Feasibility Study of Very High Bit Rate Digital Subscriber Lines", contribution TlE1/88-012 to TlEl
- J. W. Lechleider
Trellis-coded modulation, combined with sequence-estimation equalization techniques, can increase the maximum attainable bit rate and/or loop range on digital subscriber loops. The corresponding receiver is highly complex, even when reduced-state sequence estimation techniques are employed. A major source of complexity arises from the very large number of symbol intervals spanned by the typical channel impulse response in high bit rate applications. We describe an adaptive piecewise linear fit technique for closely approximating the channel response, using relatively few parameters. The approximation error and adaptation behaviour of this technique are shown for representative channel responses. The results indicate the viability of the technique for decision feedback equalizers used within or outside reduced state sequence estimators.