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为克服无线信道时变衰落特性对传输性能的影响 ,提出了基于低密度奇偶校验 (L DPC)编码的自适应调制传输方案。该方案将所有子信道传输的信息采用同一个 L DPC码进行编码 ,每个子信道根据各自当前的噪声水平动态选取调制方式 ,而各个子信道的瞬时噪声根据 L DPC译码前后信息序列的符号改变情况进行估计。仿真结果表明 :在 Nakaga-mi时变衰落信道下 ,该系统方案可以很好地适应信道的时变衰落特性 ,在满足系统输出误比特率的条件下 ,可以很低的系统复杂度实现信息的最佳传输 ,并获得距离理论极限3d B的良好传输性能
In order to overcome the impact of time-varying fading characteristics of wireless channel on transmission performance, an adaptive modulation transmission scheme based on low density parity check (L DPC) coding is proposed. In this scheme, the information transmitted by all subchannels is encoded by the same L DPC code. Each subchannel dynamically selects the modulation mode according to the current noise level, and the instantaneous noise of each subchannel changes according to the sign of the information sequence before and after L DPC decoding The situation is estimated. The simulation results show that under Nakaga-mi time-varying fading channel, this system scheme can well adapt to the time-varying fading characteristics of the channel, and can meet the system’s output bit error rate under the conditions of low system complexity to achieve the information The best transmission, and get the theoretical limit 3dB good transmission performance