Akram Al-Hourani

Optimal LAP Altitude for Maximum Coverage

Low-altitude aerial platforms (LAPs) have recently gained significant popularity as key enablers for rapid deployable relief networks where coverage is provided by onboard radio heads. These platforms are capable of delivering essential wireless communication for public safety agencies in remote areas or during the aftermath of natural disasters. In this letter, we present an analytical approach to optimizing the altitude of such platforms to provide maximum radio coverage on the ground. Our analysis shows that the optimal altitude is a function of the maximum allowed pathloss and of the statistical parameters of the urban environment, as defined by the International Telecommunication Union. Furthermore, we present a closed-form formula for predicting the probability of the geometrical line of sight between a LAP and a ground receiver.

Modeling air-to-ground path loss for low altitude platforms in urban environments

The reliable prediction of coverage footprint resulting from an airborne wireless radio base station, is at utmost importance, when it comes to the new emerging applications of air-to-ground wireless services. These applications include the rapid recovery of damaged terrestrial wireless infrastructure due to a natural disaster, as well as the fulfillment of sudden wireless traffic overload in certain spots due to massive movement of crowds. In this paper, we propose a statistical propagation model for predicting the air-to-ground path loss between a low altitude platform and a terrestrial terminal. The prediction is based on the urban environment properties, and is dependent on the elevation angle between the terminal and the platform. The model shows that air-to-ground path loss is following two main propagation groups, characterized by two different path loss profiles. In this paper we illustrate the methodology of which the model was deduced, as well as we present the different path loss profiles including the occurrence probability of each.

Stochastic Geometry Study on Device-to-Device Communication as a Disaster Relief Solution

With the unprecedented new capabilities introduced by modern broadband wireless networks, public safety (PS) agencies are increasingly depending on such networks for their mission-critical communications. One of the key enablers for this adoption is the device-to-device (D2D) communications, where mobile devices can connect directly between each other, without the need for a base station (BS) nor a switching core to handle and route the traffic. This feature is a vital communication backup in case of a network infrastructure failure or a natural disaster. In this paper, we analytically quantify the cellular network performance during massive infrastructure failure, where some terminals can play the role of low-power relay nodes forming multihop communication links to assist farther terminals outside the reach of the healthy network coverage. Namely, we analytically determine the D2D effect in alleviating the damage caused by the disaster. This paper is based on stochastic geometry analysis and presents a novel analytical methodology that is applicable to wide scenarios of network conditions and parameters. This methodology is verified through Monte Carlo simulations for practical network parameters based on the latest Third-Generation Partnership Project (3GPP) recommendations.

Path loss study for millimeter wave device-to-device communications in urban environment

In the recent years the millimeter wave spectrum is being explored as a prospective band for the next generation (5G) cellular communications. In this paper we study the propagation of the the millimetre wave spectrum using ray tracing model for an urban environment. We consider the ISM bands in 24GHz and 61GHz in particular and conduct ray tracing simulations to study the path loss behaviour in terms of the path loss exponent and the shadowing variance for both Line of Sight and Non Line of Sight conditions. As a potential application we examine the device to device (D2D) communication, which is currently being developed for LTE-A standard. The resulting pathloss exponents and the shadow variances are presented here based on ray tracing simulations for an ITU-R statistical urban model, moreover this paper shows that intelligent beam steering can significantly improve the throughput for the considered D2D scenarios.

Cognitive Relay Nodes for airborne LTE emergency networks

This paper is proposing a novel concept of Cognitive Relay Node for intelligently improving the radio coverage of an airborne LTE emergency network, considering the scenarios outlined in the ABSOLUTE research project. The proposed network model was simulated comparing the different cases of deploying relay nodes to complement the coverage of an aerial LTE network. Simulation results of the proposed Cognitive Relay Nodes show significant performance improvement in terms of radio coverage quantified by the regional outage probability enhancement. Also, this paper is presenting the methodology and results of choosing the optimum aerial eNodeB altitude.

Temporary Cognitive Femtocell Network for public safety LTE

In this paper we address the deployment of a temporary cognitive secondary LTE Femtocell network in order to supplement and enhance the coverage of a regular LTE network for public safety communications. We propose a novel approach in deploying such cognitive secondary network by exploiting the latest LTE-Advanced HetNet capabilities. We also present two interference mitigation techniques for mitigating the interference caused by the presence of the secondary cognitive LTE network. Simulation results are presented to show the enhancement in the coverage when such a secondary network is deployed together with the proposed interference mitigation techniques.

Relay-Assisted Device-to-Device Communication: A Stochastic Analysis of Energy Saving

This paper lays a mathematical framework for estimating the energy saving of a relay assisting a pair of wireless devices. We derive closed-form expressions for describing the geometrical zone where relaying is energy efficient. In addition, we obtain the probabilistic distribution of the energy saving introduced by relays that are randomly distributed according to a spatial Poisson point process. Furthermore, we present a comparison methodology for fairly evaluating the energy consumption of conventional cellular network from one side and relay-assisted device-to-device communication from another side. Results suggest that a significant energy saving can be achieved when relay-assisted device-to-device communication is adopted for distances below a certain threshold. In order to test the analytical framework, we perform Monte-Carlo simulations and compare the results with those obtained from the mathematical framework.

Modeling Cellular-to-UAV Path-Loss for Suburban Environments

Operating unmanned aerial vehicle (UAV) over cellular networks would open the barriers of remote navigation and far-flung flying by combining the benefits of UAVs and the ubiquitous availability of cellular networks. In this letter, we provide an initial insight on the radio propagation characteristics of cellular-to-UAV (CtU) channel. In particular, we model the statistical behavior of the path-loss from a cellular base station toward a flying UAV. Where we report the value of the path-loss as a function of the depression angle and the terrestrial coverage beneath the UAV. The provided model is derived based on extensive experimental data measurements conducted in a typical suburban environment for both terrestrial (by drive test) and aerial coverage (using a UAV). The model provides simple and accurate prediction of CtU path-loss that can be useful for both researchers and network operators alike.

Stochastic Geometry Methods for Modeling Automotive Radar Interference

As the use of automotive radar increases, performance limitations associated with radar-to-radar interference will become more significant. In this paper, we employ tools from stochastic geometry to characterize the statistics of radar interference. Specifically, using two different models for the spatial distributions of vehicles, namely, a Poisson point process and a Bernoulli lattice process, we calculate for each case the interference statistics and obtain analytical expressions for the probability of successful range estimation. This paper shows that the regularity of the geometrical model appears to have limited effect on the interference statistics, and so it is possible to obtain tractable tight bounds for the worst case performance. A technique is proposed for designing the duty cycle for the random spectrum access, which optimizes the total performance. This analytical framework is verified using Monte Carlo simulations.

Nearest Neighbor Distance Distribution in Hard-Core Point Processes

In this letter, we present an analytic framework for formulating the statistical distribution of the nearest neighbor distance in hard-core point processes. We apply this framework to Matérn hard-core point process (MHC) to derive the cumulative distribution function of the contact distance in three cases. The first case is between a point in an MHC process and its nearest neighbor from the same process. The second case is between a point in an independent Poisson point process and the nearest neighbor from an MHC process. The third case is between a point in the complement of an MHC process and its sibling MHC process. We test the analytic results against Monte Carlo simulations to verify their consistency.