共查询到18条相似文献,搜索用时 109 毫秒
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大气湍流光PPM通信系统中LDPC码的置信传播译码 总被引:5,自引:1,他引:4
对大气弱湍流光PPM通信系统中LDPC码的BP 解码算法进行了研究,提出了相应系统模型下的解码算法.通过理论分析和大量计算机仿真,结果表明:采用LDPC的大气弱湍流光PPM通信系统比未编码的大气弱湍流光PPM通信系统的性能好,但是系统的BER性能随着PPM的时隙数的增加而增大. 相似文献
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《光学学报》2016,(9)
针对传统线性分组码识别方法对码长较长的低密度奇偶校验(LDPC)码不适用的情况,利用蚁群算法对对偶空间进行优化搜索,完成了对LDPC码的识别。建立了大气激光通信信道模型和LDPC码的识别模型,给出了大气激光通信湍流信道下校验关系对数似然比函数表达式;将基本蚁群算法与LDPC码的识别问题结合,将对数似然比函数经过处理作为目标函数,通过不断迭代每次搜索过程中目标函数最优值和最佳搜索路径,实现对LDPC码的识别。仿真结果表明:当码长为256时,在弱湍流条件下,当信噪比不低于8dB时,识别率可达78%;在强湍流条件下,当信噪比不低于10dB时,识别率可达77%。此外,蚁群算法中的参数设置对算法性能有较大影响,应根据实际情况加以选择。 相似文献
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大气激光通信非对称限幅光正交频分复用技术 总被引:2,自引:1,他引:1
将一种新的正交频分复用调制技术运用到大气激光通信系统中,分析了采用这种非对称限幅光正交频分复用调制技术的大气激光通信系统在大气湍流信道下的性能.在此基础上,把非对称限幅光正交频分复用调制方案与传统的开关键控及直流偏置光正交频分复用调制方案进行了比较,并在大气湍流信道中进行了仿真.仿真结果表明:非对称限幅光正交频分复用调制技术增强了系统对大气湍流的抗干扰能力,该方案可以满足大气激光通信系统的需要. 相似文献
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将一种新的正交频分复用调制技术运用到大气激光通信系统中,分析了采用这种非对称限幅光正交频分复用调制技术的大气激光通信系统在大气湍流信道下的性能.在此基础上,把非对称限幅光正交频分复用调制方案与传统的开关键控及直流偏置光正交频分复用调制方案进行了比较,并在大气湍流信道中进行了仿真.仿真结果表明:非对称限幅光正交频分复用调... 相似文献
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《光学学报》2016,(11)
针对大气激光通信中多径散射效应产生的通信链路码间串扰问题,提出了一种基于退偏振比探测的大气激光通信传输方案。利用光子追迹和Stokes矢量变换进行了Monte Carlo仿真;通过设置不同的云层物理厚度和消光系数,得到接收光退偏振比与云层光学厚度的一一对应关系;基于Stotts公式,得到接收光退偏振比与平均脉冲时间展宽的对应关系。提出了在多径效应影响下的最佳通信传输速率方案,该方案在激光通信系统接收端直接进行退偏振比探测,可有效评估大气信道环境的多径强度,进而在保证激光通信传输质量的同时实现最大的通信传输速率。该研究在星地激光通信以及自适应激光通信的通信链路优化领域具有理论指导意义和应用价值。 相似文献
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基于低密度奇偶校验码的MPPM比特符号映射及系统性能研究 总被引:1,自引:0,他引:1
建立了基于低密度奇偶校验(LDPC)码和多脉冲位置调制(MPPM)的无线光通信系统模型,给出了相应系统模型下的解码算法,研究了(m,2)MPPM的比特符号映射方式,提出了用改进的遗传算法(GA)搜索的优化映射方法,最后在大气湍流信道下进行了仿真。仿真结果表明基于LDPC码和MPPM的无线光通信系统性能明显优于未编码的MPPM系统,结合LDPC码和多光束发射技术可以提高系统抗强大气湍流影响的能力;通过GA优化的映射方法在不增加系统复杂性的情况下能进一步提高系统的纠错性能,可以获得更大的编码增益。 相似文献
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针对大气激光通信中低密度奇偶校验码(LDPC)置信传播(BP)译码算法复杂度高的问题,对几类BP-Based简化译码算法进行了分析,并基于最小均方误差准则(MMSE)对Scaled BP-Based和Offset BP-Based两类改进译码算法的优化设计进行了探讨,得出两类算法的最优校正因子,并给出了数值计算.在不同的湍流强度下,对码长1008的(6,3)比特填充LDPC码进行了仿真实验,结果表明,对于短码长的LDPC码,当译码BER=10-5时,最小和算法(UMP BP-Based)相对于BP算法有0.1~0.15dB的译码性能损失;基于MMSE设计的两类算法相比BP算法大大降低复杂度的同时,译码性能与BP算法相当,甚至优于BP算法,优于UMP BP-Based算法0.075~0.15dB. 相似文献
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低密度奇偶校验码(LDPC)不仅有逼近香农限的良好性能, 而且译码复杂度较低, 结构灵活, 是近年信道编码领域的研究热点, 在光通信系统中有广泛的应用前景。针对非规则Tanner图上构造的低密度奇偶校验长码具有良好的性能, 以及其在光通信系统中的应用, 构造了几种LDPC码, 并采用置信传播(BP)译码, 在加性高期白噪声(AWGN)信道、二相移相键空(BPSK)调制下进行了计算机仿真。根据规则LDPC码和非规则LDPC码的误码率(BER)和FER曲线, 对规则码和非规则LDPC码在编译码方面以及性能方面作了分析和比较, 进而对构造在光通信系统中具有实用价值的LDPC码提出了看法。通过理论分析与仿真结果表明LDPC 码型具有良好的性能, 可以节省硬件开销, 比较适用于光通信系统中, 可作为超强前向纠错码型的候选码。 相似文献
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Atmospheric absorption, scattering, and scintillation are the major causes to deteriorate the transmission quality of terahertz(THz) wireless communications. An error control coding scheme based on low density parity check(LDPC) codes with soft decision decoding algorithm is proposed to improve the bit-error-rate(BER) performance of an on-off keying(OOK) modulated THz signal through atmospheric channel. The THz wave propagation characteristics and channel model in atmosphere is set up. Numerical simulations validate the great performance of LDPC codes against the atmospheric fading and demonstrate the huge potential in future ultra-high speed beyond Gbps THz communications. 相似文献
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Recently, the integration of cooperation with coding has proven to be a very useful technique to enhance relay system performance. Relay systems based on low-density parity-check (LDPC) codes have the potential to approach the theoretical information limits very closely. However, LDPC codes have a disadvantage in that the encoding complexity is high. To solve this problem, serially concatenated low-density generator matrix (SCLDGM) codes are attracting attention owing to their low encoding complexity. However, the performance of SCLDGM coded relaying has not been investigated. In this paper, we apply SCLDGM codes to relay channel with the motivation of lowering the encoding complexity. Since SCLDGM codes are concatenated codes, we cannot use the same method as LDPC coded relaying. We propose a new relaying system and three cooperation protocols suited for SCLDGM codes. Computer simulation results show that the bit error rate (BER) performance of the proposed system is equal to that of conventional LDPC coded relaying system. 相似文献
