Juan M. Romero-Jerez

Performance of multichannel reception with transmit antenna selection in arbitrarily distributed Nagakami fading channels

We present exact expressions for the average bit error rate (BER) and symbol error rate (SER) of different modulation techniques of a wireless system with multiple transmit and receive antennas. The receive antennas are assumed to use maximal ratio combining (MRC) or post-detection equal gain combining (EGC), whereas the transmit antenna that maximizes the output signal-to-noise ratio (SNR) is selected. Exact expressions of the moment generating function (MGF) of the output SNR and all its derivatives are also derived. We consider a Nakagami-m fading channel where the long-term SNR and fading parameters from the different transmit antennas are arbitrary and may be different from each other. For a given transmit antenna, the fading at the receive antennas is assumed to be independent and identically distributed (i.i.d). For the case when the Nakagami fading parameter m has an integer value in every channel, results are given in closed-form as a finite sum of simple terms. When fading parameters take any real value, our results are given in terms of the multivariate Lauricella hypergeometric function FA (n). Numerical results for the error rates of different modulation techniques are presented.. Our results are validated by Monte Carlo simulation.

Receive Antenna Array Strategies in Fading and Interference: An Outage Probability Comparison

We explore tradeoffs between different reception strategies of multiple receive antennas in fading channels with co-channel interference (CCI). Our tradeoff analysis is based on outage probability. We assume the signal from the desired user at the receive antenna array to be affected by Rice, Nakagami or Rayleigh fading, while CCI signals are assumed to experience Rayleigh fading. We provide closed-form analytical expressions for the outage probability of different diversity schemes, such as maximal ratio combining (MRC) and optimum combining (OC), and also for interference cancellation (IC) based on antenna beamsteering, which steers nulls in the array radiation pattern in the direction of the strongest interferers. Our analysis provides a unified framework for studying outage probability of different multiple-antenna reception strategies, and our closed- form expressions are easily computed, facilitating a performance comparison under a range of operating conditions. Our numerical results show that IC yields significantly better performance than MRC if the system is interference-limited and the number of dominant interferers is lower than the number of receive antennas, or when the output SINR is low. In addition, when the background noise can be neglected, we provide numerical results for MRC and OC when the signals from the desired user at the different receive antennas are arbitrarily distributed.

Effect of power control imperfections on the reverse link of cellular CDMA networks under multipath fading

In this paper, we present an analytical approach for the evaluation of the impact of power control errors on the reverse link of a multicell direct sequence code-division multiple access (CDMA) system with fast power control under multipath fading. Unlike many previous papers, the joint effect of multipath fading and fast power control on interference statistics is explicitly accounted for and mobiles are assumed to connect to a base station according to a minimum attenuation criterion. Both the average bit error rate (BER) and the outage probabilities that a user experiences are estimated. The results have been used to evaluate the system capacity from two points of view. First, the maximum capacity supported by the system in order to maintain an average BER below a prescribed level has been calculated. Second, the maximum capacity possible to ensure that the outage probability does not exceed a set limit is analyzed. Capacity is shown to be significantly affected by the imperfections of power control. Our results can be used to quantify the relative capacity loss due to fast power control errors in a cellular CDMA network affected by slow fading, multipath fading, and cochannel interference.

Effects of multipath fading on BER statistics in cellular CDMA networks with fast power control

An analytical approach for the calculation of the bit error rate statistics in a cellular code-division multiple access system with imperfect fast power control is presented. Usually, imperfections in power control after despreading are modeled as a lognormal random variable. It has been shown that, in a fading channel, the standard deviation of this variable is a function of whether or not the mobile is communicating with the base station where the power is measured. We show that when this fact is not taken into account the results obtained are too optimistic.

