Showing papers on "Fading distribution published in 2014"
TL;DR: It is shown that the sum and maximum distributions of independent but arbitrarily distributed κ - μ shadowed variates can be expressed in closed form and this set of new statistical results is finally applied to modeling and analysis of several wireless communication systems, e.g., the proposed distribution has applications to land mobile satellite (LMS) communications and underwater acoustic communications (UAC).
Abstract: This paper investigates a natural generalization of the κ - μ fading channel in which the line-of-sight (LOS) component is subject to shadowing. This fading distribution has a clear physical interpretation and good analytical properties and unifies the one-side Gaussian, Rayleigh, Nakagami- m, Rician, κ - μ, and Rician shadow fading distributions. The three basic statistical characterizations, i.e., probability density function (pdf), cumulative distribution function (cdf), and moment-generating function (mgf), of the κ - μ shadowed distribution are obtained in closed form. Then, it is also shown that the sum and maximum distributions of independent but arbitrarily distributed κ - μ shadowed variates can be expressed in closed form. This set of new statistical results is finally applied to modeling and analysis of several wireless communication systems, e.g., the proposed distribution has applications to land mobile satellite (LMS) communications and underwater acoustic communications (UAC).
183 citations
TL;DR: This work derives the success probability, spatial average rate, and area spectral efficiency performances for both cellular users and D2D users by taking into account the different channel propagations that they experience by employing stochastic geometry as an analysis framework to derive closed-form expressions for above performance metrics.
Abstract: Using Device-to-device (D2D) communications in a cellular network is an economical and effective approach to increase the transmission data rate and extend the coverage. Nevertheless, the D2D underlaid cellular network is challenging due to the presence of inter-tier and intra-tier interferences. With necessarily lower antenna heights in D2D communication links, the fading channels are likely to contain strong line-of-sight components, which are different from the Rayleigh fading distribution in conventional two-tier heterogeneous networks. In this paper, we derive the success probability, spatial average rate, and area spectral efficiency performances for both cellular users and D2D users by taking into account the different channel propagations that they experience. Specifically, we employ stochastic geometry as an analysis framework to derive closed-form expressions for above performance metrics. Furthermore, to reduce cross-tier interferences and improve system performances, we propose a centralized opportunistic access control scheme as well as a mode selection mechanism. According to the analysis and simulations, we obtain interesting tradeoffs that depend on the effect of the channel propagation parameter, user node density, and the spectrum occupation ratio on the different performance metrics. This work highlights the importance of incorporating the suitable channel propagation model into the system design and analysis to obtain the realistic results and conclusions.
149 citations
TL;DR: This paper quantifies the gain of SIC on the coverage probability in HCNs with nonaccessible base stations and suggests that the marginal benefit of enabling the receiver to successively decode k users diminishes very fast with k, especially in networks of high dimensions and small path loss exponent.
Abstract: This paper provides a unified framework to study the performance of successive interference cancellation (SIC) in wireless networks with arbitrary fading distribution and powerlaw path loss. An analytical characterization of the performance of SIC is given as a function of different system parameters. The results suggest that the marginal benefit of enabling the receiver to successively decode k users diminishes very fast with k, especially in networks of high dimensions and small path loss exponent. On the other hand, SIC is highly beneficial when the users are clustered around the receiver and/or very low-rate codes are used. In addition, with multiple packet reception, a lower per-user information rate always results in higher aggregate throughput in interference-limited networks. In contrast, there exists a positive optimal per-user rate that maximizes the aggregate throughput in noisy networks. The analytical results serve as useful tools to understand the potential gain of SIC in heterogeneous cellular networks (HCNs). Using these tools, this paper quantifies the gain of SIC on the coverage probability in HCNs with nonaccessible base stations. An interesting observation is that, for contemporary wireless systems (e.g., LTE and WiFi), most of the gain of SIC is achieved by canceling a single interferer.
118 citations
TL;DR: This paper derives approximate closed-form expressions of the probability density function and cumulative distribution function of the received signal-to-noise ratio of the MRC based receiver in SR fading LMS channels.