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In this paper, we investigate the joint design of channel and network coding in bi-directional relaying systems and propose a combined low complexity physical network coding and LDPC decoding scheme. For the same LDPC codes employed at both source nodes, we show that the relay can decode the network coded codewords from the superimposed signal received from the BPSK-modulated multiple-access channel. Simulation results show that this novel joint physical network coding and LDPC decoding method outperforms the existing MMSE network coding and LDPC decoding method over the AWGN and complex MAC channel. 相似文献
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N. Macris 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):51-55
This contribution is based on the contents of a talk delivered at the Next-SigmaPhi conference held in Crete in August 2005.
It is adressed to an audience of physicists with diverse horizons and does not assume any background
in communications theory.
Capacity approaching error correcting codes for channel communication known as
Low Density Parity Check (LDPC) codes have attracted considerable attention
from coding theorists in the last decade.
Surprisingly strong connections with the theory of diluted
spin glasses have been discovered. In this work we elucidate one new connection, namely that a class of correlation inequalities
valid for Gaussian spin glasses can be applied to the theoretical analysis of LDPC codes. This allows for a rigorous comparison
between the so
called (optimal) maximum a posteriori and
the computationaly efficient belief propagation decoders. The main ideas of the proofs are explained and we refer to recent
works for the more lengthy technical details. 相似文献
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In Wireless Sensor Networks (WSNs), the sensor nodes are expected to remain autonomous for a long time and the communication must be successful. So, energy efficiency and communication reliability are the main challenges for WSN. Routing protocols and, in particular, clustering is the key to energy constraints in WSNs. In a loss milieu, data shared between nodes is susceptible to corruption by errors caused by signal fading, random noise, and some other forces. For this reason, channel coding is necessary to assure efficient and reliable transmission. Therefore, energy efficiency and reliability of communications are the most crucial factors in the design of an efficient cluster-based routing protocol. In this context, to raise the reliability of the communication link and minimize the necessary transmission energy, a new adaptive coding routing protocol is proposed, which implements RS and LDPC codes to a routing protocol. Simulation results show that our proposed protocol improves energy consumption, network lifetime, stability, and throughput compared to LEACH and BRE-LEACH. In addition, it reaches a good BER performance and coding gain by using the LDPC code. 相似文献
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This paper deals with the specific construction of binary low-density parity-check (LDPC) codes. We derive lower bounds on the error exponents for these codes transmitted over the memoryless binary symmetric channel (BSC) for both the well-known maximum-likelihood (ML) and proposed low-complexity decoding algorithms. We prove the existence of such LDPC codes that the probability of erroneous decoding decreases exponentially with the growth of the code length while keeping coding rates below the corresponding channel capacity. We also show that an obtained error exponent lower bound under ML decoding almost coincide with the error exponents of good linear codes. 相似文献