM/OQAM brings 10% more bit-rate– When converted in error protection enables to go from ¾ rate to

2/3

– Gain between 1 and 1,5 dB in C/N

• Duo-binary TC offers 3,5 to 4 dB

• When combined the gain is at least 4,5 dB that allows to increase the radius by 7,6 km (17%) with QPSK modulation in a Gaussian channel.

November 2005


Slide 77

doc.: IEEE 802.22-05/0105r1

Submission

Final conclusion for WRAN PHY

• OFDMA/Channel bonding– Good answer to flexibility requirements

• Spreading QPSK– Captures multipath diversity and increases resiliency to

interference (2-4 dB gain)

• OQAM waveform– Increases efficiency and incumbent protection

• Duo-binary Turbo-codes– Powerful error protection technique

November 2005


Slide 78

doc.: IEEE 802.22-05/0105r1

Submission





• Conclusions

November 2005


Slide 79

doc.: IEEE 802.22-05/0105r1

Submission

CMAC Presentation Outline

• Introduction

• The CMAC Protocol– Architecture– Data communication

• Superframe and Frame Structures• Network entry and initialization• Downstream and Upstream scheduling

– Coexistence• Incumbents• Self-Coexistence• Synchronization of overlapping BSs• Clustering

– Security

• Performance Evaluation

November 2005


Slide 80

doc.: IEEE 802.22-05/0105r1

Submission

CMAC Presentation Outline

• Introduction




– Security


November 2005


Slide 81

doc.: IEEE 802.22-05/0105r1

Submission

Introduction

• A Cognitive MAC (CMAC) layer is proposed to be used as the future IEEE 802.22 MAC for WRANs

• Some aspects of CMAC have been inspired by the IEEE 802.16 MAC standard

• However, major enhancements have been made– Support of multiple channel operation;– Coexistence with both incumbents and itself (self-coexistence);

• Measurements (incumbents and itself)• Spectrum management (time, frequency and power)• The Coexistence Beacon Protocol (CBP)• Synchronization of overlapping BSs• The Incumbent Detection Recovery Protocol (IDRP)• Embedded wireless microphone beacon mechanism

– Clustering support; etc.

November 2005


Slide 82

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 83

doc.: IEEE 802.22-05/0105r1

Submission

Overview

• Given the very long propagation delays in WRANs, the BS regulates the medium access– Downstream: TDM

(Time Division Multiplexing)

– Upstream: DAMA (Demand Assigned Multiple Access) TDMA

Packet Size: 50 bytes Packet Size: 1500 bytes

November 2005


Slide 84

doc.: IEEE 802.22-05/0105r1

Submission

Overview (cont.)

• Combination of polling, contention and unsolicited bandwidth grants mechanisms

• Support of Unicast/Multicast/Broadcast for both management and data

• Connection-oriented MAC– Connection identifier (CID) is a key component

– Defines a mapping between peer processes

– Defines a service flow (QoS provisioning)

November 2005


Slide 85

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 86

doc.: IEEE 802.22-05/0105r1

Submission

Protocol Stack Architecture

• Flexibility, scalability and efficiency are core elements

• Spectrum manager could be implemented in many ways

Convergence Sublayer / Bridge (e.g., 802.1d)

MAC

PHY

...MAC

PHY

MAC

PHY

Spectrum Manager

Higher Layers: IP, ATM, 1394, etc.

PHY/MAC 1 PHY/MAC 2 PHY/MAC n

November 2005


Slide 87

doc.: IEEE 802.22-05/0105r1

Submission

Protocol Stack Architecture (cont.)

