共查询到20条相似文献,搜索用时 15 毫秒
1.
In this paper, optimum one-shot detection over known and partially known doubly selective Rayleigh fading channels is investigated. Reduced complexity channel models based on Gauss quadrature rules and Taylor power series are derived and are employed to develop novel analytical tools for the performance analysis of one-shot detectors. Numerical results allow to assess the implicit diversity gain provided by both channel multipath and signal fading and the energy loss due to the mismatch of the receiver filter 相似文献
2.
The reception and detection of a single digit under known channel conditions are investigated. The probability of error for an optimum one-shot receiver instantaneously matched to the channel state is averaged over an ensemble of dispersive diversity channels. The average probability of error as a function of energy to noise ratio is found to be solely dependent on the ratio of rms dispersion width to data symbol width. For these dispersive channels an implicit diversity effect is qualitatively explained in terms of eigenvalues that depend on the ensemble statistic. The one-shot receiver performance provides a bound for practical receivers. In a comparison with a decision feedback equalizer, it is shown that on moderately dispersive channels the equalizer nearly achieves optimum one-shot performance. Since an adaptive version of this equalizer exists, this means data transmission on slowly fading channels is possible at rates above the natural rate suggested by the channel dispersion spread without bandwidth expansion and with small intersymbol interference penalty. The use of one-shot receiver performance curves can also be used as estimates of equalizer performance in situations where computation of the latter is impractical. 相似文献
3.
This letter extends the theory of the matched filter bound for fading dispersive channels. We generalize to arbitrary fading, as well as delay, properties of the channel. The channel model is a standard time varying linear filter and the calculation of the matched filter bound is based on a Karhunen-Loeve expansion of the received pulse spectrum when an isolated pulse is transmitted. Results are presented illustrating the various diversity effects. We conclude that in addition to the effect on probability of bit error of implicit delay diversity there is the less well known effect of implicit Doppler diversity in fast fading. The effect on probability of bit error of pulse shaping and explicit diversity is also illustrated 相似文献
4.
DuZheng ZhuJinkang 《电子科学学刊(英文版)》2002,19(1):57-60
A novel one-shot decorrelator for asynchronous CDMA systems is developed.Com-pared with existing one-shot decorrelator, it can reduce complexity and has better performance while eliminating all MAI.This decorrelator is shown to be near-far resistant in both AWGN and fading channel. 相似文献
5.
Clark M.V. Greenstein L.J. Kennedy W.K. Shafi M. 《Vehicular Technology, IEEE Transactions on》1992,41(4):356-362
By employing the technique known as the matched filter bound, the authors derive analytical expressions for the distribution and average of the bit-error-rate in an ideal space diversity mobile radio receiver. Each diversity branch receives from a frequency-selective Rayleigh fading channel of arbitrary delay profile, and is subjected to additive Gaussian noise of arbitrary spectral shape. Numerical results calculated from the analytical expressions give insight into the relative benefits of antenna diversity and wideband transmission over the mobile radio channel 相似文献
6.
MIMO信道的GBDB模型及其信道容量分析 总被引:2,自引:0,他引:2
针对非频率选择性Rice衰落MIMO移动信道,建立GBDB模型,并推导出新的MIMO系统的GBDB模型的空时联合相关函数。新的GBDB模型统一现有的多种MIMO信道模型,新的空时联合相关函数综合考虑了无线衰落信道收发两端的多普勒扩展、非均匀角度扩展以及平均发射与到达方向,综合考虑了收发端天线阵的配置。最后基于新的空时联合相关函数,分析了非均匀散射参数以及Rice分布参数变化对MIMO信道统计容量的影响。 相似文献
7.
Jin-Fu Chang 《Communications, IEEE Transactions on》1979,27(4):737-745
We analyze the performance of a one-bit digital matched filter (DMF) responding to binary signaling through a noisy multipath channel. The output signal-to-noise ratio(SNR_{o}) plays a key role in the analysis. The SNRo performance is fully studied for a two-path channel, both fading and non-fading. For the generalN -path channel, results are obtained only for the fading case. All results are conditioned on the knowledge of the time delays of all paths, and are valid only for small input signal-to-noise ratio(SNR_{i) . Most of the results have been verified by computer simulations. 相似文献
8.
