Philippa A. Martin

University of Canterbury, Christchurch, Canterbury Region, New Zealand

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Publications (18)9.4 Total impact

  • Uzma Afsheen, Philippa A. Martin, Peter J. Smith
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    ABSTRACT: In this paper we propose a novel class of space time trellis codes based on super quasi-orthogonal space time codes for a reconfigurable antenna system. We call them Space Time State Trellis Codes (STSTCs). The proposed codes are capable of taking advantage of the additional degrees of diversity offered by reconfigurable antennas and changing propagation states. They achieve full rate, full diversity and high coding gain. Simulation results demonstrate their good performance. STSTCs achieve the diversity order expected for four transmit antennas while using only two reconfigurable transmit antennas. Our code out performs the existing super orthogonal space time trellis code, which fails to achieve full diversity in a reconfigurable antenna system.
    Vehicular Technology Conference (VTC Fall), 2013 IEEE 78th; 01/2013
  • Tri Pham, Philippa A. Martin, Desmond P. Taylor, Clive Horn
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    ABSTRACT: We consider single-h continuous phase modulation (CPM) systems that use linear prediction receivers with coefficient look up table (LUT) for mitigating the effect of multipath fading. This type of receiver shows superior performance over conventional ones; however, high channel delay spread and fast fading can still lead to a high error floor in its performance. A sub-optimal soft/iterative detection based on the soft output Viterbi algorithm (SOVA) is presented for reducing such error floors while maintaining low complexity. The design is extended with a simple spatial diversity combining scheme and the utilization of multiple coefficient LUTs. The proposed approach allows a significant performance gain to be achieved.
    Vehicular Technology Conference (VTC Spring), 2013 IEEE 77th; 01/2013
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    ABSTRACT: The performance of maximal ratio combining (MRC) in Rayleigh channels with co-channel interference (CCI) is well-known for receive arrays which are co-located. Recent work in network MIMO, edge-excited cells and base station collaboration is increasing interest in macrodiversity systems. Hence, in this paper we consider the effect of macrodiversity on MRC performance in Rayleigh fading channels with CCI. We consider the uncoded symbol error rate (SER) as our performance measure of interest and investigate how different macrodiversity power profiles affect SER performance. This is the first analytical work in this area. We derive approximate and exact symbol error rate results for M-QAM/BPSK modulations and use the analysis to provide a simple power metric. Numerical results, verified by simulations, are used in conjunction with the analysis to gain insight into the effects of the link powers on performance.
    08/2012;
  • Peter J. Smith, Abdulla Firag, Philippa A. Martin, Ross Murch
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    ABSTRACT: Reconfigurable antenna arrays offer advantages over traditional antenna selection in terms of requiring fewer physical antennas and the use of fixed antenna feeds. Hence, in this paper we analyze the signal to noise ratio (SNR) improvement offered by reconfigurable antennas and compare it to traditional selection. Both the distribution and the mean value of the link gains in a reconfigurable system are derived and used to gain insight into system performance, both for SNR gain and outage. Results demonstrate that for systems with up to four antennas and two radiation states, reconfiguration can provide at least 76% of the improvements offered by selection.
    IEEE Communications Letters 01/2012; 16(4):498-501. · 1.16 Impact Factor
  • Michael Krause, Desmond P. Taylor, Philippa A. Martin
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    ABSTRACT: We investigate the use of the minimum mean-squared- error decision-feedback-equalizer (MMSE-DFE) as a preprocessor to reduce the computational complexity of symbol detection in frequency-selective multiple- input multiple-output (MIMO) channels. The preprocessor delays and focuses the received signal energy which reduces the effects of inter-symbol- interference and multiple-access-interference. This property of the MMSE-DFE preprocessor is exploited to order and to reduce the number of symbol candidates considered by an iterative maximum- likelihood (ML) detector. Simulations show that the proposed detection scheme can achieve lower bit- error-rates than existing reduced-complexity algorithms in overdetermined and underdetermined receive scenarios. Near-optimum performance is achieved when the number of symbol candidates is increased.
