In this paper, the performance of opportunistic user scheduling in reconfigurable intelligent surface (RIS)-aided multiuser communications is investigated by invoking 1-bit coding scheme. In particular, we derive new expressions for the outage probability (OP) and delay outage rate (DOR) by leveraging copula theory to model a two-fold interdependency stemming from the presence of discrete phase noise and a shared channel. We also provide simplified expressions for the OP and DOR using Clayton and Gumbel copulas. The newly derived expressions reveal the effects of different channel and RIS parameters simply. Finally, numerical results are provided to validate the derived exact closed-form expressions.

Reconfigurable intelligent surface (RIS) has received remarkable attention for its potential to improve the capacity and coverage of wireless communication networks. In this paper, we evaluate the performance of RIS-assisted communication systems in the presence of phase noise with the help of Student-T copula in two scenarios. The first one is the cascade link or RIS link and the second scenario involves direct link in conjunction with cascade link. In particular, we first analyze the probability density function and the cumulative distribution function of the signal-to-noise-ratio with/without direct link. Then, we investigate the outage probability and ergodic capacity of the RIS-assisted network by using Student- T copula function to characterize the non-linear dependency among the signal components. Furthermore, we reveal the relation between the Student- T copula dependency parameter and Pearson correlation coefficient. Finally, numerical results are presented confirm the validity of the analytical closed-form expressions.

User-centric base station (BS) deployment has been designed for the fifth-generation (5G) dense millimeter wave (mmWave) networks for alleviating the inter-cell interference and improving the cell-edge user experience. However, the system power consumption increases sharply with the network density. In this paper, we investigate a user-centric simultaneous wireless information and power transfer (SWIPT) mmWave system employing a time-switching protocol at users to allow both energy harvesting (EH) and data decoding. To enable user-centric BS cooperation, adaptive BS clustering model is used to determine the user’s serving cluster based on its channel condition. Considering both linear and non-linear EH models, we analyze the joint coverage, namely, the probability that the user harvests enough energy in a given time slot and receives the required data from its serving cluster. The random serving clusters and the correlation between the amount of harvested energy and received data rate make the joint coverage analysis more challenging. A tractable tight approximation of the joint coverage probability is thus derived for ultra-dense networks. A mathematical optimization model for the time switching coefficient is also developed to maximize the system joint rate and energy coverage performance. All mathematical expressions are validated by Monte-Carlo simulations. Our results show that the proposed analytical framework is accurate and efficient for the design and deployment of SWIPT-enabled user-centric mmWave networks.

This paper investigates a user-centric clustering model for a hybrid network comprising both millimeter-wave (mmWave) and terahertz (THz) base stations (BSs). Based on the proposed model, a user can choose to be cooperatively served by multiple mmWave or multiple THz BSs depending on their link quality. Besides, to maximize the cooperation gains, the serving clusters are dynamically adjusted to user's channel conditions pertaining to the different properties of the mmWave and THz networks. Finally, we evaluate the coverage probability of the hybrid network by using stochastic geometric tools and validate the analysis through numerical simulations.

The user-centric base station cooperation is a new approach that allows a mobile user to be connected to a set (cluster) of base stations instead of being associated with a single one. This approach is highly valuable in millimeter wave networks where the base stations are expected to be densely deployed. In this paper, we evaluate the performance, in terms of coverage probability, of user-centric millimeter wave networks with dynamic clustering. First, we propose a dynamic clustering model for base stations that will cooperate to serve a given user. Then, based on the proposed model, we investigate analytically the coverage probability performance of the considered user-centric network using stochastic geometry tools. Finally, numerical and simulation results are provided, showing that the proposed dynamic clustering model always outperforms static clustering and single base station selection schemes for given network parameters.

