AbstractsComputer Science

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 generalrelay channel and network is still unknown. In this thesis, we propose several relay schemesfor dierent relay models.In the rst part of the thesis, we propose novel partial decode-forward (PDF) schemesfor the two-way relay channel with direct link. Dierent from pure decode-forward, eachuser divides its message into two parts and the relay decodes only one part of each. Therelay then generates its codeword as a function of the two decoded parts and forwards tothe two users. We propose PDF schemes for both the full- and half-duplex modes. Analysisand simulation show that if for one user, the direct link is stronger than the user-to-relaylink, while for the other, the direct link is weaker, then PDF can achieve a rate regionstrictly larger than the time-shared region of pure decode-forward and direct transmissionfor both full- and half-duplex modes.The second part of the thesis is based on noisy network coding, which is recently proposedfor the general multi-source network by Lim, Kim, El Gamal and Chung. Thisscheme builds on compress-forward (CF) relaying but involves three new ideas, namely noWyner-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 theimpact 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 dierent avors. The rst is a combined DFNNCscheme for the one-way relay channel which includes both DF and NNC as specialcases by performing rate splitting, partial block Markov encoding and NNC. The secondcombines two dierent DF strategies and layered NNC for the two-way relay channel.Analysis and simulation show that both proposed schemes supersede each individual schemeand take full advantage of both DF and NNC. Dans les reseaux de transmission modernes, les relais jouent un r^ole important dans lesstrategies cooperatives. Plusieurs strategies de relai, telles que decode-forward, compressforwardet amplify-forward, ont ete proposees pour les canaux et reseaux a relais. Cependant,la capacite du canal a relai general et de tels reseaux reste toujours inconnue. Danscette these, nous proposons plusieurs strategies de relai pour dierents modeles.Dans un premier temps, nous proposons de nouvelles strategies de decode-forward partiel(PDF) pour le canal a relai bidirectionnel avec lien direct. A la dierence du decodeforwardclassique, chaque utilisateur divise son message en deux parties, mais le relai nedecode que l'une d'entre elles pour chacun. Le relai genere alors un mot de code en fonctionde ces deux parties decodees et les transmet aux deux utilisateurs. Nous proposonsune stratgie PDF a la…