• Flexible channel assignment– Implementers decide on the algorithm

Used by incumbents (e.g., TV stations)

54321 6 7

Vacant and available for use by 802.22

Allo

cate

dto

PH

Y/M

AC 1

Use

d b

y ano

ther

80

2.2

2 c

ell

Use

d b

y an

oth

er

802.2

2 c

ell

Frequency

Allo

cate

dto

PH

Y/M

AC 2

November 2005


Slide 88

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 89

doc.: IEEE 802.22-05/0105r1

Submission

Basic Terms and Definitions

• Superframe– Defined and delimited by a preamble and the SCH (superframe control

header). It is comprised of a number of Frames

• Frame– Comprised of one DS and one US Subframe, where BS and CPEs use to

communicate with each other

• Subframe– Formed by a number of Bursts

• Burst– Defined by a two dimensional segment of logical channel (frequency) and

MAC slot (time). It may comprise of multiple MAC PDUs belonging to multiple CPEs

• MAC PDU– The smallest unit of transmission/reception by the MAC. It is comprised

of the MAC header, the payload, and CRC

November 2005


Slide 90

doc.: IEEE 802.22-05/0105r1

Submission

Motivation

• The problem– How to offer enhanced capacity and higher data rates?

• The fact– Spectrum occupancy measurements conducted by Shared

Spectrum Company from January/2004 to August/2005 have shown that:• “There is a significant amount of spectrum available in continuous

blocks that are 1 MHz and wider ”• “A dynamic spectrum sharing radio with a low agility, contiguous

waveform will provide high utility”

• The solution– Simultaneous use of multiple contiguous TV channels

November 2005


Slide 91

doc.: IEEE 802.22-05/0105r1

Submission

Superframe n-1 Superframe n Superframe n+1 ...Time

...

Preamble SCH frame 0 frame 1 frame m...

TV Channelt-1

TV Channelt

TV Channelt+1

Time

Preamble SCH

Preamble SCH

Fre

qu

en

cy

Preamble SCHFrame

0Frame

1

Framem-2

(Quiet)...

... Frame0

Frame1

Preamble SCH

Preamble SCH



Framen


Framem

Framem-1

Superframe Structure

Superframe Control Header (SCH)

• TV channels being bonded• Coexistence and superframe information

• Number and size of frames• Information on periodic quiet periods• ID an transmit power of transmitter

•Location configuration information

November 2005


Slide 92

doc.: IEEE 802.22-05/0105r1

Submission

Frame Structure

• CMAC is based on a TDD frame structure– Reduced complexity

– In general, less measurements overhead

– The flexible architecture (with the Spectrum Manager) already brings with it aspects of FDD

• The CMAC frame structure is comprised of two parts– A predominantly downstream (DS) subframe

– An upstream (US) subframe

November 2005


Slide 93

doc.: IEEE 802.22-05/0105r1

Submission

Frame Structure (cont.)

frame n-1 frame n frame n+1 ...Time

...

DS PHY PDU

Preamble FCH DS burst 1 DS burst 2 DS burst x...

BcastMsgs

MACPDUs

MAC PDU 1 ... MAC PDU y Pad

MACHeader

MAC Payload CRC

DS subframe

Initializationslots

BW requestslots

US PHY PDU(CPE m)

US PHY PDU(CPE p)

...

US subframe

Preamble US burst

MAC PDU 1 ... MAC PDU k Pad

MACHeader

MAC Payload CRC

Sliding self-coexistence

slots

Can appear ineither DS or US

BCH

UCSNotification

Slots

November 2005


Slide 94

doc.: IEEE 802.22-05/0105r1

Submission

Time/Frequency Structure of a MAC Frame


...

