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21.
非线性等重码的一个上界 总被引:3,自引:0,他引:3
本文给出等重码的一个上界,并且举例说明这个上界是可以达到的,作为直接推论,我们推导出等重等距码的几个结果。 相似文献
22.
B.A Fomin T.A Udalova E.A Zhitnitskii 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,86(1):73-85
Five HITRAN's editions (since 1992) and three radically new H2O spectral databases have been tested for their usefulness in line-by-line benchmark calculations for radiation code validations. The longwave calculations for the mid-latitude summer (MLS) atmosphere with the different HITRAN's editions revealed a good convergence (maximal discrepancies since decreased to in our flux calculations with 1992-2002 and 1996-2002 HITRAN's editions, respectively). The shortwave calculations with different HITRAN's editions revealed a good agreement: discrepancies in downward fluxes absorbed by the MLS atmosphere are less than , i.e. 0.5% for the all HITRAN's editions since 1992. It has been determined that it is unreasonable to replace HITRAN by any new H2O spectral database in benchmark calculations, although they contain essentially more spectral lines than HITRAN (up to ∼10 times). Moreover, it has been found that no new database could be useful for explaining the “anomalous absorption” problem. Two latest water vapor continuum models have been tested as well. It has been found out that these models are the main source of uncertainties in the present and previous calculations: discrepancies for the MLS atmosphere reached ∼3 and in the longwave and shortwave flux calculations, respectively. 相似文献
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MSK信号的Turbo同步 总被引:1,自引:0,他引:1
Turbo码的提出使系统的性能对同步参数变得极为敏感。文章利用Turbo同步的方法来对Turbo系统进行迭代参数估计,并用插值的方法来减少译码复杂度,最后针对MSK信号给出同步算法。仿真结果表明,在少量增加译码复杂度的情况下,Turbo同步能够使系统获得与严格同步近似的性能。 相似文献
25.
文章对TD-SCDMA系统中的Turbo编码器结构及编码算法进行了分析,给出了TD-SCDMA系统中Turbo算法在ZSP500 DSP核上的实现,并根据ZSP500 DSP核的特点对实现部分的进行了阐述。 相似文献
26.
K. Vasudevan 《Signal, Image and Video Processing》2007,1(3):239-252
This paper investigates the performance of various “turbo” receivers for serially concatenated turbo codes transmitted through
intersymbol interference (ISI) channels. Both the inner and outer codes are assumed to be recursive systematic convolutional
(RSC) codes. The optimum turbo receiver consists of an (inner) channel maximum a posteriori (MAP) decoder and a MAP decoder
for the outer code. The channel MAP decoder operates on a “supertrellis” which incorporates the channel trellis and the trellis
for the inner error-correcting code. This is referred to as the MAP receiver employing a SuperTrellis (STMAP). Since the complexity
of the supertrellis in the STMAP receiver increases exponentially with the channel length, we propose a simpler but suboptimal
receiver that employs the predictive decision feedback equalizer (PDFE). The key idea in this paper is to have the feedforward
part of the PDFE outside the iterative loop and incorporate only the feedback part inside the loop. We refer to this receiver
as the PDFE-STMAP. The complexity of the supertrellis in the PDFE-STMAP receiver depends on the inner code and the length
of the feedback part. Investigations with Proakis B, Proakis C (both channels have spectral nulls with all zeros on the unit
circle and hence cannot be converted to a minimum phase channel) and a minimum phase channel reveal that at most two feedback
taps are sufficient to get the best performance. A reduced-state STMAP (RS-STMAP) receiver is also derived which employs a
smaller supertrellis at the cost of performance. 相似文献
27.
基于三种调制模式下的turbo码光无线通信系统分析 总被引:1,自引:0,他引:1
从分析大气对光无线通信系统的影响出发,研究了大气信道特性,建立了大气信道信噪比和能见度的关系.为降低系统误码率,提出了基于OOK、BPSK、BPPM三种调制模式的turbo码的编码方案,推导出三种不同方案对应的turbo码迭代MAP算法.应用建立的信噪比关系,分析和计算了基于三种不同方案的系统的误码率.结果表明,基于BPSK的turbo码系统比OOK和BPPM系统的信噪比降低约3dB,且在高的信噪比情况下,BPSK系统能显著降低系统的误码率.因此,基于BPSK的turbo码方案较适合光无线通信系统. 相似文献
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本文基于Turbo码和协同通信的相关理论,提出一种新的基于Turbo协同分集的协同通信方案。在加性高斯白噪声和瑞利快衰落的两种信道条件下的仿真结果表明,基于Turbo协同分集的协同通信方案比现有的基于Turbo编码的协同通信方案具有更优的误比特率性能。 相似文献