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A study on access control scheme for multimedia CDMA ALOHA system

多媒体CDMA ALOHA系统接入控制方案的研究

基本信息

批准号：
10450148
负责人：
OGAWA Akira
金额：
$ 3.78万
依托单位：
Meijo University (2000)Nagoya University (1998-1999)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

The object of this research is to study on various access control schemes for CDMA ALOHA that can provide high efficiency under practical environments. The CDMA ALOHA is considered promising for simple and efficient multimedia mobile communications.We have developed a model with which the system performance can be evaluated, and studied on the access control schemes capable of maintaining high efficiency even in the presence of fading and near-far problems. As a result, It was shown that access controlling in accordance with the distance from a base station with a rake receiver and simple transmit power control can provide high efficiency.We have also developed a method for evaluating the performance of multimedia CDMA systems in which there coexist voice and data channels having different required quality of service, and proposed an access control scheme such that the traffic is controlled with a threshold determined by the total numbers of users for telephone service and data service, and with another threshold determined only by the number of data users. We have also proposed another scheme that can improve the throughput of data packet without degradation in the performance of telephone service, utilizing the random access feature of data packet service.To reduce the amount of multiple access interference, we have studied the application of the quasi-synchronous code sequence to CDMA slotted ALOHA, and clarify its effectiveness using the binary quasi-synchronous code sequence that can be easily generated. As another mean to reduce the effect of multiple access interference, we have analyzed the relationship between cross correlation and noise enhancement accompanied by a decorrelating detector with respect to a synchronous CDMA system, and proposed a interference canceller based on MMSE criterion, applied to the CDMA unslotted ALOHA system.

本研究的目的是研究在实际环境下能够提供高效的码分多址ALOHA的各种接入控制方案。在简单高效的多媒体移动通信中，码分多址ALOHA被认为是很有前途的。我们建立了一个可以评估系统性能的模型，并研究了在存在衰落和远近问题的情况下仍能保持高效率的接入控制方案。提出了一种评估话音和数据信道共存的多媒体码分多址系统性能的方法，并提出了一种接入控制方案，使得话务控制的门限由电话业务和数据业务的用户总数决定，而另一个门限仅由数据用户数量决定。为了减少多址干扰，研究了准同步码序列在码分多址时隙ALOHA中的应用，并以易于产生的二进制准同步码序列为例说明了其有效性。作为减小多址干扰影响的另一种方法，我们分析了同步码分多址系统中互相关和伴随去相关检测器的噪声增强之间的关系，并提出了一种基于最小均方误差准则的干扰对消器，应用于码分多址非时隙ALOHA系统。