Ashraf S. Hasan Mahmoud

Video transmission enhancement in presence of misbehaving nodes in MANETs

Mobile Ad-hoc NETworks (MANET) are infrastructureless networks where self-configuring mobile nodes are connected by wireless links. Because of its decentralized operation, these nodes rely on each other to store and forward packets. Video transmission over MANETs is more challenging than over conventional wireless networks due to rapid topology changes and lack of central administration. Most of the proposed MANET protocols assume that all nodes are working within a cooperative and friendly network context. However, misbehaving nodes that exhibit abnormal behaviors can disrupt the network operation and affect the network availability by refusing to cooperate to route packets due to their selfish or malicious behavior. In this paper, we examine the effect of packet dropping attacks on video transmission over MANETs. We also study the effects of mitigation using intrusion detection systems to MANET in presence of video traffic. To the best of our knowledge, this is the first attempt to study multimedia over such environments. We propose a novel intrusion detection system, which is an adaptive acknowledgment scheme (AACK) with the ability to detect misbehaved nodes and avoid them in other transmissions. The aim of AACK scheme is to overcome watchdog weaknesses due to collisions and limited transmission power and also to improve TWOACK scheme. To demonstrate the performance of our proposed scheme, simulation experiments are performed. The results of our experiments show that MPEG4 is more suitable for our simulation environment than H264 video traffic. The simulation results show that AACK scheme provides better network performance with less overhead than other schemes; it also shows that AACK outperforms both TWOACK and watchdog in video transmission applications in the presence of misbehaving nodes.

A multiple access scheme for wireless access to a broadband ATM LAN based on polling and sectored antennas

An adaptive polling scheme for multiple access in a broadband wireless local area networks (LANs) is proposed. It is designed to accommodate asynchronous transfer mode (ATM) traffic with a large and variable range of bit rates. The radio architecture is microcellular, with switched sectored-beam antennas and a small frequency reuse factor. Features of the multiple access scheme include polling rate depending on a terminals average bit rate, fixed-length frames divided into segments corresponding to base antenna sectors, and automatic-repeat-request (ARQ) for error control, combined with randomized sector segment ordering. The steady-state performance (cell loss, call blocking and dropping probabilities, waiting time, and buffer occupancy) are evaluated by simulation for an open indoor environment, and for handoff, ARQ, and simple power control enhancements; focusing mainly on the effects of the propagation and interference conditions.

AACK: Adaptive Acknowledgment Intrusion Detection for MANET with Node Detection Enhancement

A Mobile Ad-hoc NETwork (MANET) is an infrastructureless network consisting of self-configuring mobile nodes connected by wireless links. Nodes rely on each other to store and forward packets. Most of the proposed MANET protocols assume cooperative and friendly network context, and do not address security issues. Furthermore, MANETs are highly vulnerable for passive and active attacks because of their open medium, rapidly changing topology, lack of centralized monitoring. Encryption and authentication solutions, which are considered as the first line of defense, are not sufficient to protect MANETs from packet dropping attacks. Most of the current Intrusion Detection Systems (IDSs) for MANETS rely on the Watchdog technique. In this research we study the behavior of this technique and propose a novel mechanism, named: Adaptive ACKnowledgment (AACK), for solving two significant problems: the limited transmission power and receiver collision. This mechanism is an enhancement to the TWOACK scheme where its detection overhead is reduced while the detection efficiency is increased. NS2 is used to simulate and evaluate the proposed scheme and compare it against the TWOACK and Watchdog methods. The obtained results show that the new AACK scheme outperforms both of the TWOACK and Watchdog methods in terms of network packet delivery ratio and routing overhead.

A Heuristic Genetic Algorithm for the Single Source Shortest Path Problem

This paper addresses one of the potential graph-based problems that arises when an optimal shortest path solution, or near optimal solution is acceptable, namely the Single Source Shortest Path (SSP) problem. To this end, a novel Heuristic Genetic Algorithm (HGA) to solve the SSSP problem is developed and evaluated. The proposed algorithm employs knowledge from deterministic techniques and the genetic mechanism to achieve high performance and allow consistent convergence. In addition, the proposed HGA is implemented and evaluated using a developed software tool that is easily amenable for future extensions and variations of our HGA. The schema introduced in this proposal depends on starting with initial population of candidate solution paths constraints as an alternative of a randomly generated one. To preserve the high performance candidate solutions, the HGA also uses a new heuristic order crossover (HOC) operator and mutation (HSM) operator to keep the search limited to feasible search domain. Simulation results indicate that the developed HGA is highly efficient in finding an optimal also quantify the effect initial population size and the increase of generation numbers.

Dynamic radio resource allocation for 3G and beyond mobile wireless networks

Next generation of wireless cellular networks aim at supporting a diverse range of multimedia services to mobile users with guaranteed quality of service (QoS). Resource allocation and call admission control (CAC) are key management functions in future 3G and 4G cellular networks, in order to provide multimedia applications to mobile users with QoS guarantees and efficient resource utilization. There are two main strategies for radio resource allocations in cellular wireless networks known as complete partitioning (CP) and complete sharing (CS). In this paper, theses strategies are extended for operation in 3G and beyond network. First, two CS-based call admission controls, referred to herein as queuing priority call admission control (QP-CAC) and hybrid priority call admission control (HP-CAC), and one CP-based call admission control referred to as complete partitioning call admission control (CP-CAC) are presented. Then, this study proposes a novel dynamic procedure, referred to as the dynamic prioritized uplink call admission control (DP-CAC) designed to overcome the shortcomings of CS and CP-based CACs. Results indicate the superiority of DP-CAC as it is able to achieve a better balance between system utilization, revenue, and quality of service provisioning. CS-based algorithms achieve the best system utilization and revenue at the expense of serious unfairness for the traffic classes with diverse QoS requirements. DP-CAC manages to attain equal system utilization and revenue to CS-based algorithms without the drawbacks in terms of fairness and service differentiation.