In millimeter wave (mmWave) networks, base stations (BSs) are expected to be densely deployed in order to meet the demands of mobile users. A major challenge in dense mmWave networks is the interference experienced by the user from the neighboring BSs which limits the density of deployed BSs. A promising solution to this challenge is to adopt user-centric BS cooperation that allows a user to be connected to a set (cluster) of BSs instead of being associated with a single one. In this paper, we investigate the performance of user-centric mmWave networks with dynamic clustering. First, we propose a dynamic clustering model to enable the user-centric BS cooperation. Then, based on the proposed model, we analyze the coverage probability and average spectral efficiency (ASE) performances using stochastic geometry tools. We also propose a BS clustering optimization framework to achieve maximum ASE performance for given network configuration. Finally, numerical and simulation results are provided, showing that the proposed dynamic clustering schemes always outperform static clustering and single-BS selection schemes and yield an optimum system performance for given network parameters.

In this paper, we develop an innovative approach to quantitatively characterize the performance of ultra-dense wireless networks in a plethora of propagation environments. The proposed framework has the potential of simplifying the cumbersome procedure of analyzing the coverage probability and allowing the unification of single- and multi-antenna networks through compact analytical representations. By harnessing this key feature, we develop a novel statistical machinery to study the scaling laws of wireless networks densification considering general channel power distributions including small-scale fading and shadowing as well as associated beamforming and array gains due to the use of multiple antenna. We further formulate the relationship between network density, antenna height, antenna array seize and carrier frequency showing how the coverage probability can be maintained with ultra-densification. From a system design perspective, we show that, if multiple antenna base stations are deployed at higher frequencies, monotonically increasing the coverage probability by means of ultra-densification is possible, and this without lowering the antenna height. Simulation results substantiate performance trends leveraging network densification and antenna deployment and configuration against path loss models and signal-to-noise plus interference thresholds.

In this paper, we consider multi-aperture multiuser dual-hop amplify-and-forward (AF) free-space optical/radio frequency (FSO/RF) communication systems. The FSO-RF channels are assumed to follow Málaga- M/shadowed κ-μ fading models with pointing errors on the FSO links. Under the assumption of transmit aperture selection at the source and opportunistic user scheduling at the destination, we derive exact closed-form expressions for the outage probability and average symbol error probability (SEP). Additionally, the system performance is studied at the high signal-to-noise ratio (SNR) regime where an approximate expression for the system outage probability is derived, in addition to deriving the system diversity order and coding gain.

This paper embodies the Fox's H-transform theory into a unifying modeling and analysis of HetNets. The proposed framework has the potential, due to the Fox's N-functions versatility, of significantly simplifying the cumbersome analysis and representation of cellular coverage, while subsuming those previously derived for all known simple and composite fading models. The paper reveals important insights into the practice of densification in conjunction with signal-to-noise plus interference (SINR) thresholds and path-loss models.

This paper develops an innovative approach to the modeling and analysis of downlink cellular networks with device-to-device (D2D) transmissions. The analytical embodiment of the signal-to-noise and-interference ratio analysis in general fading channels is unified due to the H-transform theory, a taxonomy never considered before in stochastic geometry-based cellular network modeling and analysis. The proposed framework has the potential, due to versatility of the Fox's H functions, of significantly simplifying the cumbersome analysis procedure and representation of D2D and cellular coverage, while subsuming those previously derived for all the known simple and composite fading models. By harnessing its tractability, the developed statistical machinery is employed to launch an investigation into the optimal design of coexisting D2D and cellular communications. We propose novel coverage-aware power control combined with opportunistic access control to maximize the area spectral efficiency (ASE) of D2D communications. Simulation results substantiate performance gains achieved by the proposed optimization framework in terms of cellular communication coverage probability, average D2D transmit power, and the ASE of D2D communications under different fading models and link- and network-level dynamics.

We investigate the performance of mixed free-space optical (FSO)/millimeter-wave (mmWave) relay networks with interference at the destination. The FSO/mmWave channels are assumed to follow Málaga-M/generalized-K fading models with pointing errors in the FSO link. The H-transform theory, wherein integral transforms involve Fox's H-functions as kernels, is embodied to unifying the performance analysis framework that encompasses closed-form expressions for the outage probability, the average bit error rate (BER), and the average capacity. By virtue of some H-transform asymptotic expansions, the high signal-to-interference-plus-noise ratio (SINR) analysis reduces to easy-to-compute expressions for the outage probability and BER, which reveals inside information for the system design. We finally investigate the optimal power allocation strategy that minimizes the outage probability.

