Pub Date : 2012-09-01DOI: 10.1109/ITW.2012.6404675
Iñaki Estella Aguerri, Deniz Gündüz
The class of orthogonal relay channels with state in which the source and the relay are connected through a channel that depends on a state sequence is considered. It is assumed that the state sequence is fully known at the destination while it is not known at the source or the relay. The source and the relay are connected to the destination through orthogonal channels. The capacity of this class of relay channels is characterized and it is shown to be achieved by the partial decode-compress-and-forward (pDCF) scheme. To the best of our knowledge, this is the first single relay channel model for which the capacity is achieved by pDCF, while partial decode-and-forward (pDF) and compress-and-forward (CF) schemes are suboptimal in general.
{"title":"Capacity of a class of relay channels with state","authors":"Iñaki Estella Aguerri, Deniz Gündüz","doi":"10.1109/ITW.2012.6404675","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404675","url":null,"abstract":"The class of orthogonal relay channels with state in which the source and the relay are connected through a channel that depends on a state sequence is considered. It is assumed that the state sequence is fully known at the destination while it is not known at the source or the relay. The source and the relay are connected to the destination through orthogonal channels. The capacity of this class of relay channels is characterized and it is shown to be achieved by the partial decode-compress-and-forward (pDCF) scheme. To the best of our knowledge, this is the first single relay channel model for which the capacity is achieved by pDCF, while partial decode-and-forward (pDF) and compress-and-forward (CF) schemes are suboptimal in general.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"153 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128598477","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404635
S. Vadhan, C. Zheng
We provide a characterization of “pseudoentropy” in terms of hardness of sampling: Let (X, B) be jointly distributed random variables such that B takes values in a polynomial-sized set. We show that no polynomial-time algorithm can distinguish B from some random variable of higher Shannon entropy given X if and only if there is no probabilistic polynomial-time S such that (X, S(X)) has small KL divergence from (X, B). As an application of this characterization, we show that if f is a one-way function (f is easy to compute but hard to invert), then (f(Un),Un) has “next-bit pseudoentropy” at least n + log n, establishing a conjecture of Haitner, Reingold, and Vadhan (STOC '10). Plugging this into the construction of Haitner et al., we obtain a simpler construction of pseudorandom generators from one-way functions.
我们根据采样的硬度提供了“伪熵”的表征:设(X, B)是联合分布的随机变量，使得B在多项式大小的集合中取值。我们表明,没有多项式时间算法能区分B从高等夏侬熵给出一些随机变量X当且仅当没有概率多项式时间年代这样(X, S (X))小KL分歧(X, B)。作为应用程序的特征,我们表明,如果f是单向函数(f是容易计算,但难以反转),然后(f(联合国)、联合国)”下pseudoentropy”至少n + o (log n),建立一个猜想Haitner, Reingold, Vadhan(获得STOC 10)。将此代入Haitner等人的构造中，我们从单向函数中获得了更简单的伪随机生成器构造。
{"title":"Characterizing pseudoentropy","authors":"S. Vadhan, C. Zheng","doi":"10.1109/ITW.2012.6404635","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404635","url":null,"abstract":"We provide a characterization of “pseudoentropy” in terms of hardness of sampling: Let (X, B) be jointly distributed random variables such that B takes values in a polynomial-sized set. We show that no polynomial-time algorithm can distinguish B from some random variable of higher Shannon entropy given X if and only if there is no probabilistic polynomial-time S such that (X, S(X)) has small KL divergence from (X, B). As an application of this characterization, we show that if f is a one-way function (f is easy to compute but hard to invert), then (f(Un),Un) has “next-bit pseudoentropy” at least n + log n, establishing a conjecture of Haitner, Reingold, and Vadhan (STOC '10). Plugging this into the construction of Haitner et al., we obtain a simpler construction of pseudorandom generators from one-way functions.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130587106","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404648
Y. Kochman, G. Wornell
This work considers the definition of the excess-distortion exponent, used to measure the asymptotic finite blocklength behavior of joint source-channel coding. We arrive at the conclusion that it is not a meaningful measure for the operational tradeoffs of a scheme. We propose a new definition, which makes a distinction between the processing block of the coding scheme (which implies delay and may be connected to complexity), the fidelity blocklength (reflecting the quality of the reconstruction as required by the application), and the resource blocklength (depending on hardware or shared medium considerations). As an aside, the exponent of uncoded schemes is analyzed. This results in finding the joint source-channel coding excess-distortion exponent in some cases where it was not known previously.