MAC Slot Number

Pre

am

ble

FCH

DS

-MA

PU

S-M

AP

Self-

coexi

stence

Ranging

UCS Notification

Burst CPE #4

Burst CPE #2

Burst CPE #1

Burst CPE #5

Burst CPE #3

Burst CPE #7

Burst CPE #1

Burst CPE #2

Burst CPE #4

Burst CPE #5

Burst CPE #3

Burst CPE #6

Burst CPE #8

Burst CPE #9

Self-

coexi

stence

Burst CPE #6

Burst CPE #7

Burst CPE #8

TTG

k k+1 k+3 k+5 k+7 k+9 k+11 k+13 k+15 k+17 k+20 k+23 k+26 k+29

TV Channel N

TV Channel N+1

DS US

Log

ica

l MA

C C

hannel N

um

ber

s

s+1

s+2

s+L

BW Request

November 2005


Slide 95

doc.: IEEE 802.22-05/0105r1

Submission

Network Entry and Initialization

BS onchannel #52

CPE 3

CPE 1

CPE 2

Radio range of802.22 BS

• The key problem

CPE 4

TVstation onchannel

#52

Grade B contourof TV station

Radio range ofTV station

November 2005


Slide 96

doc.: IEEE 802.22-05/0105r1

Submission

Downstream (DS) Transmissions

• DS = core messages + data (transmitted in bursts)– Two core DS messages: DCD and DS-MAP– Bursts identified by DIUC (Downstream Interval Usage Code)– Each burst may contain data for several CPEs

• DCD (Downstream Channel Descriptor)– Establishes association between DIUC and actual PHY parameters (e.g.,

modulation and coding)

• DS-MAP (Downstream map)– Defines the usage (i.e., scheduling) of the downstream– Critical, hence first message in each frame– For self-coexistence purposes, the BS may choose to use part of DS

subframe for CBP protocol operation

November 2005


Slide 97

doc.: IEEE 802.22-05/0105r1

Submission

Upstream (US) Transmissions• US = core messages + data (contention and bursts)

– Two core DS messages: UCD and US-MAP– Bursts identified by UIUC (Upstream Interval Usage Code)– The upstream can be segmented into several UIUC

• Contention-based – Initialization, Bandwidth Request, Urgent Coexistence Situation (UCS), CBP slots (SCS)

• Data Bursts

• UCD (Upstream Channel Descriptor)– Establishes association between UIUC and actual PHY parameters (e.g.,

modulation and coding)

• US-MAP (Upstream map)– Defines the usage (i.e., scheduling) of the upstream– Contains “grants”addressed to a particular CPE or a set of CPEs (e.g., for

self-coexistence)

November 2005


Slide 98

doc.: IEEE 802.22-05/0105r1

Submission

Bandwidth Management: Request/Grant Scheme

• Self correcting– No acknowledgement

– All errors are handled the same way (i.e., periodic aggregate requests)

• Bandwidth requests– Are always per connection

– Can specify DS/US Traffic Constraint IEs for better self-coexistence

• Bandwidth grants– Can be either per connection or per CPE

– Grants (given as durations) are carried in US-MAP messages

– CPE converts time into amount of data using information about the UIUC

November 2005


Slide 99

doc.: IEEE 802.22-05/0105r1

Submission

Scheduling Services

• Unsolicited Grant Services (UGS)– For CBR and CBR-like flows (T1/E1)

– No specific bandwidth request issued by CPE

• Real-time Polling Service (rtPS)– For rt-VBR-like service flows such as MPEG video

– CPEs are polled to meet delay requirements

• Non-real-time Polling Service (nrtPS)– For non-real-time flows with better than best effort service such as

bandwidth-intensive file transfer

– CPEs are polled and can use contention interval

• Best Effort (BE)– E.g., Web surfing

– CPEs use contention interval only

November 2005


Slide 100

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 101

doc.: IEEE 802.22-05/0105r1

Submission

Coexistence

• Two primary types– With incumbents (TV service and Part 74 devices)– With other overlapping 802.22 cells

• Self-Coexistence

• Measurements can be classified as:– In-band

• In case of incumbents, requires quiet periods (QP)

– Out-of-band• No need for quiet periods

• Coexistence is achieved by a joint application of:– Spectrum management (frequency and power)– “Interference-free” traffic scheduling (time)

November 2005


Slide 102

doc.: IEEE 802.22-05/0105r1

Submission

Measurements

• Measurements form a key component of CMAC– Protection of incumbents and self-coexistence

• The BS may request multiple measurements in a single management message– E.g., ATSC, DVB, Wireless Microphone, 802.22

• Measurement messages may be transmitted through multicast– Allows the implementation of advanced features such as clustering

– Bandwidth efficient

November 2005


Slide 103

doc.: IEEE 802.22-05/0105r1

Submission

Measurements (cont.)

