Mahamod Ismail

A new family of optical code sequences for spectral-amplitude-coding optical CDMA systems

A new code structure for spectral-amplitude-coding optical code-division multiple-access system based on double-weight (DW) code families is proposed. The DW code has a fixed weight of two. By using a mapping technique, codes that have a larger number of weights can be developed. Modified double-weight (MDW) code is a DW code family variation that has variable weights of greater than two. The newly proposed code possesses ideal cross-correlation properties and exists for every natural number n. Based on theoretical analysis and simulation, MDW code is shown here to provide a much better performance compared to Hadamard and modified frequency-hopping codes.

Recent Advances in Wireless Indoor Localization Techniques and System

The advances in localization based technologies and the increasing importance of ubiquitous computing and context-dependent information have led to a growing business interest in location-based applications and services. Today, most application requirements are locating or real-time tracking of physical belongings inside buildings accurately; thus, the demand for indoor localization services has become a key prerequisite in some markets. Moreover, indoor localization technologies address the inadequacy of global positioning system inside a closed environment, like buildings. Based on this, though, this paper aims to provide the reader with a review of the recent advances in wireless indoor localization techniques and system to deliver a better understanding of state-of-the-art technologies and motivate new research efforts in this promising field. For this purpose, existing wireless localization position system and location estimation schemes are reviewed, as we also compare the related techniques and systems along with a conclusion and future trends.

Vehicular communication ad hoc routing protocols: A survey

Abstract Vehicular communications are now the dominant mode of transferring information between automobiles. One of the most promising applications of vehicular communications is the vehicular ad hoc network (VANET), an approach to the intelligent transportation system (ITS). VANET is a subclass of the mobile ad hoc network, which does not depend on fixed infrastructure, in which the nodes are highly mobile. Therefore, the network topology changes rapidly. The design of routing protocols in VANETs is crucial in supporting the ITS. As a prerequisite to communication, the VANET routing protocols must establish an efficient route between network nodes. Furthermore, they should adjust efficiently to the quickly varying topology of moving vehicles. In this paper, we discuss the main characteristics and the research challenge of routing in VANETs, which may be considered in designing various routing protocols. We also created taxonomy of the current routing protocols for VANETs, and we surveyed and compared symbolized instances for all the classes of protocols. This organization and description present the advantages and weaknesses of the current protocols in this field, and paves the way for solutions to unaddressed problems.

A Survey on Power Control Techniques in Femtocell Networks

Rapid increase in mobile data has raised the stakes on developing innovative new technologies and cellular topologies that can meet these demands in an energy efficient manner. One of the most interesting trends that will emerge from this cellular evolution is the femtocell networks. Femtocells are small, inexpensive, low power base stations that are generally consumer deployed, and are expected to significantly improve the coverage and capacity of the indoor users. Femtocell base stations (FBSs) have extensive auto configuration and self-optimization capability to enable simple plug-and-play deployment. The FBSs perform self-optimization function that continually adjusts the transmit power so the femtocell coverage does not leak into an outdoor area while sufficiently covering the indoor femtocell area. In this paper, different power control techniques in femtocell networks have been discussed and compared. The focus is on distributed power control techniques due to the decentralized nature of femtocell networks. The conclusion drawn from this review is that the distributed power control techniques using pilot power control schemes are simple and effective in optimizing the coverage of femtocells as well as reducing power consumption of the FBS. Furthermore a novel algorithm is still needed to perform power control optimization in femtocell networks. 

Survey of Green Radio Communications Networks: Techniques and Recent Advances

Energy efficiency in cellular networks has received significant attention from both academia and industry because of the importance of reducing the operational expenditures and maintaining the profitability of cellular networks, in addition to making these networks “greener.” Because the base station is the primary energy consumer in the network, efforts have been made to study base station energy consumption and to find ways to improve energy efficiency. In this paper, we present a brief review of the techniques that have been used recently to improve energy efficiency, such as energy-efficient power amplifier techniques, time-domain techniques, cell switching, management of the physical layer through multiple-input multiple-output (MIMO) management, heterogeneous network architectures based on Micro-Pico-Femtocells, cell zooming, and relay techniques. In addition, this paper discusses the advantages and disadvantages of each technique to contribute to a better understanding of each of the techniques and thereby offer clear insights to researchers about how to choose the best ways to reduce energy consumption in future green radio networks.

Accurate Wireless Sensor Localization Technique Based on Hybrid PSO-ANN Algorithm for Indoor and Outdoor Track Cycling

This paper aims to determine the distance between the mobile sensor node (i.e., bicycle) and the anchor node (i.e., coach) in outdoor and indoor environments. Two approaches were considered to estimate such a distance. The first approach was based on the traditional channel propagation model that used the log-normal shadowing model (LNSM), while the second approach was based on a proposed hybrid particle swarm optimization-artificial neural network (PSO-ANN) algorithm to improve the distance estimation accuracy of the mobile node. The first method estimated the distance according to the LNSM and the measured received signal strength indicator (RSSI) of the anchor node, which in turn used the ZigBee wireless protocol. The LNSM parameters were measured based on the RSSI measurements in both outdoor and indoor environments. A feed-forward neural network type and the Levenberg-Marquardt training algorithm were used to estimate the distance between the mobile node and the coach. The hybrid PSO-ANN algorithm significantly improved the distance estimation accuracy more than the traditional LNSM method without additional components. The hybrid PSO-ANN algorithm achieved a mean absolute error of 0.022 and 0.208 m for outdoor and indoor environments, respectively. The effect of anchor node density on localization accuracy was also investigated in the indoor environment.

