「無線寬頻都會網路（Wireless Metropolitan Area Network, WMAN）」為一項支援移動的新興技術，此架構亦增強了頻寬資源上的使用效率，主要方法即以時間與頻率的切割的方式將單位時間內的頻寬再細分成子頻段，而將一連續的區塊定義成一個叢集，基地台會根據每個移動使用者傳輸資料型態與服務等級，規畫上傳/下行的叢集給予一個移動使用者。然而，在IEEE 802.16e OFDMA系統的標準中，用來告知移動使用者該何時接收下行資料的下行排程（Downlink MAP）結構需要占用系統頻寬；若下行的資料封包普遍過小時，則此單位時間中可傳送的下行叢集數量變多，將會增加下行排程中下行排程資訊元素（Downlink MAP Information Element）的數量，造成下行排程放大的主因，而使整個頻寬使用率下降。再者，下行排程屬於廣播資訊，因而使用最低階調變與編碼以保證低錯誤率，但過大的下行排程資訊也會提高錯誤率。為了解決發生在下行排程上的資源浪費與正確行，此論文提出四種不同之下行排程壓縮結構，每一種壓縮結構保留原本下行排程資訊元素描述方形叢集的部分資訊，進而減少下行排程資訊元素所攜帶的訊息。針對每一個下行排程壓縮結構，基地台端會使用特定的演算法將完整的資訊轉換成下行排程壓縮結構並傳送給移動使用者端，移動者端再根據特定的演算法將下行排程壓縮結構還原為原本完整的資訊。此論文利用數據分析比較對應於標準規格所使用的資源，以及使用下行排程壓縮結構所減少的資源及比例。 The new mobile wireless metropolitan area network (WMAN) architecture imposes a demanding performance requirement on the radio resource to provide broadband internet access. The radio resource is partitioned as bursts in time and frequency domains and used by mobile stations (MS) in an exclusive manner. The base station (BS) functionally serves as a resource controller for traffic to and from the MSs associated with it, and thus naturally generates the proper downlink (DL) and uplink (UL) MAPs for active MSs based on service and traffic requirements. However, the DL-MAP construction scheme in IEEE 802.16e OFDMA standard, which was designed for handling irregular traffic pattern of MS, often produces a large DL-MAP, as a certain small amount of data distribution to each MS will render a potential overhead of information elements (IE) in DL-MAP and limit the overall capacity. Moreover, the robustness requirement on MAP broadcasting would further cause severe system overhead. As a solution, we propose four exclusive condensed DL-MAP structures, which only carry partial information of each rectangular burst in order to reduce the size of IE in DL-MAP. For each condensed DL-MAP structure, the algorithm for BS to produce the condensed DL-MAP structure and the algorithm for MS to precisely reconstruct the original DL-MAP structure are provided. As confirmed by the analysis results, the proposed condensed DL-MAP can achieve significant DL-MAP size reduction compared with standard DL-MAP structure.
