Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625266
Linda M. Davis
This paper presents a novel formulation for a posteriori probability (APP) decoding of systematic convolutional codes. The convolutional encoder and decoder are constructed to enable transition-based channel estimates to be embedded into the APP calculations. The result is joint channel estimation and decoding. The new decoder is targeted to systematic codes in flat-fading environments although the formulation may be extended for frequency-selective channels or even non-systematic codes with the penalty of additional complexity. In contrast to per-survivor processing for Viterbi decoding, the approach here does not rely on tentative decisions from survivor paths, channel estimation filter coefficients can be pre-calculated, and the APP decoder delivers soft decisions.
{"title":"APP Convolutional Decoding with Transition-Based Systematic Channel Estimation","authors":"Linda M. Davis","doi":"10.1109/AUSCTW.2006.1625266","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625266","url":null,"abstract":"This paper presents a novel formulation for a posteriori probability (APP) decoding of systematic convolutional codes. The convolutional encoder and decoder are constructed to enable transition-based channel estimates to be embedded into the APP calculations. The result is joint channel estimation and decoding. The new decoder is targeted to systematic codes in flat-fading environments although the formulation may be extended for frequency-selective channels or even non-systematic codes with the penalty of additional complexity. In contrast to per-survivor processing for Viterbi decoding, the approach here does not rely on tentative decisions from survivor paths, channel estimation filter coefficients can be pre-calculated, and the APP decoder delivers soft decisions.","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124159851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625274
M. Taouk, Matthew J. M. Peacock, I. Collings
Motivated by statistical Waterfilling, we derive statistical Mercury/Waterfilling (M/WF) for both fixed average power and fixed average rate as the infinite time limit of the spatio-temporal M/WF solution. The M → ∞ limit of the conditional mean estimate (CME) receiver for unit-energy M-QAM constellations is derived, which may be used as a low complexity approximate CME estimate for dense QAM constellations. The asymptotic CME result is used to analytically characterize an upper bound on the mutual information properties of QAM. We develop a tree-search algorithm to efficiently optimize coded bit allocation in M/WF. Two analytical tests are derived to eliminate sub-trees of the graph.
{"title":"Statistical Power Allocation and Coded Bit Allocation Optimization in Mercury/Waterfilling","authors":"M. Taouk, Matthew J. M. Peacock, I. Collings","doi":"10.1109/AUSCTW.2006.1625274","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625274","url":null,"abstract":"Motivated by statistical Waterfilling, we derive statistical Mercury/Waterfilling (M/WF) for both fixed average power and fixed average rate as the infinite time limit of the spatio-temporal M/WF solution. The M → ∞ limit of the conditional mean estimate (CME) receiver for unit-energy M-QAM constellations is derived, which may be used as a low complexity approximate CME estimate for dense QAM constellations. The asymptotic CME result is used to analytically characterize an upper bound on the mutual information properties of QAM. We develop a tree-search algorithm to efficiently optimize coded bit allocation in M/WF. Two analytical tests are derived to eliminate sub-trees of the graph.","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116016141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625251
R. Perera, K. Nguyen, T. Pollock, T. Abhayapala
This paper investigates the capacity of discrete time uncorrelated Rayleigh fading multiple input multiple output (MIMO) channels with no channel state information (CSI) at both the transmitter and the receiver. We prove that to achieve the capacity, the amplitude of the multiple input needs to have a discrete distribution with a finite number of mass points with one of them located at the origin. We show how to compute the capacity numerically in multi antenna configuration at any signal to noise ratio (SNR) with the discrete input using the Kuhn-Tucker condition for optimality. Furthermore, we show that at low SNR, the capacity with two mass points is optimal. Since the first mass point is necessarily located at the origin, we argue that at low SNR, on-off keying is optimal for any antenna number. As the number of receiver antennas increases, the maximum SNR at which two mass points are optimal decreases
{"title":"On capacity of non-coherent Rayleigh fading MIMO channels","authors":"R. Perera, K. Nguyen, T. Pollock, T. Abhayapala","doi":"10.1109/AUSCTW.2006.1625251","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625251","url":null,"abstract":"This paper investigates the capacity of discrete time uncorrelated Rayleigh fading multiple input multiple output (MIMO) channels with no channel state information (CSI) at both the transmitter and the receiver. We prove that to achieve the capacity, the amplitude of the multiple input needs to have a discrete distribution with a finite number of mass points with one of them located at the origin. We show how to compute the capacity numerically in multi antenna configuration at any signal to noise ratio (SNR) with the discrete input using the Kuhn-Tucker condition for optimality. Furthermore, we show that at low SNR, the capacity with two mass points is optimal. Since the first mass point is necessarily located at the origin, we argue that at low SNR, on-off keying is optimal for any antenna number. As the number of receiver antennas increases, the maximum SNR at which two mass points are optimal decreases","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128915406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625270
C. Kellett, S. Weller
Extrinsic Information Transfer (or EXIT) charts have provided a useful tool for analysing the convergence of iterative decoders. In this work, we abstract the EXIT chart as a feedback interconnection of two one-dimensional dynamical systems. For such feedback interconnections, we characterise the local stability properties of fixed points and demonstrate the existence of period two orbits and discuss their stability properties. Finally, we give a graphical procedure for finding the region of attraction for asymptotically stable fixed points or period two orbits.
