Research On Pre - Coding Technology In Collaborative Communication

With the rapid increase in demand tor wireless data services, LTE-A need tosupport higher peak data rates、spectral efficiency and performance of the eel I-edgeusers. As a very promising core technology in LTE-A, the cooperative communicationcould effectively expanding the network edge coverage and improving spectraleiffciency by collaborating all the nodes in wireless network transmission. Moreover,it has significant advantages in reducing interference at the cell edge and improvingthe communication quality of the cell edge users.Meanwhile, in order to make this collaborative communications system could getbetter performance; we can introduce prccoding technology into cooperativecommunication system. It will preprocessing the signal of cach transmit Fiodc byutilizing the channel state inofrmation，in order to reduce the bit error rate andimprove the system througliput.This paper focuses on the precoding technology of collaborative communicationfor the following three researches:According to the concept of cognitive radio，we consider a cognitive radioscenario that consists of multi-relay to serve for multi-primary users andmulti-secondary users. Design the precoding matrices for base station and relays tominimize the inaxiimiin MSE value of secondary users, while constraining the MSHof primary users less than a fix value and the power of relays will obey the constrainrequirement. Due to it is a non-convex problem to optimizing the prccoding matrix ofbase station and relays simultaneously, therefore, we adopt the iterative algorithm toreformulate the optimization problem into two SOCP forms. After that，the precodingmatrices of base station and relays can be solved by software package. Finally，simulation results veriyf the proposed schcmc can obtain a better MSE performanceof primary users and secondary users simultaneously.Then, due to tlic two-way relay could obtain higher spectral elficicncy thanone-way relay, vvc consider considers a more general scenario which incorporates multi-pair of primary users and multi-pair of secondary communicate with each otherby the assist of a multi-antenna bidirectional relay. With the assumption that all thechannels suffer from channel estimation errors and a norm-bounded error model, wepropose the relay precoder design that can maximize the minimum value of thesigrial-to-interference-plus-noise-ratio (SINR) of SUs while guaranteeing theinterference experienced at PUs below certain thresholds and transform theoptimization problem into a SDP problem. Then, the optimal precoding matrix can besolved by convex sotfware package. Finally, numerical results demonstrate that theproposed robust precoding algorithm outperforms the non-robust solution in term ofsuppressing the interference.Finally, according to the concept of secrecy capacity, we consider a coordinatedmulti-point transmission scenario with single eavesdropper or multiple eavesdroppersto maximizing the secrecy capacity. We jointly design the optimal precoding for allthe base stations, the problem that maximizes the rate of legal user while constrainingthe rate achieved by eavesdropper can be reformulated into a convex form and allprecoding matrices can be solved simultaneously by CVX sotfware package.Avoiding the defect of the traditional iterative optimization algorithm could not ensueobtain the global optimal solution.