Design Guidelines for Training-based MIMO Systems with Feedback

In this paper, we study the optimal training and data transmission strategies for block fading multiple-input multiple-output (MIMO) systems with feedback. We consider both the channel gain feedback (CGF) system and the channel covariance feedback (CCF) system. Using an accurate capacity lower bound as a figure of merit, we investigate the optimization problems on the temporal power allocation to training and data transmission as well as the training length. For CGF systems without feedback delay, we prove that the optimal solutions coincide with those for non-feedback systems. Moreover, we show that these solutions stay nearly optimal even in the presence of feedback delay. This finding is important for practical MIMO training design. For CCF systems, the optimal training length can be less than the number of transmit antennas, which is verified through numerical analysis. Taking this fact into account, we propose a simple yet near optimal transmission strategy for CCF systems, and derive the optimal temporal power allocation over pilot and data transmission.Comment: Submitted to IEEE Trans. Signal Processin

MIMO Channel Correlation in General Scattering Environments

This paper presents an analytical model for the fading channel correlation in general scattering environments. In contrast to the existing correlation models, our new approach treats the scattering environment as non-separable and it is modeled using a bi-angular power distribution. The bi-angular power distribution is parameterized by the mean departure and arrival angles, angular spreads of the univariate angular power distributions at the transmitter and receiver apertures, and a third parameter, the covariance between transmit and receive angles which captures the statistical interdependency between angular power distributions at the transmitter and receiver apertures. When this third parameter is zero, this new model reduces to the well known "Kronecker" model. Using the proposed model, we show that Kronecker model is a good approximation to the actual channel when the scattering channel consists of a single scattering cluster. In the presence of multiple remote scattering clusters we show that Kronecker model over estimates the performance by artificially increasing the number of multipaths in the channel.Comment: Australian Communication Theory Workshop Proceedings 2006, Perth Western Australia. (accepted

Relaying energy allocation in training-based amplify and forward relay communications

We consider relay-assisted communication in a training-based transmission scheme. Each transmission block consists of a training phase and a data transmission phase. The relay node employs the amplify-and-forward protocol during all transmissions. We focus on the relay signaling design and investigate the benefit of allowing for different relaying power during the training phase and the data transmission phase. Specifically, the relaying energy allocation between the two phases is optimized for maximizing the average received signal-to-noise ratio at the destination node. We study this optimization problem for both single-antenna relay and multi-antenna relay and derive a simple closed-form relaying energy allocation strategy that achieves near-optimal performance. This closed-form strategy depends only on the length of the data transmission phase but not on other system parameters such as the relaying energy budget, the number of antennas at the relay, and the distances between the source, relay and destination nodes.This work was supported by the Australian Research Council's Discovery Projects funding scheme (project no. DP0984950, DP110102548) and the Research Council of Norway through the project 197565/V30. The work has been carried out while T. Lamahewa was at the Australian National University

Exact pairwise error probability analysis of space-time codes in spatially correlated fading channels, Journal of Telecommunications and Information Technology, 2006, nr 1

In this paper, we derive an analytical expression for the exact pairwise error probability (PEP) of a space-time coded system operating over a spatially correlated slow fading channel using a moment-generating function-based approach. This analytical PEP expression is more realistic than previously published exact-PEP expressions as it fully accounts for antenna spacing, antenna geometries (uniform linear array, uniform grid array, uniform circular array, etc.) and scattering models (uniform, Gaussian, Laplacian, Von-Mises, etc.). Inclusion of spatial information provides valuable insights into the physical factors determining the performance of a space-time code. We demonstrate the strength of our new analytical PEP expression by evaluating the performance of two space-time trellis codes proposed in the literature for different spatial scenarios

The Australian National University Declaration

The contents of this thesis are the results of original research and have not been submitted for a higher degree to any other university or institution. Much of the work in this thesis has been published or has been submitted for publication as journal papers or conference proceedings. These papers are

Multiple 3D Far-Field/Near-Field Moving Target Localization Using Wideband Echo Chirp Signals

In this paper, we propose a technique for active detection and estimation of the range, radial velocity and direction-of-arrival (DOA) of multiple moving targets in the three-dimensional space for both far-field and near-field cases using wideband chirp signals. The proposed technique is an extension of the method recently proposed by Leong in ['Multiple target localization using wideband echo chirp signals,' IEEE Trans. Signal Process., vol. 61, no. 16, pp. 4077-4089, Aug. 2013] for the localization of multiple far-field targets in the two-dimensional space. In our approach, the received signals at a sensor array are first decomposed into the spherical harmonic components and a modal preprocessing step is then carried out on the received wideband signals so that they can be further processed using narrowband techniques for parameter estimation. The application of fractional Fourier transform on the modal preprocessed signals allows the proposed method to identify closely spaced targets. This is demonstrated via computer simulations where the proposed technique achieved low root-mean-square errors in the parameters estimated in a scenario with closely spaced targets

A fractional fourier domain approach for multiple target localization using the time-of-arrival

In this paper, a parameter estimation method for localizing multiple targets in the three-dimensional region using as few as four sensor elements is presented. It is designed based on the properties of chirp signals in fractional Fourier domains and it provides good separation to closely spaced targets. Besides that, a notable advantage of the proposed method over existing methods is its capability in detecting and localizing more targets than the number of sensors

Multiple target localization using wideband echo chirp signals

Active target detection and localization is a classical signal processing problem that arises in various military and biomedical applications. A novel method for the detection and estimation of the range, velocity and direction of arrival (DOA) of multip