多速率無線隨意網路下的實用網路編碼與編碼認知性 路由演算法設計

Abstract

網路編碼(network coding)技術已被證明可以有效提高網路容量，並且在過去幾年來受到許多重視。奠基於網路編碼理論的COPE是一被提出用來將網路編碼應用於無線網路中的轉傳機制。近年來的文獻也指出編碼認知性路由-積極改變路徑已創造更多的編碼機會-可以進一步提高網路的吞吐量。然而這些文獻作品中，包括COPE，都假設節點以單一傳輸速率來傳送封包。在現有的許多無線網路標準中皆已支援節點使用多傳輸速率，如802.11abg；但如何在多傳輸速率之網路環境下實現網路編碼至今仍少有討論。 在本篇文章中，我們討論COPE在多速率無線網路中所遇到的問題以及傳輸速率對網路編碼機會之影響。我們提出了一個創新的編碼度量，並且改良COPE來解決這些問題。利用這個新的演算法我們可以在多傳輸速率下選擇最佳的編碼機會及傳輸速率。我們也提出了一個新的編碼認知性路由協定，它同時考慮我們所提出的編碼度量以及多傳輸速率之無線隨意網路環境，以積極的增加網路編碼機會。我們的編碼度量同時考慮了網路容量，網路編碼，干擾和封包流失率。根據我們NS-2之模擬結果，它確實比其他未考慮網路編碼之路由協定擁有更顯著的效能提升。

Network coding is a promising technology to increase network capacity, which has receive much attention over the past few years. Based on the theory of network coding, a forwarding architecture for wireless network, named COPE, is proposed to put network coding in practice. Prior works have also proved that coding-aware routing can further increase network throughput if route of flows is proactively changed for creating more coding opportunities. However, these works, as well as COPE, do not consider multi-rate operation, which is supported in most of current wireless standards, such as 802.11abg. In this work, we discuss the penalties of COPE in multi-rate wireless ad hoc network and the tradeoff between transmission rate and coding opportunities. A novel coding metric and a refinement of COPE algorithm (MCOPE) are proposed to overcome the problems, which can make the best coding decision effectively. We also propose a new coding-aware routing protocol (C2AR), which incorporate with MCOPE, to increase coding opportunities in multi-rate wireless ad hoc networks. Our coding metric accounts for network capacity, network coding, interference and packet loss rate. According to our NS-2 simulation, it indeed outperforms other coding-oblivious routings.