Research on Quasi-Synchronous Spread Spectrum Wireless LAN

这个项目从1994年到1995年进行，目的是研究使用实值正交伪噪声序列的准同步扩频通信系统对室内无线局域网的适用性，以带来比任何其他系统更多的通信信道，并提供室内无线局域网的选择。将实值循环正交伪噪声序列集与移位正交实数值有限长伪噪声序列相结合，构造了在有限移位范围内各终端无信道间串扰通信的编码，并将其用于室内光无线局域网的实验。结果表明，窄带或宽带扩频光准同步多址接入中的信道间和码间串扰被抑制到与理论所建议的相近的低水平。本课题还对数字相关器的形成进行了研究，希望对实现…有一定的参考价值。ASIC提供更多的HIS系统。本课题取得的成果如下：(1)室内无线局域网多径检测通过仿真研究了柱子和墙体对电波传播的影响。在荧光灯照明下反射在墙上和天花板上的0.8微米波长的扩频信号被充分检测。(2)多址码的构造实值序列的正交集，由零值插入，由数据调制，对准同步多址接入的性能进行了分析，分析了数字信号处理的误差和噪声对相关输出的影响。(4)室内无线局域网的评级实验为了使128个终端在-1到+1码片移位内通信而设计的扩频光无线局域网的实验表明，期望和不期望的信噪比提高了44分贝。较少

This Project has been performed from 1994 to 1995, for the purpose of investigating the applicability to an indoor wireless LAN of a quasi-synchronous spread spectrum communication system using real-valued orthogonal pseudonoise sequences to bring more communication channels than any other system and of offering an option of indoor wireless LANs. The codes that each terminal should communicate without interchannel crosstalk in a limited shift range are constructed by combining an orthogonal set of real-valued cyclic pseudonoise sequences and a shift-orthogonal real-valued finite-length pseudonoise sequence, are used for the experiment of indoor optical wireless LAN.It is shown that the interchannel and intersymbol crosstalks in the optical quasi-synchronous multiple access of narrow-or wide-band spread spectrum are suppressed to the similar low level as the theory suggests. The formation of digital ccorrelator, also investigated in this project, is expected to be useful for realizing t … More his system by ASICs. The achievements of this project are the followings.(1) Examination of the multi-path in the indoor wireless LANThe effcts of pillars and walls on radio wave propagation are examined by simulation. The 0.8mu-wavelength spread spectrum signal, reflected upon the walls and ceiling under fluorescent lamp illumination, is detected at the sufficient level.(2) Construction of the codes for multiple accessThe orthogonal set of the real-valued sequences, inserted by zero values, modulated by data, convolved with the real-valued finite-length sequence and leads to the codes to supress interchannel and interssymbol crosstalks.(3) Performance analysis of the quasi-synchronous multiple accessErrors of digital signal processing and noise effect on correlation output are analized.(4) Rating experiment of the indoor wireless LANThe experiment of the spread specrum optical wireless LAN designed in order that 128 terminals communicate within -1 to +1 chip shift, shows the 44-dB improvement of desired to undesired signal ratio. Less