The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The following topics were dealt with: properties of codes; feedback and cooperation in networks; channel coding, communication techniques and estimation methods; construction, analysis and decoding of LDPC codes; sequences and permutations; universal lossless compression; capacity and coding for fading channels; network theory; statistical mechanics; turbo and turbo-like code constructions; communication...
New upper bounds on the rate of low-density parity-check (LDPC) codes as a function of the minimum distance of the code are derived. These bounds are based on combinatorial arguments and linear programming. They improve on the previous bounds due to Burshtein et al. It is proved that at least for high rate LDPC codes have worse relative minimum distance than the one guaranteed by the Gilbert-Varshamov...
We show for a large class of LDPC ensembles, including RA and IRA codes, that the bit iterative decoding threshold is essentially identical to the block iterative decoding threshold
In a recent paper, Yang et al. presented the class of extended irregular repeat-accumulate (eIRA) codes which are efficiently encodable LDPC codes possessing very low error-rate floors and are appropriate for code rates 1/2 or greater. While efficiently encodable, the left-most (n-k)-by-k submatrix of an eIRA code parity-check matrix is random in nature, making efficient decoder implementation problematic...
Cooperative optimization is a new way for finding global optima of complicated functions of many variables. It has some important properties not possessed by any conventional optimization methods. It has been successfully applied in solving many large scale optimization problems in image processing, computer vision, and computational chemistry. This paper shows the application of this optimization...
Consider data transmission over a binary-input additive white Gaussian noise channel using a binary low-density parity-check code. We ask the following question: Given a decoder that takes log-likelihood ratios as input, does it help to modify the log-likelihood ratios before decoding? If we use an optimal decoder then it is clear that modifying the log-likelihoods cannot possibly help the decoder's...
In this paper, we present a novel class of simple soft-input soft-output (SISO) detection algorithms for transmission over phase-uncertain channels. In order to limit the complexity, the set of possible phase values (i.e., the interval [0,2pi)) is properly quantized. We then use a forward-backward (FB) algorithm in correspondence to each quantized phase value. The forward and backward metrics computed...
This paper derives an iterative receiver for noncoherent fading channels that exhibit block fading with correlation between blocks. Pilot symbols and Kalman smoothing are used in conjunction with sum-product decoding of LDPC codes to implement an iterative channel estimation and decoding structure. Density evolution is employed to analyze the performance of such a structure and to optimize the degree...
We present a construction of LDPC codes that have minimum pseudocodeword weight equal to the minimum distance, and perform well with iterative decoding. The construction involves enumerating a d-regular tree for a fixed number of layers and employing a connection algorithm based on mutually orthogonal Latin squares to close the tree. Methods are presented for degrees d = ps and d = ps + 1, for p a...
Capacity-approaching codes using iterative decoding have been the main research subject of coding area during past decade. In this paper, a new channel coding scheme called irregular concatenated zigzag (ICZZ) code is proposed. ICZZ codes can be viewed as a special case of irregular low-density parity-check (LDPC) codes with linear-time encodable structure. They are different from concatenated zigzag...
We provide a thorough analysis for a class of iteratively encodable low-density parity-check codes. The iterative encoding technique is based upon the graphical representation of the code and allows the decoder circuit to also be used for encoding, thus saving circuit area. The analysis identifies a weakness in the structure of the code, which arises due to a repetitive pattern in its factor graph...
We propose a parallel concatenated coding scheme in which the constituent codes are regular systematic linear codes with low-density generator matrix (LDGM codes). The proposed system provides a simple way to reduce the error floors characteristic of single regular LDGM codes, and leads to a performance similar to that of turbo and irregular LDPC codes with less encoding/decoding complexity. Although...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.