Syed Junaid Nawaz

A Generalized 3-D Scattering Model for a Macrocell Environment With a Directional Antenna at the BS

In this paper, a generalized 3-D scattering model is presented for macrocellular land mobile radio cellular systems with a mobile station (MS) located at the center of a 3-D scattering semispheroid and a base station (BS) employing a directional antenna located outside of the semispheroid. The effect of the directional antenna is thoroughly observed on spatial and temporal characteristics of the proposed model. Closed-form expressions for joint and marginal probability density functions (pdfs) of the angle of arrival (AoA) seen at the MS and the BS in correspondence with azimuth and elevation angles are derived. Furthermore, closed-form expressions for propagation path delays and trivariate joint pdfs of the time of arrival (ToA) seen at the MS and the BS in correspondence with azimuth and elevation angles are derived. Moreover, the theoretical results, along with observations, are shown that illustrate the effect of the directional antenna on the spatiotemporal statistics of the proposed 3-D model. The proposed 3-D scattering model is shown to deduce all previously proposed 2-D and 3-D models that assume a uniform distribution of scatters with directional or omnidirectional antennas found in the literature for a macrocell environment. The obtained theoretical results are compared with some notable 2-D and 3-D scattering models to validate the generalization of the proposed model.

Effect of Directional Antenna on the Doppler Spectrum in 3-D Mobile Radio Propagation Environment

In this paper, an analytical model is proposed for a macrocellular communication system with directional antennas at elevated base station (BS) to quantify the effect of directivity of the radiated waves from antennas on the Doppler spectrum in a 3-D radio propagation environment. The impacts of antenna beamwidth and motion of mobile station (MS) are thoroughly investigated on the statistical distribution of the power Doppler spectrum. Closed-form expressions for trivariate probability density functions (pdfs) of propagation path distance, power, and Doppler shift are derived. Furthermore, general expressions for joint and marginal pdfs of elevation angle of arrival, power, and Doppler shift are established. Finally, the obtained theoretical results, along with the observations that illustrate the effect of directivity of the antenna beamwidth and the direction of the MSs motion on the distribution characteristics of the power Doppler spectrum, are presented. It is established that for motion of the MS in all directions, the spread in distribution of the Doppler shift observed is significantly reduced due to the use of a directional antenna at the BS with a narrow beam directed toward the desired user. It is also observed that, for a sharp azimuthal beam of directional antenna, the multipath components corresponding to the scatterers in the elevation plane result in the reduction of Doppler shift with an increase in their vertical distance from the MS.

A Generalized 3-D Scattering Channel Model for Spatiotemporal Statistics in Mobile-to-Mobile Communication Environment

In this paper, we develop a 3-D geometrical channel model for mobile-to-mobile (M2M) communication environment. The proposed model combines most of the existing 2-D and 3-D geometrical channel models for M2M and fixed-to-mobile (F2M) communication channels into one generalized model. Using the proposed model, closed-form expressions for the joint probability density function of angle-of-arrival and time-of-arrival in azimuth and elevation planes are derived. These results are then verified by simulations and available field measurements. Furthermore, comprehensive comparisons of the proposed channel model are carried out with the existing 2-D and 3-D channel models in the literature, which show that many notable geometrical channel models in M2M and F2M communication environments become the special cases of our proposed generalized 3-D geometrical channel model by adjusting corresponding channel parameters. Consequently, the proposed 3-D channel model can be taken as a useful tool for modeling mobile ad hoc networks , vehicular ad hoc networks, and intelligent transportation systems.

Neural Network Based MIMO-OFDM Channel Equalizer Using Comb-Type Pilot Arrangement

MIMO (Multiple Input Multiple Output) and OFDM (Orthogonal frequency division multiplexing) bringing along a number of pros; a combination of both stands a good possibility of being the next-generation (4th generation) of mobile wireless systems. The technology however imposes a challenge that is the increased complexity of channel equalization. Wireless channels are multipath fading channels, causing deformation in the signal. To remove the effect (imposed by channel) from received signal, the receiver needs to have knowledge of CIR (Channel impulse response) that is usually provided by a separate channel estimator. This paper is aimed at exploring the use of Neural Network (NN) as a tool for MIMO-OFDM channel estimation and compensation. The research attempts to gauges the usefulness of proposed system by analyzing different algorithms to train NN. Further to ascertain the performance of the proposed technique; length of the known training sequence has been varied over a reasonable range and observations are made. Finally, the results obtained by using different algorithms for training NN have been compared with each-other and against the traditional least squares channel estimator, which along with observations/comments form part of the paper.

The impact of propagation environment and velocity on the handover performance of LTE systems

In this paper, a generalized model is proposed to analyze the impact of propagation environment and velocity on the handover performance of user equipment (UE) for long term evolution (LTE) systems. An adaptive time window is defined within the generalized model, to provide additional flexibility to perform handover procedure over conventional reference signal received power (RSRP) and reference signal received quality (RSRQ) based procedures. The proposed algorithm reduces the call dropping rate during handover at the cell boundary of urban cells, due to its enhanced degree of freedom in decision making process. In providing so, the process requires additional statistics, which are readily available at the receiver. Therefore, it does not require any additional computational complexity at UE. Finally, to demonstrate the validity of the proposed algorithm, simulation results along with the observations are presented.

