臺灣博碩士論文加值系統

以IEEE 802.11為基礎的無線區域網路通常會傳送單播和廣播的流量。然而，大部分IEEE 802.11的效能研究並未考慮廣播流量的存在。此篇論文中，我們研究非飽和之單跳隨意網路下廣播與單播流量的效能。首先，我們考慮一個混合流量節點的情境來研究在不同流量比例下(也就是，以廣播為主，均勻流量和以單播為主)單播和廣播流量相映的效能。更進一步來說，我們相信藉由車輛間之無線通訊，駕駛員的安全性應可顯著改善。在車載通訊（IVC）中廣播通常用來傳輸安全性相關的資訊像是流量壅塞通知、事故警告、路況報導等。由此可知，在一些重要的應用上廣播流量相較於單播流量應該給予更高的優先權。為了在車載隨意網路中達到駕駛間的互助，我們接著考慮每個節點為單一流量的情形。對於廣播流量我們提出一個動態的傳輸機會（TXOP）方法提供不僅有服務品質（QoS）的保證，同時也能增強廣播流量的可靠度。此動態TXOP方法會根據目前行動台傳輸佇列內封包的數目來調整TXOP參數。我們可以發現動態TXOP方法可以確保廣播流量的成功送達率和平均進接延遲優於單播流量。我們所感興趣的效能指標包含成功送達率、平均進接延遲、碰撞機率、封包遺失率以及封包丟棄率。最後但非最不重要的，我們使用C語言來撰寫模擬程式，並且以模擬結果來驗證數學分析結果的正確性。

IEEE 802.11 based Wireless LANs (WLANs) usually transport both unicast and broadcast traffics. However, most studies on the performance of IEEE 802.11 network do not contemplate the existence of broadcast traffic. In this thesis, we investigate the relative performance of unicast and broadcast traffic in a one-hop ad hoc network under non-saturated conditions. We first consider a hybrid-traffic node scenario to study the respective performance of unicast and broadcast traffic in a variety of mixed traffic scenarios (i.e., broadcast-dominated, balanced, and unicast-dominated). Further, there is a growing belief that driver safety should be significantly improved by vehicle-to-vehicle wireless communications. In inter-vehicle communication (IVC), broadcast transmission is usually used for disseminating safety-related information such as traffic congestion notification, accident warning, road condition report, etc. This implies that broadcast traffic should be given priority over unicast traffic in some important applications. In order to achieve cooperative driving in vehicular ad hoc networks, we further consider a single-traffic node scenario. For broadcast traffic, we propose a dynamic TXOP scheme to provide not only Quality of Service (QoS) guarantee, but also enhance broadcast traffic’s reliability. The proposed dynamic TXOP scheme adjusts the TXOP limits of broadcast stations according to the current transmission queue occupancy. We show that the dynamic TXOP scheme can ensure broadcast traffic outperforms uncast traffic in term of throughput and service delay. The performance metrics of interest are throughput, service delay, collision probability, loss probability, and drop probability. Last but not least, analytical results are validated via simulation results, and the simulation program is written in C language.

摘要
Abstract
List of Figures
List of Tables
1. Introduction
2. IEEE 802.11 Series Review
2.1 Architecture
2.2 Physical Layer
2.3 Medium Access Control Sub-Layer
2.4 Distributed Coordination Function (DCF)
2.5 EDCA Overview
2.6 IEEE 802.11 Broadcast Operation
3. System Model
3.1. Hybrid-Traffic Node
3.1.1. Homogeneous Scenarios
3.1.2. Heterogeneous Scenarios
3.1.3. Performance Metrics
3.2. Single-Traffic node
3.2.1. Intra -plane Transitions
3.2.2. Inter -plane Transitions
3.2.3. Heterogeneous Scenarios
3.2.4. Steady-State Probability Distribution
3.2.5. Iterative Algorithm
3.2.6. Performance Metrics
4. Numerical Results
4.1. Hybrid-Traffic Node Model
4.1.1. Fixed Number of Stations
4.1.2. Fixed Arrival Rate
4.2. Single-Traffic Node Model
4.2.1. Non-TXOP Scheme
4.2.2. Fixed-TXOP Scheme
4.2.3. Dynamic-TXOP Scheme
4.2.4. Comparison of Different TXOP Schemes
5. Conclusions
References

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