Research On Channel Sparsity And Allocation Of Transferred Power In Cloud Radio Access Network

With the rapid growth of mobile traffic and the increasing number of wireless multimedia services,the traditional cellular wireless access network will not meet the growing requirements of users in the future,which forces operators to propose a brand-new access network architecture with high capacity,low cost and low power consumption.Cloud radio access network(C-RAN)is considered as one of the most promising approaches for future 5G systems.Unlike the conventional cellular base stations,C-RAN can provide great convenient for coordinated signal processing and flexible interference management.However,due to dense coverage of Remote Radio Heads(RRHs),high computational complexity and energy consumption are caused by full-centralized cooperation processing.Meanwhile,to meet the required coverage,some wireless nodes have to be arranged in places with no external energy.In this paper,a channel sparsity scheme with channel estimation error and a rechargeable RRH scheduling scheme are proposed to tackle these two challenges.First,to approach the high computational complexity of joint processing of baseband signals in large C-RANs,the research of channel sparsity is extend to practical scenarios,in which the perfect channel state information(CSI)is not available.A tractable lower bound of signal-to-interference-plus-noise ratio(SINR)fidelity is derived to evaluate the impact of channel sparsity.A Dinkelbach-based algorithm is proposed to achieve the global optimal performance of channel matrix sparsity based on the criterion of distance.Simulation results are shown to evaluate the performance of channel matrix sparsity with imperfect CSI and verify our analytical results.Second,self-sufficient rechargeable RRHs are introduced in C-RAN to work with traditional RRHs in this paper.According to the current status of energy harvesting technology and the characteristics of C-RAN itself,a scheduling strategy of rechargeable RRHs is designed in our work.Through modeling and simulation,this strategy is proved to be capable of improving the communication quality of ill-performing users of the system.Meanwhile,some important parameters in the proposed scheme,such as the number of rechargeable RRHs and time length of scheduling cycle are discussed in this paper.