Transmission error protection methods for multimedia services using soft decision processing - a comparison

This paper compares four soft decision de-mapping (SDD) methods that can provide extra decision processing information to aid decoding in the upper layers of a multimedia receiver. The four decision processing methods are combining SDD with image source layer decoding, combining SDD with simple packet-parity-bit channel coding, turbo coding and combining SDD with adaptive modulation. performance comparisons are presented for the AWGN channel, using the JPEG2000 still image standard. Results proved that soft decision driven de-mapping and decoding improve the decoded image but turbo coding offers very good performance for channels with poor SNR. For channels with good SNR, it is better to combine soft decision decoding with very light channel coding and/or with source layer coding for better image quality than with fixed rate turbo codes. Adaptive modulation is used so that the modulation mode that gives the best quality with respect to the channel conditions, so the quality improves with the channel SNR.