Abstract: In this paper, the maximal ratio combining (MRC) scheme in Shadowed-Rician (SR) fading land mobile satellite (LMS) channels is studied. The MRC scheme for SR fading LMS channels has been studied in existing literature; however, most of the existing analytical results are in the form of infinite power series, which are not in closed-form. In this paper, we derive approximate closed-form expressions of the probability density function and cumulative distribution function of the received signal-to-noise ratio of the MRC based receiver in SR fading LMS channels. Then we provide approximate closed-form expressions of the bit error rate (BER), outage probability, and capacity of the considered scheme. One of the derived closed-form BER expressions is found useful for obtaining the analytical diversity order and coding gain of the considered MRC scheme.
113 citations
TL;DR: A multiuser diversity FSO scheme in which the Nth best user is selected and the channel fluctuations can be effectively exploited to produce a selection diversity gain is proposed.
Abstract: Free-space optical (FSO) communication has become a cost-effective method to provide high data rates. However, the turbulence-induced fading limits its application to short-range applications. To address this, we propose a multiuser diversity (MD) FSO scheme in which the Nth best user is selected and the channel fluctuations can be effectively exploited to produce a selection diversity gain. More specifically, we first present the statistics analysis for the considered system over both weak and strong atmospheric turbulence channels. Based on these statistics, the outage probability, bit-error rate performance, average capacity, diversity order, and coverage are analyzed. Results show that the diversity order for the gamma-gamma fading is N min{α, β}/2, where N is the number of users, and α and β are the channel fading parameters related to the effective atmospheric conditions of the link.
89 citations
TL;DR: This paper proposes two general frameworks for analytically computing the outage probability at any arbitrary location of an arbitrarily-shaped finite wireless network: a moment generating function-based framework which is based on the numerical inversion of the Laplace transform of a cumulative distribution and a reference link power gain- based framework.
Abstract: This paper analyzes the outage performance in finite wireless networks. Unlike most prior works, which either assumed a specific network shape or considered a special location of the reference receiver, we propose two general frameworks for analytically computing the outage probability at any arbitrary location of an arbitrarily-shaped finite wireless network: (i) a moment generating function-based framework which is based on the numerical inversion of the Laplace transform of a cumulative distribution and (ii) a reference link power gain-based framework which exploits the distribution of the fading power gain between the reference transmitter and receiver. The outage probability is spatially averaged over both the fading distribution and the possible locations of the interferers. The boundary effects are accurately accounted for using the probability distribution function of the distance of a random node from the reference receiver. For the case of the node locations modeled by a Binomial point process and Nakagami-m fading channel, we demonstrate the use of the proposed frameworks to evaluate the outage probability at any location inside either a disk or polygon region. The analysis illustrates the location-dependent performance in finite wireless networks and highlights the importance of accurately modeling the boundary effects.
87 citations
TL;DR: A realistic analytic model is developed that accurately accounts for the interference correlation using stochastic geometry and derives the link success probability for dual-branch interference-aware MRC, showing that the common assumption that all receive antennas experience equal interference power underestimates the true performance.
Abstract: Despite being ubiquitous in practice, the performance of maximal-ratio combining (MRC) in the presence of interference is not well understood. Because the interference received at each antenna originates from the same set of interferers but partially decorrelates over the fading channel, it possesses a complex correlation structure. This paper develops a realistic analytic model that accurately accounts for the interference correlation using stochastic geometry. Modeling interference by a Poisson shot noise process with independent Nakagami fading, we derive the link success probability for dual-branch interference-aware MRC. Using this result, we show that the common assumption that all receive antennas experience equal interference power underestimates the true performance, although this gap rapidly decays with increasing the Nakagami parameter $m_{\rm I}$ of the interfering links. In contrast, ignoring interference correlation leads to a highly optimistic performance estimate for MRC, especially for large $m_{\rm I}$ . In the low outage probability regime, our success probability expression can be considerably simplified. Observations based from the analysis include the following: 1) For small path loss exponents, MRC and minimum mean square error combining exhibit similar performance, and 2) the gains of MRC over selection combining are smaller in the interference-limited case than in the well-studied noise-limited case.
57 citations
TL;DR: In this article, a hierarchical polar coding scheme was proposed for fading channels, focusing primarily on fading binary symmetric and additive exponential noise channels, and theoretical analysis and numerical results showed that the proposed coding scheme approaches the capacity in the high SNR regime.