Performance of MIMO MRC Systems with Co-Channel Interference

We determine exact closed-form expressions for the outage probability of multiple-input/multiple-output systems in Rayleigh fading with maximal ratio diversity combining and co-channel interference. Our analysis generalizes prior work in that we place no restrictions on the number or power of the interferers, or on the number of antennas at the transmitter and receiver. We also present an alternative mathematical approach to performance analysis that leads to an undemanding expression for the SINR moment generating function, which can then be used to evaluate average probability of error and the moments of the SINR. Our numerical results indicate that, for a fixed total interference power, system performance degrades when there are dominant interferers. In addition, for a fixed total number of transmit and receive antennas, outage probability and average bit error rate decrease when the transmitter and receiver have the same number of antennas.

Performance comparison of MRC and IC under transmit diversity

This work explores the performance of MIMO (multiple-input/multiple-output) systems in Rayleigh fading channels with co-channel interference (CCI) and thermal noise. We provide analytical expressions for the outage probability of maximal ratio transmission combined with one of two different receive antenna array schemes, maximal ratio combining (MRC) and interference cancellation (IC) via null steering of the array pattern. We derive the statistics of the signal to interference-plus- noise ratio (SINR) for each technique in a closed-form and obtain an integral expression to calculate the average bit error rate (BER) or symbol error rate (SER). Our results show the conditions under which IC yields significantly better performance than MRC and vice versa. We also determine the impact on performance of the number of antennas in the transmit array.

Outage Probability of MRC With Arbitrary Power Cochannel Interferers in Nakagami Fading

We propose a new approach to outage probability analysis of predetection maximal ratio combining (MRC) diversity reception in Nakagami-m fading channels. We generalize prior work in that we consider L independent cochannel interferers with arbitrary powers and fading parameters as well as the effects of additive white Gaussian noise (AWGN). Our approach results in a general expression for outage probability under very broad assumptions. Moreover, our approach leads to a closed-form expression for outage probability in most cases of interest. We also provide numerical results that demonstrate the performance improvement obtained through MRC diversity combining in the presence of cochannel interferers.

Interference statistics of cellular DS/CDMA systems with base station diversity under multipath fading

A theoretical characterization of intracell and intercell interference statistics in cellular direct-sequence code-division multiple-access systems in a multipath environment is presented considering both fast and slow power control. Unlike many of the previous papers, mobiles are assumed to connect to a base station according to a minimum attenuation criterion, also known as base station diversity. Interference statistics are used to estimate system capacity and results have been validated by Monte Carlo simulations. Our results confirm that much greater capacity can be achieved when multipath fading is compensated by power control, while the relative benefits of perfect compensation of multipath fading decreases as the number of resolvable paths at the receiver increases.

Performance of TAS/MRC Wireless Systems Under Hoyt Fading Channels

This paper presents the performance analysis of a wireless system with multiple transmit and receive antennas under Hoyt fading. Receive antennas are assumed to perform Maximal Ratio Combining (MRC), whereas the antenna at the transmit end that maximizes the instantaneous output signal-to-noise ratio (SNR) is selected for transmission. When the number of receive antennas is arbitrary, an exact compact expression is derived for the outage probability. For two receive antennas, closed-form expressions are presented for the ergodic capacity and the average error rates of different modulations, which are given as a finite sum of well known functions. An asymptotic error rate analysis is also performed when the number of receive antennas is arbitrary. It is shown that severe fading conditions do not always degrade wireless systems performance. Actually, our results show that severe fading can be beneficial in terms of channel capacity if the transmit array is large enough due to the antenna selection performed at the transmitter. Monte Carlo simulations have been carried out to validate the derived expressions, showing an excellent agreement with the analytical results.

A New Framework for the Performance Analysis of Wireless Communications Under Hoyt (Nakagami-

We present a novel relationship between the distribution of circular and non-circular complex Gaussian random variables. Specifically, we show that the distribution of the squared norm of a non-circular complex Gaussian random variable, usually referred to as the squared Hoyt distribution, can be constructed from a conditional exponential distribution. From this fundamental connection we introduce a new approach, the Hoyt transform method, that allows to analyze the performance of a wireless link under Hoyt (Nakagami-