Several practical wireless scenarios exist where the transmitted signal might undergo severe channel fading. This work presents the Extreme Two-Wave (ETW) fading model, encompassing simultaneously the Two-Ray and the k-µ Extreme fading models, which have been shown to provide a tight fit to empirical measurements in harsh propagation conditions. The ETW model is a limiting case of the recently introduced Multicluster Two-Ray (MTW) fading model and can be used to model wireless communications links in some of the new use cases defined in 5G and beyond wireless networks in environments experiencing severe fading. The chief probability functions are obtained for the proposed ETW model, as well as the outage probability. In addition, the ETW model is extended to incorporate shadowing effects.

We introduce and characterize the Multi-cluster Two-Wave (MTW) fading model, which generalizesboththe Durgin’s Two-Wave with Diffuse Power (TWDP) and the$\kappa $-$\mu $models under a common umbrella. The MTW model consists of an arbitrary number of clusters of waves each of which may include one or two dominant (specular) components. The chief probability functions of the MTW fading model are obtained, including the probability density function, the cumulative distribution function and the generalized moment-generating function. The proposed model is empirically validated using channel measurements in the sub-THz band and a number of applications are exemplified, including the outage probability in noise-limited and interference-limited scenarios and the energy detection probability. A composite Inverse Gamma (IG)/MTW model is also investigated, thus extending the proposed propagation model to include shadowing.

The recently introduced independent fluctuating two-ray (IFTR) fading model, consisting of two specular components fluctuating independently plus a diffuse component, has proven to provide an excellent fit to different wireless environments, including the millimeter-wave band. However, the original formulations of the probability density function (PDF) and cumulative distribution function (CDF) of this model are not applicable to all possible values of its defining parameters, and are given in terms of multifold generalized hypergeometric functions, which prevents their widespread use for the derivation of performance metric expressions. A new formulation of the IFTR model is here presented as a countable mixture of Gamma distributions which greatly facilitates the performance evaluation for this model in terms of the metrics already known for the much simpler and widely used Nakagami-mfading, and is shown to provide a better fit to empirical measurements than the original formulation. Additionally, a closed-form expression is presented for the generalized moment generating function (GMGF), which permits to readily obtain all the moments of the distribution of the model, as well as several relevant performance metrics. Based on these new derivations, performance results are presented for the IFTR model considering different metrics, which are verified by Monte Carlo simulations.

We introduce and characterize the Multi-cluster Fluctuating Two-Ray (MFTR) fading channel, generalizingboththe fluctuating two-ray (FTR) and the κ-μ shadowed fading models through a more general yet equally mathematically tractable model. We derive all the chief probability functions of the MFTR model such as probability density function (PDF), cumulative distribution function (CDF), and moment generating function (MGF) in closed-form, having a mathematical complexity similar to other fading models in the state-of-the-art. We also provide two additional analytical formulations for the PDF and the CDF: (i) in terms of a continuous mixture of κ-μ shadowed distributions, and (ii) as an infinite discrete mixture of Gamma distributions. Such expressions enable to conduct performance analysis under MFTR fading bydirectlyleveraging readily available results for the κ-μ shadowed or Nakagami-mcases, respectively. We demonstrate that the MFTR fading model provides a much better fit than FTR and κ-μ shadowed models for small-scale measurements of channel amplitude in outdoor Terahertz (THz) wireless links. Finally, the performance of wireless communications systems undergoing MFTR fading is exemplified in terms of classical benchmarking metrics like the outage probability, both in exact and asymptotic forms, and the amount of fading.

We introduce, characterize and validate the independent fluctuating two-ray (IFTR) fading model, which consists of two specular (dominant) components that fluctuate independently, plus a diffuse one resulting from the reception of multiple scattered waves. The IFTR model complements the fluctuating two-ray (FTR) model, in which the specular components are fully correlated and fluctuate jointly. The chief probability functions of the received SNR of this new model, including the PDF, CDF and MGF, are given in closed-form. The IFTR model is empirically validated using measured data from Line-Of-Sight (LOS) millimeter-wave channels, showing a better fit than the FTR model and other models previously used in these channels, and providing a remarkable improvement at 73 GHz.