In this paper, we unify the performance analysis for the outage probability (OP) and the bit-error rate (ABER) of relay-assisted dual-hop free-space optics (FSO) transmission under heterodyne detection and intensity modulation/direct detection (IM/DD). The FSO link experiences the generalized Malaga-m distribution with pointing errors. under the assumption of fixed and variable gain relaying schemes, we derive the analytical closedform expressions for the performance metrics in terms of bivariate Fox-H function (FHF). Finally, we present some Monte-carlo simulation results to corroborate the new derived expressions.

Statistical characterization of the signal-to-interference-plus-noise ratio (SINR) via its cumulative distribution function (CDF) is ubiquitous in a vast majority of technical contributions in the area of cellular networks since it boils down to averaging the Laplace transform of the aggregate interference, a benefit accorded at the expense of confinement to the simplistic Rayleigh fading. In this work, to capture diverse fading channels that appear in realistic outdoor/indoor wireless communication scenarios, we tackle the problem differently. By exploting the moment generating function (MGF) of the SINR, we succeed in analytically assessing cellular networks performance, namely the achievable rate and and the bit error probability (BEP), over the shadowed κ-μ, κ-μ and η-μ fading models. These models offer higher flexibility to capture diverse and more realistic fading environments than the classical Rayleigh, Nakagami-m, and Rician ones.

This paper investigates the impact of radio frequency (RF) cochannel interference (CCI) on the performance of dual-hop free-space optics (FSO)/RF relay network. The considered FSO/RF system operates over mixed Malaga-M/composite fading/shadowing generalized-K (GK) channels with pointing errors. The H-transform theory, wherein integral transforms involve Fox's H-functions as kernels, is embodied into a unifying performance analysis framework that encompasses closed-form expressions for the outage probability, the average bit error rate (BER), and the ergodic capacity. By virtue of some H-transform asymptotic expansions, the high signal-to-interference-plus-noise ratio (SINR) analysis culminates in easy-to-compute expressions of the outage probability and BER.

This paper provides an analytically tractable framework for investigating a fading model-free statistical distribution of the signal-to-interference-plus-noise power ratio (SINR) in Poison distributed cellular networks subject to device-to-device (D2D) transmissions. Our main finding show that a closed-form SINR distribution may be obtained for any fading scenario in which the per-link power gain follows the product of two Fox's H-function probability density function thereby subsuming most of the coverage probability expressions previously presented for all the known simple and composite fading models.

Statistical characterization of the signal-tointerference-plus-noise ratio (SINR) via its cumulative distribution function is ubiquitous in a vast majority of technical contributions in the area of cellular networks, since it boils down to averaging the Laplace transform of the aggregate interference, a benefit accorded at the expense of confinement to the simplistic Rayleigh fading. In this paper, to capture diverse fading channels that arise in realistic outdoor/indoor wireless communication scenarios, we tackle the problem differently. By exploiting the moment generating function of the SINR, we succeed in analytically assessing cellular networks performance over the shadowed κ-μ, κ-μ, and η-μ fading models. These channel models offer high flexibility by capturing diverse fading channels, including Rayleigh, Nakagami-m, Rician, and Rician shadow fading distributions. These channel models have been recently promoted for their capability to accurately model dense urban environments, future femtocells, and device-to-device shadowed channels. In addition to unifying the analysis for different channel models, this paper integrates the coverage, the achievable rate, and the bit error probability, which are largely treated separately in the literature. The developed model and analysis are validated over a broad range of simulation setups and parameters.

In this paper, the asymptotic performance of multiuser multiple-antenna (MU-MIMO) relay networks employing opportunistic scheduling and operating in the presence of Rayleigh fading and co-channel interference is investigated. Notwithstanding the system complexity, due to the newly found complementary moment generating function (CMGF) transform, an exact expression for the capacity, when the antenna counts at the source and the user number are allowed to grow unbound, is obtained. The large scale analysis embodies popular observations, so far intuitively or empirically disclosed, through analytically insightful new formulas. An interesting aspect of this analysis comes from an altered view of multiuser diversity in the context of cellular systems. Previously, multiuser diversity capacity gain has been known to grow as 0(ln ln(K)), from selecting the maximum of K exponentially-distributed powers. Because interference aware scheduling is considered, we find instead that the gain is 0(ln(K1/Q)) where Q is the number of interferers. Simulation results indicate a rather fast convergence to the asymptotic limits with the system's size, thereby demonstrating the practical importance of the scaling results.