{"title":"Fixed Points of Exit Charts","authors":"C. Kellett, S. Weller","doi":"10.1109/AUSCTW.2006.1625270","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625270","url":null,"abstract":"Extrinsic Information Transfer (or EXIT) charts have provided a useful tool for analysing the convergence of iterative decoders. In this work, we abstract the EXIT chart as a feedback interconnection of two one-dimensional dynamical systems. For such feedback interconnections, we characterise the local stability properties of fixed points and demonstrate the existence of period two orbits and discuss their stability properties. Finally, we give a graphical procedure for finding the region of attraction for asymptotically stable fixed points or period two orbits.","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130865587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625275
T. Betlehem, T. Abhayapala, T. Lamahewa
In this paper, we develop a MIMO channel model for generating the channel gains between arbitrary arrays of transmitter and receiver antennas, for a general class of non-line-of-sight (NLOS) channels. The channel scattering environment is defined by a double directional angular distribution describing the power transferred from transmitter aperture to receiver aperture in each direction. We propose several parametrized bivariate distributions that are consistent with univariate scatterer distributions separately observed at the transmitter and receiver. We derive the second order statistics of the channel gains in terms of the double directional power distribution and characterize a sample system performance as a function of distribution parameters
{"title":"Space-time MIMO channel modelling using angular power distributions","authors":"T. Betlehem, T. Abhayapala, T. Lamahewa","doi":"10.1109/AUSCTW.2006.1625275","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625275","url":null,"abstract":"In this paper, we develop a MIMO channel model for generating the channel gains between arbitrary arrays of transmitter and receiver antennas, for a general class of non-line-of-sight (NLOS) channels. The channel scattering environment is defined by a double directional angular distribution describing the power transferred from transmitter aperture to receiver aperture in each direction. We propose several parametrized bivariate distributions that are consistent with univariate scatterer distributions separately observed at the transmitter and receiver. We derive the second order statistics of the channel gains in terms of the double directional power distribution and characterize a sample system performance as a function of distribution parameters","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121501890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625268
L. Hanlen, R. Timo, R. Perera
We give a 2WT style result for the degrees of freedom of multipath signals that pass through spatially limited (sparse) scattering environments. The dimensionality scales with the circumference of the scattering region, and the total communications path length. We provide a direct comparison to the time-frequency case, where space replaces time. This is a rigorous wavefield examination of previous heuristic geometric arguments.
{"title":"On Dimensionality for Sparse Multipath","authors":"L. Hanlen, R. Timo, R. Perera","doi":"10.1109/AUSCTW.2006.1625268","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625268","url":null,"abstract":"We give a 2WT style result for the degrees of freedom of multipath signals that pass through spatially limited (sparse) scattering environments. The dimensionality scales with the circumference of the scattering region, and the total communications path length. We provide a direct comparison to the time-frequency case, where space replaces time. This is a rigorous wavefield examination of previous heuristic geometric arguments.","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125218674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625261
S. Srinivasan, S. S. Pietrobon
Tail-biting codes are suitable for high rate codes of short block length as they do not introduce any rate loss and have a simpler a posteriori Probability (APP) decoder structure than block codes. For such high rate codes, an APP algorithm working on the trellis of the dual code is preferred since the branch complexity is much less compared to the original code trellis. However, the nature of the metrics in a dual-APP decoder makes a hardware realisation quite complex, due to very fine quantisation requirements. This paper points out the problems associated with a traditional log domain approach and proposes a new metric representation scheme. The arithmetic operations involved in a trellis based implementation are discussed. The proposed scheme is applied to a sub optimum decoder for tail-biting codes and simulation results are given.