Abstract: This work presents a polar coding scheme for fading channels, focusing primarily on fading binary symmetric and additive exponential noise channels. For fading binary symmetric channels, a hierarchical coding scheme is presented, utilizing polar coding both over channel uses and over fading blocks. The receiver uses its channel state information (CSI) to distinguish states, thus constructing an overlay erasure channel over the underlying fading channels. By using this scheme, the capacity of a fading binary symmetric channel is achieved without CSI at the transmitter. Noting that a fading AWGN channel with BPSK modulation and demodulation corresponds to a fading binary symmetric channel, this result covers a fairly large set of practically relevant channel settings. For fading additive exponential noise channels, expansion coding is used in conjunction to polar codes. Expansion coding transforms the continuous-valued channel to multiple (independent) discrete-valued ones. For each level after expansion, the approach described previously for fading binary symmetric channels is used. Both theoretical analysis and numerical results are presented, showing that the proposed coding scheme approaches the capacity in the high SNR regime. Overall, utilizing polar codes in this (hierarchical) fashion enables coding without CSI at the transmitter, while approaching the capacity with low complexity.
53 citations
TL;DR: In this paper, the authors investigated the fading correlation in multiple-aperture free-space optical (FSO) communication systems and its effect on the link performance and proposed an analytical approach to evaluate the performance of the space-diversity FSO system over a correlated Gamma-Gamma fading channel.
Abstract: This paper investigates fading correlation in space-diversity free-space optical (FSO) communication systems and its effect on the link performance. We firstly evaluate the fading correlation in multiple-aperture FSO systems using wave-optics simulations. The influence of different system parameters including the link distance and aperture spacing is illustrated under realistic beam propagation conditions. In particular, we show that, at relatively large link distances where the scattering disk is much larger than the receiver aperture size, the fading correlation coefficient is almost independent of the apertures' diameter and depends only on the apertures' edge separation. To investigate the impact of fading correlation on the system's performance, we propose an analytical approach to evaluate the performance of the space-diversity FSO system over a correlated Gamma–Gamma (ΓΓ) fading channel. Our approach is based on approximating the sum of arbitrarily correlated ΓΓ random variables by an α−μ distribution. To validate the accuracy of this method, we evaluate the average bit-error-rate (BER) performance for the case of a multiple-aperture FSO system and compare it with the BER results obtained via Monte Carlo simulations.
48 citations
TL;DR: This work investigates two important performance metrics of underlay cooperative cognitive radio (CR) networks: Interference cumulative distribution function of licensed users and outage probability of unlicensed users.
Abstract: This work investigates two important performance metrics of underlay cooperative cognitive radio (CR) networks: Interference cumulative distribution function of licensed users and outage probability of unlicensed users. These metrics are thoroughly analyzed in realistic operating conditions such as imperfect fading channel information and strict transmit power constraint, which satisfies interference power constraint and maximum transmit power constraint, over Nakagami-m fading channels. Novel closed-form expressions are derived and subsequently validated extensively through comparisons with respective results from computer simulations. The proposed expressions are rather long but straightforward to handle both analytically and numerically since they are expressed in terms of well known built-in functions. In addition, the offered results provide the following technical insights: i) Channel information imperfection degrades considerably the performance of both unlicensed network in terms of OP and licensed network in terms of interference levels; ii) underlay cooperative CR networks experience the outage saturation phenomenon; Hi) the probability that the interference power constraint is satisfied is relatively low and depends significantly on the corresponding fading severity conditions as well as the channel estimation quality; iv) there exists a critical performance trade-off between unlicensed and licensed networks.
45 citations
TL;DR: This paper analyzes the error probability and ergodic capacity performance for diversity reception schemes over generalized-K fading channels using a mixture gamma (MG) distribution, and shows that a distribution of the received SNR is composed of a weighted sum of gamma distributions by exploiting the properties of the MG distribution.
