Pub Date : 2008-08-15DOI: 10.1109/ITA.2008.4601046
D. Love, Chun Kin Au-Yeung
The benefits employing channel state information (CSI) at the transmitter in a multiple antenna wireless link are well documented in the literature. One of the most popular techniques to provide the transmitter with CSI in frequency division duplexing wireless links is by sending a finite number of feedback bits. However, the effect of the overhead created by these feedback bits on the link performance is still not well understood. In this paper, we study a specific scenario of limited feedback known as limited feedback beamforming. We look at the effect of allocating resources to feedback and the scaling of these resources. Monte Carlo simulations also demonstrate the inherent tradeoff between the forward and reverse links in a wireless system.
{"title":"On resource allocation in two-way limited feedback beamforming systems","authors":"D. Love, Chun Kin Au-Yeung","doi":"10.1109/ITA.2008.4601046","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601046","url":null,"abstract":"The benefits employing channel state information (CSI) at the transmitter in a multiple antenna wireless link are well documented in the literature. One of the most popular techniques to provide the transmitter with CSI in frequency division duplexing wireless links is by sending a finite number of feedback bits. However, the effect of the overhead created by these feedback bits on the link performance is still not well understood. In this paper, we study a specific scenario of limited feedback known as limited feedback beamforming. We look at the effect of allocating resources to feedback and the scaling of these resources. Monte Carlo simulations also demonstrate the inherent tradeoff between the forward and reverse links in a wireless system.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114356424","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 : 2008-08-15DOI: 10.1109/ITA.2008.4601076
U. Salim, D. Slock
In this paper, we consider stationary time- and frequency-selective channels. No channel knowledge neither at the transmitter nor at the receiver is assumed to be available. We investigate the capacity behavior of these doubly selective channels as a function of the channel parameters delay spread, Doppler bandwidth and channel spread factor (the product of the delay spread and the Doppler bandwidth). We shed light on different capacity regimes at high values of signal to noise ratio (SNR) in which the dominant capacity term is either of order log(SNR) or log(log(SNR)), depending on the channel conditions (delay spread, Doppler Bandwidth and channel spread factor). For critically spread channels (channel spread factor of 1), it is widely believed that the dominant term of the high-SNR expansion of the capacity is of order log (log(SNR)) or in other words, that the pre-log (the coefficient of log(SNR)) is zero. We provide a very simple scheme that shows that even for critically spread channels a non-zero pre-log might exist under certain conditions. We also specify these conditions in terms of Doppler bandwidth and delay spread. We also show that a nonzero pre-log might exist even for over-spread channels (channel spread factor greater than 1). We specify the channel conditions which govern the range of existence of the log(SNR) regime. At higher channel spread factor, the log(SNR) term vanishes and a log(log(SNR)) term becomes the dominant capacity term. We specify the range of this log(log(SNR)) regime and also provide bounds for the coefficient of this log(log(SNR)) term (the pre-loglog).
{"title":"Asymptotic capacity of underspread and overspread stationary time- and frequency-selective channels","authors":"U. Salim, D. Slock","doi":"10.1109/ITA.2008.4601076","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601076","url":null,"abstract":"In this paper, we consider stationary time- and frequency-selective channels. No channel knowledge neither at the transmitter nor at the receiver is assumed to be available. We investigate the capacity behavior of these doubly selective channels as a function of the channel parameters delay spread, Doppler bandwidth and channel spread factor (the product of the delay spread and the Doppler bandwidth). We shed light on different capacity regimes at high values of signal to noise ratio (SNR) in which the dominant capacity term is either of order log(SNR) or log(log(SNR)), depending on the channel conditions (delay spread, Doppler Bandwidth and channel spread factor). For critically spread channels (channel spread factor of 1), it is widely believed that the dominant term of the high-SNR expansion of the capacity is of order log (log(SNR)) or in other words, that the pre-log (the coefficient of log(SNR)) is zero. We provide a very simple scheme that shows that even for critically spread channels a non-zero pre-log might exist under certain conditions. We also specify these conditions in terms of Doppler bandwidth and delay spread. We also show that a nonzero pre-log might exist even for over-spread channels (channel spread factor greater than 1). We specify the channel conditions which govern the range of existence of the log(SNR) regime. At higher channel spread factor, the log(SNR) term vanishes and a log(log(SNR)) term becomes the dominant capacity term. We specify the range of this log(log(SNR)) regime and also provide bounds for the coefficient of this log(log(SNR)) term (the pre-loglog).","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"148 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116338298","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 : 2008-08-15DOI: 10.1109/ITA.2008.4601091
J. Yousafzai, M. Ager, Z. Cvetković, Peter Sollich
Robustness of classification of isolated phoneme segments using discriminative and generative classifiers is investigated for the acoustic waveform and PLP speech representations. The two approaches used are support vector machines (SVMs) and mixtures of probabilistic PCA (MPPCA). While recognition in the PLP domain attains superb accuracy on clean data, it is significantly affected by mismatch between training and test noise levels. Classification in the high-dimensional acoustic waveform domain, on the other hand, is more robust in the presence of additive white Gaussian noise. We also show some results on the effects of custom-designed kernel functions for SVM classification in the acoustic waveform domain.
