Source Channel Of The Wireless Image Transmission Joint Encoding / Decoding

The limit of Shannon theorem provides a theoretical basis for joint source-channel coding/decoding(JSCC/JSCD).In this paper,the research background and significance of joint source channel coding/decoding over wireless image transmission are elaborated, the present situation and application foreground of this research task are analyzed; Then we discuss the modeling and simulation of frequency selectivity channel under mobile conditions detailed. On this basis, the channel programmes in this paper are verified seriously and scientifically from the angle of theories and practical experiments. Furthermore, a new project of joint source-channel coding/decoding for image transmission is proposed: in the JSCC scheme, When using the block training based channel estimation, OFDM data blocks experience unequal decoding error rate due to the imprecision of channel estimation .we use this property to provide unequal error protection (UEP) for transmission of bit streams which is gotten by partitioning the transform wavelet coefficients into groups and independently processing each group using a SPIHT coder.The results of simulation indicate that image quality in this scheme is improved more greatly than that in the old;In the JSCD methods,an investigation applied to a vector quantization source is presented. The proposed decoding scheme designed a feedback algorithm using error-detected source information to improve the error correction capability of the Turbo Log-MAP decoder without changing its constituent decoder. A reduction in bit error rate (BER) of at least one order of magnitude can be achieved by employing the proposed joint decoding technique. This may significantly reduce delay of decoding, making Turbo codes more appealing in many applications.