The complexity of brute force encoding of LDPC codes is proportional to the square value of the block length. Richardson and Urbanke have proposed efficient encoding algorithms for LDPC codes. These algorithms permute the parity check matrix of the code iteratively, such that it becomes approximately lower triangular. We propose a new approach for efficient encoding of LDPC codes in which we modify the code ensemble to force an approximate lower triangular structure, thus eliminating the need to apply the algorithms of Richardson and Urbanke. We prove that the new ensemble has the same asymptotic threshold as the corresponding standard ensemble. The new ensemble can be used for linear time encoding of an arbitrary code profile. Computer simulations confirm that the performances of the standard and new ensembles are also very similar when using finite length codes
{"title":"Approximately Lower Triangular Ensembles of LPDC Codes with Linear Encoding Complexity","authors":"Shay Freundlich, D. Burshtein, S. Litsyn","doi":"10.1109/TIT.2007.892771","DOIUrl":"https://doi.org/10.1109/TIT.2007.892771","url":null,"abstract":"The complexity of brute force encoding of LDPC codes is proportional to the square value of the block length. Richardson and Urbanke have proposed efficient encoding algorithms for LDPC codes. These algorithms permute the parity check matrix of the code iteratively, such that it becomes approximately lower triangular. We propose a new approach for efficient encoding of LDPC codes in which we modify the code ensemble to force an approximate lower triangular structure, thus eliminating the need to apply the algorithms of Richardson and Urbanke. We prove that the new ensemble has the same asymptotic threshold as the corresponding standard ensemble. The new ensemble can be used for linear time encoding of an arbitrary code profile. Computer simulations confirm that the performances of the standard and new ensembles are also very similar when using finite length codes","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"168 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131773173","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 : 2006-12-26DOI: 10.1109/ISIT.2006.261578
C. Abou-Rjeily, N. Daniele, J. Belfiore
This paper presents the construction of new totally-real space-time coding schemes suited for carrier-less ultra-wideband transmissions. These schemes are associated with pulse position modulation and with hybrid pulse amplitude and position modulation where the input data is modulated onto both the pulse amplitudes and positions. The new schemes have a uniform average transmitted energy per antenna and achieve full rate and full diversity with hybrid M-PPM-M'-PAM for all values of M' and for M ges 3, M ges 5 and {M = 5, M ges 7} with n = 2, 3 and 4 transmit antennas respectively
{"title":"A New Family of Space-Time Codes for Pulse Amplitude and Position Modulated UWB Systems","authors":"C. Abou-Rjeily, N. Daniele, J. Belfiore","doi":"10.1109/ISIT.2006.261578","DOIUrl":"https://doi.org/10.1109/ISIT.2006.261578","url":null,"abstract":"This paper presents the construction of new totally-real space-time coding schemes suited for carrier-less ultra-wideband transmissions. These schemes are associated with pulse position modulation and with hybrid pulse amplitude and position modulation where the input data is modulated onto both the pulse amplitudes and positions. The new schemes have a uniform average transmitted energy per antenna and achieve full rate and full diversity with hybrid M-PPM-M'-PAM for all values of M' and for M ges 3, M ges 5 and {M = 5, M ges 7} with n = 2, 3 and 4 transmit antennas respectively","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127218440","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 : 2006-12-26DOI: 10.1109/ISIT.2006.261954
S. Cheng, M. Valenti
A union bound on the performance of bit interleaved coded orthogonal modulation (BICOM) is presented. The bound is derived by representing the system as an equivalent serially concatenated convolutional code (SCCC). Differential precoding prior to orthogonal modulation is shown to provide an interleaver gain, and termination of the differential precoder with a tail bit is taken into account in the bound. The bounds are evaluated for both coherent and noncoherent detection in AWGN and fully interleaved Rayleigh fading and shown to be tight by comparison against simulation results
{"title":"Union Bound Analysis of Bit Interleaved Coded Orthogonal Modulation with Differential Precoding","authors":"S. Cheng, M. Valenti","doi":"10.1109/ISIT.2006.261954","DOIUrl":"https://doi.org/10.1109/ISIT.2006.261954","url":null,"abstract":"A union bound on the performance of bit interleaved coded orthogonal modulation (BICOM) is presented. The bound is derived by representing the system as an equivalent serially concatenated convolutional code (SCCC). Differential precoding prior to orthogonal modulation is shown to provide an interleaver gain, and termination of the differential precoder with a tail bit is taken into account in the bound. The bounds are evaluated for both coherent and noncoherent detection in AWGN and fully interleaved Rayleigh fading and shown to be tight by comparison against simulation results","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132092692","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 : 2006-12-26DOI: 10.1109/ISIT.2006.262099
