Hierarchical Quadrature Amplitude Modulation For Image Transmission Over Erroneous Wireless Channels
نویسنده
چکیده
112106-6868 IJVIPNS-IJENS © December 2011 IJENS I J E N S Abstract—Bit dependency of image compression algorithms introduce error extension effects in transmission of compressed images and considerably reduce the received image quality. Channel coding provides protection against these errors but at the cost of increased bandwidth. Asymmetric modulation methods like QAM and QPSK provide alternative means of equal error protection to all the coded bits without increasing the bandwidth. This paper examines the suitability of Hierarchical QAM (HQAM) where non-uniform signal constellation is used to provide different degrees of protection to the significant and nonsignificant bits in the compressed image data at lower channel Signal to Noise Ratio (SNR) and compares it with that of QAM. The performance of HQAM is evaluated using gray test image for different values of the modulation parameter.
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