A Reliable and Efficient Broadcasting Protocol Based on Incremental Network Coding

[[abstract]]傳統的網路編碼因需要接收到足夠數量的編碼封包才能還原原始資料，故使得解碼時間變長。若是在傳輸過程中發生封包遺失，節點所發出的要求訊息於其他節點接收後，該節點會將自身所擁有的封包傳送給要求者，但接收端所收到的封包可能與自身所擁有的封包線性相依或是部分重覆，進而造成網路資源浪費。本篇所提出方法Network Coding-Based Reliable and Efficient Broadcasting Protocol(RENC)的目標為利用下三角編碼矩陣來降低編碼延遲的時間以及利用作者所提出的封包重傳方式來減少封包傳送次數，在重傳機制方面，主要提出兩種方法，第一種重傳機制利用節點發出訊息來判斷目前節點的情況，而第二種重傳機制則是採用bitmap的方式來標記缺少的封包。 在實驗方面，我們將RENC與傳統的網路編碼進行比較，由實驗結果可以看出RENC在解碼時間延遲、可靠度與封包傳送次數方面，在網路情況多變時均有不錯的表現。 Network Coding technique has been investigated in many network protocols to increase packet delivery ratio. Traditional Network Coding mechanism needs to receive enough encoded packets to recover original packets, but this will increase the decoding latency. Even though Network Coding can increase packet delivery ratio, it is possible that some encoded packets cannot be decoded due to serious packet lost problem. To recover missing packets, a node can broadcast a request message to other nodes within its transmission range. Once a neighboring node receives the request message, it will check the packet availability within its buffer, encode the required packets, and reply the encoded packets to the node which sent request message. In this approach, the requesting node may receive multiple copies of same packets, and this may waste scarce radio resource. In this paper, a Reliable and Efficient Network Coding-based Broadcasting Protocol (RENC) which can reduce decoding latency and increase radio resource utilization is proposed. RENC utilizes merits of lower-triangular matrix to encode various numbers of packets into a single packet. RENC can reduce the decoding time by Gaussian elimination. Besides, a new retransmission scheme which can reduce the number of transmission messages is also presented. Simulation results reveal that RENC outperforms traditional network coding in terms of decoding latency and reliability