1 Spectrum Co-existence of IEEE b and a 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 b and a 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 b and a 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 b 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 b and a 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 b 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

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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 (ΔI i (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 is SINR imin

15 Spectrum Coordination Policies (cont’d) Node i will broadcast a CSCC message with power Pt i (cscc) The received power Pr ki (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 G ik (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 Pt k (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 b and a System Framework

18 Co-existence of IEEE b and a (cont’d) The SINR at the receiver j can be expressed as: where 0 ≤α lj (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 b hotspot in one a cell Applying CSCC frequency adaptation Applying CSCC power adaptation

21 Simulation (cont’d)

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

23 Simulation (cont’d) - Simulation results Multiple b hotspots with varying a SS geographic distributions in one a cell Two distribution regime (i) Randomly distributed inside the cell (ii) Clustered around each hotspot R max11 : max hotspot radius R c : cluster radius C i : clustering index R max11 /R c 0 ≦ C i ≦ 1 the lager C i, 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 larger Clustering 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