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环F2+uF2上线性码及其对偶码的二元象 总被引:1,自引:0,他引:1
利用环F2+uF2上线性码C的生成矩阵给出了码C的对偶码C^┴及其Gray象Ф(C)的生成矩阵,证明了环F2+uF2上线性码及其对偶码的Gray象仍是对偶码。并由此给出了一个环F2+uF2如上线性码为自对偶码的充要条件。 相似文献
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广义Hamming重量和等重码 总被引:8,自引:0,他引:8
本文将线性码的广义Hamming重量的概念推广到线性码上去,并导出了一种广义Elias界,对于线性等重码,本文给出了其完整的重量谱系。 相似文献
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本文利用一类准循环码的结构进行计算机搜索,再加上通常的码的变换,共得到了七个新的二元线性码,它们都改进了文「1」中二元线性码极小距离的下界,其中有三个是最优的。 相似文献
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本文证明线性码的陪集构成的线性陪集码可以渐近达到有效书写记忆介质的容量,并且说明线性码的覆盖半径是有效书写记忆介质的线性陪集码的一个重要参数。本文同时给出有效书写记忆介质的纠错码的一种构造方法。 相似文献
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一类三元线性分组码的译码 总被引:1,自引:0,他引:1
Pless[1]证明了三元(12,6,6)Golay码具有一种双层结构,并据此给出了该码的快速硬判决译码算法。本文推广了Golay码的Pless结构,给出了由三元(n,k,d)线性分组码构造的三元(3,n+k,≥min(n,2d,6))线性分组码,其中包括(12,6,6)Golay码和(18,9,6)码,并以三元(18,9,6)码为例给出了这类码的最大似然软判决译码算法。 相似文献
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为提高手持无线电台的纠错和时延特性,考虑设计一种短码长RS-CC级联码.通过对Reed-Solomon码缩短和截断以及对卷积码删余,提出了一种低时延的级联码设计方案,并进行性能分析和软硬件实现.结果表明,在高斯信道下,当Eb/No达到4.2 dB时,能够实现10-4的误码率性能.设计的RS-CC级联码码长较短,编解码固有时延低,译码速度提升30%,适合低时延应用. 相似文献
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Rajan B.S. Moon Ho Lee 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2002,48(8):2406-2412
A code is s-quasi-cyclic (s-QC) if there is an integer s such that cyclic shift of a codeword by s-positions is also a codeword. For s = 1, cyclic codes are obtained. A dyadic code is a code which is closed under all dyadic shifts. An s-QC dyadic (s-QCD) code is one which is both s-QC and dyadic. QCD codes with s = 1 give codes that are cyclic and dyadic (CD). We obtain a simple characterization of all QCD codes (hence of CD codes) over any field of odd characteristic using Walsh-Hadamard transform defined over that finite field. Also, it is shown that dual a code of an s-QCD code is also an s-QCD code and s-QCD codes for a given dimension are enumerated for all possible values of s. 相似文献
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Turbo codes have an error floor that is caused by low-weight error events. Here, it is shown that a concatenated code with a simple rectangular parity-check outer code and a turbo inner code can significantly reduce the error floor. It is also shown that in several situations, the concatenated parity-check and turbo code performs significantly better than a turbo code alone 相似文献
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The error rate performance, obtained on a Rayleigh fading channel, is determined and illustrated graphically for concatenated codes in which the outer code is a dual-k convolutional code and the inner code is either a Hadamard block code or a block orthogonal code. Comparison of the performance of these two types of concatenated codes is made on the basis of the same bandwidth utilization. It is also illustrated that the concatenated dual-k code yields a significant improvement in performance relative to the performance achieved with the inner code alone. 相似文献
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CDMA作为一种多址接入技术在无线网络中已广为应用,在多码CDMA和单码CDMA研究的基础上,构造了多码CDMA和单码CDMA在无线分组数据网络中的随机多址接入模型,并且分析了两种系统的吞吐率特性和归一化时延特性。结果证明单码CDMA和多码CDMA具有相同的多址接入性能。 相似文献
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Many software compilers for embedded processors produce machine code of insufficient quality. Since for most applications
software must meet tight code speed and size constraints, embedded software is still largely developed in assembly language.
In order to eliminate this bottleneck and to enable the use of high-level language compilers also for embedded software, new
code generation and optimization techniques are required. This paper describes a novel code generation technique for embedded
processors with irregular data path architectures, such as typically found in fixed-point DSPs. The proposed code generation
technique maps data flow graph representation of a program into highly efficient machine code for a target processor modeled
by instruction set behavior. High code quality is ensured by tight coupling of different code generation phases. In contrast
to earlier works, mainly based on heuristics, our approach is constraint-based. An initial set of constraints on code generation
are prescribed by the given processor model. Further constraints arise during code generation based on decisions concerning
code selection, register allocation, and scheduling. Whenever possible, decisions are postponed until sufficient information
about a good decision has been collected. The constraints are active in the "background" and guarantee local satisfiability
at any point of time during code generation. This mechanism permits to simultaneously cope with special-purpose registers
and instruction level parallelism. We describe the detailed integration of code generation phases. The implementation is based
on the constraint logic programming (CLP) language ECLiPSe. For a standard DSP, we show that the quality of generated code
comes close to hand-written assembly code. Since the input processor model can be edited by the user, also retargetability
of the code generation technique is achieved within a certain processor class.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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A high-speed Gray-binary code convertor (g.b.c.) using electro-optic light modulators, which translates all bits of Gray code into binary code simultaneously, and a binary-Gray code convertor, which translates binary into Gray code, are described. A digital-analogue convertor using g.b.c. is also presented. 相似文献
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《Optical Fiber Technology》2007,13(2):180-190
The purpose of this study is to investigate the multirate transmission in fiber-optic code-division multiple-access (CDMA) networks. In this article, we propose a variable-length code construction for any existing optical orthogonal code to implement a multirate optical CDMA system (called as the multirate code system). For comparison, a multirate system where the lower-rate user sends each symbol twice is implemented and is called as the repeat code system. The repetition as an error-detection code in an ARQ scheme in the repeat code system is also investigated. Moreover, a parallel approach for the optical CDMA systems, which is proposed by Marić et al., is also compared with other systems proposed in this study. Theoretical analysis shows that the bit error probability of the proposed multirate code system is smaller than other systems, especially when the number of lower-rate users is large. Moreover, if there is at least one lower-rate user in the system, the multirate code system accommodates more users than other systems when the error probability of system is set below 10−9. 相似文献
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LDPC码由于其卓越的纠错性能引起了学术界的广泛重视,当前LDPC所面临的一个主要问题是其编码复杂性的问题。本文给出了一种半代数半随机的非正则LDPC码构造方法,由该方法所构造的校验矩阵具有近似下三角特性,从而可以大大降低LDPC的编译码复杂性,同时具有与完全随机LDPC码相匹配的性能。 相似文献