1. E FFICIENT UTILIZATION OF RADIO SPECTRUM BASED ON DSA Ali Fotowat Ahmady – Faculty of EE, Sharif University Of Tech 12 th Session of SATRC Feb. 28, 2011

2. W HY DSA? Value of frequency spectrum in wireless systems Fixed freq allocation Increase of users, needs and introduction of new services Scarcity of freq spectrum 2 Cognitive Radio Dynamic Spectrum Allocation Dynamic Spectrum Access

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4. M ATURITY OF CR 4

5. SDR Complete adjustability through software of all radio operating parameters. Hardware Architecture of SDR 5

6. CR When a radio is aware, adaptive, and learns, it is a CR. Cognition cycle 6

7. CR N EEDS Sensors creating awareness in the environment. Actuators enabling interaction with the environment. Memory and a model of the environment. Learning and modeling of specific beneficial adaptations. Specific performance goals Autonomy Constraint by policy and use of inference engine to make policy-constrained decisions 7

8. C OMMERCIALIZATION ROADMAP OF COGNITIVE RADIO 8

9. CR SPECTRUM SHARING 9

10. T RANSMIT POWER ALLOCATION C OMPARISON WITH UWB 10

11. T ECHNICAL CHALLENGES Spectrum sensing Detect spectral holes to opportunistically use bands without causing harmful interference to legacy systems RF front-end and signal path Wideband elements Nonlinearity and LO Harmonics Adequate IP2 Dynamic frequency selection: DFS Adaptive modulation Power control, Sharing Management 11

12. S ENSING D ETAILS 12

13. S ENSING C HALLENGES Hardware High sampling rate, High resolution ADCs with large dynamic range High speed signal processors Broad band RF components Hidden Primary User Detecting Spread Spectrum users such as FHSS or DSSS Sensing Duration and Freq(period). Security 13

14. H IDDEN PRIMARY USER PROBLEM 14

15. S PECTRUM S ENSING M ETRICS Bandwidth Resolution Freq  Trade-off between the detection time and the detection bandwidth and the sensing resolution 15

16. S PECTRUM S ENSING M ETHODS Energy Detection Time domain Freq domain Feature based detection Matched filter Cyclostationary detection 16

17. E NERGY D ETECTOR Output is compared to the predefined threshold. Non-coherent, optimal, low signal processing. Binary hypothesis 17

18. F EATURE BASED SENSING Known patterns: Preambles, Midambles, Regularly transmitted pilot patterns, Spreading sequences. Correlative sensing with a known copy of signal. Applicable to systems with known signal patterns More performance with longer length known signal patterns. 18

19. C OOPERATIVE SENSING Solve noise uncertainty, fading, and shadowing Solve hidden primary user problem Decrease sensing time Spatial spectral joint detection Wide-band sensing 1. centralized sensing(a central unit collects sensing information from cognitive devices, identifies the available spectrum, and broadcasts this information to other cognitive radios or directly controls the cognitive radio traffic.) 2. Distributed sensing(cognitive nodes share information among each other but they make their own decisions as to which part of the spectrum they can use) 3. External sensing(an external agent performs the sensing and broadcasts the channel occupancy information to cognitive radios) 19

20. R ELATED S TANDARDS IEEE 802.22 WRAN fixed wireless access services support 6, 7 and 8 MHz channels OFDMA PHY layer Each station in an 802.22 network is required to perform spectrum sensing final decision as to the availability of a channel is made by the base station. Sensing is required for analog television, digital television and wireless microphones. required detection time for all types is 2 seconds. the probability of detection is 0.9 probability of false alarm is 0.1 20

21. O THER S TANDARDS FOR UNLICENSED ACCESS AND SENSING CAPABILITIES 802.16h – Unlicensed WiMAX license-exempt operation of 802.16 networks, that is defines a set of cognitive radio capabilities for Wimax networks. 802.11af – TV white space WiFi CogNeA – Industry standard for personal/portable application on the TV white spaces 802.19.1 - TV White Space coexistence standard 21

22. E XAMPLE OF I MPLEMENTED C IRCUITS receiver with a CR spectrum sensing capability in the UHF band A Fully Integrated UHF-Band CMOS Receiver With Multi-Resolution Spectrum Sensing (MRSS) Functionality for IEEE 802.22 Cognitive Radio Applications, Jongmin Park, Taejoong Song,, Joonhoi Hur, Sang Min Lee, Jungki Choi, Kihong Kim, Kyutae Lim, Chang-Ho Lee, Haksun Kim, and Joy Laskar, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 44, NO. 1, JANUARY 2009. 22

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24. R ESULTS 24

25. E XAMPLE OF I MPLEMENTED C IRCUITS Injection locking based sensing method A Novel RF Sensing Circuit Using Injection Locking and Frequency Demodulation for Cognitive Radio Applications”, Chien-Jung Li, Fu-Kang Wang, Tzyy-Sheng Horng, and Kang-Chun Peng, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 57, NO. 12, DECEMBER 2009. 25

26. E XAMPLE OF C OMMERCIAL PRODUCTS X G T ECHNOLOGY BSN250 Base Station TX70 Mobile VoIP handset xMSC mobile switching center Advanced cognitive radio capabilities (detect and avoid, edge-device driven handoffs, proactive alternate channel/path determination) translates the concept of mobile phones to the (unlicensed) band of 900MHz. The core of technology is it capability of sensing for other systems in the band and determine if interference has reached unacceptable levels, and in such case change band. 26

27. Thanks. 27