Du Zheng Zhu Jinkang 《电子科学学刊(英文版)》2003,20(6)
In this paper, an iterative "one-shot" decorrelator for asynchronous code Division Multiple Access(CDMA) systems is proposed. This decorrelator feedbacks the decorrelated symbols of interfering users before decision to mitigate their interferences. As a result, this decorrelator is a linear detector and does not need any amplitude information of users as in decision-feedback detectors. Compared with existing "one-shot" decorrelator, it has reduced complexity and provided better performance while eliminating all Multiple Access Interference(MAI). The performance of this decorrelator is analyzed thoeritically, and analytical result is given. Numerical results show near-far resistant capability of this decorrelator in both AWGN and fading channel. 相似文献
9.
A coherent multiuser decorrelating detector for an asynchronous CDMA, time-varying Rayleigh fading channel is proposed and analysed. The detector uses fractionally sampled correlators outputs at time instants corresponding to users relative delays to simultaneously achieve two goals: the novel realisation of a one-shot decorrelator with lower computational complexity; and to exploit a form of the time diversity for improved error performance compared to symbol spaced sampling 相似文献
10.
John H. Gass Jr. Michael B. Pursley 《International Journal of Wireless Information Networks》1994,1(3):177-186
The transmission of frequency-hop spread-spectrum signals over a frequency-selective fading channel results in correlation between the amplitudes of signals that occupy different frequency slots. This correlation produces dependent errors among symbols transmitted at different frequencies. For a system that employs block coding, this dependence results in dependent errors, even if the code symbols are interleaved over the dwell intervals. Using an appropriate mathematical model for wideband frequency-selective fading channel, we present analytical results on the code-word error probability for a simple coding scheme and simulation results for more complex codes. 相似文献
11.
In the usual application of Multiple-Input, Multiple-Output (MIMO) and space–time coding (STC) the basis of the operation is a rich-scattering fading channel and a high density of links. In this paper a different situation: cellular millimeter-wave systems are investigated. It is shown that the MIMO concept can also have advantages in this case. Rain-induced fading characteristics and the concept of route diversity are briefly introduced. A route diversity system can be regarded as a parallel MIMO channel. Basic characteristics of these channels including capacity for various cases are investigated. Optimal codes are determined for space-time convolutional coding. Conceptual design of a route-time coding (RTC) system is shown. Simulation results on coding gain, based on empirical rain attenuation data are given. 相似文献
12.
13.
The performance of antenna diversity coherent and differentially coherent linear multiuser receivers is analyzed in frequency-nonselective Rayleigh fading CDMA channels with memory. The estimates of the complex fading processes are utilized for maximal-ratio combining and carrier recovery of the coherent multiuser receiver. To analyze the impact of channel estimation errors on the receiver performance, error probability is assessed directly in terms of the fading rate and the number of active users, showing the penalty imposed by imperfect channel estimation as well as the fading-induced error probability floor. The impact of fading dynamics on the differentially coherent decorrelating receiver with equal-gain combining is quantified. While performance of multiuser receivers at lower SNR is determined by both the fading dynamics and the number of active CDMA users, performance at higher SNR is given by an error probability floor which is due to fading only and has the same value as in a single-user case. The comparison of the two receiver structures indicates that the coherent decorrelating receiver with diversity reception may be preferable to the differentially coherent one in nonselective fading CDMA channels with memory. 相似文献
14.
Mydlow Michael W. Basavaraju Sridevi Duel-Hallen Alexandra 《Wireless Personal Communications》1996,3(1-2):175-193
Diversity combining techniques are applied in mobile radio communications as a means of performance improvement in a fading multipath environment. Adaptive equalizers which incorporate diversity combining were shown to combat intersymbol interference (ISI) caused by multipath provided that the fading is sufficiently slow. However, for fast fading rates, noncoherent techniques are often desirable. In this paper, we examine the performance of several coherent and noncoherent detectors that make use of diversity combining. In particular, the decorrelating filter is shown to provide reliable performance for a frequency-selective Rayleigh fading multipath channel with ISI. Numerical and simulation results are presented for a channel with two independent Rayleigh fading paths. Signal design issues which arise in the implementation of the decorrelating detector and the zero-forcing equalizer are discussed. 相似文献
15.
