BER of MRC for M-QAM with imperfect channel estimation over correlated Nakagami-m fading

In this contribution, we provide an exact BER analysis for M-QAM transmission over arbitrarily correlated Nakagami-m fading channels with maximal-ratio combining (MRC) and imperfect channel estimation at the receiver. Assuming an arbitrary joint fading distribution and a generic pilot-based channel estimation method, we derive an exact BER expression that involves an expectation over (at most) 4 variables, irrespective of the number of receive antennas. The resulting BER expression includes well-known PDFs and the PDF of only the norm of the channel vector. In order to obtain the latter PDF for arbitrarily correlated Nakagami-m fading, several approaches from the literature are discussed. For identically distributed and arbitrarily correlated Nakagami-m channels with integer m, we present several BER performance results, which are obtained from numerical evaluation and confirmed by straightforward computer simulations. The numerical evaluation of the exact BER expression turns out to be much less time-consuming than the computer simulations

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 pilot-assisted 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. Exact analytical expressions for the symbol error rates of LS and MMSE channel estimation aided optimal diversity combining are derived. It is shown that 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 counter-example to the common perception that channel estimation with smaller mean square error leads to smaller SER. Extensive simulation results validate the theoretical results

Future transmitter/receiver diversity schemes in broadcast wireless networks

An open diversity architecture for a cooperating broadcast wireless network is presented that exploits the strengths of the existing digital broadcast standards. Different diversity techniques for broadcast networks that will minimize the complexity of broadcast systems and improve received SNR of broadcast signals are described. Resulting digital broadcast networks could require fewer transmitter sites and thus be more cost-effective with less environmental impact. Transmit diversity is particularly investigated since it obviates the major disadvantage of receive diversity being the difficulty of locating two receive antennas far enough apart in a small mobile device. The schemes examined here are compatible with existing broadcast and cellular telecom standards and can be incorporated into existing systems without change

Indoor wireless communications and applications

Chapter 3 addresses challenges in radio link and system design in indoor scenarios. Given the fact that most human activities take place in indoor environments, the need for supporting ubiquitous indoor data connectivity and location/tracking service becomes even more important than in the previous decades. Specific technical challenges addressed in this section are(i), modelling complex indoor radio channels for effective antenna deployment, (ii), potential of millimeter-wave (mm-wave) radios for supporting higher data rates, and (iii), feasible indoor localisation and tracking techniques, which are summarised in three dedicated sections of this chapter

Doppler spread estimation in mobile fading channels

The Doppler spread, or equivalently, the mobile speed, is a measure of the spectral dispersion of a mobile fading channel. Accurate estimation of the mobile speed is important in wireless mobile applications which require such as knowledge of the rate of channel variations. In this dissertation, first the performance of classical crossing- and covariance-based speed estimators is studied. Next, the problem of mobile speed estimation using diversity combining is investigated. Then, a nonparametric estimation technique is proposed that is robust to different channel variations. Finally, cyclostationarity-based speed estimators which can be applied either blindly or with the aid of pilot data, are developed. A unified framework for the performance analysis of well-known crossing and covariance based speed estimation techniques is presented. This allows a fair analytical comparison among all the methods. Interestingly, it is proved that all these methods are asymptotically equivalent, i.e., for large observation intervals. The extensive performance analysis, supported by Monte Carlo simulations, has revealed that depending on the channel condition and the observation interval, one needs to use a crossing or a covariance based technique to achieve the desired estimation accuracy over a large range of mobile speeds. Two common diversity schemes, selection combining (SC) and maximal ratio combining (MRC), are considered for Doppler spread estimation. Four new estimators are derived which rely on the inphase zero crossing rate, inphase rate of maxima, phase zero crossing rate, and the instantaneous frequency zero crossing rate of the output of SC. Two estimators, which work based on the level crossing rates of the envelopes at the output of SC and MRC, are also proposed. The performances of all these estimators are investigated in realistic noisy environments with different kinds of scatterings and different numbers of diversity branches. Then a novel speed estimation technique is proposed that is applicable to both mobile and base stations, based on the characteristics in the power spectrum of mobile fading channels. The analytic performance analysis, verified by Monte Carlo simulations, shows that this low-complexity estimator is not only robust to both Gaussian and non-Gaussian noises, but also insensitive to nonisotropic scattering observed at the mobile. The estimator performs very well in both two- and three-dimensional propagation environments. By taking advantage of resolvable paths in wideband fading channels, the robustness against both nonisotropic scattering and line of sight can be further increased, due to the differences among the Doppler spectra observed at different paths. This technique is also extended to base stations with antenna arrays. By exploiting the spatial information, the proposed space-time estimator exhibits excellent performance over a wide range of noise power, nonisotropic scattering, and the line-of-sight component. This is all verified by simulation. The utility of the new method is further demonstrated by applying it to the measured data. Finally, to design robust blind and data-aided mobile speed estimators, a proposal is made to exploit the inherent cyclostationarity of linearly modulated signals transmitted through fading channels. Two categories of cyclic-correlation- and cyclic-spectrum-based methods are developed. Extension to space-time speed estimation at the base station in macrocells is also provided. In comparison with the existing methods, the new estimators can be used without any need for pilot tones and are robust to additive stationary noise or interference of any color or distribution. Unlike the conventional multi-antenna based method, the proposed space-time speed estimator does not assume the receiver noise to be spatially white. A suboptimal training sequence is also devised for pilot-symbol assisted methods, to reduce the estimation error. The performance of the proposed estimators are illustrated via extensive Monte Carlo simulations

