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Cognitive Radio: Opportunities and Challenges

Cognitive Radio: Opportunities and Challenges. Dr Ying-Chang Liang Senior Scientist & Project Manager Institute for Infocomm Research (I 2 R) Singapore ycliang@i2r.a-star.edu.sg. Spectrum Scarcity due to Regional Coordination Requirement – Singapore Scenario.

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Cognitive Radio: Opportunities and Challenges

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  1. Cognitive Radio: Opportunities and Challenges Dr Ying-Chang Liang Senior Scientist & Project Manager Institute for Infocomm Research (I2R) Singapore ycliang@i2r.a-star.edu.sg

  2. Spectrum Scarcity due to Regional Coordination Requirement – Singapore Scenario • Spectrum Allocation in broadcasting spectrum (174 MHz – 230 MHz) Indonesia’s Batam TVR1 Malaysia’s RTM TV2 Ch5 Ch6 Ch7 Ch8 Ch9 Ch10 Ch11 Ch12 TV Channels used in SG To avoid interference in TV band with Malaysia and Indonesia, Singapore virtually looses 2/3 of the spectrum!

  3. Spectrum Measurement: 174 MHz – 230 MHz

  4. White Spaces Everywhere < 5% M. Habibul, et al, Spectrum Survey in Singapore: Occupancy Measurements and Analyses, presented in CrownCom’2008, May 15 – 17, 2008, Singapore

  5. PU-Rx SU-Rx PU-Tx SU-Tx Opportunities: Cognitive Radio to Improve the Spectrum Utilization Efficiency • Spectrum Sharing • Based on interference temperature • The secondary users co-exist with the primary users • Opportunistic Spectrum Access • Based on on/off activity of the primary users Different cognition levels: on/off status, interference temperature, …

  6. Spectrum Sharing in TV Band:174 MHz – 230 MHz Indonesia’s Batam TVR1 Malaysia’s RTM TV2 Ch5 Ch6 Ch7 Ch8 Ch9 Ch10 Ch11 Ch12 DAB Channels used in SG TV Channels used in SG Wireless Microphone Channels used in SG Spectrum allocation in Singapore

  7. WRAN Base Station Wireless MIC TV Transmitter WRAN Base Station WRAN Repeater Typical ~33km Max. 100km Wireless MIC : WRAN Base Station : CPE Primary users: TV transmission, wireless MIC (microphone) Opportunistic Spectrum Access: IEEE802.22 Wireless Regional Area Networks (WRAN) • Reuse the unused or under-utilized TV bands (54MHz – 862MHz) for broadband wireless access • Co-exist with higher priority users (TV, wireless microphones)

  8. PuTx SuTx PuRx SuRx Challenges in Spectrum Sharing • Is low power transmission for secondary users sufficient? • How low should it be? • Effective ways to estimate interference power received at primary users • Innovative mechanisms are needed especially when primary user does not cooperate

  9. Challenges in Opportunistic Spectrum Sharing • Stringent spectrum sensing requirements • Various types of primary users • e.g., 802.22: TV - 6/7/8MHz, Wireless microphone - 200 kHz (carrier not fixed) • Low SNR environment • in 802.22, TV signals are to be detected at -20 dB SNRwith 90% detection of probability and 10% false alarm probability • Fast wideband sensing • Robust sensing (to noise uncertainty, interference …) • Can the acquired on/off status be used to protect primary users? • Channel asymmetry (fading, Tx/Rx duplex, …) • Shadowing, hidden terminal issue • Transmission power asymmetry

  10. Remarks • There are opportunities to explore “spectrumwhite spaces” • To promote white space reuse (dynamic spectrum access) • technically, though challenging, effective solutions are needed to protect the primary users • economically, good business models are needed to make both primary users and secondary users happy!

  11. Remarks • Cognitive radio -> cognitive radio networks • How to acquire cognition • PHY sensing • Network layer traffic sensing • Cognitive MAC: Control information sharing, cooperation, … • Distributed processing • Other issues (security, trust, …) • Let us work together to make cognitive radio (networks) from imagination to reality!

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