因應無線通訊網路的快速發展所制定IEEE 802.16標準，設計為無線都會型網路(Wireless Metropolitan Access Network, WMAN)，提供寬頻網路較大的傳輸距離與覆蓋範圍，並具有較高的傳輸速率與較低的建置成本等特點。此外，為了保障各種多媒體(multimedia)的服務品質(Quality of Service, QoS)，在IEEE 802.16標準規範中定義了五種服務流的類型，而每一種服務流都有專屬的服務品質要求；然而，在IEEE 802.16標準中並未提出服務流的排程法或排程演算法(Scheduling or Scheduling Algorithm)。如何設計出合適的排程演算法來滿足所有服務品質類別的需求成為開放探討的議題，因此許多排程法或排程演算法被提出來，試圖滿足並達成每一種服務流的服務品質。
由於IEEE 802.16標準尚未定義各項服務流的排程演算法，亦沒有為基地台(Base Station, BS) 的輪詢方法 (Polling) 定義出相關的管理機制，而輪詢是一種傳送機制，在資料傳送之前，基地台會對用戶端工作站 (Subscriber Station, SS) 進行輪流詢問是否有資料要傳送。首先，用戶端工作站 (SS)必須先等待收到基地台 (BS) 的輪詢；第二步，被詢問的用戶端工作站再向基地台傳送頻寬需求 (Bandwidth Request)；之後用戶端工作站等待收到基地台分配的頻寬通知，才可以傳送資料，換句話說也就是「輪詢－請求－授予」機制來定義上傳頻寬如何分配使用。
根據「輪詢－請求－授予」機制，本論文提出依據封包遺失率的輪詢調整法 (Polling Adjustment Scheme based on Packet Loss Rate, PASPLR)，第一步會先計算出目前資料傳送的封包遺失率，再依據封包遺失率高低調整輪詢間隔 (Polling Interval) 的時間。除此之外，當戶端工作站被輪詢時，若即時服務流有資料需傳送，而且非即時服務流亦有頻寬要求資料需傳送，也可附掛上頻寬要求，如此基地台會根據戶端工作站的服務流要求來分配頻寬，先分配頻寬給即時服務流，若有剩餘頻寬，則將分配給非即時服務流之頻寬要求。模擬的結果顯示，此輪詢調整法能更有效率的利用頻寬。

The IEEE 802.16 standard is designed according to the rapid development of wireless communication network. It is designed as a Wireless Metropolitan Area Network (WMAN). The IEEE 802.16 standard provides broadband network transmission distance and coverage, and has a higher transmission rate and lower construction costs and so on. In addition, in order to guarantee the quality of service (QoS), in the IEEE 802.16 standard specification defines the five types of service flow, and each service flow has a unique service quality requirements. However, the scheduling or scheduling algorithm of the service flow is not proposed in the IEEE 802.16 standard. How to design a suitable scheduling algorithm to meet the needs of all service quality categories is an open topic, so many scheduling or scheduling algorithms are proposed to try to meet and achieve the quality of service for each service flow.
Because the IEEE 802.16 standard has not yet defined the scheduling algorithm for each service flow, there is no defined management mechanism for the polling of the base station (BS). The polling is a transmission mechanism, before the data transmission, the base station will be on the subscriber station (SS) in turn asked whether there is data to be transmitted. First, the subscriber station(s) must wait for the polling of the base station. Second, the subscriber station is asked to send the bandwidth request to the base station. Next, the station waits to receive the grant notification from the base station before it can send the data. In other words, the "polling - request - grant" mechanism is to define how the upload bandwidth is allocated.
According to the "polling - request - grant" mechanism, this paper proposes a polling adjustment scheme based on packet loss rate (PASPLR). The first step of PASPLR is to calculate the packet loss rate of data transmission, and then PASPLR adjusts the polling interval according to the level of packet loss rate. In addition, when the subscriber stations are polled, if the real-time service flows require sending data, and non-real-time service flows also requires transmitting data, they are capable to employ the piggyback to meet the bandwidth requests. In this way, the base station allocates bandwidth according to the service flow requirements of subscriber stations, allocating the bandwidth to the real-time service flows, and if there is the remaining bandwidth, it will allocate the bandwidth requirement to the non-real-time service flows. The simulation results show that this polling adjustment scheme can make more efficient use of bandwidth.

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