    Proceedings of the Global Communications Conference, GLOBECOM 2011, 5-9 December 2011, Houston, Texas, USA; 01/2011
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    ABSTRACT: With the ever increasing interest in multiple-input multiple-output (MIMO) cognitive radio (CR) systems, reducing the costs associated with RF-chains at the radio front end becomes a very important factor. In this paper, we propose two solutions to the problem of joint transmit-receive antenna selection with the objective of maximizing data rates and satisfying interference constraints at the primary user (PU) receiver. In the first method we approximate the original non-convex optimization problem with an iterative way of solving a series of smaller convex problems. Then we present a novel, norm-based transmit receive antenna selection technique that simultaneously improves throughput while maintaining the PU interference constraints. We show that this simple approach yields near optimal results with massive complexity reductions. In addition to making a performance comparison between the proposed approaches and the optimal exhaustive search approach, we establish that antenna selection is a promising option for future MIMO CR devices.
    IEEE Transactions on Wireless Communications. 01/2011; 10:3688-3699.
  • Michael Krause, Desmond P. Taylor, Philippa A. Martin
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    ABSTRACT: Co-channel interference (CCI) occurs in a wireless receiver when multiple signals are present. The receiver experiences excessive CCI under overload which occurs when there are more signals than receive antennas. This makes separation and estimation of the transmitted data signals difficult. We develop a novel reduced-complexity receiver structure for the separation and symbol detection of multiple co-channel signals in frequency-flat Rayleigh fading channels. Moreover, we show that list-based group-wise processing can achieve better performance at low and moderate signal-to-noise ratios than existing group-wise soft information processing schemes. The receiver is equipped with multiple antennas and developed to work under overload. Its structure consists of a linear preprocessor followed by a nonlinear reduced-complexity symbol detector. The proposed list group-search detection (LGSD) algorithm relies on list feedback and reduces complexity by iteratively searching over groups of transmitted symbols. It outputs a list of likely data symbols which is well suited to further processing using soft input error control decoders. Simulation shows that LGSD can achieve near optimum joint maximum likelihood performance under overload at significantly lower complexity.
    IEEE Transactions on Wireless Communications 01/2011; 10:1636-1644. · 2.42 Impact Factor
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    Rui Lin, Philippa A. Martin, Desmond P. Taylor
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    ABSTRACT: We propose a Decode-and-Forward (DF) scheme using distributed Turbo code (DTC) for a three-node (source, relay, and destination) wireless cooperative communication system. The relay decodes, then interleaves, and reencodes the decoded data. It then forwards the reencoded packet and its instantaneous receive SNR to the destination. The performances using both ideal and quantized SNR are studied. The destination uses a modified metric within a Turbo decoding algorithm to scale the soft information calculated for the relay code. The proposed scheme is simple to implement and performs well.
    01/2010;
  • Philippa A. Martin, Desmond P. Taylor
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    ABSTRACT: In this comment we position the work of [1], [2] in terms of the prior literature and note that many of its results are subsumed by previous papers.
    IEEE Transactions on Communications. 01/2009; 57:2517.
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    Victor Lo, Philippa A. Martin
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    ABSTRACT: In this letter we investigate the bit and frame error rate performance of various linear block codes when concatenated with a differential phase shift keying modulator. The codes considered include single parity check, Hamming and product codes. We find block codes which significantly improve the frame error rate performance over previous results. An EXIT chart analysis is included.
    IEEE Communications Letters 01/2008; 12:782-784. · 1.16 Impact Factor
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    Michael Krause, Desmond P. Taylor, Philippa A. Martin
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    ABSTRACT: We consider an overloaded wireless multiuser communication system where the number of transmitters exceeds the number of receive antennas. Each user transmits data through a single antenna to a receiver with an M-element uniform linear array. The received signals are combined using maximum ratio diversity combining. Severe co-channel interference (CCI) occurs in such a system due to multiple co-channel users. We present an iterative parallel multiuser detector with list feedback of the best estimates to separate and detect the user symbols. CCI is estimated in the detector using a novel list-based parallel interference cancellation scheme. Simulations show that our algorithm approximates joint-maximum likelihood detection at lower complexity and is well suited for practical application.
