星间无线OCDMA系统单用户检测容量研究

Capacity Research of Intersatellite W-OCDMA with Single User Detection

提出了一种新颖的异步光码分多址(OCDMA)系统,结果表明,在理论信息容量限为1bit·chip条件下,单用户检测下OCDMA系统的容量随着用户数的增加有所下降,但在用户数较多时基本保持在0.75bit/chip的水平;单用户检测下系统的最大容量限不在信号输入概率为0.50时出现;在用户数较少时,信号输入概率偏离0.50越大,系统最大容量限越低。由此推证了异步OCDMA系统在单用户检测下的理论信息容量限。

The novel optical code division multiple access (OCDMA) technology and its implementation in intersatellite free-space optical communications were presented. We modeled a discrete memoryless channel OCDMA system; evaluated the aggregate capacity from the probability of the output signal at the chip level. On the condition that the information capacity limited by 1 bit per chip, the results show that the interference caused by asynchronism reduces the capacity limit as the number of users increases, but for a sufficiently large number of users, the channel throughput limit varies slowly and the limit is around 0.75 bit&middotchip-1. The largest capacity limit doesn't appear when the input probability is 0.50. With less number of users, the more the input probability is lower than 0.50, the lower the largest capacity limit will be. So the information capacity of the asynchronous OCDMA is gotten.