共查询到20条相似文献,搜索用时 500 毫秒
1.
2.
3.
采用基于互补序列分组编码的OFDM系统性能分析与仿真 总被引:3,自引:0,他引:3
为了减小正交频分复用(OFDM)信号的峰值-平均值功率之比(PAPR),本文利用互补序列和Reed-Muller码的关系,详细提出了一种构造互补序列的分组编码方法的具体实现方案。分析了其在AWGN和选频衰落信道中的性能,并做了相应的仿真。仿真结果表明,编码后每个OFDM信号的最大PAPR不超过3dB;采用该编码方法的OFDM在AWGN中当信噪比不到11dB时就可以实现BER为10^-6,在衰落信道中如果采用软判决译码,则当信噪比达到20dB左右时可以实现BER为10^-3。 相似文献
4.
5.
In data post-processing for quantum key distribution, it is essential to have a highly efficient error reconciliation protocol. Based on the key redistribution scheme, we analyze a one-way error reconciliation protocol by data simulation. The relationship between the error correction capability and the key generation efficiency of three kinds of Hamming code are demonstrated. The simulation results indicate that when the initial error rates are (0,1.5%], (1.5,4%], and (4,11%], using the Hamming (31,26), (15,11), and (7,4) codes to correct the error, respectively, the key generation rate will be maximized. Based on this, we propose a modified one-way error reconciliation protocol which employs a mixed Hamming code concatenation scheme. The error correction capability and key generation rate are verified through data simulation. Using the parameters of the posterior distribution based on the tested data, a simple method for estimating the bit error rate (BER) with a given confidence interval is estimated. The simulation results show that when the initial bit error rate is 10.00%, after 7 rounds of error correction, the error bits are eliminated completely, and the key generation rate is 10.36%; the BER expectation is 2.96×10^-10, and when the confidence is 95% the corresponding BER upper limit is 2.17×10^-9. By comparison, for the single (7,4) Hamming code error reconciliation scheme at a confidence of 95%,the key generation rate is only 6.09%, while the BER expectation is 5.92x 10"9, with a BER upper limit of 4.34×10^-8. Hence, our improved protocol is much better than the original one. 相似文献
6.
角度多重全息存储中曝光均匀性的控制 总被引:1,自引:1,他引:0
利用单片机AT89C51作为主控单元,采用时间递减曝光法,对光折变晶体角度多重全息存储衍射效率的均匀性进行了控制。实验中,采用角度多重方案在Fe:LiNbO2晶体内存储了300幅全息图,测定全息网的衍射效率约10^-9,各全息网的衍射效率相当均匀,且系统结构简单,通用性强,使用灵活。 相似文献
7.
FAN Yong WU Zheng-de TANG Xiao-hong 《中国电子科技》2005,3(4):289-292
Two communication systems at W-band are introduced, including the system design, the modulation scheme, etc. TV delivery system delivers picture of quality meeting grade 4.5 over 8 km (no rain). Digital communication system is capable of operating at data rates up to 8.448 Mb/s beyond 10 km under a BER of 10^-6 (clear). 相似文献
8.
该文提出了用于MC DS-CDMA系统中的两种SDCMA(最陡下降常模算法)盲检测方法,一种是SDCMA盲均衡算法,在此基础上,提出了另一种联合均衡和多用户检测的SDCMA盲算法。同时还将这两种算法与基于子空间的MMSE(最小均方误差)盲检测算法进行比较。仿真结果表明,这两种SDCMA算法的BER(误比特率)性能均优于子空间法,而且联合均衡和多用户检测的SDCMA盲算法利用同时对均衡权值向量和多用户检测器向量进行自适应更新,能较大程度地改善系统性能,是这3种盲算法中性能最佳的一个。 相似文献
9.
10.