The ergodic capacity of multiuser multiple-antenna amplify and forward relay networks with co-channel interference is investigated. Notwithstanding the system complexity, the proposed capacity analysis framework was made possible owing to the newly found complementary moment generating function transform. First, the exact expression for the ergodic capacity, under interference-aware opportunistic scheduling and Rayleigh fading, is derived for finite antenna and user counts. In addition, using extreme value theory, closed-form expressions for the asymptotic ergodic rates are derived for an unlimited number of users or/and antennas at the source. The large-scale analysis embodies, through new insightful formulas, common popular observations so far disclosed intuitively or empirically. Capitalizing on these novel scaling laws, we have been able to derive new closed-form expressions for capacity losses due to intercell interference at the relay and all users. Simulation results suggest a rather fast convergence of the capacity gains to the new asymptotic limits, thereby demonstrating the practical importance of our novel scaling results.

In this paper, we analyze the ergodic capacity of a two-hop multiple-antenna amplify and forward (AF) system, where the relay is subject to co-channel interference (CCI) while the destination is corrupted by additive white Gaussian noise (AWGN) only. A novel integral transform, called the complementary moment generating function transform (CMGF), is proposed as a unified tool to compute the ergodic capacity. When both the relay and destination perform maximum ratio combining (MRC), we derive a new analytical exact expression for the ergodic capacity. It is shown that the ergodic capacity is better improved by increasing the number of antennas at the relay Nrthan that at destination Nd. Unfortunately, the system shows an incapability of canceling interference even if Nrand/or Ndgrows large.

This paper investigates spectrum-sharing cognitive amplify-and-forward (AF) relay networks employing the maximum ratio transmission/maximum ratio combining (MRT/MRC) scheme at the multiple-antenna source-destination pair. It derives closed-from expressions for the ergodic capacity as well as for the symbol error rate (SER) lower bound and its asymptotic value when considering Nakagami-m fading and interference constraints on N primary receivers.

This paper evaluates the ergodic capacity of secondary dual-hop cognitive amplify-and-forward (AF) relay networks (CRNs) subject to arbitrary Nakagami-m fading. Considering a spectrum-sharing environment, we assume that the transmit power of secondary users is solely governed by the interference power constraint at N primary users. A closed-form expression for the ergodic capacity of the secondary AF CRN is derived for the first time and shown to be affected by the distance ratio of the interference link (from the secondary transmitter to the closest primary receiver) to the relaying link (between the secondary transmitter and the secondary receiver). This new ergodic capacity expression is validated and assessed by insightful simulations against different key CRN parameters.

Relay deployment performance, such as site planing and dimensioning, highly depends on the capacity of the wireless relay link. However, latter's performance can be severely harmed due to cochannel interference (CCI), particularly with the current aggressive reuse of the available radio spectrum. In this paper, we present an analytical framework for amplify-and-forward (AF) relay capacity that can be used for the deployment of two-hop cellular relay networks operating over generalized fading channels in the presence of cochannel interference. Nakagami-m and generalized-K distributions are used to model the relay and interference links in multipath and composite multipath/shadowing environments, respectively. Multiple antenna AF relaying systems employing transmit beamforming and maximum ratio combining (TB/MRC) are also investigated in the presence of CCI. The derived analytical results provide an efficient mathematical tool for the fast evaluation of the ergodic capacity of the system as well as for the investigation of the impact of key parameters such as fading, shadowing, number of antennas and CCI on the system's ergodic capacity.

An analytical characterization of the ergodic capacity of interference-limited multihop wireless networks with amplify-and forward (AF) relaying is presented. In our analysis, we consider that transmissions are performed over Nakagami-m fading where channel state information is only known at the receiving terminals. We derive an exact expression for the ergodic capacity by exploiting the moment generating function (MGF) of the inverse signal-to-interference ratio (SIR). The result is applicable for arbitrary numbers of interfering signals at the receiving terminals and can be efficiently evaluated. Furthermore, considering the special case of dual-hop transmission, we propose a more refined characterization where the high-SIR capacity is expanded as an affine function. The zero-order term or the power offset for which we find insightful closed-form expressions, is shown to play a chief role in understanding the impact of interference and power on the system's capacity. Finally, some simulation results sustaining our analysis are provided.

