The Research Of A Transmission Strategy Based On Joint Superposition Coding And Physical-layer Network Coding

In wireless communications networks, the main advantages of cooperative relaying techniques are overcoming the fading effect of wireless channel, boosting the communications range of wireless networks and improving transmission reliability. The superposition coding is a kind of technique which can encode and modulate many signals. This technique can realize the signals superposition according to applying layed coding and modulation and systematic performance of throughput can be improved. Network coding mainly realizes the throughput maximization by exchanging and processing usefull information at nodes and improves the performance of security and robustness. Physical-layer network coding can make wireless electromagnetic waves to be superposed and mapped onto the Galois field and the mapped data operate in bitstream effectively so that it can transmit signals with less time slots and enhance the systematic spectral efficiency. Therefore, based on the analysis of superposition coding and physical-layer network coding in cooperative relaying wireless communications system, a new joint superpositon coding and physical-layer network coding tranmission strategy is proposed. This transmission strategy is based on two-way four-node cooperative relaying transmission system. The strategy system model is a wireless system aiming to realize the two-way information exchanges of two pairs through the cooperation of the two intermediate nodes. Firstly, this thesis derives the systematic throughput of two-way relaying transmission strategy based on superposition coding with four time slots, Secondly, joint superposition coding and physical-layer network coding which only needs three time slots to complete the whole transmission process is applied in the two-way four-node cooperative relaying transmission system. Finally, with the mathematical derivation, the new transmission strategy not only increases the spectral efficiency by25%, but also improves the systematic throughput.After corresponding theoretical analysis, results can be simulated by Matlab software, firstly, transmission rate ranges at nodes are analysed. Then appropriate perimeters can be selected and put into the derived throughput expressions according to comparison many times. Through the comparison and analysis of two transmission strategies throughput curves in the simulation diagram, the conclusions proposed in this thesis can be verified.