Du Yinggang Chan Kam Tai 《电子科学学刊(英文版)》2006,23(1):23-25
The Bit Error Rate (BER) performance of a Turbo Product Code (TPC) based Space-Time Block Coding (STBC) multiuser wireless system in the frequency-selective channels has been investigated. Both of the good error correcting capability of TPC and the large diversity gain of STBC can be achieved simultaneously. A Least Square Error-Recursive Least Square (LSE-RLS) algorithm is applied to estimate the channel and cancel the interference. Simulations show that the proposed system can obtain about 2.7dB gain in Es/N0 at the BER of 10^-3. 相似文献
11.
文中基于Gamma-Gamma光强起伏分布大气湍流信道模型,对无线光副载波相移键控调制系统进行了子空间盲均衡算法的研究。对比分析了经过大气湍流信道盲均衡前后的副载波调制信号星座图聚敛性,给出了均衡后不同光强起伏方差下的误码率曲线,当R2=0.1,信噪比为20 dB时,误码率从4.710-1降低到1.5610-3,均衡后误码率明显改善。同时采用两种典型实测天气数据(阴、中雨)模拟大气信道进行了子空间盲均衡实验,均衡后调制信号星座图聚敛性与相位可识别性明显优于均衡前。仿真结果表明,子空间盲均衡算法对大气湍流信道下的副载波调制信号有良好的均衡效果。 相似文献
12.
粒子滤波是一种基于贝叶斯估计的算法,在信道盲辨识和盲均衡问题上具有快收敛、抗深衰信道等优势。Turbo盲均衡在低信噪比条件下有较好的误码性能。为了在深衰信道下使通信具有良好的误码性能,对粒子滤波盲均衡算法进行改进,改进算法的重要性采样函数利用了粒子的先验信息,得到一种软输入软输出的粒子滤波盲均衡算法。依据Turbo盲均衡的框架结构实现了一种基于粒子滤波的Turbo盲均衡算法,该算法利用信道编码带来的编码增益,提高了均衡和信道辨识的性能。仿真结果表明相比粒子滤波盲均衡算法本文提出算法的误码率性能提高1dB左右,误帧率性能则提高了3dB以上,经分析可知在信道系数估计较为准确的条件下,系统数据帧几乎没有误码。 相似文献
13.
Chevreuil A. Serpedin E. Loubaton P. Giannakis G.B. 《Signal Processing, IEEE Transactions on》2000,48(6):1570-1586
The paper deals with blind identification and equalization of communication channels within the so-called modulation induced cyclostationarity (MIC) framework, where the input symbol stream is modulated by a P periodic precoder with the purpose of inducing cyclostationarity in the transmit sequence. By exploiting the cyclostationarity induced by the periodic precoder, a subspace-based channel identification algorithm that is resilient to the location of channel zeros, channel order overestimation errors, and color of additive stationary noise, is developed. The asymptotic performance of the subspace-based identification approach is analyzed and compared with the asymptotic lower bound provided by the nonlinear cyclic correlation matching approach. Criteria for optimally designing the periodic precoder are also presented. The performance of MMSE-FIR and MMSE-DFE equalizers is quantified for the proposed cyclostationarity-induced framework in terms of the MMSE. Although cyclostationarity-inducing transmitters present several advantages relative to their stationary counterparts from a channel estimation viewpoint, it is shown that from an equalization viewpoint, MIC-based systems exhibit a slightly increased MMSE/BER when compared with the stationary case 相似文献
14.
一种新的混合信道盲均衡算法 总被引:3,自引:1,他引:2
为同时提高盲均衡的稳态MSE性能和收敛速度,该文提出了一种混合信道盲均衡算法。该算法采用判决反馈均衡器结构,在判决可靠时采用DD-LMS(Directed Decision-Least Mean Square)误差项进行迭代,而判决不可靠时采用改进恒模算法(Modified Constant Modulus Algorithm,MCMA)误差项进行迭代,同时判决可靠区间根据直接判决误差进行自适应迭代。该文采用经过数字无线信道的64QAM信号进行了信道均衡仿真。仿真结果表明,相比MCMA算法,该文提出的混合盲均衡算法有效地提高了收敛速度,并具有良好的稳态MSE性能,在误比特率为10-6时,能提高SNR约2dB。 相似文献
15.
