A Case Study of QoS Provisioning in TV-band Cognitive Radio Networks

1. A Case Study of QoS Provisioning in TV-band Cognitive Radio Networks Ashwini Kumar Kang Shin University of Michigan Jianfeng Wang (presenter) Kiran Challapali Philips Research Aug-6-2009, ICCCN 2009, San Francisco

2. Outline • Introduction of TV Whitespace • System & QoS Model • QoS-Provisioned DSA Protocol (QPDP) Overview • Distributed Reservation & Channel Access • Network & Spectrum Management • Evaluation • Conclusion

3. What is TV Whitespace • TV Band Incumbents – TV, WM • TV bands only sparsely used today (see graphic) • Fewer and fewer US households rely on over-the-air TV (from FCC report) • 33 % in 1994, 15 % in 2004 • Among these, on average only a few channels watched • TV bands have nice propagation characteristics for various applications • FCC has taken steps on opening TV bands for unlicensed use Source: New America Foundation Source: FCC. Reported by New America Foundation

4. White space regulatory milestones – US Notice of Proposed Rule Making Notice of Inquiry Public Notice 2005 2004 2003 Sep.2006 Initial R & O and Further NPRM Report on Interference Rej. Cap. of DTV Rx’s Report on Sensing, Interference to DTVs & Other Radios Oct. 2006 Mar. 2007 July 2007 Mar. 2008 Sensing Proto Testing June 2008 Aug. 2008 Dec. 2008 Feb. 2009 Nov. 2008 ?. 2009 Philips CompleteCR Demo @ FCC Final rules in Federal Registry Final Rule and Order Field Tests

5. FCC 2nd Report and Order • Personal/Portable TVBD (unlicensed) Devices • Up to 100mW; limited to 40mW if operating in adjacent channels. • Any channel between 21 and 51, except channel 37. • Mode II device (Master device) must employ geo-location database to determine channel availability. • Mode I device (Client device) operates under signaling control of Mode II device. • All devices should also employ sensing mechanism to determine channel availability. • Incorporate a dynamic frequency selection (DFS) mechanism and transmission power control (TPC) mechanism. • Sensing only device operates <= 50mW.

6. System & QoS Model • Personal/portable TV band unlicensed devices equipped with one radio • Cast study to provide HDTV streaming in home WLANs • QoS met for multimedia traffic Cable/Internet AP (Residential Gateway)

7. Design Challenge • Complexity and overhead for coordinating sensing incumbents as low as -114dBm • in personal/portable mobile environments • Incumbents’ interference and interruption • Stringent requirements of real-time multimedia traffic (e.g., HDTV streaming) • Narrow channel-width (6 MHz) • Not much chance to use multiple contiguous channels

8. Self coexistence issue • Resource sharing and QP synchronization across neighboring networks

9. QPDP Overview • QPDP logically consists of Lower & Upper MAC • Upper MAC • Spectrum management and network management • Based on overlay master-slave architecture • Lower MAC • Slot reservation • Self-coexistence QPDP MAC architecture

10. QPDP Lower MAC functions • Channel access follows time-recurring superframe structure • Each superframe consists of 256 MASs • MASs divided between BP, DSSP, SW • Distributed beaconing and channel reservation • MASs reservations negotiated through beacons • BP merge for multiple network coexistence

11. QPDP Upper MAC Functions • Overlay master manages channel, sensing and device association • Channel management made intelligent to reduce disruptions • Prioritized channel list • Backup channels • Channel-imaging • Multi-level spectrum sensing to minimize overheads • Multiple short QPs within CDT • Long QPs scheduled on-demand • Network entry & device discovery automated through boot-up scan and beacons

12. Evaluation Setup • To analyze QPDP performance w.r.t. QoS provisioning • Efficiency in supporting high data-rate, low error-rate & delay • Robustness in response to incumbent disruptions • Simulations using OPNET Modeler • Home network setting, with HDTV streaming as multimedia application • Simulation parameters: • Sender-receiver pair, distance=30m • Exponential rayleigh multipath fading • Transmit power=30dbm, path loss factor=3 • PHY based on OFDM: 128 FFT

13. Results • Requirements of HDTV streaming achieved (~19.3 Mbps, <100ms delay, BER<0.05) with proper setting • Impact of sensing schedule: • FS-1 to FS-6: same long-term overhead , differ in short-term • Recovery is quick in both low & high-power incumbent case

14. Results (contd.) • Combining fast sensing with fine sensing performs better • Delay is sensitive to short-term sensing schedule

15. Results (contd.) • Fast incumbent detection and optimized channel-switch minimizes traffic loss and sustains QoS • Packet aggregation very useful in sustaining QoS

16. Conclusion • Presented a system study of HDTV streaming over single TV channel • Proposed QPDP incorporates both fine-grained and coarse-grained QoS mechanisms, including: • Distributed beaconing and channel reservation • Overlay based Master-Slave based spectrum management • Results and discussions reveal the impact of key design parameters on QoS

17. Questions? Jianfeng.wang@philips.com

18. Backup Slides

19. System Parameters

20. PHY-OFDM parameters

21. MAC Parameters

22. UHF Band After Digital Switch Over in UK Source: Ofcom Consultation Feb. 16 2009

23. Ofcom on TV White Space • Released consultation on White Spaces on Feb. 16 2009, with comments due by May 01 2009. Awaiting next statement. • Proposed parameters: Source: Ofcom Consultation Feb. 16 2009