El-Hadi M. Aggoune

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 (SSK) modulation with multiple cooperative relays

In this article, space shift keying (SSK) modulation is used to study a wireless communication system when multiple relays are placed between the transmitter and the receiver. In SSK, the indices of the transmit antennas form the constellation symbols and no other data symbol are transmitted. The transmitter and the receiver communicate through a direct link and the existing relays. In this study, two types of relays are considered. Conventional amplify and forward relays in which all relays amplify their received signal and forward it to the destination in a round-robin fashion. In addition, decode and forward relays in which the relays that correctly detect the source signal will forward the corresponding fading gain to the destination in pre-determined orthogonal time slots are studied. The optimum decoder for both communication systems is derived and performance analysis are conducted. The exact average bit error probability (ABEP) over Rayleigh fading channels is obtained in closed-form for a source equipped with two transmit antennas and arbitrary number of relays. Furthermore, simple and general asymptotic expression for the ABEP is derived and analyzed. Numerical results are also provided, sustained by simulations which corroborate the exactness of the theoretical analysis. It is shown that both schemes perform nearly the same and the advantages and disadvantages of each are discussed.

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.

Diversity techniques for a free-space optical communication system in correlated log-normal channels

Abstract. Performance analysis of free-space optical (FSO) communication systems in different channel conditions has gained significant attention in literature. Nevertheless, most existing studies consider uncorrelated channel conditions. An uncorrelated channel requires sufficient spacing between transmitters and limits the receiver field of view and link distance. However, this might not be feasible in all applications. Thereby, this paper studies repetition code (RC) and orthogonal space time block code (OSTBC) performance in correlated log-normal FSO channels using intensity modulation and direct detection. An approximate analytical expressions using moment generating function for the average bit error probability are derived. Our simulation results show that RCs are superior to OSTBCs in correlated channel conditions.

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.

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

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.

Spatial diversity for FSO communication systems over atmospheric turbulence channels

This paper investigates the bit error rate (BER) performance of spatial diversity free-space optical (FSO) communication systems using on-off keying modulation. The study considers correlated log-normal FSO channels as well as path losses due to weather effects using intensity modulation and direct detection schemes. An approximated moment generating functions (MGF) for the joint probability density function of correlated log-normal channels are considered. Using MGF approximation, BER expressions for repetition codes (RCs) and orthogonal space time block codes (OSTBCs) in correlated lognormal channels are derived. Results show that RCs outperform OSTBCs in correlated channel conditions. In addition, the effect of different weather conditions (e.g., haze, rain and fog) on the BER performance of the FSO links are studied. Monte Carlo simulation results are further provided to demonstrate the validity of the proposed mathematical analysis.

A novel Kronecker-based stochastic model for massive MIMO channels

This paper proposes a novel Kronecker-based stochastic model (KBSM) for massive multiple-input multiple-output (MIMO) channels. The proposed KBSM can not only capture antenna correlations but also the evolution of scatterer sets on the array axis. With the consideration of the evolution of scatterer sets, the overall correlation matrices of the transmitter and receiver are presented. In addition, upper and lower bounds of MIMO channel capacities in both the high and low signal-to-noise ratio (SNR) regimes are derived when the numbers of transmit and receive antennas are increasing unboundedly with a constant ratio. Furthermore, the evolution of scatterer sets on the array axis is shown to decrease spatial correlations of MIMO channels.

A General 3-D Non-Stationary 5G Wireless Channel Model

A novel unified framework of geometry-based stochastic models for the fifth generation (5G) wireless communication systems is proposed in this paper. The proposed general 5G channel model aims at capturing small-scale fading channel characteristics of key 5G communication scenarios, such as massive multiple-input multiple-output, high-speed train, vehicle-to-vehicle, and millimeter wave communications. It is a 3-D non-stationary channel model based on the WINNER II and Saleh-Valenzuela channel models considering array-time cluster evolution. Moreover, it can easily be reduced to various simplified channel models by properly adjusting model parameters. Statistical properties of the proposed general 5G small-scale fading channel model are investigated to demonstrate its capability of capturing channel characteristics of various scenarios, with excellent fitting to some corresponding channel measurements.