Resource Allocation For QoS-Driven Multicarrier Relay Networks With Energy Harvesting Nodes

Multicarrier relay(MR)cooperative technique,such as orthogonal frequency division multiplexing(OFDM),can improve spectrum utilization,expand the communication range,and reduce the signal attenuation during long-distance communication.Meanwhile,in delay sensitive wireless communication systems,quality-of-service(QoS)is an important factor to measure the system performance.On the other hand,wireless communication systems with energy harvesting nodes can reduce the dependence on external power supply devices,rely on their own energy collection to communicate and achieve the sustainability and stability of communication.Therefore,in an energy harvesting MR(EHMR)communication system,considering the delay QoS requirements,how to allocate resources such as spectrum and power to improve the communication performance of the entire system is an important content of the study on resource allocation.In this thesis,for QoS-driven EHMR communication system,the convex optimization method and robustness optimization method are used to study the subcarrier and power allocation schemes under the certain channel state information(CSI)and uncertain CSI,respectively.Then,the convex optimization problem and the robust optimization problem are formulated and solved.Finally,simulation is conducted to analyze the performance of proposed resource allocation schemes.The main works of the thesis are as follows:(1)The related background of the research on QoS-driven EHMR system is briefly described,such as the development and research on multicarrier relay communications,EH wireless communication,resource allocation in QoS-driven communication networks and research on robust resource allocation in uncertain channel.Moreover,we introduce related mathematical theories,such as convex optimization theory,Taylor approximation,and robust optimization theory.(2)Under the condition of certain CSI,we study the resources allocation in EHMR system.To achieve the goal of maximizing the effective capacity of communication system while meeting the delay QoS requirements,we build the system model and formulate the optimization problem.The optimal resources allocation scheme is obtained by using Taylor approximation,convex optimization theory and the numerical results are solved by subgradient iteration method.In order to reduce the computational complexity,we also propose a suboptimal resource allocation scheme,that is,subcarriers are allocated firstly according to CSI and then we formulate the power allocation problem and solve it.Based on the above,Monte Carlo simulation method is used to verify and analyze the optimal and suboptimal resource allocation schemes.The comparison of several schemes shows that under the same conditions,using the optimal resource allocation scheme proposed in the thesis,we can get the optimal effective capacity and the best communication performance,while meeting the QoS requirements.(3)Considering the condition where the CSI cannot be completely known,we study a robust resource allocation scheme for EHMR system while meeting the delay QoS requirements.Applying the Worstcase method,the channel power gain in uncertain CSI is representd as the sum of the estimated value and the error value,and the error value is expressed as a uncertainty set by the general norm model,while an upper bound is set for the uncertainty set.Under the constraint of harvested energy and QoS requirements,we formulate the robust optimization problem and slove it using the Lagrangian dual method.Then the robust resource strategy is obtained and includes uncertain parameters:the upper bound of uncertainty set and the probability when the channel power gain takes different values in uncertainty set.Based on the above,through theoretical calculation and simulation conduction,we analyse the relationship between the value of channel power gain and the upper bound of the certainty set and the probability,as well as the influence of different parameters including QoS parameters,harvested energy,the upper bound and the probability in the robust resource allocation strategy on the effective capacity of the communication system.It shows that under the uncertain CSI,the robust resource allocation strategy proposed by the thesis can achieve the trade-off between optimal effective capacity and robustness of the wireless communication system.