高速IEEE 802.11介質存取控制器

Abstract

在1997年定訂了IEEE 802.11的規範後，很多的無線的應用很快的就如雨後春筍般起來。原來的1M、2M速度很快的就不夠使用，所以積極的再定訂更快的標準。在1998年的IEEE 802.11b-draft2.0中又有提出5.5M及11M的規範，相信在未來一定會有更高速的規範會不斷的推出。現在的IEEE 802.11介質存取控制器大多的採用中央處理器為基礎的架構設計。但是以中央處理器為基礎的架構對於區域網路低成本及高傳輸速度的要求，不符合經濟效益。而以標準單元式積體電路來製作IEEE 802.11介質存取控制器可以達到降低成本及高傳輸速度的要求。 針對未來高速的需求，本論文以實際硬體設計一顆符合IEEE 802.11且可高速處理的介質存取控制器，達到100Mbps的處理速度。並對於需要快速回應的控制訊框及時間相關的管理訊框由硬體來做處理。

After the standardization of the IEEE 802.11 in 1997, wireless LAN market becomes a new fashion trend. In the original standard, the data transmission rate is only limited to 1/2 Mbps; the growing demand in speed quickly pushes the standard to approach higher speed. In 1998, a new draft standard (IEEE 802.11b-draft2.0) specified the data transmission rates of 5.5Mbps and 11Mbps. As expected, a higher speed specification will be brought up in the future. Perhaps up to now, the most popular structure of IEEE 802.11 media access controller (MAC) is CPU-based. Yet, the CPU-based structure suffers from its quickly increasing cost when higher speed is targeted. We therefore propose a pure cell-based IC designed MAC. This new architecture shall fit better to the low cost nature of the LAN products. In addition to CSMA/CA mechanism, considering the speciality of the IEEE 802.11 standard, we also implement some other features, such as direct response to Control frames and time-critical Management frames, partial PCF supports, and Consecutive fragment transmissions, in our MAC. Enforced with these features, a host driver only needs to handle the transmission of data frames, and hence, facilitates the system control. Finally, although the current draft only specifies 5.5 and 11Mbps, our MAC is targeted to be able to handle transmission speed upto 100Mbps.