In this paper, we study quasi-cyclic codes over the ring R = F-2 + uF(2) = {0, 1, u, u + 1} where u(2) = 0. By exploring their structure, we determine the type of one generator quasi-cyclic codes over R and the size b...
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In this paper, we study quasi-cyclic codes over the ring R = F-2 + uF(2) = {0, 1, u, u + 1} where u(2) = 0. By exploring their structure, we determine the type of one generator quasi-cyclic codes over R and the size by giving a minimal spanning set. We also determine the rank and introduce a lower bound for the minimum distance of free quasi-cyclic codes over R. We include some examples of quasi-cyclic codes of various lengths over R. In particular, we obtain a family of 2-quasi-cyclic codes from cyclic codes over the ring F-2 + uF(2) + vF(2) + uvF(2). Finally, using the Gray map we obtain a family of optimal binary linear codes as the images of quasi-cyclic codes over R. (C) 2011 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
Orthogonal frequency division multiplexing (OFDM) enables low-complexity equalization and has been adopted in several wireless standards. However, OFDM cannot exploit multipath diversity without computationally comple...
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Orthogonal frequency division multiplexing (OFDM) enables low-complexity equalization and has been adopted in several wireless standards. However, OFDM cannot exploit multipath diversity without computationally complex coding and decoding. We show here that by sampling at a rate higher than the symbol rate, which is also known as fractional sampling (FS), one can improve the diversity that the wireless channel can provide in an OFDM system. We propose maximal ratio combining at each sub-carrier for the FS-OFDM system, argue that the diversity gains acquired through this approach are related to the spectral shape of the pulse and its excess bandwidth, and derive analytical bit error and symbol error rate expressions for our scheme. We also explore extensions to differentially encoded systems that do not require channel status information at the receiver, multiple-input multiple-output (MIMO) systems that exploit space diversity, and low peak-to-average (PAR) options such as zero-padded (ZP) and cyclic-prefix only (CP-only) transmissions. We corroborate our approach with simulations.
In this paper, we study the following two hypercube coloring problems: given n and d, find the minimum number of colors, denoted as chi(d)'(n) (resp. chi(d)(n)), needed to color the vertices of the n-cube such tha...
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In this paper, we study the following two hypercube coloring problems: given n and d, find the minimum number of colors, denoted as chi(d)'(n) (resp. chi(d)(n)), needed to color the vertices of the n-cube such that any two vertices with Hamming distance at most d (resp. exactly d) have different colors. These problems originally arose in the study of the scalability of optical networks. Using methods in coding theory, we show that chi(5)'(2(r+1)) = 4(r+1) for any odd number r >= 3, and give two upper bounds on chi(d)(n). The first upper bound improves on that of Kim, Du and Pardalos. The second upper bound improves on the first one for small n. Furthermore, we derive an inequality on chi(d)(n) and chi(d)'(n). (C) 2013 Elsevier B.V. All rights reserved.
In this paper, we propose a joint contention-based bandwidth request mechanism for WiMAX two-hop relay networks. For this purpose, we considered contention by message and code mechanisms. These are normally deployed i...
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In this paper, we propose a joint contention-based bandwidth request mechanism for WiMAX two-hop relay networks. For this purpose, we considered contention by message and code mechanisms. These are normally deployed in single-hop networks. This message scheme suffers from low contention efficiency and higher access delay when the number of mobile stations (MSs) in the network increases. Conversely, this code technique undergoes transmission failure due to the inappropriate setting of the detection threshold at relay stations (RSs). However, these message and code mechanisms are advantageous when they are carried out at appropriate hops. Among the four possible options created by combining the message and code methods, the message requests from MS to RS and code requests from RS to base stations (BSs) performed better than other possible combinations. Using a comprehensive case study and simulation results, we generated signaling examples that confirmed the significance of the proposed method in terms of signaling overhead, network throughput, connection delay and queuing size. (C) 2012 Elsevier Ltd. All rights reserved.
The design of DNA or RNA strands for DNA computations poses many new questions in algorithms and coding theory. DNA strand design also arises in use of molecular bar codes to manipulate and identify individual molecul...
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The design of DNA or RNA strands for DNA computations poses many new questions in algorithms and coding theory. DNA strand design also arises in use of molecular bar codes to manipulate and identify individual molecules in complex chemical libraries, and to attach molecules to DNA chips. We survey several formulations of the DNA strand design problem, along with results and open questions in this area. (C) 2002 Elsevier Science B.V. All rights reserved.
Concurrent signatures allow two entities to generate two signatures in such a way that both signatures are ambiguous till some information is revealed by one of the parties. This kind of signature is useful in auction...