Abstract: In this paper, we analyze the error probability and ergodic capacity performance for diversity reception schemes over generalized-K fading channels using a mixture gamma (MG) distribution. With high accuracy, the MG distribution can approximate a variety of composite fading channel models and provide mathematically tractable properties. In contrast to previous analysis approaches that require complicated signal-to-noise ratio (SNR) statistics, it is shown that a distribution of the received SNR for diversity reception schemes is composed of a weighted sum of gamma distributions by exploiting the properties of the MG distribution. Then, based on this result, we can derive the exact average symbol error probability and simple closed-form expressions of diversity and array gains for maximal ratio combining and selection combining. In addition, an expression of the ergodic capacity for these schemes is obtained in independent and identically distributed fading channels. Our results lead to meaningful insights for determining the system performance with parameters of the MG distribution. We show that our analysis can be expressed with any number of receiver branches over various fading conditions. Numerical results confirm that the derived error probability and ergodic capacity expressions match well with the empirical results.
06 Apr 2014
TL;DR: This work presents the performance analysis of a dual-hop transmission system composed of asymmetric radio frequency (RF) and free-space optical (FSO) links in underlay cognitive networks and derives new exact closed-form expressions for the cumulative distribution function, the probability density function, and the moment generating function of these systems in terms of the Meijer's G functions.
Abstract: In this work, we present the performance analysis of a dual-hop transmission system composed of asymmetric radio frequency (RF) and free-space optical (FSO) links in underlay cognitive networks. For the RF link, we consider an underlay cognitive network where the secondary users share the spectrum with licensed primary users, where indoor femtocells act as a practical example for such networks. More specifically, we assume that the RF link is subject to an interference constraint. The FSO link accounts for pointing errors and both types of detection techniques (i.e. intensity modulation/direct detection (IM/DD) as well as heterodyne detection). On the other hand, RF link is modeled by the Rayleigh fading distribution that applies power control to maintain the interference at the primary network below a specific threshold whereas the FSO link is modeled by a unified Gamma-Gamma fading distribution. With this model, we derive new exact closed-form expressions for the cumulative distribution function, the probability density function, the moment generating function, and the moments of the end-to-end signal-to-interference plus noise ratio of these systems in terms of the Meijer's G functions. We then capitalize on these results to offer new exact closed-form expressions for the outage probability, the higher-order amount of fading, and the average error rate for binary and Mary modulation schemes, all in terms of Meijer's G functions. All our new analytical results are verified via computer-based Monte-Carlo simulations and are illustrated by some selected numerical results.
TL;DR: The secrecy capacity of fast fading channels under imperfect main channel estimation at the transmitter is studied and it is proved that the secrecy capacity is asymptotically equal to the capacity of the main channel as if there were no secrecy constraint.
Abstract: We study the secrecy capacity of fast fading channels under imperfect main channel (between the transmitter and the legitimate receiver) estimation at the transmitter. Lower and upper bounds on the ergodic secrecy capacity are derived for a class of independent identically distributed (i.i.d.) fading channels. The achievable rate follows from a standard wiretap code in which a simple on-off power control is employed along with a Gaussian input. The upper bound is obtained using an appropriate correlation scheme of the main and eavesdropper channels and is the best known upper bound so far. The upper and lower bounds coincide with recently derived ones in case of perfect main CSI. Furthermore, the upper bound is tight in case of no main CSI, where the secrecy capacity is equal to zero. Asymptotic analysis at high and low signal-to-noise ratio (SNR) is also given. At high SNR, we show that the capacity is bounded by providing upper and lower bounds that depend on the channel estimation error. At low SNR, however, we prove that the secrecy capacity is asymptotically equal to the capacity of the main channel as if there were no secrecy constraint. Numerical results are provided for i.i.d. Rayleigh fading channels.
TL;DR: A simple tight closed-form approximation for ASEP over log-normal fading channel is derived that facilitates the computation of average symbol error rate for a broader class of coherent digital modulation schemes.
Abstract: The average symbol error probability(ASEP) is an important measure to evaluate the performance of different modulation techniques over fading channels. The phenomenon of both shadowing and slow fading in wireless communication system is generally characterized by log-normal probability distribution. Approximating log-normal integrals by constructing Taylor series expansion of second order, a simple tight closed-form approximation for ASEP over log-normal fading channel is derived. This expression facilitates the computation of average symbol error rate for a broader class of coherent digital modulation schemes. The efficiency of the expression is numerically examined and comparison of the results is carried out in relation to the existing approximate expressions.
