估计误差下DF协作系统性能分析

信道估计误差是引起无线通信系统性能衰弱的重要因素之一。分析了瑞利信道条件下估计误差对译码前传协作系统性能的影响。推导并给出了估计误差条件下正交幅度调制信号译码前传协作系统码元错误概率的解析表达式和上界表达式,并分析了不同信道的方差对协作系统性能的影响。仿真结果显示,存在估计误差时,码元错误概率性能并未随着信噪比的增大而提高。同时发现,中继-目的链路的较大方差较源-中继链路显著改善码元错误概率性能。     

Performance analysis of ZF receivers with imperfect CSI for uplink massive MIMO systems

We consider the uplink of massive multiple-input multiple-output systems in a multicell environment. Since the base station (BS) estimates the channel state information (CSI) using the pilot signals transmitted from the users, each BS will have imperfect CSI in practice. Assuming zero-forcing method to eliminate the multi-user interference, we derive the exact analytical expressions for the probability density function of the signal-to-interference-plus-noise ratio, the corresponding achievable rate, the outage probability, and the symbol error rate (SER) when the BS has imperfect CSI. An upper bound of the SER is also derived for an arbitrary number of antennas at the BS. Moreover, we derive the upper bound of the achievable rate for the case where the number of antennas at the BS goes to infinity, and the analysis is verified by presenting numerical results.     

Hybrid decode-amplify-forward (HDAF) scheme in distributed Alamouti-coded cooperative network

In this article, a signal-to-noise ratio (SNR)-based hybrid decode-amplify-forward scheme in a distributed Alamouti-coded cooperative network is proposed. Considering a flat Rayleigh fading channel environment, the MATLAB simulation and analysis are carried out. In the cooperative scheme, two relays are employed, where each relay is transmitting each row Alamouti code. The selection of SNR threshold depends on the target rate information. The closed form expressions of symbol error rate (SER), the outage probability and average channel capacity with tight upper bounds are derived and compared with the simulation done in MATLAB environment. Furthermore, the impact of relay location on the SER performance is analysed. It is observed that the proposed hybrid relaying technique outperforms the individual amplify and forward and decode and forward ones in the distributed Alamouti-coded cooperative network.     

Moment Generating Function Based Performance Analysis of Maximal-Ratio Combining Diversity Receivers in the Generalized-K Fading Channels

In this paper, we have analyzed the performance of maximal ratio combing (MRC) diversity receiver of the wireless communication systems over the composite fading environment, which is modelled by using the generalized-K distribution. However, this distribution has been considered as a versatile distribution for the precise modelling of a great variety of the short-term fading in conjunction with the long-term fading (shadow fading) channel conditions. In this proposed analysis, we have derived the mathematical expression for the moment generating function (MGF) of the generalized-K fading channel model that is used to evaluate a novel closed-form expression of the average bit error rate for (BER) the binary phase-shift keying /binary frequency-shift keying and average symbol error rate (SER) for the rectangular quadrature amplitude modulation scheme. We have also derived the mathematical expressions for the outage probability as well as the channel capacity for the generalized-K fading channel model.     

Performance Analysis of Space-Time Block Codes with Transmit Antenna Selection in Nakagami-m Fading Channels

In this paper, multiple-input multiple-output systems employing space-time block codes (STBCs) with transmit antenna selection (TAS) are examined for flat Nakagami-m fading channels. Exact symbol error rate (SER) expressions for M-ary modulation techniques are derived by using the moment generating function based analysis method. In the SER analysis, the receiver is assumed to use maximal ratio combining whereas a subset of transmit antennas that maximizes the instantaneous received signal-to-noise ratio (SNR) is selected for STBC transmission. The analytical SER results are validated by Monte Carlo simulations. By deriving upper and lower bounds for SER expressions, it is shown that TAS/STBC schemes achieve full diversity orders at high SNRs.     

