共查询到17条相似文献,搜索用时 109 毫秒
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从Turbo码在加性高斯白噪声(AWGN additive white Gaussian noise)信道下的理论分析出发,讨论了Turbo码在瑞利衰落信道下的算法改进。 相似文献
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Turbo码作为一种新颖的信道编码,可以获得接近香农理论极限的性能,IMT-2000已经将Turbo码作为第三代移动通信系统(3G)传输高速业务数据的信道编码标准之一.文中提出了一种在衰落信道下Turbo码的实现模型,并探讨了Turbo编、译码器的设计及其算法,最后用MATLAB语言完成了算法的仿真实现.仿真结果表明,在低信噪比的无线衰落信道中,Turbo码不仅可以获得更大的编码增益,有效地改善系统的性能,而且具有很强的抗衰落、抗干扰能力,在移动通信系统中有着很大的应用潜力. 相似文献
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衰落信道中Turbo码的应用研究 总被引:1,自引:1,他引:0
Turbo码以其优异的性能而迅速成为近年来信道编码领域研究的热点。本文针对无线信道的特点,提出了在无线衰落信道中Turbo码的构造方法,并基于非选择性瑞利慢衰落信道模型,分析了Turbo码在不同信道条件下的性能。 相似文献
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分组相关快衰落信道下自适应Turbo码译码算法研究 总被引:2,自引:1,他引:1
分析了分组相关快衰落信道的特性,推导出该信道下Turbo码译码算法;研究了迭代次数对Turbo编码系统的影响,在小信噪比弥散度条件下,提出基于平均信噪比的最佳迭代译码次数自适应选择方案,可以兼顾译码性能和译码速度,得到较低的平均误比特率和较高的平均译码速度。仿真结果说明,本文提出的Turbo码译码算法,降低了对信道估计精度要求的同时,得到精确信道估计时的性能;对于目标误比特率为10^-4时,采用自适应Turbo译码算法,与固定迭代4次相比,平均误比特率降低了40%,提高了系统性能;而与固定迭代8次相比,迭代次数降低了约1/4,提高了译码速度。 相似文献
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Petri提出了超正交卷积Turbo码(Superorthogonal Convolutional Turbl Gode,SCTC)^「1」。由于 宽的扩展,这类码的性能比一般的Turbo码好,本文推导了一般SCTC码的构,同时导出了存储单元分别为2,3的SCTC的转移函数。分别给出了高斯信道下非相关瑞利衰落信道下SCTC码的误码率性能上限,以及计算机模拟的高斯信道,非相关瑞处衰落信道和相关瑞利衰 相似文献
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本文研究采用BPSK调制、相干PAKE接收的随机访问多码CDMA(RAMC-CDMA)在频率选择性Nakagami多径衰落、噪声信道(MFNC)中的容量性能.建立系统模型后,推导出了多用户条件下接收机输出的条件概率分布及判决平均比特误码率,并以Rayleigh(Nakagami的特例)多径衰落、噪声信道为例,计算了系统容量的数值解.分析表明RAMC-CDMA解决了普通DS-CDMA系统存在的用户可传信息速率受限(过低)的问题,能在不增加射频带宽的前题下为用户提供高峰值速率信息传送,而且保证了容量没有明显下降.文中还对理论分析的关键结果进行了仿真. 相似文献
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This paper proposes a new MIMO based CDMA code acquisition scheme. The pilot codes consist of a number of short Gold code sequences which are transmitted in parallel using a group of transmit antennas. Reception diversity is performed by multiple receive antennas at the receiver. Three different acquisition detection techniques are proposed and compared. Corresponding threshold optimizations are investigated as well. Detection and false alarm probabilities are derived in closed form based on the outputs of non-coherent matched filters. The acquisition performance is evaluated in terms of mean acquisition time (MAT) in Rayleigh fading environment. It is shown that the proposed MIMO acquisition scheme exhibits a much better MAT performance than the conventional single-antenna acquisition scheme. The results reveal that multiple receive antennas can be utilized to significantly reduce the MAT at the expense of receiver complexity increase. On the other hand, increasing the number of transmit antennas makes the MAT performance more robust in the presence of strong interference. 相似文献
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该文对准静态Rayleigh衰落下MIMO-CDMA系统信道容量进行了研究,分析了扩频码为Walsh函数,基于多码检测的极大似然检测器(MLD)和解相关检测器的性能,并和MMSE多用户检测器(MUD)进行了比较;分析了对不同检测器在一定的信噪比下系统天线数目和信道容量的关系。仿真结果表明:在相同的情况下,基于Walsh码CDMA系统容量按MUD、干扰方差已知的MLD,干扰方差未知的MLD和解相关检测器递减,并且后面的3种检测器在大信噪比的时候均有渐进的平台效应;在信噪比较大且一定时,CDMA系统信道容量与天线数目呈线性关系。 相似文献
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This paper examines the performance of a multicarrier CDMA system in a Rayleigh fading channel without a RAKE receiver. Since the multicarrier technique is a diversity reception technique used in the frequency domain, the signal is transmitted at different frequency bands and undergoes different fading. The superimposed signal of the multipath components after going through the mobile channel will be processed by an Fourier Transform to enter the frequency domain, where the time delays in various paths are converted to the phase shifts in the compound signal. In this paper, we use sounding bits to extract the characteristics of the mobile channel and to partly remove the multipath effect. From the simulation, it is found that the multicarrier technique is simpler than the technique used in the single carrier system with a RAKE receiver while producing a better performance than that of the RAKE receiver. 相似文献
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针对Turbo编码频选慢衰落MIMO信道,提出基于滑窗式概率数据辅助(Probabilistic Data Association)的软输出判决反馈均衡和软输入软输出Turbo信道解码器间迭代处理的Turbo均衡算法。充分利用已获得的信息,实现信道均衡与信道解码的迭代更新,克服传统判决反馈均衡器误差传播的缺陷。仿真表明,该系统经3次迭代就可获得较为满意的符号间干扰消除效果。 相似文献
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对Turbo码的编码的基夺原理和对编码中的关键元件和技术做了介绍,其中包括交织器的原理,最主要的是对Turbo码在CDMA2000中的编码进行了Matlab仿真,在Turbo码编码的设计仿真过程中对交织器和抽取器进行了算法的实现,模块的封装,计算结果与理论值较接近,有助于对Turbo码的进一步研究。 相似文献
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A low-complexity hardware emulator is proposed for wideband, correlated, multiple-input multiple-output (MIMO) fading channels.
The proposed emulator generates multiple discrete-time channel impulse responses (CIR) at the symbol rate and incorporates
three types of correlation functions of the subchannels via Kronecker product: the spatial correlation between transmit or
receive elements, temporal correlation due to Doppler shifts, and inter-tap correlation due to multipaths. The Kronecker product
is implemented by a novel mixed parallel-serial (mixed P-S) matrix multiplication method to reduce memory storage and to meet
the real-time requirement in high data-rate, large MIMO size, or long CIR systems. We present two practical MIMO channel examples
implemented on an Altera Stratix III EP3SL150F FPGA DSP development kit: a 2-by-2 MIMO WiMAX channel with a symbol rate of
1.25 million symbols/second and a 2-by-6 MIMO underwater acoustic channel with 100-tap CIR. Both examples meet real-time requirement
using only 12–14% of hardware resources of the FPGA. 相似文献