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In systems with parallel analogue-to-digital converters (ADC), diversity combining can improve the signal to noise ratio (SNR) of the digitised signal. We consider a novel architecture, where the parallel ADCs operate on differently attenuated signals, in conjunction with maximal ratio combining and gain weighted combining. Both schemes reduce the effective quantization noise and provide significant SNR improvements over a single ADC and signal averaging, which takes the unweighted average of the ADC output signals. The key to achieving these SNR gains is to carefully select branch attenuations that lead to negative correlation of the quantization noise across branches. Refereed/Peer-reviewed

Low complexity optimal (or nearly optimal) decoders for space-time codes have recently been under intensive investigation. For example, recent works by Sirianunpiboon and others show that the Silver code and the Golden code can be decoded optimally (or nearly optimally) with quadratic decoding complexity. Fast decodability makes them very attractive in practice. In implementing these decoders, floating-point to fixed-point conversion (FFC) needs to be carefully undertaken to minimize hardware cost while retaining decoding performance. The process of quantization for fixed-point representations is often ignored by research community and lacks investigation, and so FFC is often conducted heuristically based on simulations. This paper studies the effects of quantization to space-time coded systems from an information theoretic perspective. It shows the analytical relationship between quantization error and decoding performance deterioration. This paper also proposes a general finite precision implementation methodology including two FFC criteria for space-time coded systems within an integer optimization framework. As a particular example, this paper examines the finite precision implementation of the quadratic optimal decoding algorithm of the Silver code. However, our methodology and techniques can be applied to general space-time codes.

This paper considers the problem of target tracking by a multistatic radar system. In order to use linear Kalman filtering for tracking, the time delay, Doppler shift and arrival angle measurements from multiple receivers are transformed into target position and velocity estimates in Cartesian coordinates before being processed by the Kalman filter. A new multistatic tracking algorithm is proposed with the novel feature of joint adaptive selection of transmitted waveform and Cartesian estimate to minimize the mean-square error of the tracking estimate. Cramer-Rao lower bounds (CRLBs) of Cartesian estimates are derived and exploited in the development of the joint adaptive selection scheme. Three main performance advantages of the proposed algorithm are (i) reduction of bandwidth and power consumption in transmitter-receiver communication links by utilizing a single Cartesian estimate in tracking process, (ii) optimization of the tracking performance by jointly selecting waveform and Cartesian estimate, and (iii) the inherent benefits of linear estimation from use of the linear Kalman filter including stability. Simulation examples demonstrate the dependence of the CRLBs of the Cartesian estimates on the transmitted waveform, target position and velocity, radar geometry, and particular elliptic-to-Cartesian transformation. Simulations also highlight the superior performance of our proposed algorithm over existing techniques. HighlightsA new multistatic tracking algorithm is proposed.The novel feature is joint adaptive selection of waveform and Cartesian estimate.The CRLBs of Cartesian estimates are derived and exploited in the selection scheme.The elliptic-to-Cartesian transformations are derived in a general geometry.The performance advantages of the proposed algorithm are demonstrated.

This paper provides a detailed overview of the Digital Video Broadcasting Terrestrial (DVB-T) signal structure and the implications for passive radar systems that use these signals as illuminators of opportunity. In particular, we analyze the ambiguity function and explain its delay and Doppler properties in terms of the underlying structure of the DVB-T signal. Of particular concern for radar range-Doppler processing are ambiguities consistent in range and Doppler with targets of interest. In this paper we adopt a mismatched filtering approach for range-Doppler processing. We also recognize that while the structure of the DVB-T signal introduces ambiguities, the structure can also be exploited to better estimate the transmitted signal and channel, as well as any mismatch between transmitter and receiver (e.g., clock offsets). This study presents a scheme for pre-processing both the reference and surveillance signals obtained by the passive radar to mitigate the effects of the ambiguities and the clutter in range-Doppler processing. The effectiveness of our proposed scheme in enhancing target detection is demonstrated using real-world data from an (Australian) 8k-modeDVB-T system.A29 dB reduction in residual ambiguity levels over existing techniques is observed, and a 36 dB reduction over standard matched filtering; with only a 1 dB reduction in the zero-delay, zero-Doppler peak. Refereed/Peer-reviewed

In this paper, a simple and novel cross-layer adaptive modulation and coding (AMC) scheme, which increases the energy efficiency of the wireless communication system is proposed. Traditionally, AMC has been used to improve MAC-layer performance in terms of coded bit error rate, packet error rate, and throughput. The modulation and coding scheme is switched according to signal-to-noise ratio thresholds at the PHY layer. We extend the approach, proposing a framework for energy-efficient cross-layer AMC that captures the impact of both MAC layer and PHY layer parameters on the AMC switching criteria. Cross-layer designs are naturally suited to software defined radio applications. Not only are they readily implemented in software, but also they are integral to the radio components. They can optimize performance of the radio either for a given configuration or adaptively. Through examples of WLAN physical layer and Frequency Domain Equalized systems, we demonstrate our AMC scheme and verify its effectiveness by simulation. Refereed/Peer-reviewed