湍流大气中脉冲位置调制和数字脉冲间隔调制差错性能的建模与分析

Modeling and Analyzing of Error Performance for Pulse Position Modulation and Digital Pulse Interval Modulation under Turbulence

针对以往研究未在最佳解调下讨论脉冲位置调制(PPM)差错性能的不足及数字脉冲间隔调制(DPIM)调制结构不利于误符号率(SER)分析的问题,基于湍流信道,提出极大似然判决(ML)下PPM误符号率精确计算式及其联合界和一种基于包传输的DPIM误符号近似计算模型,并应用成对差错率原理,推导了系统误符号率与误比特率(BER)的变换关系。仿真分析表明,联合界为PPM提供了便于分析的降复杂度误符号率近似上界,ML下PPM较易受湍流变化影响,但性能明显优于开关键控(OOK)和DPIM,DPIM误符号率及误比特率不及OOK,适于出错重传系统,单工通信中则不宜使用。所给建模方法及分析结论对其他定长及变长调制具有适用性。

To characterize error performance of pulse position modulation（PPM） with optimal demodulation and digital pulse interval modulation（DPIM） whose variable symbol length makes it difficult to analyze performances,an exact symbol error rate（SER） expression is presented as well as its union-bound about PPM based on maximum-likelihood（ML） detection under turbulence channel,and an approximate SER mathematic model of DPIM grounding on transmitted packet is proposed.Appling pairwise error probability（PEP） theory in conjunction with SER,the bit error rate（BER） is also derived.Simulations show that,union-bound analysis of PPM can yield simple analytical upper bounds and approximations to SER,and the performance of PPM influenced more by turbulence is better than DPIM and on-off keying（OOK）.DPIM isn′t suitable for simplex communication for its poor BER and SER.The modeling methods and conclusions are applicable to other digital pulse modulations.