| The advances in wireless communication technology bring faster and more affordableaccess to the network access services. However, the development of the technology needs tomeet the user’s faster, cheaper and more stable demand for wireless communications. In orderto be able to meet the future needs of the wireless communication, we need to improve theeffectiveness of wireless communication from power, delay, bandwidth, thus providing higherspeed, better quality of service multimedia services. According to these needs, the channelcoding technology, network coding technology and cooperative diversity technology can becombined to improve the validity, reliability and throughput of wireless communicationsystems. In cooperative communication systems, the relay nodes can forward information andachieve signal processing of the information, and also can be to maximize the capacity andthe bandwidth efficiency of the wireless communication system by network codingtechnology; In the same time, the reliability of the system can be improved by using channelcoding technology in cooperative communication systems. Through the applications of jointchannel coding and network coding technology, the capacity and the error correctionperformance of the system is improved, therefore, the study on this technology has importanttheoretical and practical research significance.Specifically, this dissertation mainly investigates the applications of joint channel codingand network coding technology in wireless communication systems. The main contribution ofour works can be summarized as follows:Firstly, the dissertation studied the key technologies in cooperative communicationsystems, such as relay forwarding mode, network coding algorithm, coding cooperativecommunication system schemes, and respectively given the theoretical analysis andsimulation analysis; On this basis, the dissertation studied encoding and decoding algorithmsof typical error correction codes technologies(i.e. convolutional codes, Turbo codes, LDPCcodes), and given the simulation analysis results of three kinds of channel codes.Secondly, the dissertation proposed a cooperative diversity scheme of jointConvolutional code(CC) coding and network coding applicable to multi-source cooperativecommunication system. This scheme conducts CC encoding for information of multiple source nodes received at relay node, and then forwards the encoded code words after networkcoding, after that destination node carries out joint iterative decoding to recover theinformation of multiple source nodes. The result of simulation showed that the bit error rate(BER) performance of multi-source cooperative communication system in this scheme isremarkably improved with increase of the number of source nodes; Meanwhile, thedissertation studied the CC-network coding joint iterative decoding algorithm for two-wayrelay channel, i.e. full-state trellis decoding algorithm and reduced-state trellis decodingalgorithm, derived the two kinds of decoding algorithms, the reduced-state trellis decodingalgorithm compared with the full state trellis decoding algorithm, in the case as far as possiblewithout loss of coding gain, significantly reduced the complexity of the decoding operation.Then, a new scheme of joint design of network coding and channel coding based on theidea of diversity Turbo codes was proposed, that was the joint design of convolutional Turbocode(CTC) and network coding scheme1. This scheme has smaller decoding delay, strongererror correction performance, and for source nodes, not only improve the rate, but also besimpler than direct application of the CTC encoding algorithm. Meanwhile, according to thedefects of the above-mentioned schemes, such as, it is only suitable for application in thecooperative communication system with the case of completely correct decoding in the relaynodes, and has only one receiving antenna in relay nodes and sink nodes, meanwhile notmakes full use of the correlation of informations in the joint decoding process. Therefore, theauthors conducted a further study, and subsequently proposed joint design of CTC andnetwork coding scheme2for multiple access relay channel. This scheme consider that therelay may not correctly decode the source information, the destination can select theappropriate choice of a priori information for decoding. Simulation result shows this schemehas stronger error correction performance and more suitable for harsh communicationenvironment, in addition, with the increase of relay and destination’s receiving antenna, theerror correction performance of the system increases as well, in other words, the proposedscheme can be widely used in the multiple access relay channel environment.Finally, based on the research on channel coding and network coding in cooperativerelay communication system and in allusion to LDPC channel coding with excellentperformance, the dissertation presented a joint design scheme of LDPC coding and networkcoding specific to multi-source cooperative communication system, the result of simulation indicates that the BER performance is remarkably improved with increase of the number ofsource nodes; meanwhile the dissertation proposed an improved check matrix structurealgorithm, i.e. improved PS structure algorithm, The result of simulation shows that LDPCcodes constructed by the improved check matrix structure method proposed in thisdissertation have greater coding gain. |