Symbol error rate analysis and power allocation for hybrid cooperation in Rayleigh fading environment

In this paper, we investigate the symbol error rate (SER) performance and power allocation for hybrid cooperation (HC) system in a Rayleigh fading environment. Specifically, we derive closed‐form and approximate SER expressions for the HC system by using the moment generating function (MGF)‐based approach. However, the resultant SER expressions contain an MGF of the harmonic mean of two independent random variables, which is not tractable in SER analysis. Then, we present simple and tight bounds on the SER to show the asymptotic behavior of the HC system. It is shown that the HC system achieves full diversity order. On the basis of the tight SER bound, the power allocation is investigated. It is found that the optimal power allocation (OPA) of the HC system does not depend on the fading parameter of the source‐to‐destination channel and it only depends on the channel links related to the relay. With the increase of the ratio of mean channel power gains (i.e., the ratio of the relay‐to‐destination channel gain to the source‐to‐relay channel gain), more performance gain can be acquired by using the OPA scheme. Finally, the analytical results are validated through computer simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Performance of decorrelating receivers in multipath Rician fading channels

This letter focuses on the performance analysis of the decorrelating receiver in multipath Rician faded CDMA channels. M-ary QAM scheme is employed to improve the spectral efficiency. Approximate expressions are first derived for the two performance indexes: the average symbol error rate (SER) and the average bit error rate (BER) when the decorrelating-first receiver perfectly knows the channel information of the user of interest. To achieve desirable closed-form expressions of the SER and the BER, we exploit results in large system analysis and make assumptions of a high signal-to-interference ratio (SIR) and/or a small Rician K-factor. To measure the receiver performance in the practical scenario, we further derive expressions to approximate the average SER and BER of the decorrelating-first scheme with channel uncertainty. Simulation results demonstrate that the analytical results can also be employed to evaluate the performance of the combining-first receiver.     

Particle swarm optimization–based power allocation for Alamouti amplify and forward relaying protocol

The performance of wireless communication systems is improved over flat fading channel by using Alamouti coding scheme, which provides the quality of diversity gain. In this paper, performance analysis of symbol error rate (SER) and particle swarm optimization (PSO)–based power allocation (PA) for Alamouti amplify and forward (AF) relaying protocol using maximum ratio combining (MRC) technique is presented. Analytical expression of SER upper bound and SER approximation is derived for Alamouti AF relaying protocol with quadrature phase shift keying (QPSK) modulation over Rayleigh fading channel and Rician fading channel. In addition, PSO‐based optimum PA factor is calculated on the basis of the minimum SER of proposed method. PSO‐based optimum PA gives 0.5 dB of improved signal‐to‐noise ratio (SNR) compared with the equal power allocation (EPA). The theoretical approximate SER result is compared with the simulated SER. The proposed protocol provides full diversity gain and reduces SER compared with the existing AF and decode and forward (DF) relaying protocols over Rayleigh fading channel and Rician fading channel.     

Optimal diversity combining based on linear estimation of rician fading channels

Optimal receiver diversity combining employing linear channel estimation is examined. Based on the statistical properties of least-squares (LS) and minimum mean square error (MMSE) channel estimation, an optimal diversity receiver for wireless systems employing practical linear channel estimation on Rician fading channels is proposed. The new receiver structure includes the conventional maximal ratio combining receiver as a special case. Exact analytical expressions for the symbol error rates (SERs) of LS and MMSE channel estimation aided optimal diversity combining are derived. It is shown that, if an optimal detector is used, an MPSK wireless system with MMSE channel estimation has the same SER when the MMSE channel estimation is replaced by LS estimation. This is an interesting counterexample to the common perception that channel estimation with smaller mean square error leads to smaller SER. Extensive simulation results validate the theoretical results.     

Training-based and semiblind channel estimation for MIMO systems with maximum ratio transmission

This paper is a comparative study of training-based and semiblind multiple-input multiple-output (MIMO) flat-fading channel estimation schemes when the transmitter employs maximum ratio transmission (MRT). We present two competing schemes for estimating the transmit and receive beamforming vectors of the channel matrix: a training-based conventional least-squares estimation (CLSE) scheme and a closed-form semiblind (CFSB) scheme that employs training followed by information-bearing spectrally white data symbols. Employing matrix perturbation theory, we develop expressions for the mean-square error (MSE) in the beamforming vector, the average received signal-to-noise ratio (SNR) and the symbol error rate (SER) performance of both the semiblind and the conventional schemes. Finally, we describe a weighted linear combiner of the CFSB and CLSE estimates for additional improvement in performance. The analytical results are verified through Monte Carlo simulations.     

