PHASE FREQUENCY-MODULATION EMPLOYING ARRAY CODES

Modern voiceband modems often use a symbol rate that is not a factor o f their data rate. Combined with the possible use of multidimensional trellis-coded modulation, this means that modems must transmit a fract ional number of bits per symbol. To allow for this, bits must be mappe d in blocks of symbols. This raises the issue of how to synchronise th ese blocks. The Letter gives a fast and reliable means to do this.