无线广播信道存在噪声和多径衰落，导致无线广播性能较差。传统的无线广播重传技术更多地考虑重传效率，而忽视了重要数据包优先重传的问题，使得一些特殊应用难以优先获得那些重要性较高的丢包。为提高无线广播重传的性能，同时满足对数据包重要性敏感应用的需求，本文在传统广播重传技术的基础上提出了一种基于数据包重要性的低时延广播重传算法。此算法在利用机会式网络编码方法编码重传包时，根据各终端所含丢包重要性的级别，分别对丢包进行编码优先权排序，在满足各终端能够及时译码的基础上优先编码终端中重要性高的丢包，权衡丢包重要性与参与编码丢包总的数量，使得一次编码重传中，参与编码的丢包数尽可能的多，并且使重要性级别靠前的丢包优先参与编码，如此不仅保持了一个较好的重传效率，降低了传输时延，同时又缩短终端获取高重要性丢包的时间。仿真结果表明，在典型的无线信道条件下，此算法不仅保持了现有的经典策略好的重传增益，同时突出了重要性高的丢包能够优先获得的优点，降低了传输时延。
Because of noise and multipath fading in wireless channels, the performance of wireless broadcasting is unsatisfactory. Conventional wireless broadcasting retransmission technology takes retransmission efficiency into consideration, while the significance of lost packets is neglected, making it difficult to meet the demand of applications sensitive to packet significance. To improve the performance of wireless broadcasting and meet the demand for packet- significance- sensitive applications, a delay- sensitive broadcasting retransmission algorithm based on significance of packets (DBRA) is proposed on the basis of the conventional broadcasting retransmission technique. According to the significance level of lost packets, the algorithm gives priority to timesensitive lost packets and terminals with significant lost packets, and finds the maximum number of coding opportunities in opportunistic network coding (ONC), thus the transmission efficiency is improved, and the transfer delay of packets is decreased and terminals need less time to get significant lost packets. Simulations show that this algorithm has a probability with better efficiency than other classical algorithms and significant packets have priorities in transmission under classical wireless channel conditions.
[1] Ahlswede R, Cai N, Li S Y R., et al. Network information flow[J]. IEEE Transactions on Information Theory, 2000, 46(4): 1204-1216.
[2] Ho T, Koetter R, Medard M, Karger D, et al. The benefits of coding over routing in a randomized setting[C]// IEEE International Symposium on Information Theory (ISIT 2004), Chicago, IL, USA. 27 June-2 July, 2004.
[3] Ho T, Medard M, Koetter D, et al. A random linear network coding approach to multicast[J]. IEEE Transactions on Information Theory, 2006, 52(10): 4413-4430.
[4] Nguyen D, Tran T, Nguyen T, et al. Wireless broadcast using network coding[J]. IEEE Transactions on Vehicular Technology, 2009, 58(2): 914-925.
[5] Francesco R, Chiti F, Tassi A. An efficient network coding scheme with symbol combining: performance evaluation, optimization, and comparisons[J]. IEEE Transactions on vehicular technology, 2013, 62 (3): 1267-1275.
[6] Katti S, Rahul H, Hu W, et al. XORs in the air: practical wireless network coding[J]. IEEE/ACM Transactions On Networking, 2008, 16 (3): 497-510.
[7] 卢冀, 肖嵩, 吴成柯. 一种基于机会式网络编码的高效广播重传方法[J]. 电子与信息学报, 2011, 33(4): 858-863. Lu Ji, Xiao Song, Wu Chengke. A high efficiency retransmission approach based on opportunistic network coding[J]. Journal of Electronics &Information Technology, 2011, 33(4): 858-863.
[8] 戴彬, 曹志刚,杨军, 等. 基于匹配理论的无线广播编码重传算法[J]. 软件学报, 2011, 22(11): 2833-2842. Dai Bin, Cao Zhigang, Yang Jun, et al. Coded retransmission algorithm based on matching theory for wireless broadcasting[J]. Journal of Software, 2011, 22(11): 2833-2842.
[9] 肖潇, 王伟平, 杨路明, 等. 基于网络编码的无线网络广播重传方法[J]. 通信学报, 2009, 30(9): 69-75. Xiao Xiao, Wang Weiping, Yang Luming, et al. Wireless broadcasting retransmission approach based on network coding[J]. Journal on Communication, 2009, 30(9): 69-75.
[10] 卢冀, 肖嵩, 吴成柯. 基于机会式网络编码的低时延广播传输算法[J]. 电子学报, 2011, 39(5): 1214-1219. Lu Ji, Xiao Song, Wu Chengke. Opportunistic network coding based delay- sensitive broadcast transmission algorithm[J]. Acta Electronica Sinica, 2011, 39(5): 1214-1219.
[11] Li L, Ramjee R, Buddhikot M, et al. Network coding-based broadcast in mobile ad hoc networks[C]// INFOCOM 2007, 26th IEEE International Conference on Computer Communications, Joint Conference of the IEEE Computer and Communications Societies, Anchorage, Alaska, USA, 6-12 May 2007.