Integrating relaying techniques into cellular communications sheds new light on higher capacity and broader coverage. However, applying relaying techniques in practice has to take into account important issues such as co-channel interference (CCI). In this work, a generalized framework for the ergodic capacity analysis of dual-hop fixed-gain amplify and forward (AF) relaying systems in the presence of interference is presented. New expressions for the ergodic capacity are derived considering transmissions over independent but not necessarily identically distributed Nakagami-m fading channels in the presence of a finite number of co-channel interferers. Our results establish that the ergodic capacity is dominated by the source-relay interference power and that it improves slowly with the average signal-to-noise ratio (SNR) increasing. It slightly deteriorates, however, with a larger Nakagami-m fading parameter for interference channels. Furthermore, our results offer an analytical insight into the key impact of relay placement on performance. Our new ergodic capacity expressions could therefore provide a very practical/low-cost performance optimization tool for relayed-communication system designers.

Closed-form error analysis of dual-hop fixed-gain amplify-and-forward (AF) relaying systems for transmissions over Nakagami fading channels has, so far, been tractable only with integer fading parameters. For the general Nakagami-m fading with arbitrary m values, the exact closed-form error analysis is more challenging. This paper goes toward solving this problem by deriving a unified error analysis framework that embraces several general modulation schemes. The obtained Error Probability (EP) expressions involve common functions which can be efficiently evaluated using standard numerical softwares. This work represents a significant improvement on previous contributions, not only by unifying the error probability expressions pertaining to dual-hop fixed gain relaying over integer Nakagami-m fading, but also by extending them to the general arbitrary Nakagami-m fading. Simulation results sustaining our analysis are provided, and the impacts of various parameters on the overall AF relaying system performance are investigated.

In this paper, we introduce the Inverse Gaussian (IG) fading distribution to model the envelope and the power of the received signal in radio propagation fading channels and free-space optical (FSO) channels. The joint distribution of the IG process and its derivative and the marginal distribution of the derivative are developed. The obtained formulas are then used to derive the second-order statistics of the received signal envelope and the channel capacity under IG and Nakagami-IG (NIG) fading distributions. Numerical results sustaining our analysis are provided, and the impacts of various parameters on the system performance are investigated.

In this paper, infinite integrals involving the product of Bessel functions of different arguments are solved in closed-form. The obtained solutions form a framework for the error probability analysis of wireless amplify and forward (AF) systems with an arbitrary number of variable-gain relays operating over independent but not necessarily identical Nakagami-m fading channels. Here we show that the error probability can be described by generalized hypergeometric functions, namely, Gauss's and Lauricella's multivariate hypergeometric functions. This work represents a significant improvement over previous contributions and extends previous formulas pertaining to dual-hop transmissions over identical Nakagami-m fading channels. Numerical examples show an excellent match between simulation and theoretical results.

In this paper, infinite integrals involving the product of Bessel functions of different arguments are solved in closed-form. These solutions provide novel expressions in the error rate analysis for wireless amplify and forward (AF) systems with an arbitrary number of variable-gain relays. Here we show that the error probability can be described by generalized hypergeometric functions, namely Lauricella functions. This work represents a significant improvement on previous contributions and extends previous formulas pertaining to dual-hop transmissions over identical Nakagami-m fading channels. Numerical examples show an excellent match between simulation and theoretical results.

In this paper we investigate the end-to-end performance of dual-hop fixed gain relaying systems under asymmetric fading conditions. In such conditions, the links associated with the relay network undergo different fading phenomena. In our analysis, the source-relay and the relay-destination links are subject to fading-only or composite multi-path/shadowing environments. An outage analysis of the considered system is performed and the proposed expressions are applicable to general fading and shadowing conditions. Based on the newly derived analytical expressions of the cumulative distribution function (CDF) of the end-to-end signal to noise ratio (SNR), the average bit error probability of arbitrary rectangular QAM modulations is also computed. Some representative numerical examples of the system performance in terms of the above metrics are provided and discussed. For instance, it is confirmed analytically that the relaying system exhibits better performance when the first hop undergoes better channel conditions.