16.
Sok-Kyu Lee Seong Rag Kim 《Selected Areas in Communications, IEEE Journal on》2002,20(2):257-263
It is well known that conventional detectors of direct sequence-code division multiple access systems are interference-limited. Multiuser detection has been considered as a promising approach to combat this problem. Since an optimal multiuser detector is too complex to implement, several suboptimal multiuser detector techniques have been developed. The one-shot linear decorrelating detector (LDD) was proposed to reduce the computational complexity and delay required in the conventional LDD, but it still require high complexity. Another one-shot LDD with low complexity was proposed. To improve its performance, this detector uses a maximal ratio combining (MRC) at the two outputs of the left piece of the present bit and the right piece of the next bit in an one-shot window; this detector is called as a one-shot LDD with post-MRC. In spite of the aid of MRC, the performance of the one-shot LDD with post-MRC is worse than the one-shot LDD. To overcome this problem, we propose the one-shot LDD with pre-SDC/post-MRC that employs selection diversity combining (SDC) with multiple antenna elements in front of the one-shot LDD with post-MRC. In asynchronous random code division multiple access systems over fading channels, the largest signal-to-noise ratio (SNR) of SDC, near-far resistance (NFR) of the one-shot LDD, and the output SNR of MRC are random variables. We derive the probability density functions (PDFs) for these random variables and calculate the bit error rate) of the proposed detector using the obtained PDFs. In a comparison of mathematical analysis and computer simulation results, we observe good agreement 相似文献
17.
Lorenzo Juan Narcís 《AEUE-International Journal of Electronics and Communications》2007,61(2):135-138
It is well known that the short-term fading conditions of the received envelope in wireless communications channels can be modelled by means of the Nakagami distribution. The value of the m parameter, also called shape factor, indicates the severity of multipath fading, and is a measure of channel quality, making its estimation necessary in many applications. In this letter, a range of possible values of the m parameter based on the analysis of a measurements campaign in urban scenarios is presented. 相似文献
18.
Abu S. Amanullah Masoud Salehi 《International Journal of Wireless Information Networks》1995,2(2):83-90
The effect of the presence of a feedback channel on the transmission of information was first considered by Shannon, who showed that the capacity of a memoryless channel is not increased by the existence of a feedback link even if the feedback link is noiseless. Later it was shown that the information on a feedback channel can be used to improve considerably the performance of channel coding. In this work we study the transmission of an information source through a fading channel with feedback, modeled by a finite-state channel in the Gilbert-Elliot sense. We show that by employing the feedback information in the quantizer design for this finite-state channel, one can achieve lower overall distortion compared to the case where feedback is not available. The feedback channel is used to estimate the channel state using a hidden Markov model, and a quantizer matched to the channel state is chosen based on this information. 相似文献
19.
ZhaoZheng JiaYing YinQinye 《电子科学学刊(英文版)》2003,20(5):326-336
Delay diversity is an effective transmit diversity technique to combat adverse effects of fading. Thus far, previous work in delay diversity assumed that perfect estimates of current channel fading conditions are available at the receiver and training symbols are required to estimate the channel from the transmitter to the receiver. However, increasing the number of the antennas increases the required training interval and reduces the available time with in whichdata may be transmitted. Learning the channel coefficients becomes increasingly difficult for the frequency selective channels. In this paper, with the subspace method and the delay character of delay diversity, a channel estimation method is proposed, which does not use training symbols. It addresses the transmit diversity for a frequency selective channel from a single carrier perspective in the form of a simple equivalent flat fading model. Monte Carlo simulations give the performance of channel estimation and the performance comparison of our channel-estimation-based detector with decision feedback equalization, which uses the perfect channel information. 相似文献