• Bulk Measurement Request (BLM-REQ)– Transmitted by the BS to CPEs– Includes information such as

• Channels to measure• Multiple single measurement requests

• Bulk Measurement Response (BLM-RSP)– Transmitted by CPE to BS– If needed, acknowledges the receipt of the BLM-REQ message

• Bulk Measurement Report (BLM-REP)– Transmitted by CPE to BS– Returns multiple single measurement reports

• Bulk Measurement Acknowledgement (BLM-ACK)– Transmitted by BS to CPE– Acknowledges receipt of measurement report

November 2005


Slide 104

doc.: IEEE 802.22-05/0105r1

Submission


• Single measurements can be of various types– Signal specific measurement request

• TV system and Wireless microphones

– Beacon measurement request• CBP, BS, and Wireless microphone beacons

– CPE statistics measurement request

– Stop measurement request

– Location configuration measurement request

• A range of parameters can be specified

1 n2 . ..Time

n measurementrepetitions

Duration Restart Delay RandomizationInterval

November 2005


Slide 105

doc.: IEEE 802.22-05/0105r1

Submission


• There is almost a one-to-one correspondence between measurement requests and reports

• Some of the individual reports are:– Signal specific measurement report

• TV/Wireless Microphone system type, measured value, precision, etc.

– Beacon measurement report• Information on any CBP, BS, or Wireless microphone beacons

received

– CPE statistics measurement report• E.g., Packet error rate

– Location configuration measurement report• If known, location information (GPS, triangulization, and so on)

November 2005


Slide 106

doc.: IEEE 802.22-05/0105r1

Submission

Channel Management

• Channel management is key to effective network coordination, coexistence and sharing

• Included in two modes– Embedded

– Non-embedded

• A set of messages are defined to allow flexible management of channels, including:– Add/remove channel(s) to/from current set of channels

– Switch channel(s) of operation

– Quiet selected channel(s) – possibly to perform in-band measurement

November 2005


Slide 107

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 108

doc.: IEEE 802.22-05/0105r1

Submission

Coexistence with Incumbents

• Accomplished through the following steps:– Measurements (discussed earlier)

– Detection• TV: For more info, please see PHY proposal.

• Wireless Microphones– PHY solution: For more info, please see PHY proposal.

– MAC solution: See next slide.

– Incumbent Notification

– Incumbent Detection Recovery

November 2005


Slide 109

doc.: IEEE 802.22-05/0105r1

Submission

Coexistence with Incumbents

• Accomplished through the following steps:– Measurements (discussed earlier)

– Detection• TV: For more info, please see PHY proposal.

• Wireless Microphones– PHY solution: For more info, please see PHY proposal.

– MAC solution: See next slide.

– Incumbent Notification

– Incumbent Detection Recovery

November 2005


Slide 110

doc.: IEEE 802.22-05/0105r1

Submission

MAC Layer Detection of Wireless Microphones

• From the transmitter perspective, wireless microphone beacons (WMB) can be of two types– Embedded

• 802.22 device which has the additional capability of emitting WMBs

– Non-embedded• Currently addressed by the Part 74 Study/Task Group

• Based on the proposed MAC layer, we have developed an embedded WMB approach that:– Reliably detects multiple collocated 802.22 networks

– Upon sending WMBs, this mechanism causes minimal, if any, harmful interference to collocated 802.22 networks

– Once either BSs or CPEs detect the WMB, a dissemination is made and all present 802.22 networks vacate the channel

November 2005


Slide 111

doc.: IEEE 802.22-05/0105r1

Submission

Incumbent Notification

• The problem– How to notify the BS about the presence of incumbents in a timely

fashion?

• Two solutions are possible– CPEs with upstream bandwidth allocation

• Send report provided bandwidth and time are available; and/or• Set dedicated bits in MAC header

– CPEs without upstream bandwidth allocation• Urgent Coexistence Situation (UCS) Notification slots reserved

specifically for incumbent notification purposes– Can use either contention-based or contention-based CDMA access

• The size of a slot fits the smallest MAC frame necessary to perform the incumbent notification

November 2005


Slide 112

doc.: IEEE 802.22-05/0105r1

Submission

Incumbent Notification (cont.)


