كاربرد برنامه ريزي خطي در كد برداري وآشكار سازي

چكيده انگليسي :

Abstract In recent years there has been an increasing demand for efficient and reliable digitaldata transmission and storage systems This demand has been accelerated by theemergence of large scale high speed data networks for the exchange processing andstorage of digital information in the commercial governmental and military spheres Amerging of communications and computer technology is required in the design of thesesystems A major concern of the system design is the control of errors so that the data canbe reliably reproduced In 1948 Shannon demonstrated in a landmark paper that by proper encoding of theinformation errors induced by a noisy channel or storage medium can be reduced to anydesired level without sacrificing the rate of information transmission or storage as long asthe information rate is less than the capacity of the channel Since Shannon s work mucheffort has been expended on the problem of devising efficient encoding and decodingmethods for error control in a noisy environment Recently linear Programming LP decoding as an approximation to MaximumLikelihood ML decoding was proposed by Feldman et al ML certification a solid theoretic foundation and the capability to be used for all binary linearcodes are the main properties that have made LP decoding of great interest since its introductionby Feldman Since the complexity of Feldman s first formulation for LP decoding increasesexponentially with the degree of the check nodes in the Tanner graph of the code it has only beenused for low density parity check LDPC codes thus far Recently Yang et al suggested a new LPdecoder with polynomial complexity This allows the practical use of LP decoders for non LDPCcodes Attempts have been made to eliminate the use of a general LP solver by using iterativealgorithms Also replacing several receiver components e g demodulator channel equalizer anddecoder by one linear programming unit has been proposed These developments make LPdecoding an important candidate for future implementation On the other hand many observations suggest similarities between the performance of LPand message passing methods Hence LP decoder with its solid theoretic foundation can beused to make prediction on the performance of message passing algorithms In this research different aspects of LP decoders are investigated Then by using theidea of Feldman in relaxing an integer programming problem to obtain a linearprogramming one in his approach towards achieving the LP decoder we introduce a newlinear programming based multi user receiver The proposed receiver achieves MLperformance provided that some conditions are satisfied by different users signaturewaveforms The performance of the proposed receiver is compared with some other multi user detectors via simulation Furthermore an algorithm for improving LP decoding for animportant class of linear block codes i e cyclic codes by using a redundant parity check matrix isintroduced The key idea is to use the code structure and properties of the LP decoder to expand theparity check matrix to obtain a prescribed performance Performance results show that an LPdecoder used with the parity check matrix obtained from the algorithm surpasses that with paritycheck matrices having the same but random amount of redundancy Key Words Linear Programming decoder CDMA multiuser detection message passingalgorithms

حيدرپور، محمدرضا

كاربرد برنامه ريزي خطي در كد برداري وآشكار سازي

كد بردار برنامه ريزي خطي , CDMA , آشكارسازهاي چند كاربره , روش هاي رد وبدل پيام