微小蜂巢式非同步傳輸網路之高效率且高服務品質的交遞協定

Abstract

無線資訊網路需要使用小蜂巢來支援大量的使用人數，然而頻繁的交遞行 為會造成網路訊務控制的額外負荷。現存的快速交遞協定，其交遞過程仍 有小封包遺失及小封包違序的問題。在本論文中我們提出一個能避免小封 包遺失及保証小封包順序的新穎交遞協定，它可提高微小蜂巢式非同步傳 輸網路的效能。在交遞前藉著將小封包多點播送到新基地，我們的設計可 避免小封包遺失且可適用於非重疊的微小蜂巢環境。在交遞時透過多點播 送訊息來協調新舊基地台間的小封包傳送順序可保証小封胞順序。我們以 有限狀態圖的正規表示法來說明並驗証此協定。為確保服務品質，我們提 出一種階層式無線呼叫允許控制來限制使用中的連線數目以避免無線頻道 擁塞。我們也提出一套數學模式來分析兩個服務品質參數，分別是交遞中 斷機率與強制結束機率。實驗結果顯示，在與單層式比較下，階層式無線 呼叫允許控制能有效地降低交遞中斷機率及有較小的強制結束機率。 Wireless information networks need to employsmall radio cells to support large user population.However, this will impose extra burden onnetwork traffic control as a result of frequent handover behavior.Existing approaches to support a high handover ratestill have cell loss and cell out of sequence penalty while thehandover is in progress. This thesis proposes a novelhandover protocol that can avoid cell loss and guarantee cell sequence.It can enhance the performance of a micro-cellular ATM network.By multicasting cells to a new base station before handover,our scheme can avoid cell loss and support a non-overlappingmicro- cell environment as well. The multicast of signaling messages duringhandover is to coordinate the cell transmission order between the oldbase station and the new base station to guarantee cell sequence.A formal representation of the handover protocol using finite state diagramshas been developed to specify and verify the protocol.To guarantee quality of service, we present a hierarchical wireless calladmission control to limit the number of in-progress connections andto prevent radio channel congestion.A mathematical model has been developed to analyzetwo quality of service parameters,handover dropping probability and forced terminationprobability. Experimental results show that our hierarchical wirelesscall admission control can effectively reduce the handover droppingprobability and provide a smaller forced termination probabilityin comparision with the single-layer wireless call admission control.