The Experts below are selected from a list of 17130 Experts worldwide ranked by ideXlab platform
T Aulin - One of the best experts on this subject based on the ideXlab platform.
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on analysis and design of low density Generator Matrix codes for continuous phase modulation
IEEE Transactions on Wireless Communications, 2007Co-Authors: Ming Xiao, T AulinAbstract:We investigate the analysis and design of low density Generator Matrix (LDGM) codes for continuous phase modulation (CPM). The system uses LDGM codes as an outer code for CPM. For additive white Gaussian noise channels, we derive the union bound to analyze the error floor performance. Design principles for lowering error floors are suggested from this analysis. We propose a design approach of jointly considering the LDGM code degree and the CPM modulation index. Then we consider the rate-adaptive system for slowly fading channels. By changing the rate of the LDGM codes, the information rate of the CPM signals is adapted according to channel variations. We use a low-rate LDGM code as the mother code. Higher rates are achieved by puncturing the output of these codes. To exploit the rate-flexible property of punctured LDGM codes, a rate function is proposed to calculate the rate of each transmitted block. Thus, we can have a quasi-continuous information rate. Numerical results show that this approach can improve the energy efficiency from a discrete-rate adaptation. Using the rate-adaptive approach, up to 11 dB transmitted energy gain can be achieved from the non-adaptive scheme in the low bit-error-rate region (smaller than 10-3) for minimum shift keying (MSK).
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serially concatenated continuous phase modulation with low density Generator Matrix codes property optimization and performance analysis
Information Theory Workshop, 2005Co-Authors: Ming Xiao, T AulinAbstract:We propose a new scheme of serially concatenated continuous phase modulation (SCCPM) by using nonsystematic low density Generator Matrix (LDGM) codes as the outer code. A property of the LDGM code degree is investigated. We use the exit chart/function to optimize the LDGM codes. The exit function of CPM with a fixed SNR (signal-to-noise-ratio) is shown. We derive the union bound to analyze the error floor performance. Design principles are proposed from the analysis process. Numerical results show that this scheme converge earlier (lower SNR) than previous SCCPM for iterative decoding.
Javier Garciafrias - One of the best experts on this subject based on the ideXlab platform.
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approach for the construction of non calderbank steane shor low density Generator Matrix based quantum codes
Physical Review A, 2020Co-Authors: Patricio Fuentes, Josu Etxezarreta Martinez, Pedro M Crespo, Javier GarciafriasAbstract:Quantum low-density Generator Matrix (QLDGM) codes based on Calderbank-Steane-Shor (CSS) constructions have shown unprecedented error correction capabilities, displaying much improved performance in comparison to other sparse-graph codes. However, the nature of CSS designs and the manner in which they must be decoded limit the performance that is attainable with codes that are based on this construction. This motivates the search for quantum code design strategies capable of avoiding the drawbacks associated with CSS codes. In this article, we introduce non-CSS quantum code constructions based on classical LDGM codes. The proposed codes are derived from CSS QLDGM designs by performing specific row operations on their quantum parity check matrices to modify the associated decoding graphs. The application of this method results in performance improvements in comparison to CSS QLDGM codes, while also allowing for greater flexibility in the design process. The proposed non-CSS QLDGM scheme outperforms the best quantum low-density parity check codes that have appeared in the literature.
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serially concatenated low density Generator Matrix scldgm codes for transmission over awgn and rayleigh fading channels
IEEE Transactions on Wireless Communications, 2007Co-Authors: M Gonzalezlopez, Francisco J Vazquezaraujo, Luis Castedo, Javier GarciafriasAbstract:Low density Generator Matrix (LDGM) codes are a particular class of low density parity check (LDPC) codes with very low encoding complexity. Single LDGM codes present high error-floors, which can be substantially reduced with the serial concatenation of two LDGM (SCLDGM) codes. We propose a technique to obtain good SCLDGM codes using extrinsic information transfer (EXIT) functions in a novel way. Although the optimization is performed for AWGN channels with binary signaling, the resulting codes are also optimal for AWGN and perfectly-interleaved Rayleigh fading channels with non-binary signaling and perfect CSI at reception, provided that Gray mapping is utilized. Optimized regular and irregular SCLDGM codes outperform heuristically-designed LDGM codes existing in the literature, and have a performance similar to or better than that of irregular repeat accumulate (IRA) codes.
