Adaptive Modulation and Error Control Techniques

Abstract : This report contains the results of an investigation designed to develop, analyze, and evaluate techniques to improve the quality of digital data transmission by adapting the modulation or error control parameters to varying channel conditions. Specific systems for varying the bit rate and the alphabet size are postulated and evaluated analytically in realistic channel environments. Variable block length and variable redundancy error control techniques are described and analyzed in a computer simulation of real channels. In addition, the operation and performance of a laboratory prototype of an adaptive error correction decoder that does not require feedback is described.