Analysis of SER of MIMO‐MRC systems with imperfect channel estimation in the presence of non‐Rayleigh CCIs

In this paper, we study the average symbol error rate (SER) for a multiple input multiple output (MIMO) maximal ratio combining (MRC) system with Rayleigh fading desired signal in the presence of non‐Rayleigh fading co‐channel interferers (CCIs) and additive white Gaussian noise (AWGN). To simulate the actual environments of wireless transmission, we assume that the transceiver only obtains imperfect channel estimation (ICE). For the cases of Nakagami and Rician fading CCIs, analytic expressions for the SER have been derived approximately by introducing the modified signal‐to‐interference and noise power ratio (SINR) that can be obtained by averaging the CCI term in the original SINR over the distribution of ICE of intended user. These formulas can provide important reference of design of MIMO diversity systems. Numerical simulations verify the effectiveness of these formulas. Copyright © 2010 John Wiley & Sons, Ltd.     

A two-dimensional impulse noise model and error probability of QAM in DSL

In this letter, we extend the baseband impulse noise modeling over the subscriber loop conducted over the German Telephone Network to the passband scenario. We apply an in-phase (I) and quadrature (Q) resolution of the passband impulse noise and model these components as a generalized error distribution. We use simulation to verify our postulation. Closed-form symbol error rate (SER) expressions for M-ary quadrature amplitude modulation over this passband impulse noise channel are then derived. From the computed SER results, we conclude that the system performance is not sensitive to the dependency factor between the I and Q noise components.     

An upper bound on the SER of transmit beamforming in correlated rayleigh fading

We study the symbol error rate (SER) of maximum ratio transmission, transmit antenna selection, and codebookbased beamforming in correlated Rayleigh fading channels. Assuming maximum ratio combining is performed at the receiver, we derive a universal upper bound on the average SER of the three schemes, and prove that the bound is asymptotically tight in high signal-to-noise ratio (SNR) regions. However, numerical results show that at medium SNR, the tightness of the bound depends on the condition number of the channel correlation matrix.     

Performance analysis of hybrid transmit antenna selection/maximal‐ratio transmission in Nakagami‐m fading channels

Hybrid diversity systems have been of great importance because they provide better diversity orders and robustness to the fading effects of wireless communication systems. This paper focuses on the performance analysis of multiple‐input gle‐output systems that employ combined transmit antenna selection (TAS)/maximal‐ratio transmission (MRT) techniques (i.e., hybrid TAS/MRT). The probability density function, the moment generating function and the n ^th order moments of the output signal‐to‐noise ratio of the investigated diversity scheme are derived for independent identically distributed flat Nakagami‐m fading channels. The system capacity of the hybrid TAS/MRT scheme is examined from the outage probability perspective. Exact bit/symbol error rate (BER/SER) expressions for binary frequency shift keying, M‐ary phase shift keying and square M‐ary quadrature amplitude modulation signals are derived by using the moment generating function‐based analysis method. By deriving the upper bounds for BER/SER expressions, it is also shown that the investigated systems achieve full diversity orders at high signal‐to‐noise ratios. Also, by Monte Carlo simulations, analytical performance results are validated and the effect of feedback delay, channel estimation error and feedback quantization error on BER/SER performances are examined. Copyright © 2011 John Wiley & Sons, Ltd.     

MIMO multichannel beamforming: SER and outage using new eigenvalue distributions of complex noncentral Wishart matrices

This paper analyzes MIMO systems with multichannel beamforming in Ricean fading. Our results apply to a wide class of multichannel systems which transmit on the eigenmodes of the MIMO channel. We first present new closed-form expressions for the marginal ordered eigenvalue distributions of complex noncentral Wishart matrices. These are used to characterize the statistics of the signal to noise ratio (SNR) on each eigenmode. Based on this, we present exact symbol error rate (SER) expressions. We also derive closed-form expressions for the diversity order, array gain, and outage probability. We show that the global SER performance is dominated by the subchannel corresponding to the minimum channel singular value. We also show that, at low outage levels, the outage probability varies inversely with the Ricean A*-factor for cases where transmission is only on the most dominant subchannel (i.e. a singlechannel beamforming system). Numerical results are presented to validate the theoretical analysis.     

时变信道下ADF协作车载通信误码率分析

智能车载协作系统中车辆快速移动使得无线通信信道具有时变特性,为有效评估系统的误码性能,给出了符合车载时变信道的一阶自回归(AR1)模型,提出了一种基于AR1模型的自适应解码转发(ADF)协作误码率分析方法.该方法通过AR1模型的多普勒频偏相关系数来刻画时变信道特性,根据中继译码结果自适应选择是否协作转发,提升了智能交通系统的可靠性.此外,利用矩生成函数(MGF)推导出ADF协作下多进制正交幅度调制(M-QAM)信号误码率封闭表达式,并分析了车载移动速度和信道状态信息(CSI)估计精度对误码性能的影响.数值仿真结果表明,车载系统能通过增加CSI估计精度,有效地减少车载快速移动引起的误码平顶值.该方法相对于放大转发(AF)协作通信方式,平均误码性能提高约8.7 dB.     

