Thesis-1986-Hau.pdf (6.93 MB)
Adaptive adjustment of receiver for distorted digital signals
thesis
posted on 2013-03-06, 14:48 authored by Sau F. HauThis report describes the investigation which has led to the development
of a novel technique for the adaptive adjustment of the receiver
in a digital data-transmission system, where the latter operates with
additive noise and severe intersymbol interference in the received
signal. This technique is suitable both for the adjustment of a
conventional non-linear (decision-feedback) equaliser, and also for
the adjustment of a linear feedforward transversal filter that is
employed ahead of a near-maximum-likelihood detector. In the latter
case, the technique provides, in addition, an estimate of the sampled
impulse-response of the channel and filter, to give the information
on the received signal needed by the detector. The adaptive system
requires an estimate of the sampled impulse-response of the channel
and it involves finding the roots (zeros) of the z-transform of the
sampled impulse-response that lie outside the unit circle.
The aim of the investigation has been to develop a root-finding algorithm
which would be used to find some or all. of the roots, with
moduli greater than unity, of a high-degree (>20) complex polynomial.
The first part of the report describes the study of an on-line system,
where the receiver operates on a continuous stream of received samples
subject to both intersymbol interference and noise, and 'it presents
the results of a large number. of tests using computer simulation which
show the root-finding capability and vulnerability of the system to
white Gaussian noise. .The results of the tests point to the potential
advantages of an off-line system, which is much simpler to implement
and'requires less computation. The modified technique operates solely
and directly on the estimate of sampled impulse-response of the channel, which must,again be,provided at the receiver. The report gives the
results of computer-simulation tests measuring the speed and accuracy
of two different arrangements of the system, for different channels,
and it also studies the effects of double roots and roots just outside
the unit circle. The off-line system is suitable for a 16-point QAM system operating
at 9600 bit/s over the British public switched telephone network,
and with slight modification, it can also be used for a 64-point QAM
system operating at 19200 bit/s.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© S.F. HauPublication date
1986Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.373099Language
- en