期刊名称：Journal of Computer Networks and Communications
印刷版ISSN：2090-7141
电子版ISSN：2090-715X
出版年度：2012
卷号：2012
DOI：10.1155/2012/642649
出版社：Hindawi Publishing Corporation
摘要：We introduce an improved image transmission scheme over wireless channels with flat Rayleigh
fading. The proposed scheme jointly optimizes bit power and modulation level to maximize the peak signal-to-noise
ratio (PSNR) of the reconstructed image and hence improves the perceptual quality of the received image. In
this optimization process, the significance of bits with regard to the overall quality of the image is exploited. The
optimality of the proposed algorithm is demonstrated using the Lagrange method and verified through an iterative
offline exhaustive search algorithm. For practical implementation, a look-up table is used at the transmitter for
assigning the bit power and modulation level to each bit stream according to the received signal-to-noise ratio
(SNR) observed at the receiver. The proposed scheme has low complexity since the look-up table is computed offline, only once, and used for any image which makes it suitable for devices with limited processing capability.
Analytical and simulation results show that the proposed scheme with jointly optimized bit power and variable
modulation level provides an improvement in PSNR of about 10 to 20 dB over fixed power fixed modulation
(16-QAM). A further reduction in complexity is achieved by using the average signal-to-noise ratio rather than the
instantaneous SNR in selecting the system parameters.
