Ala Abu Alkheir

An Accurate Approximation of the Exponential Integral Function Using a Sum of Exponentials

This paper proposes a novel approximation for the exponential integral function, E1[x], using a sum of exponential functions. This approximation facilitates studying the error probability of a number of communication techniques in the presence of Co-Channel Interference (CCI). These include Hybrid Automatic Repeat Request (HARQ) with soft combining, selection relaying, incremental relaying, and opportunistic incremental relaying, just to name a few. To illustrate the usefulness and accuracy of the proposed approximation, we study the error probability of a Chase combining HARQ system operating in the presence of an unknown source of CCI where we derive an accurate closed form expression for the Moment Generating Function (MGF) of the resultant Signal to Interference plus Noise Ratio (SINR). The accuracy of the derived result is verified using computer simulation.

Performance Analysis of Cognitive Radio Relay Networks Using Decode and Forward Selection Relaying over Rayleigh Fading Channels

This article analyzes the performance of a Decode- and-Forward (DF)-based selection relaying scheme in a Cognitive Radio Relay Network (CRRN). In particular, exact closed form expressions are derived for the outage and error probabilities over dissimilar and independent and identically distributed (i.i.d.) Rayleigh fading channels. The derived expressions expose the dependence of the two performance metrics on the spectrum utilization efficiency of the the Primary User (PU) as well as the accuracy of the spectrum sensing method used. The accuracy of the derived results is verified through computer simulations.

Selective Cooperative Spectrum Sensing in Cognitive Radio Networks

This article proposes a novel Cooperative Spectrum Sensing (CSS) scheme for Cognitive Radio Networks (CRN). The proposed scheme, referred to as the Selective Cooperative Spectrum Sensing (SCSS) scheme, is capable of jointly reducing the reporting overhead and mitigating faulty reporters at the Base Station (BS). These goals are achieved by exclusively using reliably taken and delivered reports from the individual nodes to the BS. Two conditions are used to guarantee this, one on the detection reliability while the other is on the reporting reliability. These two conditions are designed to offer flexible performance, complexity and overhead tradeoff. The performance of SCSS is studied analytically and using simulations. Results show performance enhancements compared to conventional CSS schemes.

Performance Analysis of Decode and Forward Incremental Relaying in the Presence of Multiple Sources of Interference

This article studies the performance of Decode and Forward Incremental Relaying (DF-IR) in the presence of multiple dissimilar sources of Co-Channel Interference (CCI) at both, the relay and the destination. In particular, we consider the case where all links experience flat Rayleigh fading with Kr and Kd sources of CCI affecting the relay and the destination, respectively. The performance is studied in terms of three performance metrics, the normalized average spectral efficiency, the outage probability, and the error probability. The derived results unveil the incurred losses due to CCI. The accuracy of these results were verified using intensive Monte Carlo simulations.

Performance analysis of joint power control, rate adaptation, and channel selection strategies for Cognitive Radio Networks

This article proposes a joint power control, rate adaptation and channel selection strategy for Cognitive Radio Networks (CRNs) operating over vacant TV bands, also known as TV Bands Devices (TVBDs). To exploit the abundance of vacant channels available at the disposal of these devices, we combine the well-studied power and rate adaptation strategies with adaptive channel selection. The combined strategy maximizes the achievable throughput while guaranteeing a desired level of performance, i.e., error and outage probabilities. It also reduces the chances of causing or being subject to harmful interference to/from other co-channel users. Furthermore, to waive the processing complexity resulting from the frequent channel switching, we propose an alternative strategy that switches the operating channel only when the operating channel fails to support the least supportable data rate. For the two strategies, we derive closed form expressions for the average data rates and transmission powers. The accuracy of the derived results as well as the performance gains achieved are verified using intensive numerical and simulations results.

Outage performance of Decode and Forward incremental relaying in an overlay spectrum sharing environment

This article analyzes the outage performance of Decode and Forward (DF) incremental relaying when used in an overlay spectrum sharing environment. The terminals of a secondary network exploit the instances of silence of a neighboring primary user to communicate with each other. Secondary terminals utilize an arbitrary spectrum sensing method that is prone to miss-detection and false alarms. The derived closed-form results unveil the losses incurred due to inaccurate spectrum sensing and Co-Channel Interference (CCI). The accuracy of the derived results was verified using computer simulations.

Space-Time Channel Correlation of MIMO Rayleigh Fading Based on Non-isotropic 3D Scattering

In this paper, a general space time correlation function is derived for narrowband (MIMO) Rayleigh fading channels assuming 3D scattering around the mobile station (MS). Non-isotropic scattering is assumed, and the Von Mises PDF of the angle of arrival (AOA) is used. The resulting 3D based correlation functions contain general non-isotropic 2D based functions, as well as isotropic 3D based functions as special cases. It has been shown that non-isotropic scattering increases the channel correlation as functions of the MS antenna spacing. Also, as means of proving the validity of the derived correlation functions, a multichannel autoregressive (AR) simulation method is used to generate channel samples possessing those correlation statistics.

On the space-time correlation of MIMO fading channels in 3D scattering models

In this paper, the time-space correlation function for narrowband MIMO channels is derived. We consider two 3D models, the cylinder model and the sphere model. In both cases, Rician fading is assumed. Scatterers are assumed around the mobile station alone to model macrocell situation. The results show that under reasonable assumptions, both models simplify to the 2D model proposed in (Abdi et al., 2002). Eventually, the construction of the correlation matrix used in the vector autoregressive (VAR) simulation method is studied.

SINR-based spectrum sensing for Cognitive Radio Networks: An online spectrum monitoring method

This article proposes a novel spectrum sensing method based on the instantaneous Signal to Interference plus Noise Ratio (SINR) of the received signal. This method allows the terminals of a Cognitive Radio Network (CRN) to momentarily detect the presence of Co-Channel Interferers (CCI), whether Primary Users (PUs) or other Cognitive Radio (CR) users without the need to schedule a Quiet Period (QP). To achieve the virtues of cooperation, three cooperative sensing protocols are proposed. The first protocol is a centralized majority-voting protocol while the other two protocols are distributed protocols that are integrated with multihop techniques, namely Amplify and Forward (AF) and Decode and Forward (DF). The proposed method and protocols were shown to achieve good detection performance under a wide range of circumstances.

Outage capacity of bidirectional relaying in cognitive relay networks

This article studies the outage capacity of bidirectional relaying using Decode and Forward (DF) in cognitive relay networks. We consider a communication system where two sources attempt to exchange their messages through a set of cognitive relay nodes. Only relays with successful decoding and spectrum acquisition are allowed to participate in the broadcast phase (BC). We consider two schemes for selecting the relays in the BC phase. In the first scheme, successfully decoding at least one of the two signals allows a relay to participate, while the second scheme requires successful decoding of both signals for a relay to participate. Simulation results illustrate the performance advantage of the first scheme for low SNR values. Furthermore, we use high SNR approximations in deriving closed from expressions for the outage capacity.