WiMAX (Worldwide Interoperability for Microwave Access,微波存取全球互通),是一項基於IEEE802.16-2004標準的技術,主要用在都會型區域網路(MAN)。在標準裡規範MAC Layer分為三個子層,分別為聚合子層,共通子層與安全子層。本論文將探討與實做MAC Layer最上層之聚合子層(Service-specific Convergence Sublayer),而聚合子層(CS)主要有兩個工作,分別是進行分類(Classification)與檔頭壓縮(Payload Header Suppression,PHS)。 分類(Classification)目的是協助封包尋找適合的服務流(Service Flow)進行資料傳送。聚合子層在收送封包時,必須搜尋並比對規則;然而所有的分類與壓縮規則的設定必須在連線建立或服務流建立時才會產生,該規則屬於當時建立的服務流的參數之一,也就是說符合此分類規則篩選出來後的封包,應該要利用所屬的服務流進行資料傳送。該資料封包才能被授予相對應的服務流的各項參數限制。因此,如何透過分類規則快速對應到各項所需要的資訊,以及讓CS層能夠迅速地新增或刪除單一或多數的規則,就需要依賴分類規則的資料結構設計。這也是本論文最主要的實作方向與目的。 檔頭壓縮(PHS)則是為了減少頻寬的浪費。由於檔頭中部份資料在大量且連續的資料傳輸過程中是重複多餘的,因此對這些重複性高的檔頭內容可以壓縮資料(suppression)來增加WiMAX通道傳輸的效能,對需要較高頻寬需求之應用如IPTV等而言,是個很有效率的做法。 本論文將實作此兩部份,分別在PC上測試並將其移植至嵌入式系統中。
WiMAX (Worldwide Interoperability for Microwave Access), based upon the IEEE 802.16 standards, provides wireless broadband access for metropolitan area networks. The wide coverage and high data rate make it a promising technology to substitute DSL and Cable for last mile access. In the IEEE 802.16 standard, there are three sublayers defined in the MAC protocol: the convergence, common part, and security. The convergence sublayer is in charge of payload classification and payload header suppression. It plays an important role in differentiating QoS (Quality-of-Service) classes and saving radio transmission capacity. The thesis focuses on the realization of the convergence sublayer under the MAC protocol stack. We design an intelligent classifier that can categorize packets not only by well-known identifiers such as IEEE 802.1p priority, VLAN ID, port number, and ToS/DSCP, but also by examining payload type. The classification rule can quickly and automatically set up for further packet processing. In turn, the design of header suppression follows the rule given in the standard. The implementation of the convergence sublayer was first tested in PC environment and then transplanted into a Sunplus SPCE3200 embedded system. All functionalities were verified as well.