Research On Joint Design Of Turbo Decoding And Network Coding For Rayleigh Channel

Physical-layer Network Coding (PNC) applied in the wireless relay networks can improve the spectral efficiency and throughput of networks effectively. To achieve reliable communication and improve the performance of the relay networks, the joint design of channel decoding and PNC is applied in the relay node, which is widely concerned recently.Turbo code, due to its near Shannon limit performance, has become one of the channel coding standards of the third generation mobile communication system (IMT-2000). In this issue, Turbo code is applied in the wireless two-way relay channel model under Rayleigh fading environment. A new relaying scheme, named Joint Turbo Decoding - Network Coding, is proposed for the Rayleigh fading channel and is studied systematically.Firstly, a relaying scheme named Independent Turbo Decoding - Network Coding is studied. Based on the wireless two-way relay channel model under Rayleigh fading environment, we propose the corresponding soft demodulation algorithm and the modified independent decoding algorithm to handle the superposition symbols in the relay node.Secondly, according to the connection of the data among the package symbols, a new relaying scheme, named Joint Turbo Decoding - Network Coding, is presented for Rayleigh channel. In the relay node, we derive a generalized Algorithm of Joint Soft-Information-Value Demodulation. For the demodulation processes, we focus on the special joint calculation of the likelihood ratios and the soft information of the superposition symbols which come from the two source nodes. Subsequently, the corresponding Joint BCJR decoding Algorithm in relay is proposed based on the Joint Turbo encoder and the Joint Trellis.Finally, the performance of the two schemes is compared via computer simulations. Simulation results show that, the Joint Turbo Decoding - Network Coding scheme is superior to the Independent Turbo Decoding - Network Coding scheme in the high SNR region. And we can conclude that: making a new adaptive mechanism, by combining the proposed Joint Turbo Decoding -Network Coding with the Independent Turbo Decoding-Network Coding, might improve the performance of the system significantly.