Character Alignment for High-Capacity PCM Systems Using MS43 Line Code

Alphabetic pseudoternary codes, which are being used largely for high-capacity pulse-code modulation (PCM) transmission, require character alignment of the received ternary sequence for correct conversion from pseudoternary to straight binary. In this paper a method and a strategy of character alignment for MS43 line code are proposed. The method is based on the recognition of the constraints and correlations involved by the conversion rules of MS43; the strategy, which is similar to that already used for frame alignment in PCM time-division-multiplex (PCM-TDM) systems, allows limiting of the effects of simulations and line errors on the processes of loss and recovery of character alignment. Statistical properties of these processes are analyzed both theoretically and by computer simulation. The results are used to design the character alignment strategy for a 34.368 Mbit/s PCM system using MS43 as line code.