Research On Energy Effienercy Resource Optimization For Cooperative Communication Systems

Recently,the demand of high-speed data transmission for people in the wireless communication is increasing dramatically which generate even more enormous energy consumption.Due to the size of mobile terminal and the bottleneck of battery technology,the energy efficiency problem in mobile communication obtain great attention.Meanwhile,how to allocate the scarce wireless resource in order to achieve better spectrum efficiency(SE)and energy efficiency(EE)has become one of research hotspots in the 5G mobile communication system.This dissertation focuses on EE optimization problem in multi-user orthogonal frequency division multiple(OFDM)relay networks.Considering the energy harvest(EH)cooperative communication networks,a joint optimization algorithm of subcarrier pairing and power allocation is proposed.For the scenario of data and energy packets arrival independently and departure interactively,the performance of buffer aided relaying system is analyzed.Furthermore,a nonorthogonal multiple access(NOMA)resource allocation problem in the decode-and-forward(DF)relay downlink networks is addressed.Specifically,the main achievements of this research are as follows:(1)Considering the multi-user OFDM relay networks,a fairness-aware EE resource allocation algorithm is presented.In the proposed algorithm,the source is permitted to retransfer the same data transmitted in the second time slot to provide the diversity gain.With the constraint of the users’ QoS and fairness,a EE optimization model of jointly optimizing the subcarrier pairing and the power allocation is constructed.Then,the optimization model is simplified into a typical fractional programming problem,which is testified to be quasiconcave by deducing equivalent channel gain.On the basis of that,Dinkelbach method,Hungary algorithm and Subgradient algorithm are adopted to get optimal solution,which reduce the compute complexity remarkably.The convergence of the joint EE resource allocation algorithm is also proved.The simulation results indicate that the proposed algorithm is effective for improving EE performance under the minimum system service rate requirement.(2)Considering the OFDM wireless-powered cooperative communication networks(WPCCN),a EH joint resource allocation algorithm is raised.In the WPCCN scenario,the downlink is used for energy transmission and the uplink is for data transferring.In the improved HTC relay strategy,the source retransfer the same data in the last time slot in order to improve system performance.Subject to the total network power constraint,a WPC resource optimization model is constructed which aims at maximizing the average transmission rate of the system.The equivalent channel gain is also deduced to simplify optimization problem in WPCCN.By employing dual approach and Hungary algorithm,the joint optimization problem of subcarrier pairing,power allocation and EH slot assignment is solved.Simulation results show that the proposed joint optimal scheme can efficiently improve system performance.(3)Considering the EH buffer-aided relay cooperative relaying system,a performance analysis of the EH buffer-aided relay is realized.The communication scenario of data and energy packets arrival independently and departure interactively is ascribed as a coupled processor queuing model.Considering the influence of channel condition on the data departure rate,the continuous channel state interval is splitted into several discrete intervals.With fixed size of data packet and energy packet,the system data delay and throughput are improved by permiting exhausting more energy packet to send one data packet in the bad channel environment.Quasi-birth and death method is exploited to deduce steady state transition probability and the expressions of throughput,delay,and packet drop rate for both data queue and energy queue are also derived.Simulations are demonstrated to verify the analytical results under different data arrival rate,energy arrival rate.The proposed APT data and energy coupled mechanism can efficiently improve system performance.(4)Considering the downlink NOMA-based DF relay networks,a joint resource allocation algorithm is proposed.Subject to the total system power constraint and users’ QoS guarantee,an optimization model of joint user-channel assignment and power allocation is formulated which aims at maximization the average user transmission rate.The proposed optimization problem is proved to be a NP-hard problem,which is separated into two subproblems by decouple optimization method.One is a user-channel assignment problem on the base of given power allocation,another is a power allocation problem with fixed user-channel assignment.A league game with transition rule method is proposed to solve the user-channel assignment problem under fiexd power allocation.By employing dual approach and Subgradient algorithm,the power allocation under fiexd user-channel assignment is obtained.After solving the two subproblems respectively,a joint alternating optimization algorithm is proposed based on iterative method.Simulation results show that the proposed joint optimal scheme can efficiently improve system SE in the scenario of the number of channels is smaller than the number of the users.