Research Of User Grouping Schemes Based On Network Coding For Cooperative Communications

This thesis focuses on the key issues of cooperative communication technology that combined with network coding, which based on wireless cooperative networks, studys mainly and deeply on the user grouping schemes based on network coding in cooperative communications.In the thesis, a novel network-coding-based user grouping (NCUG) scheme is proposed for the wireless cooperative networks that introduced network coding technology. NCUG adopts the qualities of source-destination (s-d) channels to group users into pairs. The user which has good quality of s-d channel should pair with the one whose s-d link is poor in order to make the two users relatively complementary. With the assistance of a single relay, users'signals are forwarded effectively and the overall outage performance has been improved significantly.Compared with the traditional relay scheme, the user grouping schemes based on network coding can save the transmission time slots and the transmit power. Owing to the multiple-access relay channel (MARC), the thesis considers two different schemes:NCUG in ideal s-r channels and NCUG-AR in non-ideal s-r channels. Performance analysis in the form of average outage probability proves that NCUG and NCUG-AR outperforms the previous schemes, such as the direct transmission (DT) scheme, the traditional relay (TR or TAR) scheme and the network coded relay (NCR or NCAR) scheme with random user grouping, especially when the number of users is large, both NCUG and NCUG-AR can enhance the bandwidth efficiency and the system throughput.In addition, another user grouping scheme based on network coding is proposed for wireless relay networks with fixed relays. Considering the single-relay model and the double-relay model respectively, the thesis discusses the outage performances and execution programs each. Simulation results prove that this scheme of the single-relay model not only decreases the system outage probability, but also improves the transmission efficiency and system throughput without more hardware cost. Moreover, the user grouping scheme based on network coding combined with the traditional adaptive relay scheme can also improve the transmission in the double-relay system.