| Network coding allows the coding node to encode the packets received and then forward the encoding packet,which can make full use of the relevance between packets to recover the packets requested,break the traditional "store-forward" transmission mode.The broadcast characteristics of wireless transmission media can give full play to the characteristics and advantages of network coding.Starting from the multi-stream network scenario,this thesis studies the effect of network encoding based cache management mechanism on system performance in wireless networks and the effect of cache replacement strategy on the effectiveness of packet selection.Firstly,a cache management scheme based on network coding is proposed to solve the problem that the downstream node encoding package can not be decoded due to encoding conflicts in multi-stream situations.This scheme takes the downstream node decoding rate improvement as the goal,and reduces the impact of packet delay due to the cache waiting to a certain exten,makes a clear distinction between coding and non-coding flows according to the downstream node information,makes encoding nodes perform caching and forwarding operations reasonably,increases the probability of encoding and decoding and simutanesouly reduces the noncoding packet transmission delay.Simulation results show that this scheme can effectively improve the decoding rate and reduce the completion time of the system under multi-stream condition compared with the traditional cache management scheme.Secondly,in order to further improve the cache management scheme based on network coding and improve the hit ratio of node cache space effectively,an optimized cache replacement strategy based on network coding is proposed in this paper.This scheme combines the idea of the traditional cache replacement algorithm the least recently used(LRU)and the characteristics of network coding technology,and proposes the corresponding cache replacement algorithm for the coding node and the destination with different functional characteristics respectively.The efficiency of node cache is improved and the hit ratio of cached packets is improved simultaneously. |