Review: Vehicular communication ad hoc routing protocols: A survey

Abstract Vehicular communications are now the dominant mode of transferring information between automobiles. One of the most promising applications of vehicular communications is the vehicular ad hoc network (VANET), an approach to the intelligent transportation system (ITS). VANET is a subclass of the mobile ad hoc network, which does not depend on fixed infrastructure, in which the nodes are highly mobile. Therefore, the network topology changes rapidly. The design of routing protocols in VANETs is crucial in supporting the ITS. As a prerequisite to communication, the VANET routing protocols must establish an efficient route between network nodes. Furthermore, they should adjust efficiently to the quickly varying topology of moving vehicles. In this paper, we discuss the main characteristics and the research challenge of routing in VANETs, which may be considered in designing various routing protocols. We also created taxonomy of the current routing protocols for VANETs, and we surveyed and compared symbolized instances for all the classes of protocols. This organization and description present the advantages and weaknesses of the current protocols in this field, and paves the way for solutions to unaddressed problems.

Advanced handover techniques in LTE- Advanced system

There are always increasing demands of high speed data applications in wireless systems with fast and seamless access to voice and multimedia services and QoS guaranteed such as in Fourth Generation (4G) Long Term Evolution (LTE)-Advanced system. Moreover, as mobility speeds support is expected to reach up to 500 km/h, the handover will occur more frequent, thus the system performance in terms of delay and packet loss will be degraded. Hence, efficient radio resource management including handover techniques, load balancing and interference management are essential. In this paper, we present a comprehensive survey on the advanced handover techniques, requirements and features for LTE-Advanced system. Also, advanced handover techniques are highlighted and discussed such as Fractional Soft Handover (FSHO), Semi Soft Handover (SSHO) and multi-carrier handover (MCHO) that incorporate backward compatibility to the existing system. Meanwhile, FSHO technique based on CA with 5CCs are investigated in term of cell throughput and users handover numbers. The result shows that, FSHO with 5 CCs improves LTE-Advanced system in term of cell throughput and numbers of user handover better than Non-CA. Consequently, the existing handover techniques that have been proposed have several advantages, but they are not sufficient to solve hard handover problems. Therefore, a new handover technique is essential required to support fast and seamless handover in LTE-Advanced system. As a result, an advanced handover technique is proposed by combining FSHO, SSHO, and MCHO techniques that can enhance the system performance in term of latency, outage probability and handover reliability especially at cell boundary. Also, the expected output from this hybrid technique can reduce transmission overhead on the network cells by balancing the traffic load in the network cells.

Null steering of adaptive beamforming using linear constraint minimum variance assisted by particle swarm optimization, dynamic mutated artificial immune system, and gravitational search algorithm.

Linear constraint minimum variance (LCMV) is one of the adaptive beamforming techniques that is commonly applied to cancel interfering signals and steer or produce a strong beam to the desired signal through its computed weight vectors. However, weights computed by LCMV usually are not able to form the radiation beam towards the target user precisely and not good enough to reduce the interference by placing null at the interference sources. It is difficult to improve and optimize the LCMV beamforming technique through conventional empirical approach. To provide a solution to this problem, artificial intelligence (AI) technique is explored in order to enhance the LCMV beamforming ability. In this paper, particle swarm optimization (PSO), dynamic mutated artificial immune system (DM-AIS), and gravitational search algorithm (GSA) are incorporated into the existing LCMV technique in order to improve the weights of LCMV. The simulation result demonstrates that received signal to interference and noise ratio (SINR) of target user can be significantly improved by the integration of PSO, DM-AIS, and GSA in LCMV through the suppression of interference in undesired direction. Furthermore, the proposed GSA can be applied as a more effective technique in LCMV beamforming optimization as compared to the PSO technique. The algorithms were implemented using Matlab program.

Energy-efficient ZigBee-based wireless sensor network for track bicycle performance monitoring.

In a wireless sensor network (WSN), saving power is a vital requirement. In this paper, a simple point-to-point bike WSN was considered. The data of bike parameters, speed and cadence, were monitored and transmitted via a wireless communication based on the ZigBee protocol. Since the bike parameters are monitored and transmitted on every bike wheel rotation, this means the sensor node does not sleep for a long time, causing power consumption to rise. Therefore, a newly proposed algorithm, known as the Redundancy and Converged Data (RCD) algorithm, was implemented for this application to put the sensor node into sleep mode while maintaining the performance measurements. This is achieved by minimizing the data packets transmitted as much as possible and fusing the data of speed and cadence by utilizing the correlation measurements between them to minimize the number of sensor nodes in the network to one node, which results in reduced power consumption, cost, and size, in addition to simpler hardware implementation. Execution of the proposed RCD algorithm shows that this approach can reduce the current consumption to 1.69 mA, and save 95% of the sensor node energy. Also, the comparison results with different wireless standard technologies demonstrate minimal current consumption in the sensor node.