Compressive Parameter Estimation for Sparse Translation-Invariant Signals Using Polar Interpolation

We propose new compressive parameter estimation algorithms that make use of polar interpolation to improve the estimator precision. Our work extends previous approaches involving polar interpolation for compressive parameter estimation in two aspects: (i) we extend the formulation from real non-negative amplitude parameters to arbitrary complex ones, and (ii) we allow for mismatch between the manifold described by the parameters and its polar approximation. To quantify the improvements afforded by the proposed extensions, we evaluate six algorithms for estimation of parameters in sparse translation-invariant signals, exemplified with the time delay estimation problem. The evaluation is based on three performance metrics: estimator precision, sampling rate and computational complexity. We use compressive sensing with all the algorithms to lower the necessary sampling rate and show that it is still possible to attain good estimation precision and keep the computational complexity low. Our numerical experiments show that the proposed algorithms outperform existing approaches that either leverage polynomial interpolation or are based on a conversion to a frequency-estimation problem followed by a super-resolution algorithm. The algorithms studied here provide various tradeoffs between computational complexity, estimation precision, and necessary sampling rate. The work shows that compressive sensing for the class of sparse translation-invariant signals allows for a decrease in sampling rate and that the use of polar interpolation increases the estimation precision.Comment: 13 pages, 5 figures, to appear in IEEE Transactions on Signal Processing; minor edits and correction

Compressive Time Delay Estimation Using Interpolation

Time delay estimation has long been an active area of research. In this work, we show that compressive sensing with interpolation may be used to achieve good estimation precision while lowering the sampling frequency. We propose an Interpolating Band-Excluded Orthogonal Matching Pursuit algorithm that uses one of two interpolation functions to estimate the time delay parameter. The numerical results show that interpolation improves estimation precision and that compressive sensing provides an elegant tradeoff that may lower the required sampling frequency while still attaining a desired estimation performance.Comment: 5 pages, 2 figures, technical report supporting 1 page submission for GlobalSIP 201

A framework for achieving organisational objectives through integrated performance management

M.Com. (Business Management

Compressive Sensing for Spread Spectrum Receivers

With the advent of ubiquitous computing there are two design parameters of wireless communication devices that become very important power: efficiency and production cost. Compressive sensing enables the receiver in such devices to sample below the Shannon-Nyquist sampling rate, which may lead to a decrease in the two design parameters. This paper investigates the use of Compressive Sensing (CS) in a general Code Division Multiple Access (CDMA) receiver. We show that when using spread spectrum codes in the signal domain, the CS measurement matrix may be simplified. This measurement scheme, named Compressive Spread Spectrum (CSS), allows for a simple, effective receiver design. Furthermore, we numerically evaluate the proposed receiver in terms of bit error rate under different signal to noise ratio conditions and compare it with other receiver structures. These numerical experiments show that though the bit error rate performance is degraded by the subsampling in the CS-enabled receivers, this may be remedied by including quantization in the receiver model. We also study the computational complexity of the proposed receiver design under different sparsity and measurement ratios. Our work shows that it is possible to subsample a CDMA signal using CSS and that in one example the CSS receiver outperforms the classical receiver.Comment: 11 pages, 11 figures, 1 table, accepted for publication in IEEE Transactions on Wireless Communication

Contesting the transition from apartheid to democracy in the workplace

Paper presented at the Wits History Workshop: Forging the links between historical research and the policy process, 18-19 September 1999. Paper drawn from the Author's thesis "Trade unions in the workplace and the community 1984-1994; a case study of a steel mill.This paper explores the contestation between Highveld Steel and NUMSA over the transition from the apartheid workplace regime during 1993-1995. NUMSA wanted a radical democratisation of the workplace and the company; enhancing worker control and skills. Management wanted to retain control and disempower the workers

Distributed Remote Vector Gaussian Source Coding for Wireless Acoustic Sensor Networks

In this paper, we consider the problem of remote vector Gaussian source coding for a wireless acoustic sensor network. Each node receives messages from multiple nodes in the network and decodes these messages using its own measurement of the sound field as side information. The node's measurement and the estimates of the source resulting from decoding the received messages are then jointly encoded and transmitted to a neighboring node in the network. We show that for this distributed source coding scenario, one can encode a so-called conditional sufficient statistic of the sources instead of jointly encoding multiple sources. We focus on the case where node measurements are in form of noisy linearly mixed combinations of the sources and the acoustic channel mixing matrices are invertible. For this problem, we derive the rate-distortion function for vector Gaussian sources and under covariance distortion constraints.Comment: 10 pages, to be presented at the IEEE DCC'1

From the politics of resistance to the politics of reconstruction: The union and 'ungovernability' in the workplace

African Studies Seminar series. Paper presented 22 September 1997South Africa has undergone momentous change over the past decade. The trade union movement in the shape of COSATU has played a central role in that change. During the late 1980s it became the most organised and visible component of the internal mass democratic movement. After 1990 it became the major alliance partner of the unbanned ANC. On the one hand COSATU was an important advocate and organiser of the mass mobilisation campaigns which kept up the momentum of national political negotiations. It was the originator of the Reconstruction and Development Programme [RDP], later taken up by the ANC as the core of its election and governmental programme. COSATU also provided much of the organisation and the personnel for the ANC election campaign in 1994. At the same time the trade unions were trying to develop new policies and new strategies appropriate to the new conditions of a democratic - or democratising - society. The National Union of Metalworkers of South Africa [NUMSA] was at the forefront of developing such policies, focusing on reform of human resource policies and institutions, and on industrial strategy. These developments have been characterised by labour movement analysts as a shift from 'social movement unionism' to 'strategic unionism' founded on a strategy of 'radical reform', (see Joffe et al, 1992; Von Holdt, 1992b; Von Holdt and Webster, 1992