{"title":"On uncoded transmission and blocklength","authors":"Y. Kochman, G. Wornell","doi":"10.1109/ITW.2012.6404648","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404648","url":null,"abstract":"This work considers the definition of the excess-distortion exponent, used to measure the asymptotic finite blocklength behavior of joint source-channel coding. We arrive at the conclusion that it is not a meaningful measure for the operational tradeoffs of a scheme. We propose a new definition, which makes a distinction between the processing block of the coding scheme (which implies delay and may be connected to complexity), the fidelity blocklength (reflecting the quality of the reconstruction as required by the application), and the resource blocklength (depending on hardware or shared medium considerations). As an aside, the exponent of uncoded schemes is analyzed. This results in finding the joint source-channel coding excess-distortion exponent in some cases where it was not known previously.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"80 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130739195","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404660
N. Hassan, A. E. Pusane, M. Lentmaier, G. Fettweis, D. Costello
Window decoding schedules are very attractive for message passing decoding of spatially coupled LDPC codes. They take advantage of the inherent convolutional code structure and allow continuous transmission with low decoding latency and complexity. In this paper we show that the decoding complexity can be further reduced if suitable message passing schedules are applied within the decoding window. An improvement based schedule is presented that easily adapts to different ensemble structures, window sizes, and channel parameters. Its combination with a serial (on-demand) schedule is also considered. Results from a computer search based schedule are shown for comparison.
{"title":"Reduced complexity window decoding schedules for coupled LDPC codes","authors":"N. Hassan, A. E. Pusane, M. Lentmaier, G. Fettweis, D. Costello","doi":"10.1109/ITW.2012.6404660","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404660","url":null,"abstract":"Window decoding schedules are very attractive for message passing decoding of spatially coupled LDPC codes. They take advantage of the inherent convolutional code structure and allow continuous transmission with low decoding latency and complexity. In this paper we show that the decoding complexity can be further reduced if suitable message passing schedules are applied within the decoding window. An improvement based schedule is presented that easily adapts to different ensemble structures, window sizes, and channel parameters. Its combination with a serial (on-demand) schedule is also considered. Results from a computer search based schedule are shown for comparison.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128788477","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404676
Ben-Yue Chang, D. Divsalar, L. Dolecek
This paper presents two complementary constructions of finite-length non-binary protograph-based codes with the focus on the short block-length regime. The first class is based on the existing approaches of applying the copy-and-permute operations to the constituent protograph with unweighted edges, followed by assigning non-binary scales to the edges of the derived graph. The second class is novel and is based on the so-called graph cover of a non-binary protograph: the original protograph has fixed edge scalings and copy-and-permute operations are applied to the edge-weighted protograph. The second class is arguably more restrictive, but in turn it offers simpler design and implementation. We provide design and construction of these non-binary codes for short block-lengths. Performance, cycle distribution and the minimum distance of the binary image of selected codes over AWGN is provided for information block-lengths as low as 64 bits.
