4,627 research outputs found
Selex
A summary of the path which lead to a high energy physics group at Instituto
de Fisica de la Universidad Autonoma de San Luis Potosi is presented. This
group is the result of the initial push made by Leon Lederman at the beginning
of the 80's.Comment: Talk given at the Session honoring Leon Lederman at the VII Mexican
Workshop on Particles and Fields, Merida, Mexico, November 10-17, 1999.
Proceedings to be published by AI
A Note on Repeated-Root Cyclic Codes
In papers by Castagnoli et al. and Van Lint, cyclic codes with repeated roots are analyzed. Both papers fail to acknowledge a previous work by Chen, dating back to 1969, which includes an analysis of even, length binary cyclic codes. Results from Chen’s study are presented
Unequal Error Protection QPSK Modulation Codes
The authors use binary linear UEP (LUEP) codes, in combination with a QPSK signal set and Gray mapping, to obtain new efficient block QPSK modulation codes with unequal minimum squared Euclidean distances. They give several examples of codes that have the same minimum squared Euclidean distance as the best QPSK modulation codes of the same rate and length. A new suboptimal two-stage soft-decision decoding is applied to LUEP QPSK modulation codes
On Interference Cancellation and Iterative Techniques
Recent research activities in the area of mobile radio communications have moved to third generation (3G) cellular systems to achieve higher quality with variable transmission rate of multimedia information. In this paper, an overview is presented of various interference cancellation and iterative detection techniques that are believed to be suitable for 3G wireless communications systems. Key concepts are space-time processing and space-division multiple access (or SDMA) techniques. SDMA techniques are possible with software antennas. Furthermore, to reduce receiver implementation complexity, iterative detection techniques are considered. A particularly attractive method uses tentative hard decisions, made on the received positions with the highest reliability, according to some criterion, and can potentially yield an important reduction in the computational requirements of an iterative receiver, with minimum penalty in error performance. A study of the tradeoffs between complexity and performance loss of iterative multiuser detection techniques is a good research topic
On Primitive BCH Codes with Unequal Error Protection Capabilities
Presents a class of binary primitive BCH codes that have unequal-error-protection (UEP) capabilities. The authors use a previous result on the span of their minimum weight vectors to show that binary primitive BCH codes, containing second-order punctured Reed-Muller (RM) codes of the same minimum distance, are binary-cyclic UEP codes. The values of the error correction levels for this class of binary LUEP codes are estimated
QPSK Block-Modulation Codes for Unequal Error Protection
Unequal error protection (UEP) codes find applications in broadcast channels, as well as in other digital communication systems, where messages have different degrees of importance. Binary linear UEP (LUEP) codes combined with a Gray mapped QPSK signal set are used to obtain new efficient QPSK block-modulation codes for unequal error protection. Several examples of QPSK modulation codes that have the same minimum squared Euclidean distance as the best QPSK modulation codes, of the same rate and length, are given. In the new constructions of QPSK block-modulation codes, even-length binary LUEP codes are used. Good even-length binary LUEP codes are obtained when shorter binary linear codes are combined using either the well-known |uÂŻ|uÂŻ+vÂŻ|-construction or the so-called construction X. Both constructions have the advantage of resulting in optimal or near-optimal binary LUEP codes of short to moderate lengths, using very simple linear codes, and may be used as constituent codes in the new constructions. LUEP codes lend themselves quite naturally to multistage decoding up to their minimum distance, using the decoding of component subcodes. A new suboptimal two-stage soft-decision decoding of LUEP codes is presented and its application to QPSK block-modulation codes for UEP illustrated
Block QPSK modulation codes with two levels of error protection
A class of block QPSK modulation codes for unequal error protection (UEP) is presented. These codes are particularly suitable either for broadcast channels or for communication systems where parts of the information messages are more important than others. An example of the latter is coded speech transmission. Not much is known on the application of block UEP codes in combined coding and modulation schemes. We exhibit a method to combine binary linear UEP (LUEP) block codes of even length, using a Gray mapping, with a QPSK signal set to construct efficient block QPSK modulation codes with nonuniform error protection capabilities for bandwidth efficient transmission over AWGN (additive white Gaussian noise) and Rayleigh fading channels
Binary Multilevel Convolutional Codes with Unequal Error Protection Capabilities
Binary multilevel convolutional codes (CCs) with unequal error protection (UEP) capabilities are studied. These codes belong to the class of generalized concatenated (GC) codes. Binary CCs are used as outer codes. Binary linear block codes of short length, and selected subcodes in their two-way subcode partition chain, are used as inner codes. Multistage decodings are presented that use Viterbi decoders operating on trellises with similar structure to that of the constituent binary CCs. Simulation results of example binary two-level CC\u27s are also reported
On the Error Performance of 8-VSB TCM Decoder for ATSC Terrestrial Broadcasting of Digital Television
The error performance of various 8-VSB TCM decoders for reception of terrestrial digital television is analyzed. In previous work, 8-state TCM decoders were proposed and implemented for terrestrial broadcasting of digital television. In this paper, the performance of a 16-state TCM decoder is analyzed and simulated. It is shown that not only a 16-state TCM decoder outperforms one with 8-states, but it also has much smaller error coefficients
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