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在无线光通信中,为了提高系统的性能,提出了一种新的定长双幅度数字脉冲间隔调制码分多址方式(FDAPI M-CDMA)。分析了采用光正交码时,它在多用户同步和理想异步干扰下的误码率(BER)特性,并给出了误码率上限和下限的数学表达式。研究了码长、码重、用户总数以及接收门限对系统性能的影响,并在相同情况下与开关键控码分多址(OOK-CDMA)系统的性能进行了比较。理论分析与仿真结果表明,FDAPI M-CDMA系统的误码率性能随码长的增大、用户数量的减少而提高。对于过长的码重,可通过增加接收门限值来降低误码率。当符号比特数大于等于6且门限值等于码重时,FDAPI M-CDMA的误码率上限和下限均比OOK-CDMA小,具有较强的抗多用户干扰能力。因此FDAPI M-CDMA可作为OOK-CDMA的一个有效的替代方式。
In wireless optical communications, a new fixed-length dual-amplitude digital pulse-space modulation code division multiple access (FDAPI M-CDMA) is proposed to improve the performance of the system. This paper analyzes the bit error rate (BER) characteristics under multiuser synchronization and ideal asynchronous interference when using Orthogonal Orthogonal Codes, and gives the mathematical expressions of upper and lower error rates. The effects of code length, code weight, total number of users and receive threshold on the performance of the system are studied. The performance of the system is compared with that of the OOK-CDMA system under the same conditions. Theoretical analysis and simulation results show that the bit error rate performance of FDAPI M-CDMA system increases with the increase of the code length and the decrease of the number of users. For long code weight, lower the bit error rate by increasing the receive threshold. When the number of symbol bits is greater than or equal to 6 and the threshold is equal to the code weight, the upper and lower error rates of the FDAPI M-CDMA are smaller than that of OOK-CDMA, which has strong anti-multi-user interference capability. So FDAPI M-CDMA can be used as an effective alternative to OOK-CDMA.