-
[show abstract]
[hide abstract]
ABSTRACT: We examine the problem of determining the characteristics a slowly varying linear transmission channel by measuring the output when the input is a specially selected test signal. We assume the use of a cyclically repeating test signal and use of a linear estimator of the resulting signal to determine the echo channel. We find the optimal linear estimator and its associated test signal, which together minimises mean-squared error of the channel estimate. Ths optimization is carried out under the assumption that we know the autocovariance (or power spectrum) of the interfering noise and autocovariance of the echo channel. The test signal is also assumed to be constrained by a bound on total energy.
Complex Medical Engineering (CME), 2010 IEEE/ICME International Conference on; 08/2010
-
[show abstract]
[hide abstract]
ABSTRACT: Echo cancellation literature is reviewed, then a Bayesian model is introduced and it is shown how how it can be used to model and fit non-linear channels. An algorithm for cancellation of echo over a nonlinear channel is developed and tested. It is shown that this nonlinear algorithm converges for both linear and nonlinear channels and is superior to linear echo cancellation for cancelling an echo through a nonlinear echo-path channel.
Signal Processing and Communication Systems, 2008. ICSPCS 2008. 2nd International Conference on; 01/2009
-
[show abstract]
[hide abstract]
ABSTRACT: The existing Internet appears to provide good quality service for a very wide range of services, possibly because the TCP protocols aim to achieve fair queueing, or processor sharing. The DiffServ architecture aims to do better than this by providing different performance standards for different classes of service. The natural way to apply DiffServ is to allocate classes in accordance with the urgency or priority of the requests. However, another approach is to use DiffServ to allocate service classes according to the "size" of the requests, where the concept of "size" can be defined in a variety of ways: total bytes in a flow, rate of a flow, or by a series of token buckets. We use simple queueing models to investigate how much improvement in performance could be obtained by implementing this service discipline, and whether, as a consequence, it is unnecessary and perhaps even dangerous to assign classes of service in accordance with the type of service requested. The results suggest that shortest job first offers considerable advantages over processor sharing. Thus in spite of the difficulties of identifying the size of flows it may be worthwhile to consider how something like shortest job first can be implemented. On the other hand it appears that other priority queue strategies, not based on job size, are risky, in that the marginal advantages gained by favoured jobs are very small, and the majority of jobs can expect to suffer worse response times.
TENCON 2005 2005 IEEE Region 10; 12/2005
