论文部分内容阅读
目前世界范围内无线蜂窝系统的覆盖率已经达到了90-95%[即在小区覆盖的范围内,约有90-95%的区域中信干比(SINR)可达到期望值]。通常情况下小区范围内大部分区域的SINR值都是远高于目标值的,因为若SINR等于或者大于期望值,可以保证系统的数据速率,从而保证了语音质量。对分组数据业务来说,系统在高SINR值的情况下,可通过降低编码率或降低扩频速率和/或增加星座图密度等方法,提供更高的数据速率。用户在较好的链路下数据速率会提高,同时蜂窝系统的频谱效率(b/s/Hz/扇区)也会显著提高。目前主要的蜂窝系统标准都定义了这种速率调整过程。本文当中我们将探讨CDMA(IS-95),宽带CDMA(cdma2000和UMTSWCDMA),TDMA(IS-136)和GSM(GPRS和EDGE)中的数据速率自适应过程。
At present, the coverage of wireless cellular systems in the world has reached 90-95% [that is, about 90-95% of the region’s SINR reaches the expected value within the coverage of the cell]. In most cases, the SINR value in most areas within the cell is much higher than the target value because if the SINR is equal to or greater than the expected value, the data rate of the system can be guaranteed, so as to ensure the voice quality. For packet data services, the system can provide higher data rates at high SINR values by reducing the coding rate or reducing the spreading rate and / or increasing the constellation density. Users will have higher data rates over better links, while the cellular system’s spectral efficiency (b / s / Hz / sector) will increase significantly. Currently, the major cellular system standards define this rate adjustment process. In this article, we explore the data rate adaptation process in CDMA (IS-95), Wideband CDMA (cdma2000 and UMTSWCDMA), TDMA (IS-136) and GSM (GPRS and EDGE).