Research On Multicast Retransmission Algorithm Based On Network Coding In Wireless Networks

With the rapid development of communication technology in recent years,especially the popularization of mobile wireless communication technology and portable intelligent terminal,it has brought explosive growth to various applications based on wireless networks.People get a lot of convenience from the wireless networks.But at the same time,the wireless networks cause many problems,such as data error and packet loss because of the poor quality of the wireless network channel,interference and volatile topology.Retransmission is an effective way to ensure reliable transmission of wireless network data,but it will bring additional transmission delay and overhead.The emergence of network coding technology pointed out a new direction to the problem of the retransmission in wireless networks.This paper studies the retransmission algorithm based on network coding in wireless networks.The main work of the paper is as follows:1.This paper introduces two kinds of classical retransmission algorithms based on the network coding.In order to minimize the number of retransmission for optimization target,an Improved Weighted Opportunistic Network Coding Retransmission(IWONCR)was proposed to improve the retransmission efficiency of high-capacity file transmission and so on.First,we used the gain coefficient and the hash value to construct the weight table.Then we used the weight table for the neighborhood search to quickly find the packet combination which satisfied the solvable condition of the receivers.And it also satisfied the retransmission benefit of the receivers as much as possible.The simulation results show that the algorithm can effectively reduce the number of retransmissions required,and has lower computational complexity.It can improve the transmission efficiency and practicability of wireless networks.2.In order to reduce the ratio of over deadline constraint for optimization target,a Low-Delay Improved Weighted Opportunistic Network Coding Retransmission(LD-IWONCR)was proposed for the real-time streaming media application which is sensitive to network delay,such as webcast and so on.The algorithm calculated the average delay factor for each missing packet according to the deadline constraint,and then constructed the weight table according to the ascending order of the average delay factor with the descending order of the hash value and the gain coefficient.The search rule of IWONCR is improved.The average delay factor is the main criterion.The gain coefficient and the hash value are the second criterion.According to them,the neighborhood search was carried out.Under the condition that the receiver is solvable,the more urgent packet is given the chance of retransmission,meanwhile enables more receivers to get the benefit.It achieves the purpose of reducing the ratio of over deadline constraint.The simulation results show that the algorithm has the lowest ratio of over deadline constraint and is more suitable for wireless network applications which are sensitive to delay.