{"title":"Non-binary protograph-based LDPC codes for short block-lengths","authors":"Ben-Yue Chang, D. Divsalar, L. Dolecek","doi":"10.1109/ITW.2012.6404676","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404676","url":null,"abstract":"This paper presents two complementary constructions of finite-length non-binary protograph-based codes with the focus on the short block-length regime. The first class is based on the existing approaches of applying the copy-and-permute operations to the constituent protograph with unweighted edges, followed by assigning non-binary scales to the edges of the derived graph. The second class is novel and is based on the so-called graph cover of a non-binary protograph: the original protograph has fixed edge scalings and copy-and-permute operations are applied to the edge-weighted protograph. The second class is arguably more restrictive, but in turn it offers simpler design and implementation. We provide design and construction of these non-binary codes for short block-lengths. Performance, cycle distribution and the minimum distance of the binary image of selected codes over AWGN is provided for information block-lengths as low as 64 bits.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126664459","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404715
Kumar Viswanatha, E. Akyol, K. Rose
This paper addresses the L-channel multiple descriptions problem for a Gaussian source under mean squared error (MSE) distortion metric. We focus on particular cross-sections of the general rate-distortion region where a subset the 2L - 1 distortion constraints are not imposed. Specifically, we assume that certain descriptions are never received simultaneously at the decoder and thereby the transmitted codewords require joint typicality only within prescribed subsets. We derive a new encoding scheme and an associated rate-distortion region wherein joint typicality of codewords only within the prescribed subsets is maintained. We show that enforcing joint typicality of all the codewords entails strict suboptimality in the achievable rate-distortion region. Specifically, we consider a 3 descriptions scenario wherein descriptions 1 and 3 are never received simultaneously at the decoder and show that a strictly larger achievable region is obtained when the encoder maintains joint typicality of codewords only within the required subsets. To prove these results, we derive a lemma called the `subset typicality lemma' which plays a critical role in establishing the new achievable region.
{"title":"A new achievable region for Gaussian multiple descriptions based on subset typicality","authors":"Kumar Viswanatha, E. Akyol, K. Rose","doi":"10.1109/ITW.2012.6404715","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404715","url":null,"abstract":"This paper addresses the L-channel multiple descriptions problem for a Gaussian source under mean squared error (MSE) distortion metric. We focus on particular cross-sections of the general rate-distortion region where a subset the 2L - 1 distortion constraints are not imposed. Specifically, we assume that certain descriptions are never received simultaneously at the decoder and thereby the transmitted codewords require joint typicality only within prescribed subsets. We derive a new encoding scheme and an associated rate-distortion region wherein joint typicality of codewords only within the prescribed subsets is maintained. We show that enforcing joint typicality of all the codewords entails strict suboptimality in the achievable rate-distortion region. Specifically, we consider a 3 descriptions scenario wherein descriptions 1 and 3 are never received simultaneously at the decoder and show that a strictly larger achievable region is obtained when the encoder maintains joint typicality of codewords only within the required subsets. To prove these results, we derive a lemma called the `subset typicality lemma' which plays a critical role in establishing the new achievable region.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116754659","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404773
M. Prabhakaran, V. Prabhakaran
We investigate secure multi-party sampling problems involving more than two parties. In the public discussion model, we give a simple characterization of the distributions that can be sampled without any setup. In a model which allows private point-to-point communication, we reduce the problem of characterizing distributions that can be securely sampled using pairwise setups to the problem of characterizing distributions that can be sampled without any setups.
{"title":"On secure multiparty sampling for more than two parties","authors":"M. Prabhakaran, V. Prabhakaran","doi":"10.1109/ITW.2012.6404773","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404773","url":null,"abstract":"We investigate secure multi-party sampling problems involving more than two parties. In the public discussion model, we give a simple characterization of the distributions that can be sampled without any setup. In a model which allows private point-to-point communication, we reduce the problem of characterizing distributions that can be securely sampled using pairwise setups to the problem of characterizing distributions that can be sampled without any setups.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116763250","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404664
S. Rini, E. Kurniawan, A. Goldsmith
The cognitive interference channel models cognitive overlay radio systems, in which cognitive radios overhear the transmission of neighboring nodes. For the Gaussian case capacity is known in three subsets of the parameter space: the “weak interference”, “very strong interference” and “primary decodes cognitive” regime. Capacity in the “very strong interference” regime is achieved by superposing the cognitive message over the primary message while in the “primary decodes cognitive” regime the cognitive message is binned against the primary message. This paper provides a new capacity result obtained by combining the capacity achieving schemes in these two regimes thus generalizing and extending these results. Interestingly, the capacity achieving strategy for a given channel also depends on the level of cooperation among the users: that is, either superposition coding or binning is employed depending on the amount of power allotted by the cognitive transmitter to aid the primary user.