D. Porrat, U. Mitra
The acquisition, or synchronization, of a multipath channel profile for ultra-wideband pulse position modulation (PPM) communication systems is considered. The rate of increase of the number of paths as the bandwidth grows determines whether acquisition can occur. If the number of independent Gaussian paths increases without bound, but slower than the bandwidth, then the system cannot acquire in the limit. Acquisition is not possible on multipath channels with deterministic path amplitudes, if the number of paths diverges but not too fast. These results hold for exponential or uniform power delay profiles
{"title":"Timing Acquisition of Wideband PPM Systems over Multipath","authors":"D. Porrat, U. Mitra","doi":"10.1109/ISIT.2006.262099","DOIUrl":"https://doi.org/10.1109/ISIT.2006.262099","url":null,"abstract":"The acquisition, or synchronization, of a multipath channel profile for ultra-wideband pulse position modulation (PPM) communication systems is considered. The rate of increase of the number of paths as the bandwidth grows determines whether acquisition can occur. If the number of independent Gaussian paths increases without bound, but slower than the bandwidth, then the system cannot acquire in the limit. Acquisition is not possible on multipath channels with deterministic path amplitudes, if the number of paths diverges but not too fast. These results hold for exponential or uniform power delay profiles","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132196344","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 : 2006-12-26DOI: 10.1109/ISIT.2006.261832
Jiafeng Jin, T. Ho, H. Viswanathan
Network coding has been shown to be useful for throughput and reliability in various network topologies, under a fixed-rate, point-to-multipoint wireless network model. We study the effect of introducing a wireless network model where link capacity depends on the network geometry and the signal to interference and noise ratio. In particular, we compare strategies with and without network coding on a multicast network with and without fading, and on single-user multiple path networks with fading. For the multicast network without fading, we find that the network geometry affects which scheme attains higher throughput. For the case with fading, we compare the throughput-outage probability curves achieved by network coding and repetition schemes. For the multiple path networks, we further consider the case where multiple simultaneous transmissions of identical information signals can be combined at a receiver. We find that the relative performance of the schemes we consider depends on the network geometry, the ratio of signal to noise power, whether multiple simultaneous transmissions can be combined, and the operating point on the throughput-outage probability curve
{"title":"Comparison of Network Coding and Non-Network Coding Schemes for Multi-hop Wireless Networks","authors":"Jiafeng Jin, T. Ho, H. Viswanathan","doi":"10.1109/ISIT.2006.261832","DOIUrl":"https://doi.org/10.1109/ISIT.2006.261832","url":null,"abstract":"Network coding has been shown to be useful for throughput and reliability in various network topologies, under a fixed-rate, point-to-multipoint wireless network model. We study the effect of introducing a wireless network model where link capacity depends on the network geometry and the signal to interference and noise ratio. In particular, we compare strategies with and without network coding on a multicast network with and without fading, and on single-user multiple path networks with fading. For the multicast network without fading, we find that the network geometry affects which scheme attains higher throughput. For the case with fading, we compare the throughput-outage probability curves achieved by network coding and repetition schemes. For the multiple path networks, we further consider the case where multiple simultaneous transmissions of identical information signals can be combined at a receiver. We find that the relative performance of the schemes we consider depends on the network geometry, the ratio of signal to noise power, whether multiple simultaneous transmissions can be combined, and the operating point on the throughput-outage probability curve","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122356055","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 : 2006-12-26DOI: 10.1109/ISIT.2006.262149
P. Elia, P. V. Kumar
It has been shown by Li and Xia that there exist cooperative diversity schemes that can provide for diversity gains in wireless networks even without symbol synchronicity between cooperative network users. These asynchronicity-tolerant schemes were based on distributed space-time codes which maintained their full-rank property for specific asynchronicity cases and specific numbers of users. By expanding the signaling set, we provide constructions of schemes that maintain near-optimal error performance, given certain cooperation strategies and given synchronicity, and which are asynchronicity-tolerant, with probability one, for any asynchronicity profile and for all numbers of network users. By relating the problem of asynchronicity to the maximum degrees of freedom provided by a cooperative-diversity scheme, we are further able to provide cooperative diversity methods that are empirically shown to translate asynchronicity to reduction of the probability of error.
