© British Telecommunications plc Cognitive Radio Research at BT

© British Telecommunications plc

Cognitive Radio Research at BT

Dr Maziar NekoveeBT Innovate and Design & University College London

[email protected]


Demand for mobile wireless communications

But also • Home networks (e.g.

HDTV streaming)• Smart metering• RFID• Machine-to-machine

(e.g. intelligent transport systems)

• Developing countries


Key resource: Radio Spectrum

UK Industry paid over 20 billion pound for 140 MHz 3G spectrum


Who “owns” all the spectrum and why is it scarce?


Solution 1: spectrum trading (Cave’s Report)

Command & Control Zone

Ofcom manages it

Market Forces ZoneCompanies manage it

Licence-exempt Zone Nobody manages it

Approach that was adopted for about 94% of

the spectrum

Approach advocated by Cave and implemented

by trading and liberalisation

Approach currently adopted for 6% of

spectrum, some argue for radical increase

2004 6% 7% 20102004 0% 72% 20102004 94% 21% 2010

Source: William Webb, Ofcom


Solution 2: Opportunistic Spectrum Access

Source: Yucek and Arsalan, IEEE Comm. Surveys and Tutorial, 2009


Cognitive RadioEnabling technology for OSA, …and much more

Cognitive Cycle Joseph Mitola III


Cognitive Access to TV White Spaces: Spectrum Opportunity and Technology Challenges


What are TV White Spaces?

Cognitive radios can use channels {A1,A2,A3,B1,B2,B3,C1,C2,C3

Provided they do not cause harmful interference to TV receivers within the coverage areas of A, B, C, and to wireless microphones (PMSE)


How much TVWS is there?

Source: Ofcom Consultation on Cognitive Access, 9 February 2009

256 MHz interleaved spectrum (total UK 3G spectrum 140 MHz!)

US auction of cleared TV spectrum raised $25 billion in 2008

However, the availability varies strongly with location and trasmit power, but how exactly?


Quantifying TVWS availability in the UK

'( , ) | |cr M MM

r P r r R

1/

th

' 1

: Service radius of TV transmitter M (from database)

, : tranmit powers of TV,CR transmitters

: sensitivity threshold of TV receivers

: pathloss exponent

crM M th

M

M

M cr

PR R

P

R

P P

cognitive device

'( , ) | |cr M MM

r P r r R r r

Total number of available channels for CR at location r


Regional variations in TVWS spectrum for cognitive access

8 MHz/channels

London

Cam

bridge

Cardiff

Ipswich

Edin

burgh

Sou

tham

pton

Liverpool

Source: Nekovee, Proc. IEEE ICC 2009

Bristol

Manchester

Sw

ansea

Leeds

Plym

outh

Oxford B

irmingh

am

Glasgo

w

Thuriso N

ewcastle

Brig

hton

0n average 150 MHz at any location in the UK


Spectrum identification/interference avoidance

• Single-device detection – Sensing below thermal noise

levels!

• Cooperative detection– Certification difficult– Spectrum sensor nets– Security issues

• Spectrum database– Favoured by FCC and Ofcom

Microsoft, Google and BT– Wireless microphones are tricky– Requires location-awareness


Detecting DVBT signals below noise levels

• Energy detection

• Feature detection (increased complexity)

– Autocorrelation– Cyclic prefix– Eigen value detection

Source: Wang, Pervez, Nekovee, 2009


Potential applications: system-wide studies Home Networks Rural Broadband

Mobile Broadband without 3G/4G?