02 Jun 2014
TL;DR: Novel expressions for the probability of detection in energy detection based spectrum sensing over η - μ fading channels are derived and it is shown that the detector is highly dependent upon the severity of fading conditions as even slight variation of the fading parameters affect the corresponding performance significantly.
Abstract: This work presents analytic solutions for a useful integral in wireless communications, which involves the Marcum Q-function in combination with an exponential function and arbitrary power terms. The derived expressions have a rather simple algebraic representation which renders them convenient both analytically and computationally. Furthermore, they can be useful in wireless communications and particularly in the context of cognitive radio communications and radar systems, where this integral is often encountered. To this end, we derive novel expressions for the probability of detection in energy detection based spectrum sensing over η - μ fading channels. These expressions are given in closed-form and are subsequently employed in analyzing the effects of generalised multipath fading conditions in cognitive radio systems. As expected, it is shown that the detector is highly dependent upon the severity of fading conditions as even slight variation of the fading parameters affect the corresponding performance significantly.
10 Jun 2014
TL;DR: An approach based on the moment generating function (MGF) is introduced, which is suitable to deduce the closed-form expression for effective capacity computation and derived unified and concise expressions of effective capacity by means of Fox's H function, which can be easily calculated.
Abstract: Quality of service (QoS) guarantees play a significant role in next-generation wireless networks and the concept of effective capacity is proposed to characterize the maximum arrival rate that a time-varying fading channel can support under a delay-QoS constraint. However, the probability density function (PDF)-based analysis of effective capacity over generalized fading channels suffers from mathematical intractability in some situations of interest. In this paper, an approach based on the moment generating function (MGF) is introduced, which is suitable to deduce the closed-form expression for effective capacity computation. We start with the general case of adaptation transmission policy under the assumption of channel side information (CSI) only at the receiver, and then extend it to other adaptation policies. In addition, we derive unified and concise expressions of effective capacity by means of Fox's H function, which can be easily calculated, accommodating a wide variety of fading scenarios. Finally, the formulas of effective capacity are verified by numerical and simulation results.
TL;DR: Expressions for the cumulative distribution function (CDF) of a specially constructed random variable (RV) represented by the ratio of two generalized RVs are presented and it is proved that in the former case, the CDF is expressed in terms of elementary functions.
Abstract: In this paper, we present expressions for the cumulative distribution function (CDF) of a specially constructed random variable (RV) represented by the ratio of two generalized RVs. The obtained theoretical results are used to evaluate the outage probability in scenarios with η-μ-faded signals of interest (SoI), η-μ- or κ-μ-faded co-channel interference (CCI), and background white Gaussian noise. Our results are applicable also to scenarios where the SoI passes through the κ-μ fading channel, and the interfering signals are η-μ-faded. The derived results can be used if all parameters μi of the η-μ models representing the statistical distributions of either the SoI components or CCI components are integers. We prove, in particular, that in the former case, the CDF is expressed in terms of elementary functions.
TL;DR: Analytical and simulation results show that placing the femtocell base-station (FBS) close to the center of the house can significantly reduce the impact of the interference on the outdoor macrocell users as compared to a randomly placed FBS.
Abstract: This work considers the development of a realistic statistical model to represent the interference in heterogeneous wireless networks. The considered networks are comprised of one or more femtocells deployed in buildings with unknown internal structures and a preplanned cellular network. The proposed interference model is based on a novel random floor plan generator, which is used to construct a statistical rather than site-specific floor plans. The developed model is augmented with Nakagami fading to represent the femtocell interference signal in the outdoor environment. The model is then utilized to evaluate the performance of the macrocell users where closed-form formulae for the outage probability and signal-to-interference ratio at the receiver front-end are derived. The obtained results reveal that a femtocell signal propagating from an indoor transmitter to an outdoor receiver will experience a composite shadowing/fading process where the Nakagami distribution is adopted for the fading part while the shadowing is modeled by lognormal mixture distribution. Analytical and simulation results show that placing the femtocell base-station (FBS) close to the center of the house can significantly reduce the impact of the interference on the outdoor macrocell users as compared to a randomly placed FBS.