{"title":"Discriminative and generative machine learning approaches towards robust phoneme classification","authors":"J. Yousafzai, M. Ager, Z. Cvetković, Peter Sollich","doi":"10.1109/ITA.2008.4601091","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601091","url":null,"abstract":"Robustness of classification of isolated phoneme segments using discriminative and generative classifiers is investigated for the acoustic waveform and PLP speech representations. The two approaches used are support vector machines (SVMs) and mixtures of probabilistic PCA (MPPCA). While recognition in the PLP domain attains superb accuracy on clean data, it is significantly affected by mismatch between training and test noise levels. Classification in the high-dimensional acoustic waveform domain, on the other hand, is more robust in the presence of additive white Gaussian noise. We also show some results on the effects of custom-designed kernel functions for SVM classification in the acoustic waveform domain.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125919144","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 : 2008-08-15DOI: 10.1109/ITA.2008.4601024
S. Abu-Surra, W. Ryan, D. Divsalar
In earlier work, we presented a method for finding ensemble weight enumerator for protograph-based generalized LDPC (G-LDPC) codes, and leveraged this method to find ensemble stopping set enumerator and ensemble trapping set enumerator. The method is conceptually simple, but when the dimensionality of the constraint nodes (number of their code-words) grows, it becomes difficult to handle the computational complexity, which rise while evaluating these enumerators. To deal with this difficulty, we posed a conjecture, which greatly reduce the computational complexity. Trails to proof this conjecture showed that the proof is a challenging problem. Also, proving it will strengthen the theory of enumerating protograph-based G-LDPC code ensembles. Which in turn helps in predicating the average performances for codes drawn from these ensembles. In Section II we present a review of our method for finding finite and asymptotic weight enumerators for protograph-based G-LDPC code ensembles. Then, we present the conjecture in Section III with some examples.
{"title":"Asymptotic ensemble enumerators for protograph-based generalized LDPC codes: Computational complexity","authors":"S. Abu-Surra, W. Ryan, D. Divsalar","doi":"10.1109/ITA.2008.4601024","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601024","url":null,"abstract":"In earlier work, we presented a method for finding ensemble weight enumerator for protograph-based generalized LDPC (G-LDPC) codes, and leveraged this method to find ensemble stopping set enumerator and ensemble trapping set enumerator. The method is conceptually simple, but when the dimensionality of the constraint nodes (number of their code-words) grows, it becomes difficult to handle the computational complexity, which rise while evaluating these enumerators. To deal with this difficulty, we posed a conjecture, which greatly reduce the computational complexity. Trails to proof this conjecture showed that the proof is a challenging problem. Also, proving it will strengthen the theory of enumerating protograph-based G-LDPC code ensembles. Which in turn helps in predicating the average performances for codes drawn from these ensembles. In Section II we present a review of our method for finding finite and asymptotic weight enumerators for protograph-based G-LDPC code ensembles. Then, we present the conjecture in Section III with some examples.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122594456","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 : 2008-08-15DOI: 10.1109/ITA.2008.4601023
He Huang, Z. Ding
In recent years, there has been broad research interest in the development of beamforming and precoding techniques for MIMO wireless communication systems. Most existing works focus on the single transmission session between transceivers. We expand the MIMO precoder design to take into account the significant role that ARQ (Automatic Repeat reQuest) may play in practical systems. We investigate the design of linear precoders for maximizing the ergodic capacity of MIMO-ARQ systems. Without the precise channel knowledge, our low complexity precoder designs are based on MIMO channel statistic information to achieve significant performance gain under ARQ.
