基于成像光通信的时间-空间扩频混合光码分多址编码方案

Hybrid OCDMA Coding Scheme of Time-Spatial Frequency Spreading Spectrum Based On Optical Imaging Transmission

为了在成像光通信中充分利用时间和空间两种频带资源,以成像光通信为基础,提出一种利用二维光正交Pattern码结合时域扩频实现光码分多址(OCDMA)编码的新方案。分析在该方案中存在的多址干扰噪声,并给出了噪声的概率密度函数,然后讨论由多址噪声引起的误码率与判决门限、用户数、码长积和码重积之间的关系。在相同的码容量下与时域扩频光码分多址编码和空间扩频光码分多址编码方案相比,该方案能降低对相关器件性能(时域码片数量和空间像素规模)的要求,而且还可获得更小的误码率。最后给出编码解码的光学实现方案。

For using the time and space frequency resources in imaging transmission fully, a new hybrid optical code division multiaddress （CDMA） coding scheme is proposed, which is based on imaging transmission with twodimensional optical orthogonal pattern code and time frequency spread spectrum. Then the authors analyze the multiplex access interference noise and calculate the probability density function of interference noise in interfering optical orthogonal signature codes. The bit-error rate caused by the multiplex access interference noise is derived and plotted as a function of receiver threshold, number of users, code length and code weight product. Compared respectively with time spreading code and spatial spreading code optical CDMA, the authors＇ scheme has a lower biterror rate and releases the requisition of relative devices such as the number of code chips in time domain and the pixels in space domain. Finally a design scheme of encoder-decoder is presented.