物理层网络编码(Physical-layer Network Coding，PNC)因其可以在中继通信中大幅提高吞吐量而备受关注。为了进一步提高传输效率，减少多径的影响，在三节点双向无线PNC系统中引入 16QAM-OFDM高阶调制技术，设计了 16QAM-OFDM-PNC通信系统。由于采用16QAM-OFDM高阶调制的PNC系统存在中继映射模糊的问题，对16QAM信号的星座点重新布局，设计出相应的中继解调映射规则。为了进一步提高系统性能，在该设计中引入低密度奇偶校验码(Low Density Parity Check Code，LDPC)，设计了相应的译码映射算法。最后实验表明，上述设计相较于 16QAM-PNC系统具有更好的系统性能，同时联合LDPC编码的设计能提高系统增益约2dB。
Joint Design of Physical-Layer Network Coding and OFDM under High-Order Modulation
Physical-layer network coding(PNC)has attracted much attention due to its ability to significantly improve throughput in relay communication.In order to further improve the transmission efficiency and reduce the im-pact of multipath,this paper introduced 16QAM-OFDM high-order modulation technology in three-node bidirectional wireless PNC system to design the communication system of 16QAM-OFDM-PNC.Due to the problem of ambiguity of relay mapping in the PNC system using 16QAM-OFDM high-order modulation,this paper rearranged the constellation points of the 16QAM signal,designed the corresponding relay demodulation mapping rules,and by analyzing the performance of the OFDM-PNCsystem with 16QAM signal of different constellation point layouts,the best 16QAM scheme of them was obtained.In order to further improve the system performance,low density parity check code(LDPC)was introduced into the design,and the corresponding decoding mapping algorithm was designed.Finally,the experiments show that the design has better system performance than 16QAM-PNC system,and the design of combined LDPC coding can improve the system performance by about 2dB.
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