Mohammed M. Alwakeel

A Non-Stationary 3-D Wideband Twin-Cluster Model for 5G Massive MIMO Channels

This paper proposes a novel theoretical non-stationary three dimensional (3-D) wideband twin-cluster channel model for massive multiple-input multiple-output (MIMO) communication systems with carrier frequencies on the order of gigahertz (GHz). As the dimension of antenna arrays cannot be ignored for massive MIMO, near field effects instead of far field effects are considered in the proposed model. These include the spherical wavefront assumption and a birth-death process to model non-stationary properties of clusters such as cluster appearance and disappearance on both the array and time axes. Their impacts on massive MIMO channels are investigated via statistical properties including correlation functions, condition numbers, and angular power spectra. Additionally, the impact of elevation angles on correlation functions is discussed. A corresponding simulation model for the theoretical model is also proposed. Finally, numerical analysis shows that the proposed channel models are able to serve as a design framework for massive MIMO channel modeling.

Performance Analysis of Space Shift Keying with Amplify and Forward Relaying

In this letter, dual-hop amplify and forward relaying using space shift keying (SSK) is introduced. In SSK, information bits are mapped into a spatial symbol. The spatial symbol is the index of the active transmit antenna, where a single antenna is activated at each time instance. The relay amplifies the data received from the transmitter and forwards it to the receiver without any further processing. The receiver applies optimum maximum-likelihood detector to retrieve the transmitted information bits. In particular, an exact closed-form expression for the average bit error probability is given for the case of two transmit antennas. In addition, an upper bound is derived for an arbitrary number of transmit antennas. The analytical results are validated through Monte Carlo simulation results.

A Non-Stationary Wideband Channel Model for Massive MIMO Communication Systems

This paper proposes a novel non-stationary wideband multi-confocal ellipse two dimensional (2-D) channel model for massive multiple-input multiple-output (MIMO) communication systems. Spherical wavefront is assumed in the proposed channel model, instead of the plane wavefront assumption used in conventional MIMO channel models. In addition, the birth-death process is incorporated into the proposed model to capture the dynamic properties of clusters on both the array and time axes. Statistical properties of the channel model such as the space-time-frequency correlation function and power imbalance on the antenna array are studied. The impact of the spherical wavefront assumption on the statistical properties of the channel model is investigated. Furthermore, numerical analysis shows that the proposed channel model is able to capture specific characteristics of massive MIMO channel as observed in measurements.

Spectral, Energy, and Economic Efficiency of 5G Multicell Massive MIMO Systems with Generalized Spatial Modulation

This paper studies generalized spatial modulation (Gen-SM) schemes in multicell multiuser massive multiple-input multiple-output (MIMO) systems as a promising high-throughput and energy-efficient technique for fifth-generation (5G) wireless networks. A detection algorithm for such systems is proposed based on linear processing techniques. By applying the concept of order statistics, a general framework for approximating the achievable sum rates with linear detection is also given. The probability of detecting antenna combinations is analyzed and is used to approximate the sum-rate performance with practical channel conditions, such as antenna correlation, imperfect channel information, and pilot contamination. The fundamental trade-off between spectral efficiency (SE) and energy efficiency (EE) is also investigated. Despite offering less SE, spatial modulation (SM) with a single active antenna per user is shown to be the most energy-efficient transmission mode among the Gen-SM class. Within the operating range of SM (i.e., in the low-to-moderate SE regime), SM is demonstrated to achieve better EE compared with conventional massive MIMO schemes. The performance in terms of economic efficiency, indicating economic profitability (in monetary unit per second), is also analyzed and is shown to serve as a complementary performance metric, enabling an implicit trade-off between SE and EE.

3D Wideband Non-Stationary Geometry-Based Stochastic Models for Non-Isotropic MIMO Vehicle-to-Vehicle Channels