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on the application of error correcting codes with low density Generator Matrix over different quantum channels
Turbo Codes&Related Topics; 6th International ITG-Conference on Source and Channel Coding (TURBOCODING) 2006 4th International Symposium on, 2006Co-Authors: Hanqing Lou, Javier GarciafriasAbstract:We propose the use of linear codes with low-density Generator Matrix in the context of error correction over different quantum channels. The basic idea is to construct a Calderbank-Shor-Steane (CSS) code based on the Generator Matrix and the parity-check Matrix of an LDGM code, applying row operations in both matrices to achieve the desired quantum rate. Decoding is performed in an iterative manner, using message passing over the corresponding graphs. The proposed codes allow greater flexibility and are easier to design than existing sparse-graph quantum codes, while leading to better performance.
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design of serially concatenated low density Generator Matrix codes using exit charts
Turbo Codes&Related Topics; 6th International ITG-Conference on Source and Channel Coding (TURBOCODING) 2006 4th International Symposium on, 2006Co-Authors: M Gonzalezlopez, Francisco J Vazquezaraujo, Luis Castedo, Javier GarciafriasAbstract:Serially-Concatenated Low-Density Generator Matrix (SCLDGM) codes are an attractive scheme to approach channel capacity on several channel models. Performance of SCLDGM codes depends basically on the rates of the two component codes, as well as on the connection degrees of the bits involved in a codeword. SCLDGM codes proposed so far have been constructed setting the values of these parameters heuristically. In this paper we present two SCLDGM codes constructed using an optimization procedure based on tracking the decoding behaviour of the Sum-Product Algorithm (SPA) by means of EXtrinsic Information Transfer (EXIT) functions. We present results for both Binary-Input AWGN (BIAWGN) and Rayleigh fading channels. In both cases the optimized SCLDGM codes exhibit better performance than other recent schemes, such as Irregular Repeat-Accumulate (IRA) codes, at similar coding/decoding computational cost.
Martin J Wainwright - One of the best experts on this subject based on the ideXlab platform.
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lossy source compression using low density Generator Matrix codes analysis and algorithms
IEEE Transactions on Information Theory, 2010Co-Authors: Martin J Wainwright, Elitza Maneva, Emin MartinianAbstract:We study the use of low-density Generator Matrix (LDGM) codes for lossy compression of the Bernoulli symmetric source. First, we establish rigorous upper bounds on the average distortion achieved by check-regular ensemble of LDGM codes under optimal minimum distance source encoding. These bounds establish that the average distortion using such bounded degree families rapidly approaches the Shannon limit as the degrees are increased. Second, we propose a family of message-passing algorithms, ranging from the standard belief propagation algorithm at one extreme to a variant of survey propagation algorithm at the other. When combined with a decimation subroutine and applied to LDGM codes with suitably irregular degree distributions, we show that such a message-passing/decimation algorithm yields distortion very close to the Shannon rate-distortion bound for the binary symmetric source.
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lower bounds on the rate distortion function of ldgm codes
arXiv: Information Theory, 2008Co-Authors: Alexandros G Dimakis, Martin J Wainwright, Kannan RamchandranAbstract:A recent line of work has focused on the use of low-density Generator Matrix (LDGM) codes for lossy source coding. In this paper, wedevelop a generic technique for deriving lower bounds on the rate-distortion functions of binary linear codes, with particular interest on the effect of bounded degrees. The underlying ideas can be viewing as the source coding analog of the classical result of Gallager, providing bounds for channel coding over the binary symmetric channel using bounded degree LDPC codes. We illustrate this method for different random ensembles of LDGM codes, including the check-regular ensemble and bit-check-regular ensembles, by deriving explicit lower bounds on their rate-distortion performance as a function of the degrees.
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lower bounds on the rate distortion function of ldgm codes
Information Theory Workshop, 2007Co-Authors: Alexandros G Dimakis, Martin J Wainwright, Kannan RamchandranAbstract:We analyze the performance of low-density Generator Matrix (LDGM) codes for lossy source coding. We first develop a generic technique for deriving lower bounds on the effective rate-distortion functions of binary linear codes. This result provides a source coding analog of a classical result due to Gallager for channel coding over the binary symmetric channel. We illustrate this method for the ensemble of check-regular low- density Generator Matrix (LDGM) codes by deriving an explicit lower bound on its rate-distortion performance as a function of the check degree.
Ming Xiao - One of the best experts on this subject based on the ideXlab platform.
