Network Coded Modulation for Two Way Relay Networks


Modern wireless networks use cooperative relaying to expand its coverage area. Wireless relaying allows mobile terminals to participate in transmission even when these terminals are not being the initial source or final destination. This can be achieved in different ways ranging from simple conventional relaying to more sophisticated coding at terminal and relay nodes to improve transmission performance. The proposed work here studied such system by simulating different coding techniques to be used in two way relay network coding (TWRC). Some of these techniques were previously proposed to improve transmission performance in conventional data communication systems. BER performance of different arrangements of coding and relaying schemes are evaluated using computer simulation tests. Ideal AWGN channel model and standard wireless channel models for wireless networks are considered in the simulation tests. The results have been shown that coding schemes such as Trellis Coded Modulation (TCM) and Repeat Accumulate (RA) codes are more suitable in two way relaying networks. Over AWGN, TCM-8PSK improves BER performance by at least 2 dB at high SNR for different relaying arrangements. For fading channels, this advantage is slightly reduced. Regenerative repeating at relay node seems to be a promising arrangement. It seems that there is no sense in using RA codes over fading channels due to its poor performance and relatively lower speed caused by repetitions.