{"title":"Constructions of Cooperative Diversity Schemes for Asynchronous Wireless Networks","authors":"P. Elia, P. V. Kumar","doi":"10.1109/ISIT.2006.262149","DOIUrl":"https://doi.org/10.1109/ISIT.2006.262149","url":null,"abstract":"It has been shown by Li and Xia that there exist cooperative diversity schemes that can provide for diversity gains in wireless networks even without symbol synchronicity between cooperative network users. These asynchronicity-tolerant schemes were based on distributed space-time codes which maintained their full-rank property for specific asynchronicity cases and specific numbers of users. By expanding the signaling set, we provide constructions of schemes that maintain near-optimal error performance, given certain cooperation strategies and given synchronicity, and which are asynchronicity-tolerant, with probability one, for any asynchronicity profile and for all numbers of network users. By relating the problem of asynchronicity to the maximum degrees of freedom provided by a cooperative-diversity scheme, we are further able to provide cooperative diversity methods that are empirically shown to translate asynchronicity to reduction of the probability of error.","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127801998","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 : 2006-07-09DOI: 10.1109/ISIT.2006.261721
Sanjay Karmakar, B. Rajan
It is well known that Alamouti code and, in general, space-time block codes (STBCs) from complex orthogonal designs (CODs) are single-symbol decodable/symbol-by-symbol decodable (SSD) and are obtainable from unitary matrix representations of Clifford algebras. However, SSD codes are obtainable from designs that are not CODs. Recently, two such classes of SSD codes have been studied: (i) coordinate interleaved orthogonal designs (CIODs) and (ii) minimum-decoding-complexity (MDC) STBCs from quasi-ODs (QODs). In this paper, we obtain SSD codes with unitary weight matrices (but not CODs) from matrix representations of Clifford algebras. Moreover, we derive an upper bound on the rate of SSD codes with unitary weight matrices and show that our codes meet this bound. Also, we present conditions on the signal sets which ensure full-diversity and give expressions for the coding gain
{"title":"Minimum-Decoding-Complexity, Maximum-rate Space-Time Block Codes from Clifford Algebras","authors":"Sanjay Karmakar, B. Rajan","doi":"10.1109/ISIT.2006.261721","DOIUrl":"https://doi.org/10.1109/ISIT.2006.261721","url":null,"abstract":"It is well known that Alamouti code and, in general, space-time block codes (STBCs) from complex orthogonal designs (CODs) are single-symbol decodable/symbol-by-symbol decodable (SSD) and are obtainable from unitary matrix representations of Clifford algebras. However, SSD codes are obtainable from designs that are not CODs. Recently, two such classes of SSD codes have been studied: (i) coordinate interleaved orthogonal designs (CIODs) and (ii) minimum-decoding-complexity (MDC) STBCs from quasi-ODs (QODs). In this paper, we obtain SSD codes with unitary weight matrices (but not CODs) from matrix representations of Clifford algebras. Moreover, we derive an upper bound on the rate of SSD codes with unitary weight matrices and show that our codes meet this bound. Also, we present conditions on the signal sets which ensure full-diversity and give expressions for the coding gain","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115495814","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 : 2006-07-09DOI: 10.1109/ISIT.2006.262042
M. Haenggi
A new fading model is proposed and discussed that combines the uncertainties in the transmission distance as well as small-scale fading. If nodes are assumed to be distributed according to a Poisson point process and the fading is Rayleigh, the joint fading distribution is particularly simple. Interpreting fading as a stochastic mapping, we show that a node cannot infer on the presence of fading by measuring link qualities. Other applications of the fading model include connectivity, opportunistic communication, and probabilistic progress
