Abstract
無線非同步傳輸 (Wireless ATM) 已經被視為是下一代個人通訊網路的標準，用於整合多媒體通訊服務。而且，無線非同步傳輸網路必須能保證服務品質 (quality of service)。然而，以現行的IEEE 802.11 無線區域網路的標準，並沒有考慮提供服務品質保證。在本論文中，我們將提供一個新的能保證服務品質的介質存取控制層通訊協定，並且配合一個名為 "動態權值且最早到達期限者優先，且能節省與預支權值" (DynamicWeighted EarliestDeadline First with Save and Borrow) 的排程機制。 過去有關無線介質存取控制層通訊協定的方法大致上可分為兩類，競爭模式 (contention-based) 和預約模式 (reservation-based)。在競爭模式方面我們將以著名的 IEEE 802.11 為例，另外預約模式我們以美國 NEC 實驗室的 WATMnet 系統為例，分別加以說明比較。 經過模擬測試分別針對四個項目加以比較：平均延遲 (mean delay)、傳輸損壞率(loss ratio)、頻道使用率 (channel utilization)、輸出量(throughput)。且模擬結果顯示，建議的方法在上述四個項目均能表現的較IEEE 802.11 及 WATMnet 系統為佳。 由模擬結果證實我們建議的方法確實能符合無線非同步網路的需要，並且能提供服務品質的保證。這個新的介質存取控制層通訊協定能夠提供低延遲、平均輸出、低傳輸損壞率和高的頻率使用率的品質保證。即使在系統流量很重時，其效能都比IEEE 802.11 與 WATMnet 為佳。 未來的研究方向，可以繼續朝多蜂巢式 (multi-cell) 的環境來設計，並且把能源節省、錯誤控制等也列入考量。Wireless ATM has been proposed for next-generation personalcommunicationnetworks (PCN) to support the integrated multimediacommunication services.Guaranteed quality of service (QOS) isrequired for the Wireless ATM networksto support multimediacommunications. However, emerging standards, such as the IEEE802.11 Wireless LAN, are designed to provide wireless access ina conventional way without considering QOS provision. In thispaper, we presentan important system design issue for wirelessATM networks in general, is thedesign of an advanced mediumaccess control (MAC) protocol for supporting allATM QoSrequirements for heterogeneous traffic. In the past, thetypical MAC protocols of wireless ATM are based on FDMA,CDMA andTDMA. Most previous MAC protocols in the area use an adaptiveTDMAscheme, due to its ability to flexibly accommodate aconnection's bit rateneeds by allocating more or fewer timeslots depending on current trafficconditions. There are two maincategories used in the TDMA scheme are"contention" and"reservation". These contention-based protocols (like IEEE802.11) attain good performanceunder light traffic, basicallydue to the short delays when the number ofcollision is limited.The reservation-based protocols (like MDR-TDMA) are morecomplexand introduce some extra delays due to the required reservationphase.Their performance depends to a large extent on thescheduling mechanism usedfor the allocation of the availablebandwidth. Thus, we propose a novel guaranteed QOS MACprotocol with Dynamic WeightedEarliest Deadline First with Saveand Borrow (DWEDF/SB) scheduling mechanismfor wireless ATMnetwork. The MAC protocol can provide low latency,fairnessthroughput, low cell loss ratio and efficient channelutilization for QoSguaranteed.