{"title":"Ergodic capacity maximizing MIMO ARQ precoder design based on channel mean information","authors":"He Huang, Z. Ding","doi":"10.1109/ITA.2008.4601023","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601023","url":null,"abstract":"In recent years, there has been broad research interest in the development of beamforming and precoding techniques for MIMO wireless communication systems. Most existing works focus on the single transmission session between transceivers. We expand the MIMO precoder design to take into account the significant role that ARQ (Automatic Repeat reQuest) may play in practical systems. We investigate the design of linear precoders for maximizing the ergodic capacity of MIMO-ARQ systems. Without the precise channel knowledge, our low complexity precoder designs are based on MIMO channel statistic information to achieve significant performance gain under ARQ.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116520779","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}
We consider a single server discrete-time system with K users where the server picks operating points from a compact, convex and co-ordinate convex set in R+ K. For this system we analyse the performance of a stablising policy that at any given time picks operating points from the allowed rate region that maximise a weighted sum of rate, where the weights depend upon the workloads of the users. Assuming a large deviations principle (LDP) for the arrival processes in the Skorohod space of functions that are right-continuous with left-hand limits we establish an LDP for the workload process using a generalised version of the contraction principle to derive the corresponding rate function. With the LDP result available we then analyse the tail probabilities of the workloads under different buffering scenarios.
{"title":"Large deviations of max-weight scheduling policies on convex rate regions","authors":"V. Subramanian","doi":"10.1287/moor.1100.0462","DOIUrl":"https://doi.org/10.1287/moor.1100.0462","url":null,"abstract":"We consider a single server discrete-time system with K users where the server picks operating points from a compact, convex and co-ordinate convex set in R+ K. For this system we analyse the performance of a stablising policy that at any given time picks operating points from the allowed rate region that maximise a weighted sum of rate, where the weights depend upon the workloads of the users. Assuming a large deviations principle (LDP) for the arrival processes in the Skorohod space of functions that are right-continuous with left-hand limits we establish an LDP for the workload process using a generalised version of the contraction principle to derive the corresponding rate function. With the LDP result available we then analyse the tail probabilities of the workloads under different buffering scenarios.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132919330","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 : 2008-08-15DOI: 10.1109/ITA.2008.4601043
Moshe Laifenfeld
Many practical problems in networks such as fault detection and diagnosis, location detection, environmental monitoring, etc, require to identify specific nodes or links based on a set of observations, which size is a subject of optimization. In this paper we focus on a combinatorial approach to these problems, which is closely related to coding techniques, and specifically to identifying codes. The identifying code problem for a given graph involves finding a minimum set of vertices whose neighborhoods uniquely overlap at any given graph vertex. In this paper we show efficient reductions between the identifying code problem and well-known covering problems, resulting in a tight hardness of approximation result and provable good centralized and distributed approximations. We further provide empirical and theoretical results on identifying codes in random networks and efficient constructions of these codes in infinite grids.
{"title":"Localization and identification in networks using robust identifying codes","authors":"Moshe Laifenfeld","doi":"10.1109/ITA.2008.4601043","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601043","url":null,"abstract":"Many practical problems in networks such as fault detection and diagnosis, location detection, environmental monitoring, etc, require to identify specific nodes or links based on a set of observations, which size is a subject of optimization. In this paper we focus on a combinatorial approach to these problems, which is closely related to coding techniques, and specifically to identifying codes. The identifying code problem for a given graph involves finding a minimum set of vertices whose neighborhoods uniquely overlap at any given graph vertex. In this paper we show efficient reductions between the identifying code problem and well-known covering problems, resulting in a tight hardness of approximation result and provable good centralized and distributed approximations. We further provide empirical and theoretical results on identifying codes in random networks and efficient constructions of these codes in infinite grids.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134218774","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 : 2008-08-15DOI: 10.1109/ITA.2008.4601015
S. Yuksel, T. Başar, S. Meyn
For Markov sources, the structure of optimal causal encoders minimizing the total communication rate subject to a mean-square distortion constraint is studied. The class of sources considered lives in a continuous alphabet, and the encoder is allowed to be variable-rate. Both the finite-horizon and the infinite-horizon problems are considered. In the finite-horizon case, the problem is non-convex, whereas in the infinite-horizon case the problem can be convexified under certain assumptions. For a finite horizon problem, the optimal deterministic causal encoder for a kth-order Markov source uses only the most recent k source symbols and the information available at the receiver, whereas the optimal causal coder for a memoryless source is memoryless. For the infinite-horizon problem, a convex-analytic approach is adopted. Randomized stationary quantizers are suboptimal in the absence of common randomness between the encoder and the decoder. If there is common randomness, the optimal quantizer requires the randomization of at most two deterministic quantizers. In the absence of common randomness, the optimal quantizer is non-stationary and a recurrence-based time-sharing of two deterministic quantizers is optimal. A linear source driven by Gaussian noise is considered. If the process is stable, innovation coding is almost optimal at high-rates, whereas if the source is unstable, then even a high-rate time-invariant innovation coding scheme leads to an unstable estimation process.