Actual vehicle-to-vehicle (V2V) channel measurements have shown that the wide-sense stationary (WSS) modeling assumption is valid only for very short time intervals. This fact motivates us to develop non-WSS V2V channel models. In this paper, we propose a novel three-dimensional (3D) theoretical non-WSS regular-shaped geometry-based stochastic model (RS-GBSM) and the corresponding sum-of-sinusoids (SoS) simulation model for non-isotropic scattering wideband multiple-input multiple-output (MIMO) V2V fading channels. The movements of the transmitter (Tx), scatterers, and receiver (Rx) result in the time-varying angles of departure (AoDs) and angles of arrival (AoAs) that make our models non-stationary. The proposed RS-GBSMs, combining line-of-sight (LoS) components, a two-sphere model, and multiple confocal elliptic-cylinder models, have the ability to study the impacts of vehicular traffic density (VTD) and non-stationarity on channel statistics, and jointly consider the azimuth and elevation angles by using the von Mises Fisher (VMF) distribution. The proposed RS-GBSMs are sufficiently generic and adaptable to model various V2V scenarios. Based on the proposed 3D non-WSS RS-GBSMs, important local channel statistical properties are derived and thoroughly investigated. The impacts of VTD and non-stationarity on these channel statistical properties are investigated by comparing them with those of the corresponding WSS model. The proposed non-WSS RS-GBSMs are validated by measurements in terms of the channel stationary time. Finally, numerical and simulation results demonstrate that the 3D non-WSS model is more practical to characterize real V2V channels.

Serial Amplify-and-Forward Relay Transmission Systems in Nakagami-

In this paper, the end-to-end performance of a wireless relay transmission system that employs amplify-and-forward (AF) relays and operates in an interference-limited Nakagami- m fading environment is studied. The wireless links from one relay node to another experience Nakagami- m fading, and the number of interferers per hop is Poisson distributed. The aggregate interference at each relay node is modeled as a shot-noise process whose distribution follows an α-stable process. For the considered system, analytical expressions for the moments of the end-to-end signal-to-interference ratio (SIR), the end-to-end outage probability (OP), the average bit-error probability (ABEP), and the average channel capacity are obtained. General asymptotic expressions for the end-to-end ABEP are also derived. The results provide useful insights regarding the factors affecting the performance of the considered system. Monte Carlo simulation results are further provided to demonstrate the validity of the proposed mathematical analysis.

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This study presents a comprehensive performance analysis of an energy detector over Gamma-shadowed Rician fading channels, namely Rician fading channels with the fluctuating line-of-sight components following the Gamma distribution. This composite multi-path/shadowing model has been shown to provide a remarkably accurate fading characterisation while leading to closed-form expressions for important channel statistics. Rapidly convergent infinite series representations are firstly derived for the average probability of detection and the area under the receiver operating characteristic curve for the no-diversity reception case. These results are then extended to the case of maximal ratio, equal gain and selection diversity. To this end, novel analytical expressions for the statistics of the end-to-end signal-to-noise ratio of equal gain and selection diversity receivers, operating over Gamma-shadowed Rician fading channels are derived. Analytical results are substantiated by Monte Carlo simulation, as well as by extensive numerically evaluated results.

Fading Channels With a Poisson Interference Field

In this paper, the bit error rate (BER) performance of spatial modulation (SM) systems under a novel 3-D vehicle-to-vehicle (V2V) multiple-input multiple-output (MIMO) channel model is investigated both theoretically and by simulations. The impact of vehicle traffic density, Doppler effect, and 3-D and 2-D V2V MIMO channel models on the BER performance are thoroughly investigated. Simulation results show that the performance of SM is mainly affected by the spatial correlation of the underlying channel model. Compared with other MIMO technologies, the SM system can offer a better tradeoff between spectral efficiency and system complexity.

Energy detection of unknown signals in Gamma-shadowed Rician fading environments with diversity reception

In this paper, single amplify and forward (AF) relay is placed between the source and the destination in space shift keying (SSK) multiple-input single output (MISO) system. In SSK, transmit-antenna indices form a spatial constellation diagram where each group of base two logarithm of the input data bits are mapped to one spatial constellation point. Hence, at each time instant, only single transmit antenna is active, which transmits certain energy that contains no data symbol, and all other antennas are off. The receiver, with single receive antenna, decodes the received signal from the single antenna AF relay and estimates the index of the active transmit-antenna to retrieve the transmitted information bits. Closed-form bit error ratio (BER) is derived for the considered system in correlated and uncorrelated channels assuming a transmitter with two transmit antennas. The analytical framework is generalized for an arbitrary number of transmit antennas and a tight upper bound on the BER performance is derived. Additionally, asymptotic analysis are carried out to investigate the effect of the different system parameters on the overall system performance. The analytical results are validated through Monte-Carlo simulation results.

BER Performance of Spatial Modulation Systems Under 3-D V2V MIMO Channel Models

Vehicular networking applications often use multi-hop wireless broadcasting as a primary data dissemination mechanism. Therefore, protocols that efficiently and thoroughly propagate application data while adapting to a wide range of network density, vehicle distribution pattern, channel quality, and other conditions are critical for vehicular communications. Here, we design the Statistical Vehicular Broadcast SVB protocol to efficiently distribute data via multi-hop broadcast in vehicular networks.