論文摘要
在無線ATM網路的環境之中，若架構為Infrastructure(由一個Base Station服務數個Mobile Station的架構)，則其提供QoS保證的服務方法大致可以分為兩種，Reservation-Base和Polling-Based。Reservation-Based的方法是由MS (Mobile Station)主動向BS (Base Station)提出要求，BS在收到MS所提出的要求後決定是否給予資源與資源的多寡，並進行schedule的工作。Reservation-Based的優點是能提供較為動態的資源分配，然而Reservation-Based的方法卻有一項致命的缺點 ，即為request collision的發生，因而使系統的執行效率變差。Polling-Based則是由BS直接並輪流地去詢問每一個MS，以集中管理的方式分配無線ATM網路的頻寬。由這樣的一個方式去得知MS是否需要分配資源及其需求量以傳輸資料。因為由BS主動去負責資源分配的工作，所以Polling-Based的優點在於不會有request collision的發生，然而當有MS需要額外的資源時(如：VBR traffic)，系統卻也因此無法動態和適時的反應其需求。因此為了克服Reservation-Based和Polling-Based的缺點並使用其各自的優點，於是我們初步的構想在於結合這兩種方法來設計MAC protocol。

我們將所設計的媒介擷取控制層通訊協定命名為CRPMA/DS(Combination of Reservation and Polling Multiple Access with Distributed Scheduling)。比起使用Random access的方式來做reservation的無線ATM網路系統，藉有我們所設計的contention resolution方法可以達到更低的collision probability。CRPMA/DS亦可以服務多種不同型態的ATM 服務類別 (如: CBR, VBR, ABR, UBR)。 CRPMA/DS的優點在於使系統擁有很高的throughput，並可適時的服務各種ATM服務類別，使系統整體而言有良好的執行效率。

Abstract
The future of broadband and wireless communications is expected to support multimedia services. In order to provide efficient performance in the wireless networks, wireless ATM (WATM) is suitable to be the framework. With an appropriate medium access control (MAC) protocol, WATM can support multimedia service efficiently and guarantee their QoS requirements. Due to the limited wireless bandwidth problem in the wireless environment, an efficient wireless ATM MAC protocol is needed. In this thesis, a new MAC protocol, named CRPMA/DS, is proposed to support various ATM services, such as CBR, VBR, ABR and UBR. Combination of Reservation and Polling Multiple Access with Distributed Scheduling (CRPMA/DS) is based on a distributed scheduling architecture to access the shared wireless bandwidth. Thus, each mobile terminal (MT) can handle its connections more efficiently according to its requirements. CRPMA/DS also uses a combination scheme with proposed splitting algorithm to solve the request collision and VBR bursty problems.

We simulate our proposed MAC protocol and compare its performance with DTDMA/PR and PRMA/DA. The simulation results show that CRPMA/DS has higher throughput of data traffic (ABR and UBR traffic) and still guarantees the QoS of CBR and VBR traffic. With the splitting algorithm, CRPMA/DS also provides a low collision probability when the MTs send their requests in the reservation period.

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