Raed M. Shubair

An overview of localization techniques for Wireless Sensor Networks

Localization of sensor nodes is an important aspect in Wireless Sensor Networks (WSNs). This paper presents an overview of the major localization techniques for WSNs. These techniques are classified into centralized and distributed depending on where the computational effort is carried out. The paper concentrates on the factors that need to be considered when selecting a localization technique. The advantages and limitation of various techniques are also discussed. Finally, future research directions and challenges are highlighted.

Computationally efficient DOA estimation in a multipath environment using covariance differencing and iterative spatial smoothing

High-resolution signal processing using sensor arrays to estimate the directions of unknown correlated signals in multipath environments is associated with high computational complexity. This paper proposes a computationally efficient direction of arrival (DOA) estimation algorithm. The algorithm is based on two stages of detection: a first stage for discriminating uncorrelated signals and a second stage for resolving the directions of arrival of correlated signals using covariance differencing and iterative spatial smoothing. Simulation results show that the proposed algorithm operates at a much lower computational cost compared to standard methods.

Self-Optimization of Pilot Power in Enterprise Femtocells Using Multi objective Heuristic

Deployment of a large number of femtocells to jointly provide coverage in an enterprise environment raises critical challenges especially in future self-organizing networks which rely on plug-and-play techniques for configuration. This paper proposes a multi-objective heuristic based on a genetic algorithm for a centralized self-optimizing network containing a group of UMTS femtocells. In order to optimize the network coverage in terms of handled load, coverage gaps, and overlaps, the algorithm provides a dynamic update of the downlink pilot powers of the deployed femtocells. The results demonstrate that the algorithm can effectively optimize the coverage based on the current statistics of the global traffic distribution and the levels of interference between neighboring femtocells. The algorithm was also compared with the fixed pilot power scheme. The results show over fifty percent reduction in pilot power pollution and a significant enhancement in network performance. Finally, for a given traffic distribution, the solution quality and the efficiency of the described algorithm were evaluated by comparing the results generated by an exhaustive search with the same pilot power configuration.

Survey on device-to-device communications: Challenges and design issues

Device-to-Device (D2D) communications has been proposed to cellular networks in order to optimize spectrum efficiency and resources utilization. In D2D-assisted networks, the traditional cellular communication techniques are not applicable but rather need to be redesigned to fulfill new requirements. Therefore, new communication techniques are proposed to take the advantages of the D2D connectivity in the network. In this paper, we describe the concept of D2D communications. Then, we review the main challenges and design issues of D2D-assisted networks. This survey focuses on cooperative communications in D2D-assisted networks and addresses challenges which limit the performance of the cooperative D2D-assisted networks such as relay selection, power consumption and multi-casting. Moreover, design issues and approaches to overcome these limitations are explained.

Deployment challenges of femtocells in future indoor wireless networks

Femtocell technology is expected to improve both coverage and capacity, especially indoors. Providers of cellular services are increasingly implementing this technology in their networks. However, the decentralized manner of femtocells operation introduces several challenges. This paper presents an overview of the femtocells. It highlights the network requirements for deploying femtocells and discusses the major issues that affect their operation and performance. The paper also describes the key challenges of deploying femtocells and some of the proposed solutions. It then presents the future direction on applying optimization to enhance femtocell performance.

A Compact CSRR-Enabled UWB Diversity Antenna

The purpose of this letter is to introduce a compact ultrawideband (UWB) diversity antenna with a very low envelope correlation coefficient (ECC). The design employs a hybrid isolation enhancing and miniaturization technique. The antenna consists of two counter facing monopoles, and is miniaturized by using not only inverted-L stubs but also a complementary split-ring resonator (CSRR) on the ground plane. The added components enhance isolation and enable tighter packing of the antennas. The result is a very compact multiple-input–multiple-output (MIMO) array with an overall size of 23

In vivo wireless body communications: State-of-the-art and future directions

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Hybrid RSS-DOA technique for enhanced WSN localization in a correlated environment

29 mm2 , which covers the entire UWB spectrum from 3 to 12 GHz, with mutual coupling lower than –15 dB. Moreover, the CSRR unit that acts as a resonator is applied for the first time to suppress the interference of RF currents flowing through the ground plane of this UWB-MIMO/diversity antenna. The performance of the fabricated prototype in terms of scattering parameters, broadside (peak) gain, radiation patterns, efficiency, and ECC is presented and discussed.

Robust interference suppression using a new LMS-based adaptive beamforming algorithm

The emerging in vivo communication and networking system is a prospective component in advancing health care delivery and empowering the development of new applications and services. In vivo communications construct wirelessly networked cyber-physical systems of embedded devices to allow rapid, correct and cost-effective responses under various conditions. This paper surveys the existing research which investigates the state of art of the in vivo communication. It also focuses on characterizing and modeling the in vivo wireless channel and contrasting this channel with the other familiar channels. MIMO in vivo is as well regarded in this overview since it significantly enhances the performance gain and data rates. Furthermore, this paper addresses current challenges and future research areas for in vivo communications.

Performance evaluation of direction finding algorithms for adapative antenna arrays

This paper proposes a modified hybrid method for WSN localization that combines Received Signal Strength (RSS) and Direction of Arrival (DOA) estimation based on MUSIC (Multiple Signal Classification) using circular antenna array with smoothing capability. Simulation results proves the enhanced performance obtained using the proposed hybrid method. This takes the form of successful detection of a mixture of correlated and uncorrelated signals at a higher accuracy and lower Root Mean Square Error (RMSE) in comparison with conventional method.