TL;DR: In this article, the performance of MIMO systems employing spatial multiplexing and zero-forcing detection (ZF) is analyzed for Rician-Rayleigh fading and Rayleigh-Rician fading.
Abstract: We analyze the performance of multiple input/multiple output (MIMO) communications systems employing spatial multiplexing and zero-forcing detection (ZF). The distribution of the ZF signal-to-noise ratio (SNR) is characterized when either the intended stream or interfering streams experience Rician fading, and when the fading may be correlated on the transmit side. Previously, exact ZF analysis based on a well-known SNR expression has been hindered by the noncentrality of the Wishart distribution involved. In addition, approximation with a central-Wishart distribution has not proved consistently accurate. In contrast, the following exact ZF study proceeds from a lesser-known SNR expression that separates the intended and interfering channel-gain vectors. By first conditioning on, and then averaging over the interference, the ZF SNR distribution for Rician-Rayleigh fading is shown to be an infinite linear combination of gamma distributions. On the other hand, for Rayleigh-Rician fading, the ZF SNR is shown to be gamma-distributed. Based on the SNR distribution, we derive new series expressions for the ZF average error probability, outage probability, and ergodic capacity. Numerical results confirm the accuracy of our new expressions, and reveal effects of interference and channel statistics on performance.
TL;DR: The outage probability of spatial modulation (SM) multiple input multiple output (MIMO) systems incorporated with transmit antenna selection (TAS) over Rayleigh fading channels for binary phase shift keying signals is analysed.
Abstract: The outage probability of spatial modulation (SM) multiple input multiple output (MIMO) systems incorporated with transmit antenna selection (TAS) over Rayleigh fading channels for binary phase shift keying signals is analysed. A MIMO system with N t transmit and N r receive antennas in the Rayleigh fading environment is considered. S N t antennas are selected at the transmitter side to maximise the received signal power. A closed form expression for the outage probability of the SM MIMO systems with TAS is derived and validated using the simulation results.
TL;DR: In this article, an exhaustive analysis of the small-scale fading amplitude in the 60 GHz band is addressed for line-of-sight conditions (LOS) from a measurement campaign carried out in a laboratory.
Abstract: An exhaustive analysis of the small-scale fading amplitude in the 60 GHz band is addressed for line-of-sight conditions (LOS). From a measurement campaign carried out in a laboratory, we have estimated the distribution of the small-scale fading amplitude over a bandwidth of 9 GHz. From the measured data, we have estimated the parameters of the Rayleigh, Rice, Nakagami-m, Weibull, and - distributions for the small-scale amplitudes. The test of Kolmogorov-Smirnov (K-S) for each frequency bin is used to evaluate the performance of such statistical distributions. Moreover, the distributions of the main estimated parameters for such distributions are calculated and approximated for lognormal statistics in some cases. The matching of the above distributions to the experimental distribution has also been analyzed for the lower tail of the cumulative distribution function (CDF). These parameters offer information about the narrowband channel behavior that is useful for a better knowledge of the propagation characteristics at 60 GHz.
TL;DR: The spectral efficiency achievable by interference alignment in a K-user multiple-input-multiple-output interference channel is studied in the face of time-selective continuous fading explicitly estimated through pilot-symbol observations and the robustness of IA in such operationally relevant conditions is assessed.
Abstract: The spectral efficiency achievable by IA (interfer- ence alignment) in a K-user MIMO (multiple-input multiple- output) interference channel is studied in the face of time- selective continuous fading explicitly estimated through pilot- symbol observations. The robustness of IA in such operationally relevant conditions is assessed through a joint optimization of the pilot overhead and the IA update interval, which are characterized—in high-power conditions—as solutions of a fixed- point equation. Variations of the formulation are given for both FDD (frequency-division duplexing) and TDD (time-division duplexing), the former requiring explicit feedback of the fading estimates and the latter relying on fading reciprocity. For the FDD variation, analog feedback is considered. In addition to arbitrary numbers of users and antennas, and arbitrary tem- poral fading correlation functions, the derivations accommodate forward and reverse links with asymmetric power levels.