...

MAC Slot Number

Pre

am

ble

FCH

DS

-MA

PU

S-M

AP

Self-

coexi

stence

Ranging

UCS Notification

Burst CPE #4

Burst CPE #2

Burst CPE #1

Burst CPE #5

Burst CPE #3

Burst CPE #7

Burst CPE #1

Burst CPE #2

Burst CPE #4

Burst CPE #5

Burst CPE #3

Burst CPE #6

Burst CPE #8

Burst CPE #9

Self-

coexi

stence

Burst CPE #6

Burst CPE #7

Burst CPE #8

TTG

k k+1 k+3 k+5 k+7 k+9 k+11 k+13 k+15 k+17 k+20 k+23 k+26 k+29

TV Channel N

TV Channel N+1

DS US

Log

ica

l MA

C C

hannel N

um

ber

s

s+1

s+2

s+L

BW Request

RTG

November 2005


Slide 113

doc.: IEEE 802.22-05/0105r1

Submission

Incumbent Notification (cont.)

• The BS can use various strategies depending upon how reliable it wants the notification to be– Trade-off between overhead and data efficiency

– Scalability

1 n2 . ..Time

n QuietPeriods

Duration

Quiet PeriodNotification Phase

Normal System OperationNotification Phase

November 2005


Slide 114

doc.: IEEE 802.22-05/0105r1

Submission

Incumbent Detection Recovery

• The problem– How does the 802.22 cell recover from an UCS with incumbents

in a timely fashion?

November 2005


Slide 115

doc.: IEEE 802.22-05/0105r1

Submission

Incumbent Detection Recovery (cont.)

• The Incumbent Detection Recovery Protocol (IDRP)– Introduces the concept of Backup Channel

– The 802.22 network not only performs in-band measurements, but also out-of-band measurements• Out-of-band measurements will determine a suitable Backup Channel

– The 802.22 network falls back to the Backup Channel in case communication is preempted by an incumbent

– The algorithms at both the BS and CPEs are provided• These algorithms also account for the case when no Backup Channel

is available

November 2005


Slide 116

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 117

doc.: IEEE 802.22-05/0105r1

Submission

Self-Coexistence

• The general problem

TDMA Schedule

November 2005


Slide 118

doc.: IEEE 802.22-05/0105r1

Submission

Self-Coexistence (cont.)

• Indeed a major issue– E.g., 802.16h

• Becomes even more critical in 802.22 given– The large coverage

range

– Its unlicensed nature

• Directional antennas at CPEs do not address the problem

November 2005


Slide 119

doc.: IEEE 802.22-05/0105r1

Submission


• Some approaches to better self-coexistence– Over the backhaul

• Pros– 802.22 can wash its hands (throw the “hot potato” to somebody else)

• Cons– Will there be really a “common backhaul” between competing WISPs? Can 802.22

rely on that?

– What if this “common backhaul” is down?

– Can 802.22 rely on the “upper layers” to take care of self-coexistence?

– Coordination is an active process (e.g., quiet periods), and not a “once-in-a-month thing”

– Over-the-air• Pros

– Built-in and self-healing 802.22 system

• Cons– More complex MAC layer (but just a little more)

November 2005


Slide 120

doc.: IEEE 802.22-05/0105r1

Submission


• Two solutions are proposed– BS beacon based– The Coexistence Beacon Protocol (CBP)

• Both solutions:– Can be implemented either over-the-air or via a backbone

• Here, we focus on the over-the-air implementation

– Allow either one-way or two-way (i.e., negotiation) communication

• The BS and its CPEs shall participate in the self-coexistence task

November 2005


Slide 121

doc.: IEEE 802.22-05/0105r1

Submission


• BS beacon based– Implemented through

overheard BS beacons

– BS beacons carry various information:

• Channels used

• Quiet periods

• Frame information

• Transmit power level

– If needed, can use sensing antenna for this purpose

– Allows better TPC and sharing in frequency only

Case 1:

Case 2:

November 2005


Slide 122

doc.: IEEE 802.22-05/0105r1

Submission


• Coexistence Beacon Protocol (CBP)

– CBP is executed by CPEs but under BS control

– CPEs transmit coexistence packets carrying two types of information

• About the cell

• About a CPE’s reservations with the BS

– Allows better TPC and sharing in both frequency and time

CBP beaconCBP beacon

November 2005


Slide 123

doc.: IEEE 802.22-05/0105r1

Submission



...

