| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 90 === In wireless communications, the channel quality varies during the connection period of a call, due to user mobility or channel interference. Therefore, the throughput degrades if only a fixed coding scheme is selected. To maximize the throughput, radio channel conditions must be taken into account for data transmission. Link adaptation (LA) allows the selection of proper coding scheme based on the channel conditions. In other words, LA can provide adaptive data rates within a resource variation environment. LA has been proposed for General Packet Radio Service (GPRS), Enhance Data rates for GSM Evolution (EDGE), and Code Division Multiple Access (CDMA) standards to enhance data rate.In our thesis, an approximated analysis using queueing model is proposed to study the system level performance of LA. To simplify the analysis, we focus on the GPRS environment. The performance metric is in terms of the mean blocking probability, system time, number of GPRS, and preemption probability for GRPS service. The accuracy of this approximation will be validated by simulation results. Buffer effect for mean blocking probability and system time of GPRS is also considered. In addition, a comparison of throughput performance with and without LA is made to investigate what extent the throughput is improved.
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