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on analysis and design of low density Generator Matrix codes for continuous phase modulation
IEEE Transactions on Wireless Communications, 2007Co-Authors: Ming Xiao, T AulinAbstract:We investigate the analysis and design of low density Generator Matrix (LDGM) codes for continuous phase modulation (CPM). The system uses LDGM codes as an outer code for CPM. For additive white Gaussian noise channels, we derive the union bound to analyze the error floor performance. Design principles for lowering error floors are suggested from this analysis. We propose a design approach of jointly considering the LDGM code degree and the CPM modulation index. Then we consider the rate-adaptive system for slowly fading channels. By changing the rate of the LDGM codes, the information rate of the CPM signals is adapted according to channel variations. We use a low-rate LDGM code as the mother code. Higher rates are achieved by puncturing the output of these codes. To exploit the rate-flexible property of punctured LDGM codes, a rate function is proposed to calculate the rate of each transmitted block. Thus, we can have a quasi-continuous information rate. Numerical results show that this approach can improve the energy efficiency from a discrete-rate adaptation. Using the rate-adaptive approach, up to 11 dB transmitted energy gain can be achieved from the non-adaptive scheme in the low bit-error-rate region (smaller than 10-3) for minimum shift keying (MSK).
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serially concatenated continuous phase modulation with low density Generator Matrix codes property optimization and performance analysis
Information Theory Workshop, 2005Co-Authors: Ming Xiao, T AulinAbstract:We propose a new scheme of serially concatenated continuous phase modulation (SCCPM) by using nonsystematic low density Generator Matrix (LDGM) codes as the outer code. A property of the LDGM code degree is investigated. We use the exit chart/function to optimize the LDGM codes. The exit function of CPM with a fixed SNR (signal-to-noise-ratio) is shown. We derive the union bound to analyze the error floor performance. Design principles are proposed from the analysis process. Numerical results show that this scheme converge earlier (lower SNR) than previous SCCPM for iterative decoding.
Javier Garcia-frias - One of the best experts on this subject based on the ideXlab platform.
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Combining the Burrows-Wheeler Transform and RCM-LDGM Codes for the Transmission of Sources with Memory at High Spectral Efficiencies
'MDPI AG', 2019Co-Authors: Imanol Granada, Pedro M Crespo, Javier Garcia-friasAbstract:In this paper, we look at the problem of implementing high-throughput Joint Source- Channel (JSC) coding schemes for the transmission of binary sources with memory over AWGN channels. The sources are modeled either by a Markov chain (MC) or a hidden Markov model (HMM). We propose a coding scheme based on the Burrows-Wheeler Transform (BWT) and the parallel concatenation of Rate-Compatible Modulation and Low-Density Generator Matrix (RCM-LDGM) codes. The proposed scheme uses the BWT to convert the original source with memory into a set of independent non-uniform Discrete Memoryless (DMS) binary sources, which are then separately encoded, with optimal rates, using RCM-LDGM codes
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Rate-compatible low-density Generator Matrix codes
IEEE Transactions on Communications, 2008Co-Authors: Hanqing Lou, Javier Garcia-friasAbstract:We propose a family of rate-compatible codes based on the concatenation of two linear codes with low-density Generator Matrix, which are a special class of LDPC codes with low encoding complexity. The proposed scheme is characterized by its simplicity of construction, and does not require optimization of the puncturing pattern.
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LDGM codes for channel coding and joint source-channel coding of correlated sources
EURASIP Journal on Advances in Signal Processing, 2005Co-Authors: Wei Zhong, Javier Garcia-friasAbstract:We propose a coding scheme based on the use of systematic linear codes with low-density Generator Matrix (LDGM codes) for channel coding and joint source-channel coding of multiterminal correlated binary sources. In both cases, the structures of the LDGM encoder and decoder are shown, and a concatenated scheme aimed at reducing the error floor is proposed. Several decoding possibilities are investigated, compared, and evaluated. For different types of noisy channels and correlation models, the resulting performance is very close to the theoretical limits.
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Approaching Shannon performance by iterative decoding of linear codes with low-density Generator Matrix
IEEE Communications Letters, 2003Co-Authors: Javier Garcia-frias, Wei ZhongAbstract:We propose the use of linear codes with low density Generator Matrix to achieve a performance similar to that of turbo and standard low-density parity check codes. The use of iterative decoding techniques - message passing -over the corresponding graph achieves a performance close to the Shannon theoretical limit. As an advantage with respect to turbo and standard low-density parity check codes, the complexity of the decoding and encoding procedures is very low.
