Research On Key Technology Of Network Coding Based On Convolution Code

Network coding has changed the traditional information processing model,network node can encode multiplex data into one data before sending, making thenetwork transmission rate to reach the maximum flow. Based on this idea, networkcoding technology has been widely used in the wireless network in order to improvethe performance of the transmission system. So to ensure that wireless networktransmission efficiency, and improve the performance of the system, this paper willcombine network coding technology and channel coding technology, focus onthe performance of network coding based on convolutional codes in a wirelesscommunication system.Firstly, this paper introduces the basic theory of network coding and convolutioncode, and then focus on the transmission performance of network coding in unicastcommunication system and multiple access relay system is mainly researched. Themain contents of this paper are as follows:For wireless unicast communication, convolutional codes are used as channelcoding in the sender, and combining it with network coding technology. an improvedscheme for data retransmission is proposed to improve the performance of the biterror rate in unicast wireless link.The sender does not directly retransmission of original signal after receivingNACK from receiver in the improved retransmission system. the retransmission phasewill consist of combining a incorrectly decoded codeword after the initialtransmission with a new codeword in the transmitter, both of which are coded atdifferent rate respectively. then the corresponding hybrid information is destined tothe same receiver. Moreover, in order to recover original information, the receiveruses soft combining to combine the retransmitted packet with the initial packet duringthe previous transmission phase and then makes a decoding process. Simulationresults show that the performance of bit error rate of the proposed scheme is lowerthan the traditional automatic repeat request(ARQ) scheme.For the multiple access relay channel transmission scenario, based on relaytechnology of network coding, this dissertation has designed two kinds of jointdecoding scheme to improve the ability of error correction at the receiver.In the design of transmission scheme, convolutional codes are chosed as the onlychannel coding, at the same time, two relay protocols which are Decode and Forward and Demodulation and Faward are combined with network codingrespectively in the relay node, and the information from the source nodes is processedand forwarded to the destination node. In addition, the destination node adopts twojoint network channel decoding (JNCD) algorithms for each relay transmission mode.In the first JNCD case, three different data from the source nodes of MS1,MS2andrelay node R separately is inputted joint network channel decoder after channeldecoding in the destination node; In the second JNCD case, three different data fromthe source nodes of MS1,MS2and relay node R separately is inputted channeldecoding after joint network channel decoder. The simulation results show that BERperformance of two algorithms with multiple iterations in DF protocol is superior toDMF protocol in Rayleigh fading channels.