We present a composite wireless fading model encompassing multipath fading and shadowing based on fluctuating two-ray (FTR) fading and inverse gamma (IG) shadowing. We first determine an alternative framework for the statistical characterization and performance evaluation of the FTR fading model, which is based on the fact that the FTR fading distribution can be described as an underlying Rician Shadowed (RS) distribution with continuously varying parameter$K_{T}$(ratio of specular to diffuse components). We demonstrate that this new formulation permits to obtain a closed-form expression of the generalized moment generating function (GMGF) of the FTR model, from which the PDF and CDF of the composite IG/FTR model can be obtained in closed-form. The exact and asymptotic outage probability of the IG/FTR model are analyzed and verified by Monte Carlo simulations.

We present two alternative frameworks for the statistical characterization and performance evaluation of the fluctuating two-ray (FTR) fading model which simplify previous approaches. The new formulations are based on the fact that the FTR fading distribution can be described, for arbitrary$m$, as an underlying Rician Shadowed (RS) distribution with continuously varying parameter$K_{r}$(ratio of specular to diffuse power components), while for the special case of$m$being an integer, it is demonstrated that the FTR fading model can be described in terms of a finite number of underlying squared Nakagami-$m$distributions. It is shown that any performance metric that is computed by averaging over the probability density function (PDF) of the FTR fading model can be expressed in terms of a finite-range integral over the corresponding performance metric for the simpler RS (for arbitrary$m$) or Nakagami-$m$(for integer$m$) fading models, for which many results are available in closed-form. New expressions for some Laplace-domain statistics of interest are also obtained; these are used to analyze the outage probability of FTR fading under co-channel interference, as well as to obtain closed-form expressions for the main statistics of a composite wireless channel model encompassing FTR fading and shadowing.

We present a general and tractable fading model for line-of-sight (LOS) scenarios, which is based on the product of two independent and non-identically distributed κ-μ shadowed power envelopes. Simple closed-form expressions for the probability density function, cumulative distribution function and moment-generating function are derived, which are as tractable as the corresponding expressions derived from a product of Nakagami-m random variables. This model simplifies the challenging characterization of LOS product channels, as well as combinations of LOS channels with non-LOS ones. We leverage these results to analyze performance measures of interest in the contexts of wireless powered and backscatter communications, where both forward and reverse links are inherently of LOS nature, as well as in device-to-device communications subject to composite fading. In these contexts, the proposed model shows a higher flexibility when fitting field measurements with respect to conventional approaches based on product distributions with deterministic LOS, together with a more complete physical interpretation of the underlying propagation characteristics.

The F composite fading model was recently proposed as an accurate and tractable statistical model for the characterization of the composite fading conditions encountered in realistic wireless communication scenarios. In the present contribution we capitalize on the distinct properties of this composite model to evaluate the achievable effective rate over F composite fading channels. To this end, we derive an exact closed-form expression for the effective rate, which is subsequently used as a benchmark for the derivation of tight upper and lower bounds, as well as of an accurate approximation. The derived analytic expressions are provided in closed-form and benefit from being tractable both analytically and numerically. This enables the development of meaningful insights on the effect of fading conditions and/or latency on the overall system performance. Also, it allows the accurate quantification of the signal to noise ratio required in target quality of service requirements under different composite fading conditions.

The Beckmann fading is a general multipath fading model which includes Rice, Hoyt and Rayleigh fading as particular cases. However, the generality of the Beckmann fading also implies a significant increased mathematical complexity. Thus, relatively few analytical results have been reported for this otherwise useful fading model. The performance of energy detection for multi-branch receivers operating under Beckmann fading is here studied, and the inherent analytical complexity is here circumvented by the derivation of a closed-form expression for the generalized moment generating function (MGF) of the received signal-to-noise ratio (SNR), which is a new and useful result, as it is key for evaluating the receiver operating characteristics. The impact of fading severity on the probability of missed detection is shown to be less critical as the SNR decreases. Monte Carlo simulations have been carried out in order to validate the obtained theoretical expressions.

The incomplete moment generating function (IMGF) has paramount relevance in communication theory, since it appears in a plethora of scenarios when analyzing the performance of communication systems. We here present a general method for calculating the IMGF of any arbitrary fading distribution. Then, we provide exact closed-form expressions for the IMGF of the very general κ-μ shadowed fading model, which includes the popular κ-μ, η-μ, Rician shadowed, and other classical models as particular cases. We illustrate the practical applicability of this result by analyzing several scenarios of interest in wireless communications: 1) physical layer security in the presence of an eavesdropper; 2) outage probability analysis with interference and background noise; 3) channel capacity with side information at the transmitter and the receiver; and 4) average bit-error rate with adaptive modulation, when the fading on the desired link can be modeled by any of the aforementioned distributions.

