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.
