封包壅塞控制協定是一種屬於傳輸層的網路通訊協定，其針對非可靠性的資料傳輸流提供壅塞控制機制，可以視為傳輸控制協定(TCP)與用戶數據封包協定(UDP)的混和。封包壅塞控制內建的壅塞控制機制是依據當前的網路傳輸環境調整其資料傳輸速率。然而，封包壅塞控制協定運行在無線網路環境時，因為無法準確的估算出傳輸路徑上的網路壅塞情形，導致傳輸速率調整上的效率低落。
本篇論文提出一個機制，用於提升封包壅塞控制機制在無線網路環境運行時的效率。本篇論文提出的機制為基於跨階層式的錯誤分辨機制，以分辨出因壅塞導致的封包遺失以及因無線環境訊號衰減導致的封包遺失。跨層式的設計是基於即時地偵測底層的訊框遺失率而計算出傳輸層因訊號衰減影響的封包遺失。當真實的網路壅塞情形被準確地分辨出來，封包壅塞控制機制便能適當地調整封包傳輸速率以提升頻寬使用效率。此外，在本篇論文中，亦在封包壅塞控制協定中加入了錯誤回復機制以復原因訊號衰減導致的資料遺失。

DCCP (Datagram Congestion Control Protocol) is a transport layer protocol that provides congestion control for unreliable data transmission. The congestion control mechanism embedded in DCCP adjusts the packet sending rate according to the network condition. However, DCCP does not discriminate congestion loss and fading loss, which results in wireless link errors, and thus it leads to unnecessary rate adjustment. In this thesis, we proposed a mechanism, DCCP-LDwl, to enhance the efficiency of DCCP over the wireless network. We employed a cross-layer loss discrimination scheme to distinguish congestion loss and fading loss. The cross-layer based mechanism detects frame loss in the data link layer in real-time to infer the actual fading loss rate. Thereafter, the fading loss can be excluded from the packet loss observed in the transport layer. Once the accurate congestion loss rate is calculated, the sender can make appropriate adjustment for the transmission rate that reflects the current congestion state along the transmitting path using the DCCP rate control procedure. Furthermore, in order to improve the transmitting efficiency against fading loss over the wireless link, we adopt the adaptive FEC (Forward Error Correction) mechanism into the proposed scheme over DCCP to recover the corrupted packets. Simulation results show that DCCP with our proposed CCID 3 rate control scheme can discriminate fading loss and achieve from 4.7% to 15.5% improvement on transmission throughput when the fading loss rate varies from 5% to 15% in the wireless network.

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[23] DCCP patch in NS2 http://lifc.univ-fcomte.fr/~dedu/ns2/
[24] Microsoft Windows Native Wifi API http://msdn.microsoft.com/zh-tw/library/windows/desktop/ms705969.aspx