The Beckmann distribution is a general multipath fading model for the received radio signal in the presence of a large number of scatterers, which can thence be modeled as a complex Gaussian random variable where both the in-phase and quadrature components have arbitrary mean and variance. However, the complicated nature of this distribution has prevented its widespread use and relatively few analytical results have been reported for this otherwise useful fading model. In this paper, we derive a closed-form expression for the generalized moment-generating function (MGF) of the signal-to-noise ratio (SNR) of Beckmann fading, which permits to circumvent the inherent analytical complexity of this model. This is a new and useful result, as it is a key for evaluating several important performance metrics of different wireless communication systems and also permits to readily compute the moments of the output SNR. Thus, we obtain simple exact expressions for the energy detection performance in Beckmann fading channels, both in terms of the receiver operating characteristic (ROC) curve and of the area under ROC curve. We also analyze the outage probability in interference limited systems affected by Beckmann fading, as well as the outage probability of secrecy capacity in wiretap Beckmann fading channels. Monte Carlo simulations have been performed to validate the derived expressions.

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-q) fading in a very simple way. We illustrate that many performance metrics for Hoyt fading can be calculated by leveraging well-known results for Rayleigh fading and only performing a finite-range integral. We use this technique to obtain novel results for some information and communication-theoretic metrics in Hoyt fading channels.

We introduce the fluctuating two-ray (FTR) fading model, a new statistical channel model that consists of two fluctuating specular components with random phases plus a diffuse component. The FTR model arises as the natural generalization of the two-wave with diffuse power (TWDP) fading model; this generalization allows its two specular components to exhibit a random amplitude fluctuation. Unlike the TWDP model, all the chief probability functions of the FTR fading model (PDF, CDF, and MGF) are expressed in closed-form, having a functional form similar to other state-of-the-art fading models. We also provide approximate closed-form expressions for the PDF and CDF in terms of a finite number of elementary functions, which allow for a simple evaluation of these statistics to an arbitrary level of precision. We show that the FTR fading model provides a much better fit than Rician fading for recent small-scale fading measurements in 28 GHz outdoor mm-wave channels. Finally, the performance of wireless communication systems over FTR fading is evaluated in terms of the bit error rate and the outage capacity, and the interplay between the FTR fading model parameters and the system performance is discussed. Monte Carlo simulations have been carried out in order to validate the obtained theoretical expressions.

A channel capacity analysis is presented in this work for a spectrum-sharing cognitive radio link in which the fading experienced by the signal is modeled with the Hoyt (Nakagami-q) distribution. Based on a novel formulation of the squared Hoyt distribution derived by the authors, simple expressions for the capacity of the secondary link in a number of scenarios of interest are derived, which are given in terms of easy-to-compute finite-range integrals of elementary functions. The effect of fading severity in the secondary transmitter-primary receiver (ST-PR) and secondary transmitter-secondary receiver (ST-SR) links, and the impact of different antenna gains on the system performance are analyzed. We show that in the presence of severe fading for the ST-PR link, the capacity of the ST-SR link is increased.

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 squared Hoyt distribution, can be constructed from a conditional exponential distribution. Leveraging this approach, we provide novel results on the Shannon capacity of adaptive transmission techniques in Hoyt fading channels, showing that the asymptotic capacity loss per bandwidth unit in the high-SNR regime is up to 1.83 bps/Hz, compared to the AWGN case.

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.

This work presents exact closed-form expressions for the channel capacity of wireless communication systems with multiple receive antennas under correlated Rayleigh fading, where spatial diversity is exploited with the maximal ratio combining (MRC) technique. Instantaneous channel state information is assumed to be known at both the transmit and receive ends, allowing different adaptation strategies to optimize the performance. Unlike previous related works, correlation among the receive antennas is assumed to be arbitrary and no particular requirement about the eigenvalues of the correlation matrix is considered. Additionally, the average received power per antenna is assumed to be also arbitrary.

Closed-form expressions for the average symbol error rate (ASER) of general rectangular quadrature amplitude modulation (QAM) in Rayleigh fading are derived in this work for MIMO MRC systems. The number of antennas are assumed to be arbitrary at both the transmit and receive ends. An expression is derived in terms of a finite summation where all the terms are explicitly given and can be easily calculated. Additionally, a compact result is also provided in terms of coefficients which must be numerically computed. Monte Carlo simulations have also been carried out, showing an excellent agreement with the theoretical results.