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Concurrent signatures allow two entities to generate two signatures in such a way that both signatures are ambiguous till some information is revealed by one of the parties. This kind of signature is useful in auction protocols and in a wide range of scenarios in which involving participants are mutually distrustful. In this study, to have quantum-attack-resistant concurrent signatures as recommended by National Institute of Standards and Technology (NISTIR 8105), the first concurrent signature scheme based on coding theory is proposed. Then, its security is proved under Goppa Parameterized Bounded Decoding and the Goppa Code Distinguishing assumptions in the random oracle model. In addition, performance evaluation shows that the proposal is approximately as efficient as Dallot scheme. The authors should highlight that their proposal can be a post-quantum candidate for fair exchange of signatures without a trusted third party in an efficient way (without a high degree of interactions).
A high-throughput lossless data compression IP core built around a CAM-based dictionary whose number of available entries and data word width adjust to the characteristics of the incoming data stream is presented. The...
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A high-throughput lossless data compression IP core built around a CAM-based dictionary whose number of available entries and data word width adjust to the characteristics of the incoming data stream is presented. These two features enhance model adaptation to the input data, improving compression efficiency, and enable greater throughputs as a multiplicity of bytes can be processed per cycle. A parsing mechanism adjusts the width of dictionary words to natural words while the length of the dictionary grows from an initial empty state to a maximum value defined as a run-time configuration parameter. The compressor/decompressor architecture was prototyped on an FPGA-based PCI board. An ASIC hard-macro was subsequently implemented and achieved a throughput of more than 1 gigabyte per second when clocking at 277 MHz on a high-performance, 0.13 mu m, eight-layer copper CMOS process.
A new angular discretization scheme based on the Daubechies' wavelets has been developed in recent studies. A decoupled S-N and wavelet expansion method was proposed. This paper discusses the limitations and impro...
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A new angular discretization scheme based on the Daubechies' wavelets has been developed in recent studies. A decoupled S-N and wavelet expansion method was proposed. This paper discusses the limitations and improvements of this decoupled scheme. The scaling function, instead of the wavelet function, is applied as the basis function. It significantly improved the efficiency and computational stability. A new series of wavelets on the interval are applied instead of the 'wrapped wavelets', which eliminate the edge effect in the angular subdomain scheme. Based on the improvements, a wavelet-based neutron transport code package WAVTRAN is developed and the previous work is extended to the three-dimensional calculation and anisotropic scattering calculation. Numerical results demonstrate that the improvements are effective. Further investigations demonstrate that the wavelet-based angular discretization scheme is more powerful than the traditional ones in some highly anisotropic angular flux problems. (C) 2009 Elsevier Ltd. All rights reserved.
Pulse position modulation (PPM) schemes have been proposed as a method of utilising the bandwidth available in optical fibres, with a 5-11 dB improvement in sensitivity being achieved compared to an equivalent pulse c...
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Pulse position modulation (PPM) schemes have been proposed as a method of utilising the bandwidth available in optical fibres, with a 5-11 dB improvement in sensitivity being achieved compared to an equivalent pulse code modulation (PCM) system. However, this improvement comes at a cost. If digital PPM is used, the final data rate can be almost 23 times that of the original PCM, and this makes implementation difficult. The author describes a novel coding technique that combines dicode, a tertiary code sometimes used in magnetic recording, and digital PPM to form dicode PPM. It is shown that dicode PPM gives a receiver sensitivity greater than digital PPM while operating at only four times the original data rate. Original results presented predict that a high fibre bandwidth dicode PPM system can give sensitivities of -50.44 dBm and -44.27 dBm when operating with 155.52 Mbit/s and 1 Gbit/s PCM data, respectively. This should be compared to typical PCM sensitivities of -38 dBm and -28 dBm. It is also shown that dicode PPM outperforms digital PPM at low fibre bandwidths by 3.02 dB.
Containment atmosphere mixing is an important nuclear power safety issue related to hydrogen explosion risk. Extensive experimental and numerical research effort has been applied to this issue internationally, includi...
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Containment atmosphere mixing is an important nuclear power safety issue related to hydrogen explosion risk. Extensive experimental and numerical research effort has been applied to this issue internationally, including several international standard problems. One of the findings was that containment atmosphere mixing using lumped-parameter codes common in the safety analyses is complicated due to limitations inherent in the lumped-parameter method. However, it was also found, that in the cases when the user had selected appropriate nodalisation schemes, results obtained with the lumped-parameter codes were satisfactory. The paper presents simulations of one of the containment atmosphere mixing experiments - MISTRA M5 (formation of stratified conditions by a jet/plume steam release and vertical thermal gradient) - performed using a lumped-parameter code COCOSYS. Special nodalisation features required to compensate for the method limitations are described and used. Additionally, an uncertainty and sensitivity analysis of the simulation is presented. The parameters with large uncertainties having high influence on the results are identified. The importance of an adequate nodalisation to account for the occurring processes, e.g., in this case, plume/jet releases, is showed. (C) 2013 Elsevier B.V. All rights reserved.
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