Topics in Signal Design and Signal Analysis for Wireless Communication

无线通信信号设计和信号分析主题

• 批准号: 9612864
• 负责人: P. Vijay Kumar
• 金额: $ 27万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-09-01 至 2001-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9612864&HistoricalAwards=false
• 关键词: Topics; Signal; Design; Analysis; Wireless

Some signal design/analysis problems relevant to wireless communication are under investigation. Problems in the first class relate to a code-division multiple-access (CDMA) communication scheme in which the receiver makes optimum multi-user decisions. The effect the selection of a particular sequence family has on the performance of the system is under study. One measure of performance is the capacity, i.e., the number of active users that the system can support. Signature sequences influence this number through their periodic and aperiodic correlation properties. These correlation values tend to diminish performance by reducing the minimum Euclidean distance between distinct multi-user signal sets. Preliminary investigations turned up an interesting example involving Gold sequences of small length in which correlations reduced the Euclidean distance between a multi-user signal and its nearest neighbour to zero. The obvious upper bound on capacity obtained by replacing each aperiodic correlation by the maximum over the entire sequence family provides much too conservative an estimate. Thus improved upper bounds are currently being sought. This requires a better understanding of the distribution of aperiodic correlation values obtained by picking a randomly-delayed random subset of the entire family of signature sequences. This distribution is under study both for a family of signature sequences in general as well as for specific families known to be efficient with respect to periodic correlation measures. The understanding gained, will be used in the design of improved signal sets. For example, preliminary investigations suggest that when communicating data using phase-shift keying, improved performance will result if each user's phase transitions never exceed 90 degrees since this has the effect of distributing the aperiodic correlations across the real and imaginary axes as opposed to simply the real axis. The second class of problems under investigation deals with the IS-54/IS-136 North American digital cellular standard. Here the goal is to come up with an efficient forward error-correction (FEC) scheme well matched to the IS-54/136 channel. The motivtion came from previous work in which a nonlinear binary FEC code identified by the author (the Nordstrom Robinson code) turned out under soft-decision decoding, to improve uniformly upon the performance of the convolutional code used in the current IS-54 standard. This was to the surprise of many in both industry and academia as the binary code is of short block length (16) and has a small minimum distance (6), whereas the IS-54 employs a rate 1/2 convolutional code of contraint length (6). The reason for this improved performance is under investigation and attempts are under way to identify the code best matched to this channel. Some other problems of a miscellaneous nature, all relevant to improved wireless communcation are also being studied.

一些与无线通信相关的信号设计/分析问题正在研究中。 头等舱中的问题与代码分区多访问（CDMA）通信方案有关，其中接收器做出最佳的多用户决策。 研究特定序列家族对系统性能的影响正在研究。 性能的一种衡量标准是能力，即系统可以支持的活跃用户数量。 签名序列通过其周期性和多维分相关性能影响此数字。 这些相关值通过减少不同多用户信号集之间的最小欧几里得距离来降低性能。 初步研究提出了一个有趣的例子，涉及较小长度的金序列，其中相关性降低了多用户信号与其最近的邻居之间的欧几里得距离。 通过在整个序列家族中替换每个Aperiodic相关性的最大值，可获得的能力上的明显上限提供了估计值得太保守的。 因此，目前正在寻求改善的上限。 这需要更好地理解通过选择整个签名序列家族的随机随机子集获得的植物相关值的分布。对于一般的签名序列家族以及已知在周期性相关措施方面有效的特定家族，都在研究这种分布。 获得的理解将用于改进信号集的设计。例如，初步研究表明，当使用相移键合传达数据时，如果每个用户的相转换永远不超过90度，则会提高性能，因为这具有分布在真实和想象的轴上与简单相反的跨真实和想象的轴的效果真实轴。 正在调查的第二类问题涉及IS-54/IS-136北美数字蜂窝标准。 在这里，目标是提出一个与IS-54/136通道相匹配的有效远期错误校正（FEC）方案。 动机来自以前的工作，在该工作中，作者（Nordstrom Robinson Code）确定的非线性二进制FEC代码在软否决解码下发现，以统一改善当前IS-54标准中使用的卷积代码的性能。 由于二进制法规的长度很短，而且最小距离（6），因此在行业和学术界，许多人都感到惊讶（6）。 这种改善的性能的原因正在调查中，并正在尝试确定与此渠道最匹配的代码的尝试。 还研究了其他一些杂项性质的问题，这些问题与改进的无线通讯有关。