Method and apparatus for wireless image transmission

Abstract

An image, whether compressed or uncompressed, can be transmitted via a fading communication channel to provide at the receiver an image of good perceptual quality despite the impaired channel. Diversity improves wireless transmission by using highly uncorrelated signal paths to combat channel noise. The apparatus and method of the present invention operates in the wavelet domain by using the properties of the original image or its wavelet transform. For an uncompressed image, one computes the two-dimensional wavelet transform of the source image and scalar quantizes the resulting wavelet coefficients. These coefficients are transmitted as a wireless bit stream with diversity to obtain multiple copies of the decomposed image data. At the receiver, the coefficients of the individual decomposed images are combined to form a composite wavelet transform. The final received image is reconstructed from the composite transform. A compressed image is first error protected and then transmitted by wireless using diversity. Multiple bit streams representing the image are decoded with appropriate channel decoding algorithms followed by image decompression up to the point where the wavelet representations of the multiple images are obtained. Before computing the inverse wavelet transform, the individual wavelet representations are combined using rules based on wavelet transform characteristics. After diversity combining, a composite wavelet representation is obtained, and the received image is reconstructed by performing the inverse wavelet transform on this composite representation.