01 Dec 2014
TL;DR: The results demonstrate that the effective rate is a monotonically increasing function of channel fading parameters α and μ, as well as the number of transmit antennas, while it decreases to zero when the delay constraint becomes stringent.
Abstract: The effective rate is an important performance metric of real-time applications in next generation wireless networks. In this paper, we present an analysis of the effective rate of multiple-input single-output (MISO) systems over α-μ fading channels under a maximum delay constraint. More specifically, novel and highly accurate closed-form approximate expressions of the effective rate are derived for such systems assuming the generalized α-μ channel model. In order to examine the impact of system and channel parameters on the effective rate, we also derive closed-form expressions of the effective rate in asymptotically high and low signal-to-noise ratio (SNR) regimes. Furthermore, connections between our derived results and existing results from the literature are revealed for the sake of completeness. Our results demonstrate that the effective rate is a monotonically increasing function of channel fading parameters α and μ, as well as the number of transmit antennas, while it decreases to zero when the delay constraint becomes stringent.
TL;DR: The authors exploit a known exponential-type integral representation for the generalised Marcum Q-function Qv (a, b) that is valid for any ratio of a/b but for positive integer order v to greatly simplify the task of finding the statistical expectations over the fading signal-to-noise ratio random variables in the computation of the average detection probability metric.
Abstract: In this paper, the authors present a novel moment generating function-based technique to unify the performance evaluation of an average energy detector for detecting unknown deterministic signals over generalised fading environments (including the η-μ, κ-μ, α-μ, K, G and KG generalised fading distributions) with diversity reception. Specifically, the authors exploit a known exponential-type integral representation for the generalised Marcum Q-function Qv (a, b) that is valid for any ratio of a/b but for positive integer order v to greatly simplify the task of finding the statistical expectations over the fading signal-to-noise ratio random variables in the computation of the average detection probability metric. This new approach leads to a very compact and an elegant solution for many practical cases of interest including the independent but non-identically distributed fading statistics and/or arbitrarily correlated diversity branches in maximal-ratio combining, square-law combining and square-law selection diversity receivers. The authors’ numerical results also show that the performance of average energy detector is superior to the classical total energy detector with the increasing number of samples owing to the noise averaging effect. We have also demonstrated the versatility and utility of the proposed analytical framework to investigate the impact of dissimilar mean signal strengths, fading parameters, time-bandwidth product, diversity order and signal combining techniques on the receiver operating characteristics of diversity energy detectors in a myriad of fading environments that had heretofore resisted simple solutions.
10 Jun 2014
TL;DR: Close-form expressions for the average capacity of multiple-input-multiple-output FSO systems over strong atmospheric turbulence using Gamma-Gamma fading channel model are presented, quantitatively verifying the advantages of spatial diversity techniques.
Abstract: Atmospheric turbulence is one of the main impairments degrading the performance of free-space optical (FSO) systems. Similar to radio-frequency communications, the use of spatial diversity techniques in FSO can significantly mitigate the fading effect caused by atmospheric turbulence. In this paper, closed-form expressions for the average capacity of multiple-input-multiple-output FSO systems over strong atmospheric turbulence using Gamma-Gamma fading channel model are presented. Our analysis is carried out for both equal gain combining and maximal ratio combining diversity techniques. Numerical examples compare analytical and simulation results, quantitatively verifying the advantages of spatial diversity techniques.
TL;DR: Using this expression, the expression for the probability density function (PDF) of the output SNR of maximal ratio combining (MRC) receiver is obtained and expressions of outage probability and average symbol error rate for coherent and non-coherent m-ary modulation schemes are derived.
Abstract: An expression of characteristic function of signal-to-noise ratio (SNR) for two waves with diffused power (TWDP) fading channel is derived. Using this expression, the expression for the probability density function (PDF) of the output SNR of maximal ratio combining (MRC) receiver is obtained. Expressions for the performance matrix of MRC receiver over TWDP fading channels are also deduced. PDF based approach is followed to derive expressions of outage probability and average symbol error rate for coherent and non-coherent m-ary modulation schemes. Effects of the number of branches M and the fading parameters K and Δ on the system performance are studied. The results obtained are verified by Monte Carlo simulation.
