Delay-aware Cross-layer Design In Green Communication System

In recent years,to improve the quality of communication at a relative low cost,energy efficient techniques have been applied in the wireless communication system-s.However,these energy efficient designs are all based on the physical layer designs.Considering the fact that upper layer service is difficult to obtain the Quality of Service(QoS)of delay in the physical layer designs,it is necessary to investigate the energy efficient design which takes delay requirements into account.In this dissertation,en-ergy efficient cross-layer designs are investigated for the multiple input and multiple output(MIMO)systems and the cooperation system.By exploiting the intrinsic relationship among the constellation size,the packet size,the symbol error rate(SER)and delay,we propose an adaptive transmission mode for different delay demands for MIMO systems.For the case of user's buffer overflow,we use the congestion control algorithm to schedule the average queue length,and maintain the optimal delay performance for energy efficiency.Simulations show that in order to maximize the energy efficiency and offer different QoS of delay simulta-neously,the transmitter should adaptively choose the constellation size and the packet size as well as the transmission mode between the MIMO and single input and multiple output(SIMO).In the current cellular systems,different users may have different delay-aware services.The energy efficient designs have attracted much research attention is this case,especially for the multi-user MIMO(MU-MIMO)systems.We propose adap-tive techniques for MU-MIMO cellular communication systems,to solve the problem of energy efficient communications with heterogeneous delay-aware traffic.In order to minimize the total transmission power of the MU-MIMO,we investigate the relation-ship between the transmission power and the M-ary quadrature amplitude modulation(MQAM)constellation size and get the energy efficient modulation for each transmis-sion stream based on the minimum mean square error(MMSE)receiver.Since the total power consumption is different for MU-MIMO and multi-user single input and multi-ple output(MU-SIMO),by exploiting the intrinsic relationship among the total power consumption model,and heterogeneous delay-aware services,we propose an adaptive transmission strategy,which is a switching between MU-MIMO and MU-SIMO.Fi-nally,the methods we have proposed are verified to have the better performance than the existing method.On the other hand,the service state is a challenging problem for the energy ef-ficient communications of the practical application.We propose a cross-layer design framework for transmitting Markov modulated Poisson process(MMPP)traffic over Nakagami-m fading channel with delay demands.The adaptive modulation and cod-ing(AMC)technique is used at physical layer,where both of throughput and transmit power have full consideration of the queuing system.We first derive the closed-form expressions of the delay and the energy efficiency with the stationary distribution of the system.We then derive the energy efficient thresholds to choose the AMC trans-mission modes.At last,we derive the transmission policy to maximize the energy efficiency with delay constraints.Numerical results are provided to support the theo-retical development.To further extend the coverage of the wireless communication with lower costs,data transmission in the long distance is completed with the aid of the relays.Then we propose a cross-layer design framework for transmitting MMPP traffic over cognitive cooperative networks.The AMC is also used in the cooperative transmission system.The queuing process is considered in the buffer aided relay and source.We first inves-tigate the energy efficiency for both the direct transmission and relay assisted trans-mission.We obtain an optimum strategy of power and time allocation to maximize the energy efficiency of the relay assisted cooperative system.With the stationary distri-bution of the system state,we derive the closed-form expression of the delay and the energy efficient transmission policy with AMC.Then,we derive the energy efficient strategy for packet transmission with different delay requirements,which is switching between the direct transmission and the relay assisted transmission.In summary,energy efficient wireless communications for delay-aware services are proposed and closed-form solutions are derived in this paper.Our study not on-ly enriches the state-of-art results of the energy efficient cross-layer design,but also provides guidelines for the practical system.