This work explores the average bit error rate (BER) of uncoded MIMO systems in Rayleigh fading channels with co-channel interference (CCI) and background noise. We consider that maximal ratio transmission (MRT) is used at the transmit end. At the receiver we consider two different schemes: maximal ratio combining (MRC) and interference cancellation (IC) via null steering of the receive array radiation pattern. We provide analytical expressions of the BER for different modulation techniques and provide a comparison between the two proposed receiver schemes.

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.

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.

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), whereas the transmit antenna that maximize the instantaneous post-processing signal-to-noise ratio (SNR) is selected. We consider an independent but non- identically distributed (i.n.d.) 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 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 For the case when fading parameters take any real value, our results are given in terms of the multivariate Lauricella hypergeometric function FA(n). Monte Carlo simulations are shown to validate our theoretical analysis.

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.

We provide a comparative performance of two different array processing techniques in a wireless system with multiple receive antennas in fading channels with co-channel interference (CCI). The signal from the desired user at the receive antenna array is assumed to be affected by Rice, Nakagami or Rayleigh fading, while CCI signals are assumed to experience Rayleigh fading. We provide analytical expressions for the outage probability and provide a comparative performance of MRC (to provide diversity) and IC (to cancel the strongest interferers). Our 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.

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.

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.

This paper presents an approach for determining the benefits of macrodiversity on the uplink channel of cellular CDMA networks with fast power control under multipath fading. The case of single cell-site reception, where mobiles connect to only one base station on a minimum attenuation basis, is compared with the case of simultaneous reception of the users' signal by multiple base stations, also known as macrodiversity or cell-site diversity. It is shown that the use of macrodiversity results in a significant increase in the uplink system capacity.

We show the results of the evaluation of the downlink capacity of CDMA systems by using simulation. The proposed simulator analyses the system performance with time by measuring the power received by each mobile terminal from its own cell site and the total energy from all the cell site transmitters. Both measurements depend on path losses and on the traffic model. The introduction of the behavioural models of a wide range of services, which are expected to be supported by third generation (3G) wireless networks, is the most important benefit of the proposed simulation technique. A 3G system based on WCDMA, such as UMTS (Universal Mobile Telecommunication System) is evaluated considering voice traffic and a complex data traffic such as Web browsing.

Close form analytical expressions are derived for the outage probability of predetection maximal ratio combiner (MRC) diversity reception with M branches in both Rayleigh and Nakagami-m fading channels. This formulation is obtained in the presence of the white Gaussian noise and Q interferers, without restrictions about the power, number or distribution parameters of interferers. Closed-form expressions are derived and results are easily computable.

In this paper, the reverse link capacity is analysed for a multicode direct sequence-code division multiple access (multicode DS/CDMA) system with SIR-based power-control in a multiple-cell environment. Mean and variance statistics of total interference power are derived in order to investigate the effect of two important factors on capacity: (1) the required signal to interference ratio (SIR) and (2) the required number of codes, for each type of user. Unlike most previous works related to SIR-based power control, the effect of multipath fading is explicitly accounted for and mobiles are assumed to connect to the base station whose pilot signal is received with the highest power.

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.

This paper analyses the reverse link capacity of a SIR-based power-controlled code-division multiple access (CDMA) system in a multiple-cell environment where the radio channel is affected by multipath Rayleigh fading. Unlike most previous works related to SIR-based power control, the effect of multipath fading is explicitly accounted for and mobiles are assumed to connect to the base station whose pilot signal is received with the highest power. In other papers the derivation of the interference statistics has been greatly simplified since the intracell interference was considered constant. However, in our analysis a complete characterization of the intracell interference statistics is also derived.

This paper deals with the study of the uplink mechanisms of medium access within an UTRA system which offers the possibility of holding on to voice and data services. The voice service is beamed off through a dedicated channel whereas a common channel is used for a very widespread service nowadays like the Web traffic. The first investigations on homogeneous systems reveal that the access channel is longer occupied in the data system than in the voice system. The simulations related to the integrated voice and data system show that, in spite of the fact that the voice experiences a greater delay than in the homogeneous system, the QoS parameters for voice and data are guaranteed with no need to use all the available system resources. Following this, the integrated system allows for certain losses in the common RACH (random access channel).