| Summary: | 碩士 === 龍華科技大學 === 電子工程研究所 === 96 === The IEEE 802.16e Standards provides the characteristics for networks of high transmission data rates and wide coverage range, and it supports Mobile Subscribers for high speed mobility. It performs a good signal quality without interruption for Mobile Station during migration as well.
There are four types of ranging request specified in IEEE 802.16e Standards, Mobile Station can send the ranging request to the Base Station through the contention-based scheme. By using the CDMA (Code Division Multiple Access) techniques, MS can randomly transmit the selected CDMA Code parameters to Base Station. After receiving the CDMA Codes, BS will identify which kind of requests by matching the CDMA Code group.
Since there are no prescriptions describing the allocations about the four groups of CDMA Code range in the IEEE 802.16e standards and it is pending and left for industrial and academy to study and define.The critical problem is the case when the CDMA Code group range is narrow for BS, in this case,the MS randomly selects one CDMA Code parameter from this group and transmit to the BS, it might simultaneously select the same CDMA Code for the other MSs, and in such a case collision occurs and it will decrease the system performance of transmission throughput and delay time.
In this thesis we propose a Dynamic CDMA Code Range Allocation Algorithm and compare with other Allocation Algorithm. Through simulation and evaluation, this algorithm is proved to have higher throughput and less delay time then other algorithms.
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