On alphabet size selection for video signal coding

Communications systems with various alphabet sizes for transmission of video signals are compared on the basis of equal information rate, bandwidth, and average power. Two cases are considered: when the bandwidth constraint is tight and when it is somewhat loose. It is observed that the ternary alphabet yields the best performance among the systems employing various alphabet sizes, when the bandwidth is fixed. Nonbinary systems outperform the binary system only above a threshold. For the case when the bandwidth can be expanded, there is a threshold above which a nonbinary system is superior to the binary system. The threshold values in this case are larger than for the fixed bandwidth case and depend on the bandwidth expansion factor and the size of the alphabet