最近幾年, 寬頻分碼多工存取(W-CDMA)技術已被採用為第三代行動系統的無線存取技術。無線資源管理(Radio Resource Management, RRM) 主要負責空中介面資源的有效利用，期盼在有限的無線頻寬中能滿足最大的系統資源使用率。本論文主要針對W-CDMA系統中的無線資源管理議題，提出有效的網路層面資源管理機制，包含允入控制(Call Admission Control) 和正交可變展頻係數碼(OVSF)分配機制來有效使用系統資源。
為了支援不同需求的可變傳輸速率，W-CDMA系統使用OVSF碼做為展頻和通道化碼。OVSF碼藉由改變展頻係數來變更不同的傳輸速率以支援不同的使用需求，然而為了維持正交以區隔不同的使用者，OVSF碼的配置也有一些限制，這樣的限制可能會造成碼阻斷(code blocking),即可用的OVSF碼太過分散，以致於即使有足夠的系統容量,卻因找不到適用的OVSF碼分配給新來的需求，而造成阻斷。由此可知，OVSF碼在W-CDMA系統的有效資源利用上扮演一個很重要的角色。
在本論文中，我們提出了一個針對OVSF碼的分析模式來評估資源配置機制的系統效能，此分析模式可以反應OVSF所受限制的特性，可被應用到W-CDMA系統的資源管理議題。
考慮到OVSF所受限制的特性，我們也提出一種以OVSF碼為基礎的資源預留機制給特定具優先權限的使用者，以滿足允入控制的QoS需求。和現有的一些以頻道為主的資源預留機制比較起來，以OVSF碼為基礎的資源預留機制更適用於第三代行動通訊系統。
最後，由於有效的OVSF碼配置和重配置策略，將減少阻斷機率，提昇整體系統使用率和效能。現有大部份的OVSF碼配置策略都是以使用空間為考量，儘量集中使用中的分配碼，以空出更大的空間來容納未來的高速率傳輸需求。我們基於未來行動通訊系統將大量支援多媒體和及時系統應用，以滿足不同的QoS應用需求。我們以OVSF碼佔用的剩餘時間為考量，驗證了佔用剩餘時間的因素對OVSF碼配置的系統效能有重大影響, 進而提出二種以時間為考量的OVSF碼配置和重配置策略Maximum Remaining Time First (MF) 及Nearest Sibling Remaining Time First (NSF)，經實驗證明以時間為考量的配置策略，系統效能優於現有以空間為考量的配置策略。

In recent years, the wideband code division multiple access (W-CDMA) technology has been chosen as the radio access technology for the third generation communication systems. Radio Resource Management (RRM) is responsible for utilizing the air interface resource, and is designed to maximize the number of satisfied users within the available radio bandwidth. In this dissertation, we focus on the RRM issues for W-CDMA systems, and propose some network-based resource management schemes such as call admission control and Orthogonal Variable Spreading Factor (OVSF) code allocation schemes to improve the system performance.
To support variable bit rate for different requirements, OVSF codes are used to spread and channelize codes in W-CDMA systems. The use of OVSF codes allows the spreading factors to be changed for variable bit rate. However, to keep the orthogonoality between the user’s physical channels, there are some restrictions in OVSF code allocation. These restrictions may cause code blocking, that is, the free codes are too fragmental in the OVSF code tree, and such that there is no suitable code to be allocated to the new coming calls even the available capacity is enough. As a result, the OVSF codes management will play an important role on efficient resource utilization in W-CDMA systems.
In this dissertation, we propose an analytical model for OVSF code tree to evaluate the system performance of resource allocation schemes. The proposed model reflects the characteristics of OVSF restriction, and can be applied to resource management schemes in W-CDMA systems.
Considering the restriction of OVSF codes in W-CDMA systems, we propose code-based resource reserved schemes for prioritized call admission control for Quality of Service (QoS) requirements. The proposed reserved schemes are more suitable to W-CDMA systems than well-known channel-based reserved schemes.
In the future mobile communication system, it is essential to support multimedia and real-time applications with different QoS guarantees. In most multimedia and real-time applications, such as video on demand, downloading music files etc., the service time of the requests can be obtained a priori. Thus, we investigate the impact of the remaining time factor on the performance of the OVSF code allocation and propose two time-based allocation schemes, Maximum Remaining Time First (MF) and Nearest Sibling Remaining Time First (NSF), that take the remaining time of each call as the main factor to assign and reassign codes. The experimental results show that the proposed time-based schemes outperform the well-known space-based schemes.

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