臺灣博碩士論文加值系統

由於通訊需求的多樣化，下一代無線網路預期將支援極多種服務，例如語音、數據、與視訊。如眾所知，不同之服務可能具有極為不同之特徵。舉例而言，數據之連結服務時間通常遠大於語音之連結服務時間。具有較長連結服務時間之連結在其服務時間中平均而言會導致較多的交遞請求。頻繁之交遞請求可能對於服務品質造成重大影響。在無線網路中，連結允入控制是提供服務品質保證的一個關鍵要素。一般相對於新連結的阻塞，通話中的交遞連結所造成的中斷是更令人無法接受的。所以相對於新連結，我們為交遞請求預留資源使其有較高的進接優先權。我們提出一種動態優先權化連結允入控制方法，以提供動態適應型優先權化的連結允入。此方法會在每個細胞中根據其鄰近細胞目前進行連結的數目與移動圖樣所估算的交遞連結抵達率，來調整保護通道的數目，以維持交遞阻塞機率在目標值以內，並使新連結阻塞機率之惡化減到最低。為了讓系統模型趨近於真實的環境，我們採用一個具有許多不同但有限數目細胞的多細胞組態，以及假設每個細胞間行動台之轉移機率可有所不同並取決於一天的時間。我們同時考慮靜態與非靜態負載狀況的效能評估。我們以C語言撰寫電腦模擬程式來求得感興趣之效能量度，並且藉由模擬來證明我們方法之效果。我們探討每種細胞與每個時段對系統效能所造成的影響。同時我們也將比較所提出的動態保護通道方法與靜態保護通道方法。結果顯示，總體而言，我們的方法能得到較好的效能量度。

Due to the diversity of communication needs, the next generation wireless network is expected to support a wide range of services, such as voice, data, and video. As is well known, different services may have very distinct characteristics. For example, the call holding time of data is usually much longer than that voice. One call with longer call holding time on average leads to more handoff requests during its lifetime. Frequent handoff requests may give a serious impact on quality of service (QoS). Call admission control (CAC) is one of the key elements to provide quality of service guarantee in wireless mobile networks. In general, compared to new call blockings, forced termination of ongoing calls due to handoff blocking is less tolerable. We give a higher access priority to handoff requests over new calls by reserving them resources. We propose a call admission control scheme to provide dynamic adaptive prioritized admission of different traffic classes. The scheme adapts the number of guard channels in each cell according to the estimate of the handoff call arrival rate computed from the number of ongoing calls in neighboring cells and the mobility pattern, in order to maintain the handoff failure probability at the target objective while minimizing the degradation to the new call blocking probability. In order to make the system model more realistic, we adopt a multi-cell configuration, where cells may have different mobility pattern and the number of cells is finite. We assume the transit probability of a mobile station from one cell to another cell depends on both the cell type and the time of day. We study both stationary and non-stationary scenarios. We write simulation program in C language to obtain performance measures of interest, and we demonstrate the effectiveness of our method by simulations. We study the effect of cell types and time intervals on performance measures. We also compare the proposed dynamic guard channel scheme and the static guard channel scheme. The results show that, overall speaking, our scheme results in better performance.

中文摘要 I
英文摘要 II
目錄 III
圖目錄 V
表目錄 XVII
第一章 緒論 1
第二章 系統模型 4
2.1 基本假設 4
2.1.1 新連結及交遞連結抵達速率 5
2.1.2 連結服務時間 5
2.1.3 停留時間 5
2.1.4 通道服務時間 5
2.2 多細胞模型 6
2.3 行動台的移動性……………………………………..7
2.4 連結允入控制 10
2.4.1 靜態保護通道方法…………………………….10
2.4.2 動態保護通道方法…………………………….11
2.4.2.1 多重保護通道........…………………..11
2.4.2.2 瞬間交遞連結抵達率之估測……………..12
2.4.2.3 阻塞機率近似演算法……………………..15
2.4.2.4 保護通道適應型控制……………………..20
第三章 模擬結果與分析…………………………………....24
3.1靜態流量模型 25
3.1.1單一服務之效能分析 25
3.1.1.1 全天時段…………………………………..25
3.1.1.2 早上通勤時段……………………………..27
3.1.1.3 尖峰時段…………………………………..27
3.1.1.4 下午通勤時段……………………………..28
3.1.2兩種服務之效能分析 28
3.1.2.1 全天時段…………………………………..29
3.1.2.2 早上通勤時段……………………………..31
3.1.2.3 尖峰時段…………………………………..32
3.1.2.4 下午通勤時段……………………………..33
3.2非靜態流量模型 34
3.2.1單一服務之效能分析 35
3.2.2兩種服務之效能分析 37
3.3總結分析 39
第四章 結論………………………………………………..124
參考文獻 126
附錄A 流程圖………………...…………………………..130

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