Energy Efficient Resource Allocation in Cognitive Radio Wireless Ad Hoc Networks
Song Gao, Lijun Qian, D.R. Vam · InTech eBooks · 2011
A framework (POMDP) while assuming the transition probability of each channel is known.In Y. T. Hou (2007), the CR spectrum sharing problem is formulated in multi-hop networks with objective to minimize the space-bandwidth product (SBP).However, the transmission power allocated on each subcarrier is assumed to be the same which may lead to significant performance loss.The effect of power control is analyzed in a subsequent work Y. Shi (2007).Dynamic Frequency Hopping Community (DFHC) is proposed in W. Hu (2007) for the spectrum sharing in CR based IEEE 802.22 wireless regional area networks (WRANs) to ensure QoS satisfaction and reliable protection to licensed users.In this chapter, a new constrained optimization problem is formulated and solved that minimizing energy per bit across users subject to QoS and power constraints in a multi-user ad hoc network.A novel concept, "energy-efficient waterfilling", is given in this section that is fundamentally different from the rate-adaptive waterfilling or margin-adaptive waterfilling 2 .I n this case the optimal point is located in the constraint interval rather than on the boundary.In fact, the rate-adaptive and margin-adaptive waterfilling can be considered as special cases of the energy-efficient waterfilling presented in this work.The results obtained provide a valuable insight that the optimal solution of energy efficient resource allocation is not best subcarrier selection for multiple transmitting receiving pairs in an OFDMA network S. Gao (2008).The proposed distributed subcarrier selection and power allocation scheme provides an efficient and practical solution for dynamic spectrum access in CR wireless ad hoc networks employing OFDMA.By combining the optimal resource allocation of individual users and distributed power control, the proposed method guarantees fast convergence speed, computational efficiency and implementation simplicity.Motivated by iterative waterfilling (IWF) algorithm in W. Yu (2002), another distributed solution may be obtained by solving the multi-user distributed channel and power allocation problem iteratively.However, it may take many steps for the iterative algorithm to converge if it converges at all and the delay may be too large to be tolerable.The cost of the additional computation complexity is high.On the contrary, the proposed optimal resource allocation of individual users is easy to obtain and distributed power control algorithm has well-known fast convergence speed.Furthermore, it will be shown that the proposed distributed algorithm performs closely to the global optimal point.