Digital encoding and detection of voiceband data signals

The codecs considered for investigation are Pulse Code Modulation (PCM), Differential PCM, and Delta Modulation operating at bit rates from 16 to 64 kb/sec. A central result of this study was the identification and evaluation of sampling phase differential effect present in a digital encoding system when sampling clock is not synchronous with an integral multiple of the data modern bit clock. PSK voiceband data signals are allowed to pass through these codecs that are designed for speech or data input signals. Digital encoders considered for investigation are ranked using the above performance metrics. Performance results of these coders are fully discussed and analyzed. Recognition algorithm for voiceband data, speech, and silence signals is developed for complete automation in digital channel efficiency models to achieve the optimum system performance. Pattern recognition approaches are sought to formulate and solve this problem. Maximum likelihood estimation procedure with recursive implementation of algorithm is developed.