A Cross Layer Design for Efficient Rate and Power Control in W-CDMA System

若要保證多媒體服務的成功，QoS就必須小心的處置，在W-CDMA網路下，RRA是控制QoS的機制中所不可或缺的，而其中最重要的就是速率分配以及能量控制。我們在媒體存取控制層提出一套速率分配的方法；首先，將通道與緩衝器的狀況區分成六種情況，每種情況都有其對應的分數，我們再結合這兩種分數來做為分配速率的參數。接下來，依照通道與緩衝器的危機程度區分成六種情況，每種情況也都有其對應的分數，我們再結合這兩種分數來做為危機程度的參數。最後，我們利用所計算出來的兩種參數做為分配速率的依據，目標是所分配的速率能在相同的QoS條件下，可使平均的封包遺失率降至最低。由於重新分配速率的緣故，以致於SNR值在同時間會有劇烈的變動，因此我們另外在實體層提出一套能量控制的方法來改善此效應。我們將在最後對於所提出的方法作一個效能上的分析，並展示此方法在封包遺失率上有較佳的效能。To ensure the success of wireless multimedia service, quality of service (QoS) has to be implemented with care. Radio resource allocation (RRA) is one of the most important issue and is essential in wireless networks. Among the elements of RRA, both rate allocation and power control play important roles in multimedia W-CDMA networks. A rate allocation power control scheme is proposed to take considerations at both the channel state and the buffer state in MAC layer. First, channel state and buffer state are divided into six conditions. The score of each condition is determined by two kinds of allocation parameter. Second, the score of risk parameter is determined by the score of both channel risk state and buffer risk sate. Third, based on allocation parameter and risk parameter, we propose a rate allocation scheme for wireless multimedia W-CDMA systems, which aims at minimizing average packet dropping rate while maintaining QoS requirement of all active mobiles. Finally, we also apply a multiple step-size power control method which can avoid large variation of SNR while the rate allocation scheme is activated. The simulation results show that the efficiency and performance of the proposed rate allocation scheme and multiple step-size power control can effectively decrease average packet dropping rate.Chapter 1 Introduction…………………………………………………………1 1.1 Motivation……………………………………………………………………1 1.2 The Evolution of the Cellular Telephone System…………………………4 1.3 The Benefits of CDMA Systems……………………………………………6 1.4 Organization of Thesis………………………………………………………8 Chapter 2 Related Knowledge………………………………………………9 Services and Application in W-CDMA System…………………9 2.1 QoS Classes…………………………………………………………………9 2.1.1 General………………………………………………………………9 2.1.2 Conversational Class………………………………………………10 2.1.3 Streaming Class……………………………………………………11 2.1.4 Interactive Class……………………………………………………12 2.1.5 Background Class……………………………………………………13 2.2 Service Capabilities with Different Terminal Classes…………14 Power Control in W-CDMA System………………………………15 2.3 Uplink Power Control………………………………………………………15 2.3.1 General………………………………………………………………15 2.3.2 Algorithm 1 for processing TPC commands………………………16 2.3.3 Algorithm 2 for processing TPC commands………………………18 2.4 Downlink Power Control…………………………………………………21 2.4.1 General……………………………………………………………21 2.4.2 UE Behavior………………………………………………………21 2.4.3 UTRAN Behavior…………………………………………………22 Chapter 3 System Model and Proposed Algorithm in MAC and Physical Layer…………………………………………………24 3.1 System Model……………………………………………………………24 3.2 Proposed Rate Allocation Scheme in MAC………………………………28 3.2.1 General……………………………………………………………28 3.2.2 Calculate the Allocation Parameter……………………………29 3.2.3 Calculate the Risk Parameter……………………………………31 3.2.4 Combine Si with Si-R to Allocate Transmission Rate……33 3.3 Find Optimum Weight………………………………………………………35 3.4 Proposed Multiple Step-Size Power Control in Physical………37 Chapter 4 Performance Analysis of Proposed Algorithms………41 4.1 Environment………………………………………………………………41 4.2 Numerical Results…………………………………………………………43 Chapter 5 Conclusions………………………………………………………50 5.1 Conclusions…………………………………………………………………50 Reference…………………………………………………………………………5