MAC Slot Number

Pre

am

ble

FCH

DS

-MA

PU

S-M

AP

Self-

coexi

stence

Ranging

UCS Notification

Burst CPE #4

Burst CPE #2

Burst CPE #1

Burst CPE #5

Burst CPE #3

Burst CPE #7

Burst CPE #1

Burst CPE #2

Burst CPE #4

Burst CPE #5

Burst CPE #3

Burst CPE #6

Burst CPE #8

Burst CPE #9

Self-

coexi

stence

Burst CPE #6

Burst CPE #7

Burst CPE #8

TTG

k k+1 k+3 k+5 k+7 k+9 k+11 k+13 k+15 k+17 k+20 k+23 k+26 k+29

TV Channel N

TV Channel N+1

DS US

Log

ica

l MA

C C

hannel N

um

ber

s

s+1

s+2

s+L

BW Request

November 2005


Slide 124

doc.: IEEE 802.22-05/0105r1

Submission

But what does the CPEs do with this information?

• If previously requested by the BS, report it

• Future upstream bandwidth reservation requests can contain time allocation constraints– For example, a CPE can specify: “Give me 100Kb of airtime, but

not between T1 and T2”

• Note on the BS– Traffic Constraint (TRC-REQ/RSP) management messages are

also available to the BS• For example, can be used before the BS allocates any time for the

CPE• Allow the BS to inquire CPE about possible time allocation

constraints

November 2005


Slide 125

doc.: IEEE 802.22-05/0105r1

Submission

Then, what does the BS do about all this?

• If possible and desirable, avoid each other by switching channels

• Better TPC

• Implement “interference-free” scheduling– Sharing in time and

frequency

November 2005


Slide 126

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 127

doc.: IEEE 802.22-05/0105r1

Submission

Synchronization of Overlapping BSs

• The problem– Frames of co-channel overlapping BSs are asynchronous, which makes

coexistence even harder

• Numerous benefits to synchronization– Incumbent protection

• Quiet period synchronization of overlapping BSs• Improved detection

– Self-Coexistence• Logical channel amongst overlapping BSs• Efficient sharing of resources

frame 0 frame 1 frame m...

frame 0 frame 1 frame m...

BS1:

BS2:

Time

November 2005


Slide 128

doc.: IEEE 802.22-05/0105r1

Submission

Synchronization of Overlapping BSs (cont.)

• Synchronization is proposed amongst multiple collocated 802.22 networks

MAC Slot Number

Pre

am

ble

FCH

DS

-MA

PU

S-M

AP

Se

lf-co

exi

ste

nce

UCS Notification

Burst CPE #4

Burst CPE #2

Burst CPE #1

Burst CPE #5

Burst CPE #3

Burst CPE #1

Burst CPE #2

Burst CPE #4

Burst CPE #3

TTG

k k+1 k+3 k+5 k+7 k+9 k+11 k+13 k+15 k+17 k+20 k+23 k+26 k+29

Lo

gic

al M

AC

Ch

an

ne

l Nu

mb

er

s

s+1

s+2

s+L

BW Request

Frame n at BS1:

Frame m at BS2:

Pre

am

ble

FCH

DS

-MA

PU

S-M

AP

Se

lf-co

exi

ste

nce

UCS Notification

Burst CPE #4

Burst CPE #2

Burst CPE #1

Burst CPE #5

Burst CPE #3

Burst CPE #1

Burst CPE #2

Burst CPE #4

Burst CPE #3

TTG

Lo

gic

al M

AC

Ch

an

ne

l Nu

mb

er

s

s+1

s+2

s+L

BW Request

CBP packets

Time

November 2005


Slide 129

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 130

doc.: IEEE 802.22-05/0105r1

Submission

Clustering

• Alleviate much of the redundancy involved in the execution of the coexistence mechanisms – So, very suitable for 802.22– Can be employed in all coexistence

mechanisms, except for the protection of Wireless Microphone services

• Based on key observations– Sensing outcome of close-by CPEs are

likely to be “similar”– CPEs are stationary

• It is a two-step process conducted by the BS– Formation of Physical Cluster– Formation of Logical Cluster

CPE

Cluster

BS

November 2005


Slide 131

doc.: IEEE 802.22-05/0105r1

Submission

Clustering: Physical Cluster (cont.)

