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Traditional user technology for communication, such as phones, computers, television, and radio, may not directly work for people who have sensory disabilities. Five classes of communication access technology are discussed: hearing enhancement technology, deaf technology, vision enhancement technology, blind technology, and deaf-blind technology. These technologies are discussed in the social context of the people who use the technology. Broad technical research challenges are delineated and new directions for exploration are discussed. [ABSTRACT FROM AUTHOR]

Entropy-constrained vector quantization (ECVQ) offers substantially improved image quality over vector quantization (VQ) at the cost of additional encoding complexity. We extend results in the literature for fast nearest neighbor search of VQ to ECVQ. We use a new, easily computed distance that successfully eliminates most codewords from consideration.

We propose a new maximum a posteriori (MAP) detector, without the need for explicit channel coding, to lessen the impact of communication channel errors on compressed image sources. The MAP detector exploits the spatial correlation in the compressed bitstream as well as the temporal memory in the channel to correct channel errors. We first present a technique for computing the residual redundancy inherent in a compressed grayscale image (compressed using VQ). The performance of the proposed MAP detector is compared to that of a memoryless MAP detector. We also investigate the dependence of the performance on memory characteristics of the Gilbert-Elliott channel as well as average channel error rate. Finally, we study the robustness of the proposed MAP detector's performance to estimation errors.