Cancellation of linear intersymbol interference for two-dimensional storage systems

This paper discusses the cancellation of linear intersymbol interference (ISI) in two-dimensional (2-D) systems. It develops a theory for the error rate of receivers that use tentative decisions to cancel ISI. It also formulates precise conditions under which such ISI cancellation can be applied effectively. For many 2-D systems, these conditions are easily met, and therefore the application of ISI cancellation is of significant interest. The theory and the conditions are validated by simulation results for a 2-D channel model. Furthermore, results for an experimental 2-D optical storage system show that, for a single-layer disk with a capacity of 50 GB, a substantial performance improvement may be obtained by applying ISI cancellation

Algorithms and structures for long adaptive echo cancellers

The main theme of this thesis is adaptive echo cancellation. Two novel independent approaches are proposed for the design of long echo cancellers with improved performance. In the first approach, we present a novel structure for bulk delay estimation in long echo cancellers which considerably reduces the amount of excess error. The miscalculation of the delay between the near-end and the far-end sections is one of the main causes of this excess error. Two analyses, based on the Least Mean Squares (LMS) algorithm, are presented where certain shapes for the transitions between the end of the near-end section and the beginning of the far-end one are considered. Transient and steady-state behaviours and convergence conditions for the proposed algorithm are studied. Comparisons between the algorithms developed for each transition are presented, and the simulation results agree well with the theoretical derivations. In the second approach, a generalised performance index is proposed for the design of the echo canceller. The proposed algorithm consists of simultaneously applying the LMS algorithm to the near-end section and the Least Mean Fourth (LMF) algorithm to the far-end section of the echo canceller. This combination results in a substantial improvement of the performance of the proposed scheme over both the LMS and other algorithms proposed for comparison. In this approach, the proposed algorithm will be henceforth called the Least Mean Mixed-Norm (LMMN) algorithm. The advantages of the LMMN algorithm over previously reported ones are two folds: it leads to a faster convergence and results in a smaller misadjustment error. Finally, the convergence properties of the LMMN algorithm are derived and the simulation results confirm the superior performance of this proposed algorithm over other well known algorithms

Digital processing of signals in the presence of inter-symbol interference and additive noise

Imperial Users onl

An investigation into the effects of using limited precision integer arithmetic in digital modems

The main aim of this thesis is to study the effects of using a reduced level of arithmetical precision (as found in a 16-bit microprocessor) whilst running various algorithms in the detection stages of a digital modem. The reason for using a lower precision is to see if these algorithms will run on a limited precision device, such as a Texas Instruments TMS320C25 digital signal processor, in real time. [Continues.

Investigation of coding and equalization for the digital HDTV terrestrial broadcast channel

Includes bibliographical references (p. 241-248).Supported by the Advanced Telecommunications Research Program.Julien J. Nicolas

Multi-User Signal and Spectra Coordination for Digital Subscriber Lines

The appetite amongst consumers for ever higher data-rates seems insatiable. This booming market presents a huge opportunity for telephone and cable operators. It also presents a challenge: the delivery of broadband services to millions of customers across sparsely populated areas. Fully fibre-based networks, whilst technically the most advanced solution, are prohibitively expensive to deploy. Digital subscriber lines (DSL) provide an alternative solution. Seen as a stepping-stone to a fully fibre-based network, DSL operates over telephone lines that are already in place, minimizing the cost of deployment. The basic principle behind DSL technology is to increase data-rate by widening the transmission bandwidth. Unfortunately, operating at high frequencies, in a medium originally designed for voice-band transmission, leads to crosstalk between the different DSLs. Crosstalk is typically 10-15 dB larger than the background noise and is the dominant source of performance degradation in DSL. This thesis develops practical multi-user techniques for mitigating crosstalk in DSL. The techniques proposed have low complexity, low latency, and are compatible with existing customer premises equipment (CPE). In addition to being practical, the techniques also yield near-optimal performance, operating close to the theoretical multi-user channel capacity. Multi-user techniques are based on the coordination of the different users in a network, and this can be done on either a spectral or signal level

Orthogonal multicarrier modulation for high-rates mobile and wireless communications

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN037085 / BLDSC - British Library Document Supply CentreGBUnited Kingdo