Coding Schemes for the Two-Way Relay Channels

In modern transmission networks, relay plays an important role for cooperative strategies. Several relaying strategies, such as decode-forward, compress-forward and amplify-forward, have been proposed for relay channels and networks. However, the capacity for the general relay channel and network is still unknown. In this thesis, we propose several relay schemes for different relay models. In the first part of the thesis, we propose novel partial decode-forward (PDF) schemes for the two-way relay channel with direct link. Different from pure decode-forward, each user divides its message into two parts and the relay decodes only one part of each. The relay then generates its codeword as a function of the two decoded parts and forwards to the two users. We propose PDF schemes for both the fulland half-duplex modes. Analysis and simulation show that if for one user, the direct link is stronger than the user-to-relay link, while for the other, the direct link is weaker, then PDF can achieve a rate region strictly larger than the time-shared region of pure decode-forward and direct transmission for both fulland half-duplex modes. The second part of the thesis is based on noisy network coding, which is recently proposed for the general multi-source network by Lim, Kim, El Gamal and Chung. This scheme builds on compress-forward (CF) relaying but involves three new ideas, namely no Wyner-Ziv binning, relaxed simultaneous decoding and message repetition. In this part, using the one-way and two-way relay channel as the underlining example, we analyze the impact of each of these ideas on the achievable rate region of relay networks. In the third part of the thesis, we propose two coding schemes combining decode-forward (DF) and noisy network coding (NNC) with different flavors. The first is a combined DFNNC scheme for the one-way relay channel which includes both DF and NNC as special cases by performing rate splitting, partial block Markov encoding and NNC. The second combines two different DF strategies and layered NNC for the two-way relay channel. Analysis and simulation show that both proposed schemes supersede each individual scheme and take full advantage of both DF and NNC.