The SER Analysis of Rayleigh, Rician and Nakagami Channels at Various Relay Locations in Cooperative Networks

Reliable communication between transmitter and receiver is accomplished by cooperative diversity techniques. Sending of data in various paths has greatly improved the performance of communication. We have studied the performance of Amplify-and-Forward (AF) based network in this work for diverse relay location at Nakagami, Rician and Rayleigh fading channels. The relay performance in Amplify-and-Forward (AF) protocol based on Symbol Error Rate (SER) against Signal-to-Noise Ratio (SNR) in dBs is calculated. The software that is used to construct Monte-Carlo link level simulation is MATLAB. The effects of a relay at changed location in diverse channels accompanied with Additive White Gaussian noise (AWGN) is also calculated. BPSK modulation scheme is used for the transfer of information between the source, relay and destination node. The signals are combined through Maximum Ratio Combining method (MRC).Reliable communication between transmitter and receiver is accomplished by cooperative diversity techniques. Sending of data in various paths have greatly improved the performance of communication. We have studied the performance of Amplify-and-Forward (AF) based network in this work for diverse relay location at Nakagami, Rician and Rayleigh fading channels. The relay performance in Amplify-and-Forward (AF) protocol based on Symbol Error Rate (SER) against Signal-to-Noise Ratio (SNR) in dBs is calculated. The software that is used to construct Monte-Carlo link level simulation is MATLAB. The effects of relay at changed location in diverse channels accompanied with Additive White Gaussian noise (AWGN) is also calculated. BPSK modulation scheme is used for the transfer of information between the source, relay and destination node. The signals are combined through Maximum Ratio Combining method (MRC)

Performance Model for MRC Receivers with Adaptive Modulation and Coding in Rayleigh Fading Correlated Channels with Imperfect CSIT

RTUWO Advances in Wireless and Optical Communications 2015 (RTUWO 2015). 5-6 Nov Riga, Latvia.This paper presents a performance model of the packet reception process in a wireless link with one antenna transmitter and a multiple-antenna maximum-ratio combining (MRC) receiver. The objective is to address the performance evaluation of multiple antenna systems enabled with adaptive modulation and coding (AMC). Two main assumptions are used: 1) Rayleigh fading correlated channels, and 2) imperfect (outdated) channel state information at the transmitter side (CSIT). The results presented here suggest that spatial correlation not always affects the performance of the MRC receiver: at low signal-to-noise ratio (SNR), correlation can improve performance rather than degrading it. By contrast, at high SNR, correlation is found to always degrade performance. At high SNR, correlation tends to worse the degrading effects of imperfect CSIT, particularly when the number of antennas increases. Imperfect CSIT causes errors in the assignment of MCSs, thus reducing throughput performance. These errors become more evident at high SNR, particularly when the values of branch correlation and the number of antennas increase

Relative measurement error analysis in the process of the Nakagami-m fading parameter estimation

An approach to the relative measurement error analysis in the process of the Nakagami-m fading signal moments estimation will be presented in this paper. Relative error expressions will be also derived for the cases when MRC (Maximal Ratio Combining) diversity technique is performed at the receiver. Capitalizing on them, results will be graphically presented and discussed to show the influence of various parameters, such as diversity order and fading severity on the relative measurement error bounds