由於傳送資源在無線領域的不足，因此資源配置在無線細胞網路是一個至關重要的議題。連結允入控制(CAC)是資源配置當中非常重要的組成元件，因為連結允入控制決定如何配置資源給新連結與交遞連結來滿足服務品質的限制。在這篇論文裡，我們考慮一個具有多種使用者之階層式細胞網路，其中各種使用者可具有不同的頻寬需求、平均連結時間、移動性，另外快速移動的使用者是指配給上層的巨細胞，而且慢速移動的使用者是指配給下層的微細胞。對於所考慮的系統，我們建議並且研究具有虛擬分割(virtual partitioning)之連結允入控制方法(CAC-VP)。CAC-VP 分配適當的名義容量給每一群組的使用者，其中過載使用者能夠使用欠載使用者的名義容量，假如必要的話，但是過載使用者必須付出可能被欠載使用者所佔先(preempted)的代價。另外，阻塞一個新連結比丟棄一個交遞連結更可以被容忍。因此，在所考慮的系統當中，一個使用預留(guard channel)的機制被實現來使交遞連結的優先權高於新連結。在數學分析方面，我們使用多維的馬可夫鏈(Markov chains)來分別描述巨細胞和微細胞。我們以C 語言撰寫模擬程式來印證分析結果的準確性。連結服務等級(GoS) ,例如新連結阻塞機率、佔先機率以及中斷機率被用來當作效能量度。我們也比較CAC-CS 以及CAC-VP的效能。結果顯示使用CAC-VP的新連結阻塞機率與中斷機率低於使用CAC-CS的新連結阻塞機率與中斷機率。

Resource allocation is a vital issue of wireless cellular networks since the transmission resource is scarce in the wireless domain. Call admission control (CAC) is a very important component of resource allocation since CAC determines how to allocate resource to new calls and handoff calls in order to satisfy the quality of service (QoS) constraints. In this thesis, we consider hierarchical cellular networks supporting a multiple of classes of users with different bandwidth requirements, average call holding times, and mobility, where fast users are assigned to macrocells in the upper layer, whereas slow users are assigned to the microcells in the lower layer. We propose and study CAC with virtual partitioning (CAC-VP) for the system considered. CAC-VP assigns a nominal capacity to each class of users, and each overloaded class of users can use the nominal capacity of underloaded classes of users at the expense of being preempted by the underloaded classes of users if necessary. Furthermore, blocking a new call is much tolerable than dropping a handoff call. Therefore, one guard channel scheme is implemented to prioritize handoff calls over new calls in the system considered. For the mathematical analysis, we use multi-dimensional Markov chains to describe the microcell and macrocell. Simulation program is written in C language verify the accuracy of analytical results. Call-level grade of service (GoS), such as new call blocking probability, preemption probability and forced termination probability are used as performance measures. We also compare the performance of CAC-CS (Complete Sharing) and CAC-VP. The results show that the blocking probability and forced termination probability of CAC-VP are lower than those of CAC-CS.

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