On Efficient Turbo Coded Cooperation Scheme

Cooperative communication is one of fastest growing research field in recent years, and also will be the most likely techniques of saveing resources in the future. The core idea of this technique rests with sharing resource among communication nodes in the networks. The reason of developing this is to save resource by sharing frequency among nodes. Till now, there are many achievements in cooperative communication, especially in cooperative diversity and cooperative coding techniques, including RCPC,Turbo,LDPC,LDGMå'ŒLT-LDPC, and Rateless, cooperative coding have already covered many excellent channel coding techniques. Movere, the analysis of relay channel capacity and how to use cooperative coding to approach capacity bounds are obtained many achievements. Nevertheless, many problems are sill leaved to deal with, because capacity analysis about many users and efficient cooperative scheme for many users haven't been resolved.Firstly, three-node wireless relay channels in AWGN channels are considered. The upper and lower bounds for the capacity of relay channels are derived. It is shown that the gap between the upper and lower bounds is the largest when the gain of the channel to the relay is worse than that of the direct channel. And also, the optimization of the power for the full-duplex is derived.Secondly, several cooperative schemes are produced. One of these is distributed communication system; it is shown the performace of that distributed communication is better than the traditional non-cooperative modle. Then a cooperative coding approach between two users is proposed. The scenario under consideration is one in which two "partners" (Node 1 and Node 2) cooperate in transmitting information to a single destination; each partner transmits both locally generated information and relayed information that originated at the other partner. A key observation is that Nodel already knows Node2's relayed information (Because it originated at Node 2) and can exploit that knowledge when decoding Nodel's local information. This leads to an encoding scheme in which each partner transmits the superposition of its local and relayed information. And at the destination node, based on the prior knowledge, decoding at the destination is carried out by iterative between the codewords from the two partners.Thirdly, network cooperative coding schemes are introduced. The aim to investigate how network coding gain may be achieved in a wireless networks even when the transmission to the relay can not be recovered perfectly. Network coding over a butterfly-like network is studied. The basic idea of our scheme if the following:Instead of decoding the messages from the sources, the relay node transmits the logarithm likelihood ratio (LLR) of the network coded message to the destination. And a technique for two-way relay channel is prosoed. In the proposed scheme, the relay nodes does not decode the source information from the two ends separately, but rather directly maps the combined signals received simultaneously to a signal. Given a network code, we could also use different estimation techniques (MMSE/MAP) at the relay node to compute the relayed value.Finally, three efficient network cooperation schemes for multiple access relay model with two sources is proposed based on the IDMA (interleave-division multiple-access) technology. These three sheme improve the system reliabity and efficiency at the cost of complexity. Rather different from the scheme as before, this scheme include two source node, and each node may achieve the data transmission throughput as high as about 1 symbol/source/channel use or 0.667symbol/source/channel use. All the three schemes can attain almost the same performace at the high signal to noise ratio (SNR). Moreover, it is shown through numerical analysis that the increase in the number of available relays will have a significant influence on the achieved reliability improvement for the proposed network coded cooperation scheme.