• Creation of Physical Clusters is totally localized at the BS– No direct involvement from

CPEs

• The BS groups together CPEs sensing “similar” characteristics of the incumbent signal– Could also be based on location

relative to the incumbent transmitter

CPE

PhysicalCluster

BS

November 2005


Slide 132

doc.: IEEE 802.22-05/0105r1

Submission

Clustering: Physical Cluster (cont.)

• Based on the well-known k-means clustering algorithm

• The algorithm– Initially, no clustering

– CPEs report measurements to the BS (BLM-REP) which constructs incumbent profiles

– Then, the BS runs the clustering algorithm

Frequency

Rec

eive

d in

cum

ben

tsi

gn

al s

tren

gth

Far away (orlow power)incumbent

Nearby (orhigh power)incumbent

November 2005


Slide 133

doc.: IEEE 802.22-05/0105r1

Submission

Clustering: Logical Cluster (cont.)

• Formed by CPEs belonging to different Physical Clusters

• Allows the BS to group those CPEs that are less likely to contend for the same airtime

• CPEs within a Logical Cluster perform the same “coexistence task”

BS

CPE

LogicalCluster

CBP at T1AllCBP at T2

CBP at T3ATSC NTSC All

Exemplary assignment forincumbent measurements:

Exemplary assignmentfor CBP:

DVB

PhysicalCluster

November 2005


Slide 134

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 135

doc.: IEEE 802.22-05/0105r1

Submission

Security Sublayer

• Based on IEEE 802.16e/D12 security sublayer– Generic security framework made specifically for BWA networks

– Meets all the security requirements identified for the 802.22 WRAN Standard

– Deeply studied and improved by various security experts (including IEEE and IETF ones)

• Composed of two sublayers– A Privacy Key Management protocol (PKM) which provides

authentication, authorization and secure key distribution between the BS and the CPE

– An encapsulation protocol which provides data packets protection

November 2005


Slide 136

doc.: IEEE 802.22-05/0105r1

Submission

Security Sublayer (cont.)

• Mutual Authentication of the devices– Either using RSA and digital certificates

– Or using EAP and EAP-method specific credentials

• Authentication of the subscribers (optional)– Using EAP and EAP-method specific credentials

• Authorization based on authenticated CPE and/or subscriber identity– Give access to dedicated service flows

November 2005


Slide 137

doc.: IEEE 802.22-05/0105r1

Submission

Security Sublayer (cont.)

• Data packets encryption– Using strong cryptographic algorithms (AES)

• Management frames integrity protection– Using keyed message authentication codes

• Protection against Deny of Service and other attacks– Protection of management frames against forgery and replay attacks

– Protection of data frames against replay attacks

– Protection of EAP packets during subscribers authentication

– Protection of every key negotiation phase, using digital signatures and random numbers

November 2005


Slide 138

doc.: IEEE 802.22-05/0105r1

Submission


• Introduction




– Security


November 2005


Slide 139

doc.: IEEE 802.22-05/0105r1

Submission

Performance Evaluation

• All aspects of CMAC are being implemented in OPNET– OPNET is considered the most well-reputated and reliable network

simulation tool available today

• In all simulations:– In case of quiet periods (QP), every CPE performs detection in all in-band

channels (e.g., N-1, N, and N+1 in case of a single TV channel)– DFS model is implemented as per the requirements document– No fragmentation or packing

• Some common simulation parameters– Superframe size = 12 frames, where Frame size = 40 ms– Packet size = 1 Kbyte– Detection time per TV channel = 13 ms– 64-QAM rate 2/3 and Symbol time = 310 µs

November 2005


Slide 140

doc.: IEEE 802.22-05/0105r1

Submission

Throughput at the MAC SAP

• Evaluate the throughput of CMAC under varying number of bonded TV channels

• 1 BS and 127 CPEs

November 2005


Slide 141

doc.: IEEE 802.22-05/0105r1

Submission

Throughput at the MAC SAP (cont.)

