基于最大似然准则的多波长OCDMA接收机的最佳判决门限研究

Research on Receiver′s Optimum Threshold in Multi-Wavelength OCDMA Based on Maximum Likelihood Principle

采用最大似然准则,研究了多波长光码分多址接收机的最佳判决门限值.通过检测信道的光信号能量,接收端估计出信道的并发用户数,并通过最大似然准则得到了最佳判决门限值与并发用户数、码字参量的变化关系.当并发用户数超过一定值后,最佳判决门限值将随并发用户数量变化,相应地改变接收机的判决门限值.根据最佳判决门限值,得到了多波长光码分多址系统误码率与并发用户数的关系.理论分析和模拟结果表明,采用最大似然准则得到的最佳判决门限值,MWOCDMA系统的误码率将明显降低.

Optimum threshold in multi-wavelength optical CDMA（MW OCDMA） was researched according to maximum likelihood principle.The number of simultaneous users on channel was estimated at receiver by detecting energy of optical signal. Relationship between optimum threshold and number of simultaneous users on channel and code parameters was achieved.When MW OCDMA system had large number of simultaneous users on channel, optimum threshold value would vary with the number of simultaneous users,and the receiver would adjust the optimum threshold accordingly.Relationship between simultaneous users and bit error rate（BER） of MW OCDMA system was achieved according to the optimum threshold value.Theoretical analysis and analogy simulation show that BER of MW OCDMA system will degrade greatly while employing the proposed optimum threshold value by maximum likelihood principle.