In this paper we investigate the end-to-end performance of dual-hop relaying systems over non identical-Nakagami-m fading channels. Our analysis considers channel state information (CSI-) assisted relays that just amplify and retransmit the information signal also known as "non-regenerative" relays. New closed-form expressions for the average bit error probability (ABEP) are derived. The proposed expressions apply to general operating scenarios with distinct Nakagami-m fading parameters and average signal to noise ratios (SNRs) between the hops. When the fading parameter is an odd multiple of one half, the ABEP is expressed in terms of hypergeometric functions. When m takes any real non integer value, the obtained results involve the fourth Appell's hypergeometric function. For an arbitrary fading parameter, an analysis of such a scheme is performed using the well known moment-based approach.

A novel distribution referred to as N*generalized K, constructed as the product of N statistically independent, but not necessarily identically distributed, generalized K random variables (RVs) is introduced. Statistical characterization of the proposed distribution is carried out via the derivation of closed-form expressions for its moment generating, probability density, cumulative distribution and moment functions. Using the obtained formulas, we present new closed-form expressions for the outage probability, the bit error probability and the average channel capacity of a digital communication system operating over the N cascaded generalized K distributed channels.

This paper presents an outage analysis of wireless systems operating in gamma-shadowed Nakagami-faded environments where the desired signal also suffers from co-channel interference. The interfering signals are also subject to fading and shadowing. Based on the obtained signal to interference ratio (SIR) probability density function (pdf), closed- form expressions for the outage probability are obtained in both cases of statistically identical interferers and multiple interferers with different parameters. The effects on the aforementioned performance metric of the reuse distance and of the combined fading, shadowing and co-channel interference are analyzed subsequently. The newly derived closed-form expressions for the outage probability allow as to assess the effects of the different channel and interference parameters easily.

This paper presents an analytical framework for performance evaluation of mobile radio systems operating in composite fading/shadowing channels in the presence of colocated co-channel interference. The desired user and the interferers are subject to Nakagami fading superimposed on gamma shadowing. The paper starts by presenting generic closed-form expressions for the signal-to-interference ratio (SIR) probability density function (pdf). From this pdf, closed-form expressions for the outage probability, the average bit error rate and the channel capacity are obtained in both cases of statistically identical interferers and multiple interferers with different parameters. The newly derived closed-form expressions of the aforementioned metrics allow us to easily assess the effects of the different channel and interference parameters. It turns out that the system performance metrics are predominantly affected by the fading parameters of the desired user, rather than by the fading parameters of the interferers.

In this paper, we consider composite multipath/shadowing fading channels characterized by Nakagami- m fading with inverse Gaussian shadowing, and Rice fading with inverse Gaussian shadowing. These channel models are very convenient for land mobile satellite systems and communications with low mobility or stationary users. From an analytical standpoint, one major advantage of these models is that they lead to closed-from expressions for the envelope probability density function (pdf) and the cumulative density function (CDF). Moreover, in this paper, we derive mathematically tractable new expressions for fundamental channel statistics such as the level crossing rate (LCR) and the average fade duration (AFD). Also, we validate our analytical results by providing several numerical examples showing the LCR and the AFD as a function of the Nakagami-m factor, Rice factor, and shadowing spread.

In this paper, we consider a pulse shaping OFDM/BFDM system operating over a doubly dispersive channel. We propose to search the optimal pulse maximizing the signal to interference ratio (SIR). We show that the impact of interference, composed by both inter-symbol interference (ISI) and inter-carrier interference (ICI), occurring in such a system, depends crucially on time frequency localization of transmit and receive pulses. We propose to maximize the SIR, written as a ratio of two quaternary forms, by altering between transmit and receive pulse spaces both generated by Hermite Waveforms. Numerical results show that optimized BFDM systems can outperform conventional OFDM systems with respect to SIR. In fact, biorthogonality offers more freedom to design pulses improving robustness of the multi-carrier system against channel dispersion.