| || Punctured Turbo Codes for Bandwidth-efficient Transmission
Author : Rekh, Shobha;Subha Rani, S.;Shanmugam, A.;Joshua, John Kulothungan
Source : Defence Science Journal ; Vol:56(4) ; 2006 ; pp 585-590
Subject : 681.3 Computer Science
Keywords : Wireless transmission;Turbo codes;Error-coding schemes;Rate-compatible punctured turbo codes;Additive white Gaussian noise;MAP algorithm;Soft output viterbi algorithm;RCPC;Rate-compatible punctured codes;Recursive systematic convolutional encoders
Abstract : Turbo codes are the error-coding schemes applied nowadays in wireless networks. In naval applications, the information is mostly sent through wireless networks and the data is more prone to noise. Since very important data has to be communicated, it is necessary to get back the original data in the receiver. In military applications also, the soldiers wear electronic jackets which are connected by wireless networks. In such applications, the data loss is not affordable and there is also a need to utilise the bandwidth efficiently through puncturing by means of which certain bits are deleted before transmission from the output of encoder. By means of this punctured turbo codes, bandwidth-efficient coding is achieved. Hence, it is necessary to design turbo codes with an efficient puncturing pattern so that the performance of the punctured code is also improved in spite of deletion of few bits before transmission. This paper deals in choosing the puncturing patterns that lead to systematic rate-compatible punctured turbo codes (RCPTCs) which also give a reduction in bit-error rate. The design criterion for choosing the best puncturing patterns is based on the minimum weight of code words and their multiplicities. The best puncturing pattern chosen is tested for its performance by simulating turbo codes for an additive white Gaussian noise (AWGN ) channel. Compared with the existing puncturing pattern, the pattern proposed is able to achieve a gain of 0.5 dB at a bit-error rate of 10-3.