Phase-Jitter based SER of MPSK Scheme over Generalised Mixture Gamma Fading

ABSTRACT

Extensive literature exists for simple and exact expressions of symbol error rate (SER) over fading channels under different modulation schemes whose boundaries meet at right angles. In cases where boundaries do not meet at right angles, integrals of special function in the expressions make the exact calculation most complex. In such cases only approximate solutions are possible. Also, it is noteworthy to mention that when detection is performed with proper use of the phase (phase-jitter-based approach), noise performance of the receiver improves significantly. This paper applies phase-jitter PDF-based approach to present exact and closed-form SER expression of MPSK scheme over Mixture Gamma (MG) distribution for an arbitrary array of signal points. The proposed expression is generic as MG distribution can be approximated in almost all fading/shadowed fading channel models. As a proof to the authenticity, SERs of MPSK scheme over Rayleigh and Nakagami-m fading channels are deduced from the proposed SER over generalised MG distribution. Further, a significant improvement in SER has been achieved with phase-jitter-based approach as compared to conventional (non-phase-jitter-based) approach. Finally, to confirm the correctness of the proposed expression, results are validated through comparison with the existing results and Monte Carlo simulation.     

Performance analysis of dual-hop fixed-gain AF relaying systems with OSTBC over Nakagami-m fading channels

In this paper, we present outage probability and symbol error rate (SER) performance analyses of a dual-hop transmission using fixed-gain amplify-and-forward relaying in flat Nakagami-m fading channels. The system under consideration is equipped with multiple antennas at source and destination adopting orthogonal space-time block coding to provide transmit diversity and maximum ratio combining to provide receive diversity, respectively. For integer and half-integer m values, closed forms of exact outage probability and moment generating function (MGF) expressions are derived through cumulative distribution function (CDF) of the overall system signal-to-noise ratio. Closed-form exact SER expressions based on the overall CDF are obtained for binary phase shift keying, binary frequency shift keying and M-ary pulse amplitude modulation. Exact SER expressions based on the MGF method are also obtained for binary differential phase shift keying, M-ary phase shift keying and M-ary quadrature amplitude modulation. Moreover, the asymptotic diversity order analysis is performed through derivations of asymptotic outage probability and SER. Theoretical analyses are validated by Monte Carlo simulations showing perfect match between each other.     

Average SER Performance of Distributed Antenna Systems Over Shadowed Generalized-Gamma Channels for Different Modulation Schemes

Recently, much attention has been drawn to distributed antenna systems (DAS), which are proposed to improve the performance of mobile communication systems. This paper focuses on the analysis of the average symbol error rate (SER) of DAS over a generic composite channel. Initially, a new composite channel model is considered for DAS, which is a mixture of path loss, lognormal shadowing and generalized-Gamma fast fading. This composite channel model is a generic model, which includes many well-known composite channel models as special cases. Based on the channel model, the cumulative distribution function of the output signal-to-noise ratio is obtained by employing selective transmission scheme. Moreover, by averaging the channel conditions and the positions of the MS in the cell, an approximate expression of the average SER is derived, which is a unified form of expression for many commonly used modulation schemes. Numerical results show that the derived expression of the average SER can provide sufficient precision for evaluating the SER performance of DAS under different modulation schemes.     

Error probability minimizing pilots for OFDM with M-PSK modulation over Rayleigh-fading channels

Orthogonal frequency division multiplexing (OFDM) with pilot symbol assisted channel estimation is a promising technique for high rate transmissions over wireless frequency-selective fading channels. In this paper, we analyze the symbol error rate (SER) performance of OFDM with M-ary phase-shift keying (M-PSK) modulation over Rayleigh-fading channels, in the presence of channel estimation errors. Both least-squares error (LSE) and minimum mean-square error (MMSE) channel estimators are considered. For prescribed power, our analysis not only yields exact SER formulas, but also quantifies the performance loss due to channel estimation errors. We also optimize the number of pilot symbols, the placement of pilot symbols, and the power allocation between pilot and information symbols, to minimize this loss, and thereby minimize SER. Simulations corroborate our SER performance analysis, and numerical results are presented to illustrate our optimal claims.