Performance improvement of dynamic source routing protocol the mobility effect of nodes in cache management

In this paper we propose a new method of improving the performance of dynamic source routing (DSR) protocol. In DSR, as well as other on-demand routing protocols, every established path is considered as temporary to reflect the mobility effect, therefore, once a path is established, it is associated with an expiration time. After that expiration time the path is deleted from the route cache of the nodes. In practice the mobility of nodes are not equal all the time and we propose to treat paths differently according to their stationary, rather than deleting them after every expiration time to improve performance. By simulation we show that this method improves the performance of DSR

Adaptive Power Allocation Algorithm to Support Absolute Proportional Rates Constraint for Scalable OFDM Systems

It is generally hard to find the optimal solution for sub-channel and power allocation for a multiuser Orthogonal Frequency Division Multiplexing (OFDM) system that maximizes the overall system capacity given the proportional rate constraint. Most existing solutions either utilize a suboptimal sub-channel allocation and attempt to compute the optimal power allocation or assume uniform power distribution among sub-channels and attempt to optimize using the sub-channel allocation. It is observed that derived solutions do not necessarily satisfy the proportional rate constraint, also referred to as the fairness constraint, supplied in the problem formulation. This paper proposes an iterative algorithm that computes the optimal power allocation for a given sub-channel allocation scheme. Unlike previous solutions, the proposed solution does not make any assumptions regarding the channels or regarding the proportionality constants. Furthermore, the proposed solution satisfies the proportional rate constraint in the strictest sense and therefore can provide absolute or hard rate guarantees as opposed to soft ones as the case for previous algorithms. Presented numerical example, shows that the our algorithm outperforms the original optimal power allocation algorithm and achieves strict satisfaction of the fairness constraint.

A survey on developing publish/subscribe middleware over wireless sensor/actuator networks

Publish/subscribe (Pub/Sub) interaction paradigm is receiving more attention in commercial and academic research nowadays. It is an effective interaction scheme for large-scale distributed systems due to its ability of decoupling communicating entities in time, space, and synchronization. The decoupling properties are well-suited for Wireless Sensor Network (WSN) applications because of their special characteristics such as data-centricity, dynamicity, and many-to-many communications. Many studies have been conducted to adapt Pub/Sub communication model to WSN. In this paper, we review the Pub/Sub interaction paradigm in the context of WSN. Moreover, we classify, analyze and synthesize different Pub/Sub based solutions proposed recently for WSN and discuss the open problems and new research directions in this area. Also, we propose a new reference model for pub/sub middleware in wireless sensor and actuator networks. To the best of our knowledge this is the first survey on this specific subject.

Comparative Performance Study for Integrated 3G/WLAN Networks Using Mobile IP, SIP, and m-SCTP Protocols

The 3rd Generation Partnership Project (3GPP) has adopted an interworking architecture between Universal Mobile Telecommunication System (UMTS) and Wireless Local Area Networks (WLANs). This architecture imposes a set of security requirements on subscribers connecting from within interworked WLANs to be able to access their 3G home packet-switched services. Providing seamless handoff and session continuity of ongoing communication is a critical task in UMTS/WLAN integrated networks. However, the 3GPP does not specify how mobility can be supported. This paper provides a performance evaluation for the three candidate solutions: Mobile IP (MIP), Session Initiation Protocol (SIP), and mobile Stream Control Transmission Protocol (mSCTP) that may be used to provide session continuity in the integrated network. The vertical handoff delay figure is analyzed using simulations for different WLAN speeds and its major components due to the involved signaling procedures are quantified. The results are derived from our developed OPNET based simulation model that accounts for the detailed prescribed signaling procedures as per the related standards and Request for Comments (RFCs) documents, and the main network entities in the adopted architecture. The presented analysis provides insight into the potential performance bottlenecks in the integrated network. Major findings of the work show that the security related signaling and the signaling pertaining to obtaining a new Internet Protocol (IP) address, each contribute about 40% of the total delay for all the three solutions. Enhancements targeting these procedures will help reduce the overall delay while supporting seamless handoff between the two networks.

New Quadrature-Based Approximations for the Characteristic Function and the Distribution Function of Sums of Lognormal Random Variables

Characterizing the distribution of the sum of lognormal random variables (RVs) is still an open issue. This paper proposes simple and new quadrature-based approximations of the characteristic function (CF) and the cumulative distribution function (cdf) of the sum of independent and correlated lognormal RVs. Exploiting the recent Hermite-Gauss quadrature-based approximation, which is provided for the CF of a single lognormal RV, this paper proposes expressions that are given in terms of quadrature nodes and weights, as well as in terms of the parameters of individual lognormal RVs and the covariance matrix for the correlated RV case. More importantly, the developed expression for the cdf does not require prior knowledge of the actual cdf or the employment of specialized numerical integration methods. Numerical examples and comparisons with approximation techniques for the cdf of the sum found in the literature are provided. The examples show that while most of the known approximation techniques are valid for either small or large values of the abscissa, but not both, the proposed cdf formula provides reasonable approximation over a wide range of the abscissa. Furthermore, the study shows that as the actual cdf of the sum departs from the straight-line shape and its concavity increases, when plotted on a normal probability scale, even techniques that specialize in approximating the low-end tail of the cdf start to produce higher errors. The proposed formula continues to accurately approximate the actual cdf.