Spectrum Co-existence of IEEE 802.11b and 802.16a Networks using the CSCC Etiquette Protocol

1. Spectrum Co-existence of IEEE 802.11b and 802.16a Networks using the CSCC Etiquette Protocol Xiangpeng Jing and Dipankar Raychaudhuri, WINLAB Rutgers University IEEE DySPAN 2005 Presenter: Han-Tien Chang

2. Outline • Introduction • The CSCC Protocol • Spectrum Coordination Policies • Co-existence of IEEE 802.11b and 802.16a • Simulations • Conclusion and Future Work • Comments

3. Current WiMAX spectrum status • Korea (WiBRO): 2.3~2.4GHz • Taiwan (Mobile: 2.5~2.68GHz, Static: 3.5GHz, 700MHz) • India: 2.5~2.69GHz、3.4~3.6GHz、2.3~2.4GHz and 700MHz • America: 2.5~2.7GHz • U.S. • Japan (2.5~2.69GHz) • Europe: 3.4~3.6GHz

4. Introduction • Feasibility of spectrum co-existence between IEEE 802.11b and 802.16a networks • In the same unlicensed band (2.4GHz) • Using the Common Spectrum Coordination Channel (CSCC) etiquette protocol • Common Spectrum Coordination Channel • A common edge-of-band control channel for coordination between transceivers using different radio technologies • In [2], implement between 802.11b and Bluetooth • Consider wide-area/short-range hybrid scenario currently • Hidden-receiver problems [2] D. Raychaudhuri and X. Jing, “A spectrum etiquette protocol for efficient coordination of radio devices in unlicensed bands,” In Proceedings of PIMRC 2003, Beijing, China, September, 2003.

5. Introduction (cont’d) • Reactive cognitive radio techniques • In [5], based on channel sensing and distributed adaptation of transmit parameters such as frequency, power, bit-rate, and time occupancy • Only on local observation • Hidden-receiver problems • CSCC Protocol • Listening to announcements and broadcasting its own parameters at CSCC Channel • Frequency, power, modulation, duration, interference margin, service type, etc. [5] X. Jing, S. Mau, D. Raychaudhuri and R. Matyas, “Reactive Cognitive Radio Algorithms for Co-Existence between IEEE 802.11b and 802.16a Networks,” will appear In Proceedings of IEEE Globecom, 2005.

6. Introduction (cont’d) • Spectrum sharing policies • Resolve conflicts in spectrum demand and share the resource or power • FCFS (First-Come-First-Served), priority or dynamic pricing auction • Specific problem in this paper • Evaluating the CSCC etiquette protocol for co-existence between Wi-Fi and Wi-Max networks. • Discuss the problem under different scenarios

7. The CSCC Protocol • Utilized a simple Common Control Radio • Equipped with each device, which is a low bit-rate, narrow-band radio, such as a prototype IEEE 802.11b 1Mbps radio (Coverage: 600m) • The control channel is at the edge of the available spectrum bands. • Each node announces its parameter to neighboring nodes by broadcasting CSCC messages through the CSCC channel

8. The CSCC Protocol (cont’d) • Spectrum Coordination Policy • Runs on the top of the CSCC protocol stack • Independent from the CSCC protocol mechanism • Reflect regional or application-specific requirements

9. The CSCC Protocol (cont’d) • Since interference needs to be considered at receivers rather than transmitters • CSCC announcements may also be made by receivers involved in active data sessions • How to coordinate? (another transmitter) • Switch to other available spectrum bands • Reducing its transmit power

11. Spectrum Coordination Policies • Coordination by adaptation in frequency

12. Spectrum Coordination Policies (cont’d) • Coordination by adaptation in power • Interference Margin (IM) is defined as the maximum interference power that a receiver can tolerate without disturbing its data communication • Radio nodes can determine appropriate transmit power levels required to reduce interference in a specific frequency band.

13. Spectrum Coordination Policies (cont’d)

14. Spectrum Coordination Policies (cont’d) • The interference margin (ΔIi(n)) can be calculated by: • The received power at node i from node j is Pr(n)ij • Its current signal to interference and noise radio is SINR(n)ij • The minimum SINR required to maintain the on-going communication at node i isSINRimin

15. Spectrum Coordination Policies (cont’d) • Node i will broadcast a CSCC message with power Pti(cscc) • The received powerPrki(cscc)can be reported by the PHY of node k. • The path loss gain of the control channel from node i to node k is Gik(cscc) • Assume the CSCC channel is symmetric, so • The path loss gain in the data channels can be estimated:

16. Spectrum Coordination Policies (cont’d) • We can find out the maximum transmit power of node k at data channel #n then is bounded by the constraint in order not to disturb the signals received at node i: • If Ptk(n) is too small for node k to reach its receiver (node l), • Switch channels seeking a band with less interference temperature or keep silent by backing off it transmissions

17. Co-existence of IEEE 802.11b and 802.16a • System Framework

18. Co-existence of IEEE 802.11b and 802.16a (cont’d) • The SINR at the receiver j can be expressed as: • where 0 ≤αlj(n)≤ 1 is the spectrum overlapping ratio of node l and j at channel #n. • CSCC Implementation (Using NS2) • Each node with a dual radio structure • FCFS-based spectrum coordination policy

19. Simulation • Simulation Parameters

20. Simulation (cont’d) - Simulation results • One 802.11b hotspot in one 802.16a cell • Applying CSCC frequency adaptation • Applying CSCC power adaptation

21. Simulation (cont’d)

22. Simulation (cont’d) 802.16a SS is benefited Average throughput Is improved 802.11b throughput is slightly degraded

23. Simulation (cont’d) - Simulation results • Multiple 802.11b hotspots with varying 802.16a SS geographic distributions in one 802.16a cell • Two distribution regime • (i) Randomly distributed inside the cell • (ii) Clustered around each hotspot • Rmax11: max hotspot radius • Rc: cluster radius • Ci: clustering index • Rmax11/Rc • 0≦Ci ≦1 • the lager Ci, the high interference

24. Simulation (cont’d) - Simulation results

25. Simulation (cont’d) - Simulation results Power adaptation (fixed center frequency at 2412MHz for both systems) Compare with RTPC (Reactive Transmit Power Control) and TA (Time Agility)[5]

26. Simulation (cont’d) - Simulation results The largerClustering Index, the larger interference level between two systems.

27. Conclusion and future work • Using the CSCC spectrum etiquette protocol to explicitly coordinate the two wireless systems and reduce interference. • CSCC coordination can significantly improve system throughput by solving the hidden-receiver problem. • Future work • alternative spectrum coordination algorithms • additional system performance metrics (such as delay and control overhead) • prototype implementation for experimental verification

28. Comments • Like “Pilot Channel” idea • The real network condition • Control packet overhead consideration