Blind source separation/channel equalization of nonlinear channels with binary inputs 总被引:1,自引:0,他引:1
Er-Wei Bai Qingyu Li Zhiyong Zhang 《Signal Processing, IEEE Transactions on》2005,53(7):2315-2323
In this paper, we consider blind source separation/channel equalization problems for an unknown nonlinear channel. By using the property of the binary alphabets, we show that blind nonlinear source separation/channel equalization problems can be easily solved by existing linear methods. 相似文献
16.
17.
Zhi Ding Ge Li 《Selected Areas in Communications, IEEE Journal on》1998,16(8):1493-1505
This paper focuses on the study of blind equalization global system for mobile communications (GSM) systems using a single antenna. In order to utilize the well-known linear system model in conventional studies of blind equalization, an equivalent baseband quadrature amplitude modulation (QAM) approximation is used for the nonlinear GMSK signal in GSM systems. Since the GMSK signal in GSM has very little excess bandwidth to warrant oversampling, a derotation scheme is developed to create two subchannels for each received GMSK signal sampled at the baud rate. Linear approximation of the GMSK signal makes the traditional QAM blind equalization system model applicable for GSM. Derotation induces channel diversity without an additional antenna and reduces the number of necessary radio frequency (RF) receivers (sensors) without increasing hardware or computational costs. Several second-order statistical and higher order statistical methods of blind equalization are adopted for GSM signals 相似文献
18.
Valenzuela J.L. Valdovinos A. Casadevall F.J. 《Vehicular Technology, IEEE Transactions on》1997,46(2):369-374
This paper analyzes the performance of blind equalization using the complex cepstrum of third-order moments applied to 4-QAM time division multiple access (TDMA) indoor radio communication systems. In particular, we have modeled a dispersive indoor channel with Rice statistics. We used the blind algorithms to estimate the channel-impulse response, and from this, we computed the equalizer coefficients using a classical minimum mean square error (MMSE) algorithm. In order to evaluate the system performance, we calculated the bit error rate (BER) of a decision feedback equalizer (DFE) that uses a tricepstrum algorithm to estimate the channel-impulse response. The results are compared with those obtained using a least sum of square errors (LSSE) algorithm as a channel estimator and considering the exact channel response. The results obtained show that this kind of blind equalizer performs better than the more classically trained equalizer when Rice channels with a strong direct path and signal-to-noise ratios (SNRs) lower than 20 dB are taken into account. However, some problems relating to the length of time needed for convergence must be solved 相似文献
19.
We propose a direct blind zeroforcing approach to cancel intersymbol interference (ISI) in multiple user finite impulse response (FIR) channels. By selectively anchoring columns of the channel convolution matrix, we present two column-anchored zeroforcing equalizers (CAZE), one without output delay and one with a chosen delay. Unlike many known blind identification algorithms, these equalizers do not need an accurate estimate of the channel orders. Exploiting second-order statistics (SOS) of the received signals, they can retain preselected d columns in the channel convolution matrix (d is the number of users) and force the remaining columns to zero. CAZE can effectively equalize single-input-multiple-output (SIMO) systems and can reduce dynamic multiple-input-multiple-output (MIMO) systems into a memoryless signal mixing system for source separation. Simulation results show that the CAZE is not only effective for blind equalization of linear quadrature amplitude modulation (QAM) systems, but it is also applicable to the nonlinear GMSK modulation in the popular wireless GSM systems when computational cost severely limits the use of nonlinear methods such as the Viterbi algorithm 相似文献
20.
This paper proposes an adaptive maximum-likelihood sequence estimation (MLSE) by means of combined equalization and decoding, i.e., adaptive combined MLSE, which employs separate channel estimation for respective states in the Viterbi algorithm. First, an approximate metric including channel estimation is derived analytically for this proposed adaptive combined MLSE. Secondly, procedures to accomplish blind equalization are investigated for the proposed MLSE. Finally, its excellent BER performance on fast time-varying fading channels is confirmed by computer simulation, when the proposed MLSE operates as a blind equalizer 相似文献