Haitham S. Hamza

A Survey on Inter-Cell Interference Coordination Techniques in OFDMA-Based Cellular Networks

Orthogonal Frequency Division Multiplexing Access (OFDMA) has been increasingly deployed in various emerging and evolving cellular systems to reduce interference and improve overall system performance. However, in these systems Inter-Cell Interference (ICI) still poses a real challenge that limits the system performance, especially for users located at the cell edge. Inter-cell interference coordination (ICIC) has been investigated as an approach to alleviate the impact of interference and improve performance in OFDMA-based systems. A common ICIC technique is interference avoidance in which the allocation of the various system resources (e.g., time, frequency, and power) to users is controlled to ensure that the ICI remains within acceptable limits. This paper surveys the various ICIC avoidance schemes in the downlink of OFDMA-based cellular networks. In particular, the paper introduces new parameterized classifications and makes use of these classifications to categorize and review various static (frequency reuse-based) and dynamic (cell coordination-based) ICIC schemes.

Wavelength-exchanging cross connects (WEX)-a new class of photonic cross-connect architectures

All-optical wavelength division multiplexing (WDM) networks are expected to realize the potential of optical technologies to implement different networking functionalities in the optical domain. A key component in WDM networks is the optical switch that provides the basic functionality of connecting input ports to output ports. Existing WDM switches make use of space switches and wavelength converters (WCs) to realize switching. However, this not only increases the size and the complexity of the switch but also bears heavily on the cost. In this paper, the authors propose a new class of photonic switch architectures called wavelength-exchanging cross connect (WEX) that provides several advantages over existing switches by enabling a single-step space switching and wavelength conversion and thus eliminating the need for a separate conversion stage. This greatly enhances the switch architecture by reducing its size and complexity. The new class of cross-connect architectures is based on the proposed concept of a wavelength-exchange optical crossbar (WOC). The WOC concept is realized using the simultaneous exchange between two optical signals. The proposed WEX architecture is highly scalable. To establish scalability, the authors present a systematic method of developing instances of the switch architectures of an arbitrary large size

An algorithm for boundary discovery in wireless sensor networks

Wireless Sensor Networks (WSNs) consist of a large number of nodes networked via wireless links. In many WSN settings, sensor nodes are deployed in an ad hoc manner. One important issue in this context is to detect the boundary of the deployed network to ensure that the sensor nodes cover the target area. In this paper, we propose a new algorithm that can be used to discover the boundary of a randomly deployed WSN. The algorithm does not require the sensor nodes to be equipped with positioning devices and is scalable for large number of nodes. Simulation experiments are developed to evaluate the performance of the proposed algorithms for different network topologies. The simulation results show that the algorithm detects the boundary nodes of the network with high accuracy.

Secure multicast routing protocols in mobile ad-hoc networks

A mobile ad-hoc network MANET is a collection of autonomous nodes that communicate with each other by forming a multi-hop radio network. Routing protocols in MANETs define how routes between source and destination nodes are established and maintained. Multicast routing provides a bandwidth-efficient means for supporting group-oriented applications. The increasing demand for such applications coupled with the inherent characteristics of MANETs e.g., lack of infrastructure and node mobility have made secure multicast routing a crucial yet challenging issue. Recently, several multicast routing protocols MRP have been proposed in MANETs. Depending on whether security is built-in or added, MRP can be classified into two types: secure and security-enhanced routing protocols, respectively. This paper presents a survey on secure and security-enhanced MRP along with their security techniques and the types of attacks they can confront. A detailed comparison for the capability of the various routing protocols against some known attacks is also presented and analyzed. Copyright

A survey on security enhanced multicast routing protocols in Mobile Ad hoc Networks

A Mobile Ad-hoc Network (MANET) is a collection of autonomous nodes that communicate with each other by forming a multi-hop radio network. Routing protocols in MANETs define how routes between source and destination nodes are established and maintained. Multicast routing provides a bandwidth-efficient means for supporting group-oriented applications. The increasing demand for such applications coupled with the inherit characteristics of MANETs (e.g., lack of infrastructure and node mobility) have made secure multicast routing crucial yet challenging issue. Recently, several multicast routing protocols have been proposed in MANETs. This paper presents a comprehensive survey on multicast routing protocols along with their security techniques and the types of attacks they can confront. A comparison for the capability of the various secured multicast routing protocols against the identified attacks is also presented.