IEEE 802.22 standard

Living Room

Bedroom 1Bedroom 2

Kitchen

Den

Deck/Patio

Broadband Internet Connection

CogNea Standard


Proposition A: Home Networks

TVWS Set-top Box

HDTV data via TVWS

HDTV

mobile device BT Homehub

network

BT TVWS database

1. Queries TVWS database

2. Provides available TVWS channels and power levels

device data via WiFi

• Architecture– Point-to-Multipoint– Master-Slave

CogNea Standard (Philips, Samsung, BT)


Interference study, scenario modeled

• Square kilometre of central London• 40% houses (out of total 5000)

selected with home hubs• Same service requirement 2 Mb/s, 6

Mb/s @ 12m range• With three interference loadings

– Video-streaming only traffic profile – worst case scenario

– Traffic profile mix of voice, video, data corresponding to 2 Mb/s

– Traffic profile mix of voice, video, data corresponding to 6 Mb/s

TVWS Spectrum in Central London

available channels

Source: Kawade, Nekovee, IEEE DySPAN 2010 (submitted)


Technical assumptions for comparing various options

Parameters LTE HSPA [email protected] GHz 11n [email protected] GHz 11n802.11 TVWS

Centre Frequency 2.6 GHz 2.1 GHz 2.4 GHz 5.4, 5.8 GHz 400-862 MHz

EIRP 20d dBm 14 dBm 20 dBm 23, 30 dBm 3, 9 dBm

Channel Bandwidth 20 MHz 5 MHz 20 MHz20 (40 MHz

optional) 8 MHz

Antenna scheme None None 2x1 STBC 2x1 STBC None

Wireless Interface OFDM D/L CDMA OFDM OFDM OFDM

Duplex FDD FDD TDD TDD TDD

Modulation & Coding schemes

1/2, 3/4 QPSK1/2, 3/4 16-QAM

1/2, 2/3, 3/4, 5/6, 1/1 64-QAM

1/2, 3/4 QPSK1/2, 3/4, 5/6, 1/1 16-

QAM5/6, 1/1 64-QAM

1/2, 3/4 BPSK1/2, 3/4 QPSK1/2 16 QAM

2/3, 3/4 64 QAM

Other assumptions: • MAC layer overheads were assumed to be approximately 30% of the raw wireless link rate• No antenna scheme considered for TVWS band due to λ/2 restriction

however CogNeA (Philips, Samsung, Texas, HP) propose some antenna scheme/MIMO for laptops in higher UHF (in the other end of TVWS spectrum)


Outage clients (< 1 Mb/s) : 3%

Service requirement 2 Mb/s: 97%

Service requirement 6 Mb/s :50%

TVWS performance results (3/3)

Source: Kawade, Nekovee, IEEE DySPAN 2010 (submitted)


Nomadic/Mobile broadband with BT FON

•Cooperative scheme for sharing home WiFi

•Over 1 million BT FONs, and growing

TV transmitter


Cognitive Radio: A longer term view


A quasi-continuum spectrum

CR2CR1 CR3

Now Future

Dynamic spectrum pooling based on user requirements, availability, and price

An elementary sub-channel

Source: Nekovee, Proc. CrownCom 2008


Spectrum portfolio

Choose a spectrum band Click on the item below to connect to BT Network via one of the available spectrum bands

TV White Spaces

free of charge (cognitive only)

free of charge (cognitive only)

3G Spectrum Vodafone

£0.0012 per second (licensed or cognitive only)

Radar spectrum

ISM bands

free of charge (best effort)

2G Spectrum Orange


3G Spectrum 3


Refresh spectrum list

Setup an automated spectrum manager

Learn about cognitive spectrum access

Change the order of preferred spectrum

Change advanced settings

Cognitive Spectrum Access


Our research interests/activities

• Technologies and models• System-wide issues: multi-user access (etiquette), capacity and

coverage, QoS and mobility• Agile modulation (NC-OFDM) and channel bundling techniques• Cognitive radio testbed and trials • Sensing, antenna arrays and MIMO for cognitive access• Cognitive radio +optical communication?• Spectrum micro auctions• Spectrum databases

• Application Scenarios• Future home networks• Mobile/nomadic broadband• Smart metering • Cognitive Femtocells• Cognitive radio in vehicles

Collaborations

•2 large FP7 projects (starts Jan 2010)

•Microsoft, Google, BBC, CogNea

•Scottish Universities

•Open to exploring new ones!


In press

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