Cooperative Resource Management in Cognitive WiMAX with Femto Cells Jin Jin, Baochun Li Department of Electrical and Computer Engineering University of Toronto IEEE INFOCOM 2010

Outline Introduction Network Environment Resource Management Policies Performance Evaluation Conclusion

Introduction WiMAX with femto cells is a cost-effective next-generation broadband wireless communication system. –Users that reside in femto cells experience increased throughput due to the shorter ranges. Macro BS Femto BS user a a

Introduction Cognitive Radio (CR) has recently emerged as a promising technology to improve spectrum utilization by allowing dynamic spectrum access. Macro BS Femto BS Primary users a a n n Secondary users

Problem There will be large potential benefits by applying the CR technique to WiMAX with femto cells, which are barely explored in the literature. –Power Control –Flow Routing –Cooperative Scheduling –Interference Avoidance –Buffer Management Macro BS Femto BS Primary users a a n n Secondary users CH1 CH2 CH1 CH2 CH3 CH1 CH2 CH1 CH2 CH3

Goal This paper proposes the resource management policies to maximize the spectrum utilization in cognitive WiMAX with Femto Cells. –Power constraints –Channel Constraints –Cooperative Constraints –Flow Constraints

Network Environment The network consists of one macro BS and F femto cells with A PUs and N SUs, sharing C orthogonal channels supported by OFDMA CH1 CH2 CH1 CH2 CH3 CH1 CH2 CH1 CH2 CH3 Macro BS Femto BS Primary users a a n n Secondary users

Network Environment The network consists of one macro BS and F femto cells with A PUs and N SUs, sharing C orthogonal channels supported by OFDMA. –Each PU resides in a dedicated femto cell and communicates with the corresponding femto BS over one pre-allocated channel to support guaranteed QoS CH1 CH2 CH1 CH2 CH3 CH1

Network Environment The network consists of one macro BS and F femto cells with A PUs and N SUs, sharing C orthogonal channels supported by OFDMA. –Both macro BS and SUs are equipped with ultra-sensitive cognitive radios to perform spectrum sensing and power and frequency adjustment. –SUs are fully mobile and served opportunistically by the macro BS without generating interference to PUs CH1 CH2 CH1 CH2 CH3 CH1 CH2 CH1 CH2 CH3

Network Environment S(t)={S a c (t)} A  C : channel states of PUs on each time slot t –If S a c (t)=0, PU a is using channel c. H(t)={h n c (t)} N  C : channel accessibility information for SUs –If h a c (t)=1, SU n can access channel c. Y(t)={Y a c (t)} A  C : the probability that channel c is not occupied by PU a at time slot t CH1 CH2 CH1 CH2 CH3 CH1

Network Environment P BS (t)={P BS c (t)} C : macro BS’s transmission power on each channel. U BS (t)={  n c (t)} N  C : channel allocation to SU in a macro cell. (for the link between macro BS and SU) P SU (t)={P n c (t)} N  C : SU n ’s transmission power on each channel. U SU (t)={  mn c (t)} NN  C : the cooperative transmission from SU m to SU n CH3 CH1 P BS (t) P SU (t)

Power Constraints CH3 CH1 P BS c (t) Pnc(t)Pnc(t) upper bound of transmission power for BS tolerable level of inference to PU upper bound of transmission power for SU n distance between BS and PU a j: pass loss index channel states of PUs

Channel Constraints channel allocation to SU in a macro cell Macro BS Cooperative comm. m m n n channel accessibility information for SUs interference Cooperative comm.

Cooperative Constraints n n channel state for the transmission from SU m to SU n channel c’ channel c multi-hop cooperative transmissions m m n n m’ channel c channel c’ channel c’’ m m

Flow Constraints n n m m m m throughput (macro) flow rate (cooperative) flow rate

Flow Constraints m m n n fnc[m]fnc[m] f nm c capacity

Resource Management Policies Macro Allocation SU n ’s data buffered in BS n n channel c

Resource Management Policies Cooperative Allocation n n m m buffer: 10 buffer: 5 Interference index (1/0) m m buffer: 20 Interference level Probability that channel c is occupied by PUa PUa

Performance Evaluation Channels: 12 Femto cells: 8 PUs: 20

Performance Evaluation

Conclusion This paper proposes cognitive WiMAX with femto cells and study the resource management problem in the network. –Power constraints –Channel constraints –Cooperative constraints –Flow constraints –Resource management policies TheEND Thanks for your attention !