WDM optical interconnects: a balanced design approach

In this paper, we develop a new design approach to wavelength division multiplexing (WDM) optical interconnects with the objective of designing cost-effective and scalable interconnects. Our design philosophy strikes a balance between switching and conversion costs, and requires wavelength conversion only between two fixed and predefined wavelengths. The proposed design approach exploits the potential of the wavelength exchange optical crossbar (WOC) - a device that can switch signals simultaneously and seamlessly both in space and wavelength domains. We propose a novel crossbar switch that minimizes hardware and control complexity and use it as a building block for developing a new class of three-stage Clos-like WDM optical interconnects. The design space of the proposed interconnect is characterized and its hardware complexity is analyzed. We also show that the proposed crossbar switch and the new class of WDM interconnects admit most existing routing algorithms with simple modifications. In addition, we show that our design approach can be generalized to develop a class of k-stage interconnects, 3 < k les 2 log2 N-1.

Demonstration of a nanoparticle-based optical diode

We present the operation of an optical device that exhibits diodelike properties based on two adjacent layers of quantum dots (QDs) encased in a fiber-optic jacket. The possibility of a multilayered device is also discussed. A significant change in the emission spectrum of CdSe/ZnS core-shell QDs was observed when excited by the input laser and the fluorescence of other CdSe/ZnS core-shell QDs. The output of the diode can be taken to be either the incoming laser wavelength of light similar to a conventional diode, or the output may be considered to be one of the QD fluorescence wavelengths. Current work has applications in biological fluorescence monitors and sensors as well as in telecommunications applications.

New attacks and efficient countermeasures for multicast AODV

Security in multicast routing in MANETs is crucial in order to enable effective and efficient multicast-based applications. Multicast Ad-hoc On-demand Distance Vector (MAODV) protocol is one of the well-known multicast routing protocol in MANET. In this paper, we identify and describe, for the first time, three new protocol-dependant attacks on multicast operations of MAODV namely, Group Leader Selection (GLS); False Link Breakage (FLB) and Group Leader Pruning (GLP) attack. For each attack, we implement a scenario to demonstrate the impact of the attack on the performance of the network. Implemented scenarios show a considerable degradation in the Packet Delivery Ratio (PDR) of the protocol. Accordingly, we propose security countermeasures for the identified attacks. Simulation results of the secured and unsecured MAODV show that the proposed countermeasures are effective and efficient. In particular, compared to unsecured MAODV, the proposed countermeasures improve the PDR with 85%

A Framework for Identifying Reusable Software Components Using Formal Concept Analysis

Component-based development (CBD) is concerned with enabling the design of software systems by reusing predeveloped components. One important activity in CBD is to analyze the business domain and identify potential reusable domain components. Identifying business components, however, can be challenging due to the different nature of the application requirements even within the same domain. Moreover, the rapid change in customer needs and business requirements might render domain components obsolete if these components can not accommodate changes with minimal cost and effort. This paper presents a novel framework for identifying and encapsulating stable domain components. The framework makes use of the theory of Formal Concept Analysis (FCA) and the concepts of Software Stability Model (SSM) to identify stable domain components. The details of the proposed framework are described and then demonstrated by the means of a case study.

Applying Analysis Patterns Through Analogy: Problems and Solutions

Traceability and generality are among the main qualities that determine the effectiveness of developed analysis patterns. However, satisfying both qualities at the same time is a real challenge. Most of the analysis patterns are thought of as templates, where they can be instantiated, and hence reused through an analogy between the original pattern and the problem in hand. Developing analysis patterns as templates might maintain the appropriate level of generality; however, it scarifies patterns’ traceability once they are applied in the developed system. In this paper, we illustrate the main problems with developing analysis patterns as templates and reusing them through analogy. In addition, we demonstrate, through examples, how stable analysis patterns [Hamza, 2002a,Hamza and Fayad 2002a] can satisfy both the generality and traceability, and hence, enhance the role of analysis patterns in software development.