Abstract
Cooperative communication has received great attention for its capability to significantly improve the system performance by introducing relays. In such systems, bandwidth efficiency, interference cancellation, power allocation, relay selection, and relay deployment are important issues. Due to the half-duplex restriction at each node, however, the throughput of cooperative transmission is reduced to one half as compared with that of direct transmission. This problem can be solved by using an alternately relaying pair to form a two-path successive relay system (TPSRS), but this approach causes inter-relay interference (IRI) at the destination. Although a full interference cancellation (FIC) scheme was proposed to totally remove the IRI, the other issues regarding further performance enhancement of the TPSRS with FIC (TPSRS-FIC) are scarcely studied. In this dissertation, we propose power allocation, relay pair selection, and relay pair deployment methods based on a derived symbol error rate (SER) closed-form for the TPSRS-FIC. To reduce the computational complexity of the proposed schemes, we use a simplified cost function (SCF) derived from a partial Taylor series extension of the SER analysis. With the SCF, the optimization problems of the proposed power allocation and relay pair deployment can be reduced to root-finding problems of quadratic equations, where the closed-form solutions can easily be obtained. Simulation results show that the proposed schemes approach the SER lower bounds. Finally, we extend the TPSRS-FIC to multiuser environments, where the multicarrier code division multiple access technique is adopted. As the sources transmit data information simultaneously, multiple access interference (MAI) occurs at the destination. To mitigate the MAI, we propose variance-reduced partial parallel interference cancellation on the output signal of the FIC operation. Simulation results show that the proposed signal process can effectively reduce the MAI for the TPSRS-FIC in multiuser scenarios.