{"title":"Efficient Dual Domain Decoding of High Rate Tail-biting Codes","authors":"S. Srinivasan, S. S. Pietrobon","doi":"10.1109/AUSCTW.2006.1625261","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625261","url":null,"abstract":"Tail-biting codes are suitable for high rate codes of short block length as they do not introduce any rate loss and have a simpler a posteriori Probability (APP) decoder structure than block codes. For such high rate codes, an APP algorithm working on the trellis of the dual code is preferred since the branch complexity is much less compared to the original code trellis. However, the nature of the metrics in a dual-APP decoder makes a hardware realisation quite complex, due to very fine quantisation requirements. This paper points out the problems associated with a traditional log domain approach and proposes a new metric representation scheme. The arithmetic operations involved in a trellis based implementation are discussed. The proposed scheme is applied to a sub optimum decoder for tail-biting codes and simulation results are given.","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126329116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625263
Greg Day, S. Nordholm, H. H. Dam
This paper presents a unifying technique for robust feedback filter design in the decision feedback equaliser (DFE). The robustness is needed for combatting error propagation effects which is the major limitation when using DFEs. Numerous constraint strategies for the design of robust DFEs are available in the literature, however, they have been presented in their own ad-hoc context. Consequently there is a desire to give a unified approach to robust feedback filter design. The approach in the current presentation is to first develop a mean square error (MSE) measure which is a function of the feedforward and feedback filters. This measure is then combined with a feedback filter constraint using four existing norm constraint approaches (the L1, L2, Linfin and the "two tap" norm). The use of second order cone programming allows these existing norm constraint strategies to be unified and solved in a computationally efficient manner. The evaluation is performed with respect to the impact on error propagation, through the mean and the variance of the burst error length
{"title":"A unifying study of robust decision feedback equalisers","authors":"Greg Day, S. Nordholm, H. H. Dam","doi":"10.1109/AUSCTW.2006.1625263","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625263","url":null,"abstract":"This paper presents a unifying technique for robust feedback filter design in the decision feedback equaliser (DFE). The robustness is needed for combatting error propagation effects which is the major limitation when using DFEs. Numerous constraint strategies for the design of robust DFEs are available in the literature, however, they have been presented in their own ad-hoc context. Consequently there is a desire to give a unified approach to robust feedback filter design. The approach in the current presentation is to first develop a mean square error (MSE) measure which is a function of the feedforward and feedback filters. This measure is then combined with a feedback filter constraint using four existing norm constraint approaches (the L1, L2, Linfin and the \"two tap\" norm). The use of second order cone programming allows these existing norm constraint strategies to be unified and solved in a computationally efficient manner. The evaluation is performed with respect to the impact on error propagation, through the mean and the variance of the burst error length","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126056290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625272
V. Trajkovic, P. Rapajic
In this paper we propose a new Turbo Equalization algorithm with Decision Aided Equalizer (DAE). The algorithm takes into account that the soft feedback decisions from the previous iteration contain errors that cannot be neglected. The proposed algorithm finds the error variance and recalculates DAE coefficients at each turbo iteration. The algorithm shows Bit Error Rate (BER) performance improvement relative to the conventional Turbo DAE for severe frequency-selective channels. The achieved improvement is 0.8 dB at BER of 10-5.
{"title":"New Improved Decision Aided Turbo Equalization","authors":"V. Trajkovic, P. Rapajic","doi":"10.1109/AUSCTW.2006.1625272","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625272","url":null,"abstract":"In this paper we propose a new Turbo Equalization algorithm with Decision Aided Equalizer (DAE). The algorithm takes into account that the soft feedback decisions from the previous iteration contain errors that cannot be neglected. The proposed algorithm finds the error variance and recalculates DAE coefficients at each turbo iteration. The algorithm shows Bit Error Rate (BER) performance improvement relative to the conventional Turbo DAE for severe frequency-selective channels. The achieved improvement is 0.8 dB at BER of 10-5.","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"225 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124236780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-05-08DOI: 10.1109/AUSCTW.2006.1625259
H. H. Dam, S. Nordholm, S. Low, K. Teo
Sensor arrays are used in various applications such as radar, sonar, communications, radio links and voice input systems. In this paper, we propose a new variable array structure, which allows array characteristics such as the look direction or the passband/stopband region to be varied easily. Most importantly, these characteristics can be changed by varying only a single steering or tuning parameter. The design problem is formulated to minimize the integral squared error between the array response and the desired response, which is reduced to a quadratic optimization problem. Design examples are presented to show that the look direction of the array can be designed to effectively steer over the angles of the required range.
{"title":"Steerable Far-field Circular Array","authors":"H. H. Dam, S. Nordholm, S. Low, K. Teo","doi":"10.1109/AUSCTW.2006.1625259","DOIUrl":"https://doi.org/10.1109/AUSCTW.2006.1625259","url":null,"abstract":"Sensor arrays are used in various applications such as radar, sonar, communications, radio links and voice input systems. In this paper, we propose a new variable array structure, which allows array characteristics such as the look direction or the passband/stopband region to be varied easily. Most importantly, these characteristics can be changed by varying only a single steering or tuning parameter. The design problem is formulated to minimize the integral squared error between the array response and the desired response, which is reduced to a quadratic optimization problem. Design examples are presented to show that the look direction of the array can be designed to effectively steer over the angles of the required range.","PeriodicalId":206040,"journal":{"name":"2006 Australian Communications Theory Workshop","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125633535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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