Design For Physical Layer Network Coding Based On Decode-and-Forward Relay

Today from MAN (metropolitan area network), WAN (wide area network), LAN (local area network), PAN (personal area network) to home network, wireless technology has been widely applied in all aspects of daily life. In factory automation network, there are a large number of nodes but throughput is low. PNC (Physical Layer Network Coding) technology can achieve maximum throughput, so it has obvious advantages to improve system throughput. This paper is research of design of PNC in factory automation wireless network framework.Although PNC is easy to implement based AF (Amplify-to-Forward) relay, but noise amplification defect causes the system error rate increased.Factory automation network proposes require extremely high reliability for wireless communications. DF (Decode-and-Forward) relay PNC properties are studied, meanwhile, the high-order QAM modulation and OFDM/OFDMA technology are used, multi-node parallel interface is implemented, and real-time system is improved.PNC with M-QAM modulation, demodulation mapping exists ambiguity problem. Available solutions are higher computational complexity, lower communications reliability. This paper designs a PNC scheme that is joint design of M-QAM modulation and block codes. Demodulation mapping ambiguity problem is solved, at the same time, it can reduce the computational complexity and improve communication reliability. Even in the unequal power or unequal channel coefficients, the scheme can still improve communication reliability, thereby enhance the robustness of the system.Further, in the two-way DF relay, jointly design PNC and OFDM and the PAPR (Peak-to-Average Power Ratio) performance are analyzed. PTS (Partial Transmit Sequence) principle is analyzed and the relay node demodulation mapping table is given.Phase factor information needs to be added to the table, this increases the complexity of demodulation mapping of the relay node and the transmission delay of system. The method to calculate the phase factor is improved. The method takes phase factor in the unit circle in discrete uniform distribution.The method reduces the computational complexity, and avoids PAPR regeeration caused by side information. It is a compromise between complexity and PAPR performance.Based upon the two-way DF relay, jointly design PLNC and OFDMA and analyze the PAPR performance of the system in multi-way DF relay. OFDMA technology achieves parallel access to multiple nodes, in the TDD mode, further enhance OFDMA system throughput by combining PNC. Throughput of PNC scheme increases 100% than the traditional storage forwarding scheme, increases 50% than straightforward network coding scheme. The system uses DFT Spreading to reduce the PAPR. The PAPR performance of multiple access system is analyzed.