IMAGE BROADCAST BY APPLYING DIVERSITY METHOD: A STATE OF THE ART REVIEW

Abstract

 For digital images that are created by digital photography, JPEG is a lossy compression process. Data compression is required in order for an image to support hundreds of colours and to be transmitted at a faster rate. There are disadvantages to JPEG image transmission using existing technologies, such as quality degradation and computational complexity. An efficient scheme to transmit JPEG images over wireless channels is given by the proposed method. The compression takes place primarily in four steps: DCT, Quantization, Zig-Zag, Huffman encoding. Each 8*8 block of the image is arranged by DCT into 64 coefficients with 1 DC and 63 DC coefficients. A number of values is compressed by quantization to a single quantum value. Using the CDMA process, the encoded bits are distributed. Here, a very wide bandwidth signal called the spreading signal multiplies the narrowband message signal. The Gold code of chosen length 31 is the Spreading sequence used. Diversity techniques are used in the channel to boost the efficiency of the scheme and to reduce the effects of multipath fading. The signal is "distributed" on the receiver side using a synchronized replica of the PN code.