## Source, channel and modulation coding – complete

Having highlighted the major benefits of combining channel (bit level) and modulation (symbol level) coding, it begs the question of whether adding intelligent source coding to the pot will yield even further benefits.

The answer is undoubtedly yes, with some schemes already in use. Modern speech coders, for example, assign priority to certain bit patterns which are in turn assigned extra protection within the channel code. Similarly, key bits of information in an image are being given priority in the more recent image transmission systems. A number of research groups are also looking at the viability of mapping the source information directly to M-ary symbols, bypassing the bit encoding level altogether, in an attempt to further integrate and optimize the source, channel and modulation processing tasks. |