{"title":"Optimal causal quantization of Markov Sources with distortion constraints","authors":"S. Yuksel, T. Başar, S. Meyn","doi":"10.1109/ITA.2008.4601015","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601015","url":null,"abstract":"For Markov sources, the structure of optimal causal encoders minimizing the total communication rate subject to a mean-square distortion constraint is studied. The class of sources considered lives in a continuous alphabet, and the encoder is allowed to be variable-rate. Both the finite-horizon and the infinite-horizon problems are considered. In the finite-horizon case, the problem is non-convex, whereas in the infinite-horizon case the problem can be convexified under certain assumptions. For a finite horizon problem, the optimal deterministic causal encoder for a kth-order Markov source uses only the most recent k source symbols and the information available at the receiver, whereas the optimal causal coder for a memoryless source is memoryless. For the infinite-horizon problem, a convex-analytic approach is adopted. Randomized stationary quantizers are suboptimal in the absence of common randomness between the encoder and the decoder. If there is common randomness, the optimal quantizer requires the randomization of at most two deterministic quantizers. In the absence of common randomness, the optimal quantizer is non-stationary and a recurrence-based time-sharing of two deterministic quantizers is optimal. A linear source driven by Gaussian noise is considered. If the process is stable, innovation coding is almost optimal at high-rates, whereas if the source is unstable, then even a high-rate time-invariant innovation coding scheme leads to an unstable estimation process.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134400782","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 : 2008-08-15DOI: 10.1109/ITA.2008.4601075
Vitaly Skachek
Several expander code constructions and their parameters are surveyed. New generalized expander codes are introduced and their properties are compared with the properties of the existing constructions. Finally, some possible directions to extend the current research on expander codes are discussed.
{"title":"Minimum distance bounds for expander codes","authors":"Vitaly Skachek","doi":"10.1109/ITA.2008.4601075","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601075","url":null,"abstract":"Several expander code constructions and their parameters are surveyed. New generalized expander codes are introduced and their properties are compared with the properties of the existing constructions. Finally, some possible directions to extend the current research on expander codes are discussed.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116104670","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 : 2008-08-15DOI: 10.1109/ITA.2008.4601056
F. J. Piera, P. Parada
We consider a stochastic dynamical system whose output evolves in time as the solution to a functional coefficients, Itopsilas stochastic differential equation, excited by an input process. This general class of stochastic systems encompasses a wide variety of engineering models appearing through a whole range of applications, extending in particular the classical communication channel models. We find analogous of known relationships linking input-output mutual information and causal and noncausal minimum mean-square errors in the context of additive Gaussian noise communication channels. The introduction in this general framework of an appropriate signal-to-noise ratio notion expressed through a signal-to-noise ratio parameter is also taken into account, identifying conditions for a proper and meaningful interpretation.
{"title":"On the connections between information and estimation theory: from AWGN Channels to dynamical systems with feedback","authors":"F. J. Piera, P. Parada","doi":"10.1109/ITA.2008.4601056","DOIUrl":"https://doi.org/10.1109/ITA.2008.4601056","url":null,"abstract":"We consider a stochastic dynamical system whose output evolves in time as the solution to a functional coefficients, Itopsilas stochastic differential equation, excited by an input process. This general class of stochastic systems encompasses a wide variety of engineering models appearing through a whole range of applications, extending in particular the classical communication channel models. We find analogous of known relationships linking input-output mutual information and causal and noncausal minimum mean-square errors in the context of additive Gaussian noise communication channels. The introduction in this general framework of an appropriate signal-to-noise ratio notion expressed through a signal-to-noise ratio parameter is also taken into account, identifying conditions for a proper and meaningful interpretation.","PeriodicalId":345196,"journal":{"name":"2008 Information Theory and Applications Workshop","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121201519","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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