Application of 16-State TCM-UGM and TCM for Improving the Quality of Compressed Color Image Transmission

Abstract

Abstract —The aim of this paper is to investigate the quality of transmitted color images using 16-state TCM-UGM or TCM channel code over Rayleigh fading channel. Considering SPIHT-based compression algorithm and image quality metrics (IQMs), the simulation results for throughput of 2 bit/s/Hz, showed that the communication system using TCM-UGM allows better performance compared to TCM and better protects the compressed color image during transmission. For transmission tests compressed colors images, the TCM-UGM system outperforms the performance of the TCM by 3 dB at BER = -10 5 and 4.59 dB at FER = 3.10 -3 . For example, for Lena color image, the 16-state TCM-UGM system gives best performance that the 16-state TCM system. The gain is the 5.02 dB and 17.90 % for the PSNR and MMSIM respectively. Index Terms —TCM-UGM, TCM, compressed color image, SPIHT. I. I NTRODUCTION The trellis-coded modulation (TCM) was introduced by Ungerboeck in 1982 [1]. This coding technique improves error performance of synchronous data links without sacrificing data rate or requiring more bandwidth. This is achieved by channel coding with expanded sets of multilevel/phase signals in a manner which increases free Euclidean distance. The TCM codes can be interpreted as binary convolutional codes with a mapping of coded bits into channel signals using mapping by set partitioning. A new variant of the TCM modulation based on Ungerboeck mapping combined with Gray coding, called ‗Trellis-Coded Modulation with Ungerboeck-Gray Mapping‘ (TCM-UGM) has been proposed by Bassou [2]. Bassou and Djebbari have proposed this new schema for a spectral efficiency greater than or equal to 3 bits/s/Hz. The difference between these two structures resides in the positioning of the uncoded bits out in the encoder. Indeed, for TCM-UGM the uncoded bits are placed before the parity bit. The latter cannot in any way represent the MSB or the LSB of the transmitted symbol. In the absence of uncoded bits, the TCM-UGM is equivalent to the proposed Ungerboeck TCM. A variant of the TCM-UGM for spectral efficiency of 2 bits/s/Hz, 8PSK modulation and rate equal to 2/3 is proposed by Benaissa