{"title":"A Geometry-Inclusive Fading Model for Random Wireless Networks","authors":"M. Haenggi","doi":"10.1109/ISIT.2006.262042","DOIUrl":"https://doi.org/10.1109/ISIT.2006.262042","url":null,"abstract":"A new fading model is proposed and discussed that combines the uncertainties in the transmission distance as well as small-scale fading. If nodes are assumed to be distributed according to a Poisson point process and the fading is Rayleigh, the joint fading distribution is particularly simple. Interpreting fading as a stochastic mapping, we show that a node cannot infer on the presence of fading by measuring link qualities. Other applications of the fading model include connectivity, opportunistic communication, and probabilistic progress","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"197 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124393789","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 : 2006-07-09DOI: 10.1109/ISIT.2006.262000
Wan Choi, J. Andrews
As an alternative to traditional static frequency reuse patterns, this paper investigates cooperatively scheduling among neighboring base stations in a cellular multiple antenna system, where each cell adopts dirty paper coding. It is shown that cooperatively scheduled transmission can achieve almost the same amount of interference reduction as conventional frequency reuse and achieve an extra capacity gain. We analytically quantify the capacity gain of cooperatively scheduled transmission over conventional frequency reuse in an Mt times Mr dirty paper coded MIMO system. The theoretical analysis of this paper also provides an altered view of multiuser diversity in the context of a multi-cell system. Because the positions of the users are important in a multi-cell system, we find that the gain is O(radiclog K), from selecting the maximum of a compound lognormal-exponential distribution, whereas multiuser diversity capacity gain has been previously known to grow as O(log log K), from selecting the maximum of K exponentially-distributed powers
{"title":"The Capacity Gain from Base Station Cooperative Scheduling in a MIMO DPC Cellular System","authors":"Wan Choi, J. Andrews","doi":"10.1109/ISIT.2006.262000","DOIUrl":"https://doi.org/10.1109/ISIT.2006.262000","url":null,"abstract":"As an alternative to traditional static frequency reuse patterns, this paper investigates cooperatively scheduling among neighboring base stations in a cellular multiple antenna system, where each cell adopts dirty paper coding. It is shown that cooperatively scheduled transmission can achieve almost the same amount of interference reduction as conventional frequency reuse and achieve an extra capacity gain. We analytically quantify the capacity gain of cooperatively scheduled transmission over conventional frequency reuse in an Mt times Mr dirty paper coded MIMO system. The theoretical analysis of this paper also provides an altered view of multiuser diversity in the context of a multi-cell system. Because the positions of the users are important in a multi-cell system, we find that the gain is O(radiclog K), from selecting the maximum of a compound lognormal-exponential distribution, whereas multiuser diversity capacity gain has been previously known to grow as O(log log K), from selecting the maximum of K exponentially-distributed powers","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115755655","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 : 2006-07-09DOI: 10.1109/ISIT.2006.261549
Martin Hell, T. Johansson, A. Maximov, W. Meier
A new stream cipher, Grain-128, is proposed. The design is very small in hardware and it targets environments with very limited resources in gate count, power consumption, and chip area. Grain-128 supports key size of 128 bits and IV size of 96 bits. The design is very simple and based on two shift registers, one linear and one nonlinear, and an output function
{"title":"A Stream Cipher Proposal: Grain-128","authors":"Martin Hell, T. Johansson, A. Maximov, W. Meier","doi":"10.1109/ISIT.2006.261549","DOIUrl":"https://doi.org/10.1109/ISIT.2006.261549","url":null,"abstract":"A new stream cipher, Grain-128, is proposed. The design is very small in hardware and it targets environments with very limited resources in gate count, power consumption, and chip area. Grain-128 supports key size of 128 bits and IV size of 96 bits. The design is very simple and based on two shift registers, one linear and one nonlinear, and an output function","PeriodicalId":115298,"journal":{"name":"2006 IEEE International Symposium on Information Theory","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125225251","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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