41204462
Differential trellis decoding of convolutional codes
This paper investigates the principle of metric differences for trellis decoding of convolutional codes. Based on this differential method, a new algorithm, referred to as differential trellis decoding (DTD), is proposed. DTD offers an alternative to the conventional "add-compare-select" (ACS) method for implementing the Viterbi algorithm.
15293330
A Two-Stage Iterative Decoding of LDPC Codes for Lowering Error Floors
In iterative decoding of LDPC codes, trapping sets often lead to high error floors. In this work, we propose a two-stage iterative decoding to break trapping sets. Simulation results show that the error floor performance can be significantly improved with this decoding scheme.
45763221
Some Results on Linear Unequal-Error-Protection Codes Specified by their Generator Matrix
There are many applications in which it is required to design a code that protects messages against different levels of noise (or messages with different levels of importance over a noise stable channel). Examples of such situations are: broadcast channels, multi-user channels, and PCM digital telemetry systems, among others. A code that offers multiple levels of error protection is called an unequal-error-protection (UEP) code. In this paper, the UEP capabilities of certain classes of linear codes, obtained by combining shorter linear codes, are investigated. Linear UEP (LUEP) codes based on generator matrices of shorter codes were considered previously in [1], for the case of the \(\left| {\bar u\left| {\bar u + \bar v} \right.} \right|\)construction of MacWilliams and Sloane [3]. In this paper, we examine linear codes obtained from combining shorter codes using the more interesting constructions X and X4 of Sloane et al. [2]. Both construction X and construction X4 use cosets of a subcode in a linear code as building blocks, and constitute generalizations to the \(\left| {\bar u\left| {\bar u + \bar v} \right.} \right|\)construction. We provide specific examples of families of codes obtained from construction X, using very simple component codes, which yield good LUEP codes. Furthermore, we discuss two-stage decoding methods for LUEP codes obtained using these constructions. Finally, we present the alternative of using an LUEP code as one of the component codes in construction X. An example shows that in this way optimal LUEP codes may be constructed.
1486934
Linear block codes for error detection
The probability of undetected error of linear block codes for use on a binary symmetric channel is investigated. Upper hounds are derived. Several classes of linear block codes are proved to have good error-detecting capability.
20336793
On linear structure and phase rotation invariant properties of block M-PSK modulation codes
Two important structural properties of block M(=2/sup '/)-ary PSK modulation codes, linear structure and phase symmetry, are investigated. An M-ary modulation code is first represented as a code with symbols from the integer group S/sub M-PSK/=(0,1,2,---,M-1) under modulo-M addition. Then the linear structure of block M-PSK modulation codes over S/sub M-PSK/ with respect to modulo-M vector addition is defined, and conditions are derived under which a block M-PSK modulation code is linear. Once the linear structure is developed, the phase symmetry of block M-PSK modulation codes is studied. In particular, a necessary and sufficient condition for a block M-PSK modulation code that is linear as a binary code to be invariant under 2/sup h/180 degrees /M phase rotation, for 1 >
10540664
Construction of nonbinary cyclic, quasi-cyclic and regular LDPC codes: a finite geometry approach
This paper presents five methods for constructing nonbinary LDPC codes based on finite geometries. These methods result in five classes of nonbinary LDPC codes, one class of cyclic LDPC codes, three classes of quasi-cyclic LDPC codes and one class of structured regular LDPC codes. Experimental results show that constructed codes in these classes decoded with iterative decoding based on belief propagation perform very well over the AWGN channel and they achieve significant coding gains over Reed-Solomon codes of the same lengths and rates with either algebraic hard-decision decoding or Kotter-Vardy algebraic soft-decision decoding at the expense of a larger decoding computational complexity.
14063870
Impact of Manufacturing Practices on Adoption of Plant Information Systems
Firms have invested over $15 billion in the past three years on new information technology and software in their manufacturing plants. In this study, we document how the implementation of new types of manufacturing practices has impacted the types of information technology investments in manufacturing plants. We present a conceptual model to develop hypotheses about relationships between manufacturing practices and the choice of information systems at the plant level. Analysis of cross-sectional survey data from 932 manufacturing plants provides strong empirical support for our hypotheses about how manufacturing practices influence decisions regarding adoption of plant-level IT applications.