TL;DR: Interestingly, it is shown that the low-power regime analysis provides a specific insight into the maximum achievable rate behavior of CR that has not been reported by previous studies.
Abstract: We study the achievable rate of cognitive radio (CR) spectrum sharing systems at the low-power regime for general fading channels and then for Nakagami fading. We formally define the low-power regime and present the corresponding closed-form expressions of the achievable rate lower bound under various types of interference and/or power constraints, depending on the available channel state information of the cross link (CL) between the secondary-user transmitter and the primary-user receiver. We explicitly characterize two regimes where either the interference constraint or the power constraint dictates the optimal power profile. Our framework also highlights the effects of different fading parameters on the secondary link (SL) ergodic achievable rate. We also study more realistic scenarios when there is either 1-bit quantized channel feedback from the CL alone or 2-bit feedback from both the CL and the SL and propose simple power control schemes and show that these schemes achieve the previously achieved rate at the low-power regime. Interestingly, we show that the low-power regime analysis provides a specific insight into the maximum achievable rate behavior of CR that has not been reported by previous studies.
04 Dec 2014
TL;DR: This contribution documents and discusses recent wideband radio channel measurements carried out in the intra-vehicle environment and presents a channel modeling approach based on a decomposition of spatially specific Channel Impulse Responses (CIRs) into the large and small scale fading.
Abstract: This contribution documents and discusses recent wideband radio channel measurements carried out in the intra– vehicle environment. Channels in the millimeter-wave (MMW) frequency band have been measured in 55–65GHz using openended rectangular waveguides. We present a channel modeling approach based on a decomposition of spatially specific Channel Impulse Responses (CIRs) into large and small scale fading. The decomposition is done by the Hodrick-Prescott filter. We parametrize the small scale fading utilizing Maximum-likelihood estimates for the parameters of a generalized extreme value (GEV) distribution. The large scale fading is described by a two dimensional polynomial curve. We also compare simulated results with our measurement exploiting the two-sample Kolmogorov-Smirnov test.
01 Dec 2014
TL;DR: The derived ABER expressions are very generic and convenient to handle both numerically and analytically, allowing simple unconstrained performance evaluation and accurate system planning.
Abstract: In this paper, a novel unified performance analysis of wireless communications over generalized fading channels in terms of the Average Bit Error Rate (ABER) is presented. We derive simple and accurate, exact and approximate, closed-form expressions for ABER, encapsulating all coherent modulations, for the α-η-μ, the α-λ-μ and the α-λ-μ-η, generalized fading distribution, which accurately characterize the nonlinear and at the same time the non-homogeneous nature of the propagation medium, and include the α-μ, the λ-μ, the η-μ, the Weibull, the Hoyt, the Rice, the Nakagami-m, the Rayleigh, the Exponential, the Lognormal, the Gamma and the One-sided Gaussian models as special cases. We extend the generality of the derived ABER expressions by assuming Additive White Generalized Gaussian Noise (AWGGN) environment which includes the Gaussian, the Laplacian, the Gamma and the impulsive noise as special cases. The derived expressions are very generic and convenient to handle both numerically and analytically, allowing simple unconstrained performance evaluation and accurate system planning. Numerical testing and existing results for the special cases of these generalized distributions have been used to validate the derived expressions showing an excellent match.
TL;DR: A comprehensive literature review on the gamma-gamma signal fading model and its use in the performance analysis of different communication systems, with more elaboration on wireless radio-frequency communication networks, including cellular and relay networks, and wireless optical networks is presented.
Abstract: In a wireless communication medium, the received signal envelope fluctuates randomly due to the scattering nature of these channels. This paper is intended to present a comprehensive literature review on the gamma-gamma signal fading model and its use in the performance analysis of different communication systems, with more elaboration on wireless radio-frequency (RF) communication networks, including cellular and relay networks, and wireless optical networks. First, the different communication channels where the gamma-gamma distribution is used to model the signal-fading phenomena are described. Second, the reported results on the statistics for the gamma-gamma distribution, including the product, the quotient, the sum, and the order statistics are presented. Finally, the performance analyses carried out in the open literature for wireless RF systems, relay networks, and wireless optical systems are summarized, and some possible directions for future research are highlighted.