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Enabling Co-channel Coexistence of 802.22 and 802.11af Systems in TV White Spaces

Enabling Co-channel Coexistence of 802.22 and 802.11af Systems in TV White Spaces. Xiaojun Feng , Qian Zhang, and Bo Li Hong Kong University of Science and Technology IEEE ICC 2013. Outline. Background Coexistence Problem Busy-tone based Coexistence Framework Simulation Results

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Enabling Co-channel Coexistence of 802.22 and 802.11af Systems in TV White Spaces

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  1. Enabling Co-channel Coexistence of 802.22 and 802.11af Systems in TV White Spaces XiaojunFeng, Qian Zhang, and Bo Li Hong Kong University of Science and Technology IEEE ICC 2013

  2. Outline • Background • Coexistence Problem • Busy-tone based Coexistence Framework • Simulation Results • Conclusions

  3. TV White Spaces • TV White Spaces • Free TV channels after Analog to Digital Transition • FCC rules • Sep. 2010

  4. Standards • IEEE 802.22 • Target: Wireless Regional Area Networks (WRAN) • MAC: TDMA-like • Power: 4W (36dBm) • Sensitivity: -97 dBm. • Range: up to 100 km

  5. Standards • IEEE 802.11af • Target: Wireless Local Area Networks (WLAN) • MAC: CSMA • Power: 100mW (20dBm) • Sensitivity: -64 dBm. • Range: about 1km Source: MSR

  6. Heterogeneities • 802.22 and 802.11af are different at almost all levels in the protocol stack. • Comparison of some key specifications

  7. Outline • Background • Coexistence Problem • Busy-tone based Coexistence Framework • Simulation Results • Conclusions

  8. Coexistence Problem • Challenge 1: Hidden Terminal to 802.22 • Low sensitivity of 802.11af • 802.11af cannot detect 802.22 and becomes a hidden terminal • Challenge 2: Exposed Terminal to 802.11af • High transmission power of 802.22 and TDMA MAC • 802.11af can be badly blocked

  9. Illustrated Example • A: 802.22 Base Station (BS) • B: 802.22 CPE • C: 802.11af access point (AP) • D: 802.11af client device

  10. Illustrated Example • Challenge 1: Hidden Terminal to 802.22 • Distance between A and B/C: • Distance between B and C/D: • Interference from C to B: • Signal from A to B:

  11. Illustrated Example • Challenge 2: Exposed Terminal to 802.11af • Distance between B and C/D is • Distance from C to D is • Interference from B to D: • Signal from C to D:

  12. Existing Solutions • 802.19 protocol • Centralized control • Assume devices have common interface • [7] X. Zhang and K. Shin, “Enabling Coexistence of Heterogeneous Wireless Systems: Case for Zigbee and Wi-Fi”, in ACM MobiHoc 2011. • [8] H. Rahul, N. Kushman, D. Katabi, C. Sodini, and F. Edalat, “Learning to Share: Narrowband-Friendly Wideband Networks”, in ACM MobiCom 2008.

  13. Our New Observations • 802.22 node has two antennas in both BS and CPE • TX/RX antenna: • BS: omni-directional antenna • CPE: directional antenna • Sensing antenna: • Omni-directional • We can leverage the sensing antenna for busy tone

  14. Outline • Background • Coexistence Problem • Busy-tone based Coexistence Framework • Simulation Results • Conclusions

  15. Basic Idea of Busy-tone • Let the sensing antenna at the 802.22 CPE send out busy-tone signal with known pattern with 100 mW power. • Self-interference cancellation at the 802.22 CPE

  16. Busy-tone Design • Busy-tone Feasibility • 70 dB self-interference cancellation can be achieved in the literature • Busy-tone Duration

  17. Busy-tone Design • Exposed CPE detection • Leverage the busy-tone pattern at the CPE. • First weak patterned busy-tone signal • Then strong non-patterned 802.22 signal

  18. Outline • Background • Coexistence Problem • Busy-tone based Coexistence Framework • Simulation Results • Conclusions

  19. Simulation Setup • The distance between the 802.22 BS and CPE: 5km~15km • We randomly generate one 802.11af AP and one 802.11af client within the carrier sense range of the busy-tone • Results are averaged with 10000 randomly generated topologies.

  20. Simulation Scenarios • 802.11 only • Only the 802.11af network occupying the entire channel • 802.22 only • Only the 802.22 network occupying the entire channel • Coexistence without busy-tone • Coexistence with busy-tone

  21. Impact of the Busy-tone Scheme on 802.22 Throughput

  22. Impact of the Busy-tone Scheme on 802.11af Throughput

  23. Impact of the Busy-tone Scheme on the Total Throughput

  24. Outline • Background • Coexistence Problem • Busy-tone based Coexistence Framework • Simulation Results • Conclusions

  25. Conclusions • We investigate the coexistence scenario and identify the coexistence challenges between the 802.22 and the 802.11af networks. • We proposed a busy-tone based scheme to enable the co-channel coexistence of the two systems. • Through extensive simulation, we show that the spectrum utilization can be increased with the proposed scheme.

  26. Thanks! Enabling Co-channel Coexistence of 802.22 and 802.11af Systems in TV White Spaces XiaojunFeng xfeng@cse.ust.hk

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