臺灣博碩士論文加值系統

我們考慮應用於智慧型運輸系統之兩層式分碼多重進接細胞網路，其中每個行動使用者都是在道路上移動的車輛或載具，而且每個行動使用者都只可沿兩個方向之一移動。我們假設所考慮之系統可提供語音的窄頻服務和多媒體的寬頻服務給行動使用者。寬頻服務是分配到相關之巨細胞以便降低使用者的交遞次數，而語音服務則是分配到相關之微細胞。為了提高交遞連結的通道使用優先權，我們使用一種保護通道機制來限制新連結的允入。為了使巨細胞的資源能夠受到充份利用，我們允許在微細胞的語音連結溢流到巨細胞來使用資源。但也為了避免過多的溢流連結充斥在巨胞而影響寬頻連結的效能，我們使用另一種保護通道機制來降低溢流連結的流量。另一種降低巨細胞之溢流流量的方法是讓溢流之語音連結可被取回至微細胞。為比較起見，我們討論三種不同的系統模型：Model A為獨立的兩層；Model B可允許微細胞的使用者溢流到巨細胞，但不允許取回；Model C可允許微細胞的使用者溢流到巨細胞，且也允許取回。在這個系統的數學分析方式上，我們使用兩個多維的馬克夫鏈分別表示微細胞和巨細胞，來推導我們所感興趣的效能量度，例如新連結阻塞機率、交遞失敗機率、強迫中斷機率以及通道利用率。最後但並非最不重要，除了用數學分析來得到效能量度以外，我們也同時利用以C語言撰寫之電腦模擬程式來驗証數學分析結果的正確性。

We consider two-tier cellular CDMA networks for ITS (Intelligent Transpor- tation System), where mobile users can move in only one of two directions. Both narrowband voice service and broadband services are supported in the considered system. The broadband calls are assigned to the associated macrocell in order to reduce the times of handoff and the voice calls are assigned to the associated microcell. One guard channel scheme is implemented to prioritize handoff calls over new calls in the system. To avoid macrocell resource under-utilization, voice calls in microcells can be allowed to overflow to macorcells. To avoid excessive overflow from the microcells, another guard channel scheme is adopted to prioritize broadband calls over voice calls. Another way to avoid excessive overflow in macrocells is to allow overflowed voice calls to be taken back to microcells. For comparison purposes, we study three models: Model A (no overflow), Model B (overflow without takeback), and Model C (overflow and takeback).Two multi-dimensional Markov chains are used to describe microcells and macrocells, respectively, and the analytical results for the performance measures of interest are derived, e.g., new call blocking probability, handoff failure probability, forced termination probability, and utilization. Last but not least, simulation programs are written in C to collect simulation results for verifying the analytical results.

摘要 I
Abstract III
Contents of Tables VI
Contents of Figures VI

I. Introduction 1
II. System and Traffic Models 5
A. System Model 5
B. Traffic Model 6
C. Call admission control 7
a. New Call Arrivals 7
b. Handoff Call Arrivals 7
c. Overflow 8
d. Takeback 8
e. Call Completion 8
f. Region Change 8
III. Analytical Method 9
Model B 9
1. Microcell 9
2. Macrocell 15
Model C 25
1. Microcell 25
2. Macrocell 29
IV. Numerical Results 43
A. Accuracy of Analytical Results 43
B. Effect of Overflow and Takeback 43
C. Effect of Overflow Guard Channel 45
D. Effect of call holding time of broadband calls45 45
E. Effect of offered load of broadband calls 45
F. Effect of handoff guard channels 46
a. Effect of handoff guard channels in microcells 46
b. Effect of handoff guard channels in macrocells 46
c. Mixing effect of handoff guard channels in microcells and macrocells 47

V. Conclusion 49
Reference 93

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