    Military Communications Conference, 2007. MILCOM 2007. IEEE; 12/2007
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    Motohiko Isaka, Philippa A. Martin, Marc P. C. Fossorier
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    ABSTRACT: In this paper we look at the serial concatenation of short linear block codes with a rate-1 recursive convolutional encoder, with a goal of designing high-rate codes with low error floor. We observe that under turbo-style decoding the error floor of the concatenated codes with extended Hamming codes is due to detectable errors in many cases. An interleaver design addressing this is proposed in this paper and its effectiveness is verified numerically. We next examine the use of extended BCH codes of larger minimum distance, resulting in an improved weight spectrum of the overall code. Reduced complexity list decoding is used to decode the BCH codes in order to obtain low decoding complexity for a negligible loss in performance.
    IEICE Transactions. 01/2007; 90-A:1754-1762.
  • Philippa A. Martin, Motohiko Isaka, Marc P. C. Fossorier
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    ABSTRACT: In this paper we look at the serial concatenation of linear block codes with a rate-1 recursive convolutional code (accumulator). In particular, we present results for extended Bose Chaudhuri Hocquenghem (eBCH) codes. These codes offer low error floors, good performance and more flexible rate choices than product codes. Reduced complexity list decoding is used to decode the eBCH codes in order to maintain low decoding complexity.
    Turbo Codes&Related Topics; 6th International ITG-Conference on Source and Channel Coding (TURBOCODING), 2006 4th International Symposium on; 01/2006
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    ABSTRACT: The use of multiple-input multiple-output (MIMO) configurations in wireless systems is becoming increasingly popular, due to the potential capacity enhancing properties. The use of such configurations, requires deployment of multiple RF chains and results in an increase in cost and complexity. This paper focuses on transmitter design, where cost is often dominated by the need to utilise linearized power amplifiers. Thus, the effect of reducing the number of active transmit antennae through selection can yield a significant cost advantage. Three criteria for transmit antenna selection are evaluated and characterised through the use of real channel data in the UHF band. The criteria are based only on the channel gains and have relatively low complexity; thus are suitable for practical purposes. This study examines the performance of the tested selection algorithms under a variety of operating conditions. The paper also considers the issue of delayed switch time due to reverse-link communication latency
    Proceedings of the 63rd IEEE Vehicular Technology Conference, VTC Spring 2006, 7-10 May 2006, Melbourne, Australia; 01/2006
  • IEEE Transactions on Communications. 01/2004; 52:252-262.
  • Philippa A. Martin, Desmond P. Taylor
    IEEE Communications Letters 01/2004; 8:458-460. · 1.16 Impact Factor
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    James S. K. Tee, Desmond P. Taylor, Philippa A. Martin
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    ABSTRACT: Single parity-check (SPC) codes are applied in both parallel and serial concatenated structures to produce high-performance coding schemes. The number of concatenations or stages, M, is increased to improve system performance at moderate-to-low bit-error rates without changing the overall code parameters (namely, code rate and code block length). Analytical bounds are presented to estimate the performance at high signal-to-noise ratios. The SPC concatenated codes are considered with binary phase-shift keying and with 16-quadrature amplitude modulation bit-interleaved coded modulation on the additive white Gaussian noise channel and the independent Rayleigh fading channel. Simulations show that the four-stage serial or parallel concatenated SPC codes can, respectively, outperform or perform as well as 16-state turbo codes. Furthermore, decoding complexity is approximately 9-10 times less complex than that of 16-state turbo codes. The convergence behavior of both serial and parallel concatenated SPC codes is also discussed.
    IEEE Transactions on Communications 01/2003; 51:1666-1675. · 1.75 Impact Factor
  • Philippa A. Martin, Desmond P. Taylor
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    ABSTRACT: This paper develops an approach to iterative multistage decoding of multilevel codes. This involves passing reliability information to previous and subsequent decoders instead of only hard decisions to subsequent decoders. The paper also develops an adaptive version of the suboptimal soft output decoding algorithm of Picart and Pyndiah (1996). This adaptive algorithm provides a gain of approximately 0.24 dB at a bit error rate (BER) of 10<sup>-5</sup> after four iterations and approximately 0.43 dB after ten iterations over the algorithm of Picart et al. If the adaptive algorithm is used in conjunction with iterative multistage decoding then a gain of approximately 0.62 dB is obtained at a BER of 10<sup>-5</sup> after four iterations and approximately 0.9 dB after ten iterations over the algorithm of Picart et al
    IEEE Transactions on Communications 01/2001; 49:1916-1925. · 1.75 Impact Factor