Transmission Performance of Mu-255 Quantization in a Local Digital Office

T h e piecewise uniform, logarithmically companded, /i = 255 quantizing characteristic is the logical choice for an analog-to-digital converter in a digital office because of its widespread use in the North American telephone network in digital facility terminals and No. 4 ESS switch applications. This paper describes the theoretical and practical voice transmission performance attainable with this quantization law and discusses the requirements imposed on the quantizer in order for it to meet reasonable transmission objectives for a local digital switch, 1 and the implications of introducing quantization on crosstalk performance. We address in this paper only the transmission performance parameters that are affected by the choice of quantizer characteristic. These include tracking (net loss and overload), idle channel noise (noise in the absence of signal), crosstalk, and signal-to-distortion ratio. The nonlinear effects introduced into the above transmission parameters by quantization are examined. 1943