• Impact of QP on throughput is more confined to high load scenarios– The scheduler

can properly handle this

• Channel bonding provides significant performance improvement

November 2005


Slide 142

doc.: IEEE 802.22-05/0105r1

Submission

Channel Efficiency

• Evaluate the channel utilization– The overall

impact of QPs is only noticeable in high loads

• Fragmentation and packing can improve these figures even more

November 2005


Slide 143

doc.: IEEE 802.22-05/0105r1

Submission

Network Joining Time

• Evaluate, for the worst case scenario, the average network joining time by a CPE– CPEs first scan channel for a

time equivalent to a frame size

– CPE stays in a channel for a superframe duration after that

– This is followed by network entry and initialization

• More efficient algorithms can be easily implemented

November 2005


Slide 144

doc.: IEEE 802.22-05/0105r1

Submission

Network Joining Time (cont.)

• 1 BS and 127 CPEs– BS is powered

up at simulation startup

– CPEs power up at random times

• 802.22 FRD requires joining time under 10 sec

November 2005


Slide 145

doc.: IEEE 802.22-05/0105r1

Submission

Impact on QoS

• Evaluate the impact of quiet periods and incumbents on QoS

• Traffic pattern– A total of 3 Mbps constant

aggregate US traffic

– DS traffic varies between 3 Mbps and 15 Mbps

• All 127 CPEs establish connections with BS

– Out of these, 4 real time (QoS) connections at 32 Kbps each

– Other connections are BE or non-real time

November 2005


Slide 146

doc.: IEEE 802.22-05/0105r1

Submission

Impact on QoS (cont.)

• The overall impact on average downstream delay is very small– QoS can be

satisfied to a large extent

(sec

)

Effect of Queuing

November 2005


Slide 147

doc.: IEEE 802.22-05/0105r1

Submission

Impact on QoS (cont.)

• The overall impact on average upstream delay is not so small as in the downstream case– Despite of

that, QoS can still be satisfied to a significant extent

(sec

)

November 2005


Slide 148

doc.: IEEE 802.22-05/0105r1

Submission

Handling of Incumbents

• Evaluate the detection, notification and recovery capability of CMAC

• 1 BS and 9 CPEs

• TV station starts in-band operation at a random time– Incumbent is detected

during quiet period

November 2005


Slide 149

doc.: IEEE 802.22-05/0105r1

Submission

Handling of Incumbents (cont.)

• Network operation is quickly restored– BS and

unaffected CPEs switch to Backup Channel

– CPEs who do not receive switch message go to Backup Channel after timeout (2 frames)

Channel A Channel B

November 2005


Slide 150

doc.: IEEE 802.22-05/0105r1

Submission

Handling of Incumbents (cont.)

• Evaluate the dynamics of channel bonding – Together with

handling of incumbents

– Network can switch to one or more Backup Channel

Channel A Channel B

November 2005


Slide 151

doc.: IEEE 802.22-05/0105r1

Submission





• Conclusions

November 2005


Slide 152

doc.: IEEE 802.22-05/0105r1

Submission

Conclusions

• Proposed a PHY and MAC that addresses the requirements set forth by the 802.22 WG

• PHY– Based on OFDMA

• Spreaded OFDMA• O-QAM

– Flexible channel configurations (6, 12, and 18 MHz)– TV and Part 74 detection

• MAC– Coexistence is a key feature

• Incumbent protection• Self-coexistence

– CBP and IDRP protocols, superframes, support of channel bonding, etc.

doc.: ieee 802.22-05/0105r1 submission november 2005 carlos cordeiro, philipsslide 1 a cognitive...

Documents