Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/7428
標題: 第三代行動通訊之隨機存取通道之效能分析和改良
The Investigation and Performance Analysis of Random Access Scheme in Third Generation Mobile Communication System
作者: 蔡鴻彰
Tsai, Hong-Zhang
關鍵字: Random Access Scheme;通道碼;ASC;IMT-2000;WCDMA;Preamble;Packet transmission;時槽;隨機存取機制;寬頻分碼多工;存取服務等級;第三代行動通訊
出版社: 電機工程學系
摘要: 
在第三代行動通訊架構中,每個傳輸要求都有其屬於的存取服務等級(Access Service Class ASC).等級愈高,將擁有愈高的優先權.再加上無線資源有限,故無法對於每個傳輸要求都給予服務,因此基地台必須有效的安排不同的媒體傳送的資源來達到最佳的效能.然而在第一代和第二代的行動通訊架構裡面,並無法在隨機存取機制中給予有效的資源分配機制.由於在第三代行動通訊中,資料傳輸是採用寬頻分碼多工處理的技術.並且在隨機存取上,先發射一組短封包來搶得與基地台之間的聯繫,再以分碼多工的技術來傳輸資料封包.因此我們可以在封包傳送之前藉由對短封包的控制,來做有效的資源分配.每個短封包都被對應到一組特定的資源組-時槽(TIME SLOT),通道碼(channel code).每個短封包在傳送之前都要先通過自己本身的等級測試,這個測試是以自我產生的隨機變數跟自己所屬的存取服務等級所具有的參數做比較,通過測試的短封包才可以被傳送.藉由這樣的優先權機構,將可保證擁有較高存取服務等級的傳輸要求,會擁有較高的成功率和較短的傳輸延遲.除此之外,在論文中提出的絕對等級測試(Absolutely Class Check, ACC)架構,則是以一個由基地台發出的絕對等級參數來加以測試每個短封包,達到絕對的優先權控制.使其能夠更全面的保證擁有高優先權的傳輸要求,能夠有更穩定的服務品質.

In this thesis, we introduce the International Mobile Telecommunication 2000 (IMT — 2000) and discuss the effect of the random access scheme in each personal mobile communication system. The mobile host starts the initial transmission between base and itself must communicates by using the random access scheme. In order to satisfy the multiple access service and multimedia service, a priority mechanism in transmission is added. However, in the first or second generation personal communication systems, they do not effectively offer a priority mechanism in random access scheme to guarantee the QoS for different packet source. In Third Generation personal communication system, using the WCDMA technology, it can offer the better performance of packet transmission of different access service source. The Third Generation Personal Communication System uses a preamble to initiate a call before the packet transmitting. The transmitted preamble is specified to the class of the packet source, hence support the priority of different packet source. From this idea we propose an access algorithm to improve the random access performance. We also adjust the parameters and change the flow of priority mechanism, and compare to the original 3G system. Using the proposed algorithm, we can ensure the priority of transmission for each random access attempt of different Access Service Class.
URI: http://hdl.handle.net/11455/7428
Appears in Collections:電機工程學系所

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