3D Ellipsoidal Model for Mobile-to-Mobile Radio Propagation Environments

Geometrical models are mostly used for the study and analysis of the characteristics of radio communication channels. In this paper, a three-dimensional semi-ellipsoidal scattering model is proposed for mobile-to-mobile communication channels, where uniformly distributed scatterers are assumed to be confined within the semi-ellipsoids around mobile stations. The semi-ellipsoidal shape with adjustable dimensions is considered to model the scattering phenomenon in urban streets and canyons. Using the proposed scattering model, a closed-form expression for the joint probability density function of the Angle-of-Arrival in azimuth and elevation planes of the incoming multipath signals is derived at each mobile station. Moreover, various observations are made, which show the impact of scatterers’ elevation and streets’ orientation on the spatial characteristics of mobile-to-mobile communication channel.

Temporal Analysis of a 3D Ellipsoid Channel Model for the Vehicle-to-Vehicle Communication Environments

In vehicle-to-vehicle (V2V) communication scenarios, the antenna heights of the communicating nodes are typically lower than the heights of scattering objects in the vicinity of these nodes such that signal propagation in the elevation plane cannot be ignored. Therefore, it is necessary to consider three-dimensional (3D) space for modeling radio propagation in V2V communication environments. In this paper, the temporal characteristics of a 3D semi-ellipsoid geometrical channel model for V2V communication scenarios is presented by assuming uniform scatterer distribution around the mobile stations (MSs). Using the 3D semi-ellipsoid channel model, closed-form expressions for the joint probability density function (PDF) of the time-of-arrival (ToA) and angle-of-arrival (AoA) in azimuth and elevation planes is derived. A closed-form expression for the marginal PDF of ToA of the received signal is also provided. The proposed analytical results are compared with those obtained from some notable geometric channel models found in the literature.

A 3-D Propagation Model for Emerging Land Mobile Radio Cellular Environments.

A tunable stochastic geometry based Three-Dimensional (3-D) scattering model for emerging land mobile radio cellular systems is proposed. Uniformly distributed scattering objects are assumed around the Mobile Station (MS) bounded within an ellipsoidal shaped Scattering Region (SR) hollowed with an elliptically-cylindric scattering free region in immediate vicinity of MS. To ensure the degree of expected accuracy, the proposed model is designed to be tunable (as required) with nine degrees of freedom, unlike its counterparts in the existing literature. The outer and inner boundaries of SR are designed as independently scalable along all the axes and rotatable in horizontal plane around their origin centered at MS. The elevated Base Station (BS) is considered outside the SR at a certain adjustable distance and height w.r.t. position of MS. Closed-form analytical expressions for joint and marginal Probability Density Functions (PDFs) of Angle-of-Arrival (AoA) and Time-of-Arrival (ToA) are derived for both up- and down-links. The obtained analytical results for angular and temporal statistics of the channel are presented along with a thorough analysis. The impact of various physical model parameters on angular and temporal characteristics of the channel is presented, which reveals the comprehensive insight on the proposed results. To evaluate the robustness of the proposed analytical model, a comparison with experimental datasets and simulation results is also presented. The obtained analytical results for PDF of AoA observed at BS are seen to fit a vast range of empirical datasets in the literature taken for various outdoor propagation environments. In order to establish the validity of the obtained analytical results for spatial and temporal characteristics of the channel, a comparison of the proposed analytical results with the simulation results is shown, which illustrates a good fit for 107 scattering points. Moreover, the proposed model is shown to degenerate to various notable geometric models in the literature by an appropriate choice of a few parameters.

Superimposed training-based compressed sensing of sparse multipath channels

In a number of wireless communication applications, the impulse response of multipath communication channels has sparse nature. In this study, physical model for various propagation environments exhibiting sparse channel structure is considered. A superimposed (SI) training-based compressed channel sensing (SI-CCS) technique is proposed for such sparse multipath channels. A non-random periodic pilot sequence is SI over the information sequence at the transmitter, which avoids the use of dedicated time slots for training sequence. At the receiver, first-order statistics and the theory of compressed sensing is applied to estimate the wireless communication channels with sparse impulse response. A simulation analysis is presented to demonstrate the effectiveness of the proposed-channel estimation technique, where mean-square error and bit-error rate are used as the performance measures. Exploiting the proposed SI-CCS technique, the simulation results along with the observations are presented, which illustrate the effect of various channel parameters on the performance of the proposed technique. Furthermore, obtained simulation results for the proposed SI-CCS technique along with its comparison with other techniques in literature are also presented. It is established that for the cases of sparse multipath channels, the proposed SI-CCS technique can potentially achieve significant improvement in the performance of channel estimator over the existing estimation techniques of such sparse channels.

A Real-time Control System for Home/Office appliances automation, from mobile device through GPRS network

There are numbers of publications addressing control systems for home/office appliance involving infrared remote controls but there is no such publication/protocol/standard addressing solution for mobile-to-home/office appliance controlling through general packet radio services (GPRS) networks without involving any Internet based servers. This paper addresses recent research and development efforts in constructing wireless real-time control system based on server/client architecture through GPRS networks. This paper includes an implementation example designed to control home/office appliance from anywhere & anytime even when user is not at home/office. The paper demonstrates a micro Java application as example of real-time control system for home/office appliances and addresses the development-time and implementation-time experiences.