Spectrally constrained codes for high rate ISDN subscriber loop

The authors consider the H0 service (384 kb/s). They examine vector coding as an alternative to the decision-feedback equalizer (DFE). Vector coding uses block symbols formed from a set of orthogonal vectors to partition the local-loop channel into parallel, independent subchannels. They model the local loop as an IIR channel and describe the partitioning procedure. The authors then use a 16-state, 4-dimensional coset code on the partitioned channel and compare coding gains against a DFE using the same code. For the additive white Gaussian noise (AWGN) case, vector coding provides a 3-dB gain over a DFE using the same code; for non-white Gaussian noise, where crosstalk dominates the noise, it is shown that vector coding will tolerate significantly greater crosstalk coupling than the DFE, providing gains of 4 dB or more.<>