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Efficient multichannel methods for high-rate data transmission with application to ISDN (or) pouring water to get more out of copper


Ramesh, Rajaram (1992) Efficient multichannel methods for high-rate data transmission with application to ISDN (or) pouring water to get more out of copper. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/s4r5-wm48.


In this thesis, we are concerned with the transmission of data over channels with intersymbol interference. We consider input signals which are multiplexed versions of several parallel input signals, with the aim of splitting the input signal spectrum into disparate frequency bands and shaping the input spectrum by adjusting the power on each of the frequency bands. We introduce a multirate signal processing framework for the representation of the channel under these conditions and derive simple equivalents for the channel and the associated processors.

Using the equivalent circuits, we derive simple equalization schemes for the channel by drawing from the theory of polynomial matrices. We show that vector equalization can be reduced to a combination of prefiltering, postfiltering and scalar equalization of a few of the parallel input signals. We also discuss several interesting properties of this decomposition.

In the case when the channel is corrupted by colored noise, we derive expressions for the optimum prefilters and postfilters with decision feedback equalization that minimize the mean-squared error between the input and the output, given a constraint on the input power. For uncorrelated inputs, the scheme leads to a set of parallel independent scalar channels with the optimum postfilter whitening the noise, which permits the optimal use of trellis codes for data transmission.

We apply the scheme to a special channel, viz., the ISDN digital subscriber loop. The main impairments on this channel are intersymbol interference and crosstalk due to adjacent loops in the same binder group. Crosstalk is an especially interesting case of noise since it depends on the signal being transmitted; we assume that all loops in a binder group transmit using the same scheme. We consider two cases of crosstalk noise: when transmission between different loops in a binder group is synchronized, the crosstalk noise is wide-sense cyclostationary, and with a lack of synchronization between loops, the crosstalk noise is wide-sense stationary. We present methods to determine the optimum filters for data transmission and the optimum input power distributions for both these cases. We demonstrate the possibility of data transmission at the T1 rate, i.e., 1.544 Mb/s over most loops in the local loop plant. We also find that synchronizing transmission between different loops in a binder group does not get us much; the difference in the throughputs for the cases of cyclostationary crosstalk and wide-sense stationary crosstalk does not seem to justify the effort involved in synchronization.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Posner, Edward C.
Thesis Committee:
  • Posner, Edward C. (chair)
  • Franklin, Joel N.
  • Vaidyanathan, P. P.
  • McEliece, Robert J.
  • Abu-Mostafa, Yaser S.
Defense Date:1 August 1991
Record Number:CaltechETD:etd-08082007-081649
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3052
Deposited By: Imported from ETD-db
Deposited On:14 Aug 2007
Last Modified:16 Apr 2021 23:04

Thesis Files

PDF (Ramesh_r_1992.pdf) - Final Version
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