{"title":"Combining superposition coding and binning achieves capacity for the Gaussian cognitive interference channel","authors":"S. Rini, E. Kurniawan, A. Goldsmith","doi":"10.1109/ITW.2012.6404664","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404664","url":null,"abstract":"The cognitive interference channel models cognitive overlay radio systems, in which cognitive radios overhear the transmission of neighboring nodes. For the Gaussian case capacity is known in three subsets of the parameter space: the “weak interference”, “very strong interference” and “primary decodes cognitive” regime. Capacity in the “very strong interference” regime is achieved by superposing the cognitive message over the primary message while in the “primary decodes cognitive” regime the cognitive message is binned against the primary message. This paper provides a new capacity result obtained by combining the capacity achieving schemes in these two regimes thus generalizing and extending these results. Interestingly, the capacity achieving strategy for a given channel also depends on the level of cooperation among the users: that is, either superposition coding or binning is employed depending on the amount of power allotted by the cognitive transmitter to aid the primary user.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131568544","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404745
Shirish S. Karande
We consider a network where multiple sources communicate via a single relay to sinks with non-uniform and unequal demands. The LT distributions employed at the sources may be ill-matched to the demands of the sinks connected to the relay. We consider a probabilistic “morphing” of two or more fountain-encoded streams into a single stream better suited for the demand patterns downstream of the relay. The relay observes symbols generated from two distinct fountain codes, and can decide to forward a symbol from one source, or the other source, or the X-OR of the two symbols. We propose a linear programming based design of Generalized LT codes, which with appropriate substitutions is utilized to design the probabilities for the relay. Simulation results show that the designs obtained on the basis of the proposed optimization problem, when compared with multiplexing or simple mixing, reduce the number of symbols that have to be downloaded to guarantee a desired probability of successful decoding.
{"title":"Retargeting LT codes using XORs at the relay","authors":"Shirish S. Karande","doi":"10.1109/ITW.2012.6404745","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404745","url":null,"abstract":"We consider a network where multiple sources communicate via a single relay to sinks with non-uniform and unequal demands. The LT distributions employed at the sources may be ill-matched to the demands of the sinks connected to the relay. We consider a probabilistic “morphing” of two or more fountain-encoded streams into a single stream better suited for the demand patterns downstream of the relay. The relay observes symbols generated from two distinct fountain codes, and can decide to forward a symbol from one source, or the other source, or the X-OR of the two symbols. We propose a linear programming based design of Generalized LT codes, which with appropriate substitutions is utilized to design the probabilities for the relay. Simulation results show that the designs obtained on the basis of the proposed optimization problem, when compared with multiplexing or simple mixing, reduce the number of symbols that have to be downloaded to guarantee a desired probability of successful decoding.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127752519","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 : 2012-09-01DOI: 10.1109/ITW.2012.6404721
D. Declercq, Erbao Li, B. Vasic, S. Planjery
We introduce a generic approach, called FAID diversity, for improving the error correction capability of regular low-density parity check codes, beyond the belief propagation performance. The method relies on operating a set of finite alphabet iterative decoders (FAID). The message-passing update rules are interpreted as discrete dynamical systems, and are judiciously chosen to ensure that decoders have different dynamics on a specific finite-length code. An algorithm is proposed which uses random jumps in the iterative message passing trajectories, such that the system is not trapped in periodic attractors. We show by simulations that the FAID diversity approach with random jumps has the potential of approaching the performance of maximum-likelihood decoding for finite-length regular, column-weight three codes.
{"title":"Approaching maximum likelihood decoding of finite length LDPC codes via FAID diversity","authors":"D. Declercq, Erbao Li, B. Vasic, S. Planjery","doi":"10.1109/ITW.2012.6404721","DOIUrl":"https://doi.org/10.1109/ITW.2012.6404721","url":null,"abstract":"We introduce a generic approach, called FAID diversity, for improving the error correction capability of regular low-density parity check codes, beyond the belief propagation performance. The method relies on operating a set of finite alphabet iterative decoders (FAID). The message-passing update rules are interpreted as discrete dynamical systems, and are judiciously chosen to ensure that decoders have different dynamics on a specific finite-length code. An algorithm is proposed which uses random jumps in the iterative message passing trajectories, such that the system is not trapped in periodic attractors. We show by simulations that the FAID diversity approach with random jumps has the potential of approaching the performance of maximum-likelihood decoding for finite-length regular, column-weight three codes.","PeriodicalId":325771,"journal":{"name":"2012 IEEE Information Theory Workshop","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115083300","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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