Khaleel W. Mershad

COACS: A Cooperative and Adaptive Caching System for MANETs

This paper introduces a cooperation-based database caching system for Mobile Ad Hoc Networks (MANETs). The heart of the system is the nodes that cache submitted queries. The queries are used as indices to data cached in nodes that previously requested them. We discuss how the system is formed and how requested data is found if cached, or retrieved from the external database and then cached. Analysis is performed and expressions are derived for the different parameters, including upper and lower bounds for the number of query caching nodes as well as the average load they experience, generated network traffic, node bandwidth consumption, and other performance-related measures. Simulations with the ns-2 software were used to study the performance of the system in terms of average delay and hit ratio, and to compare it with the performance of two other caching schemes for MANETs, namely CachePath and CacheData. The results demonstrate the effectiveness of the proposed system in terms of achieved hit ratio and low delay.

ROAMER: Roadside Units as message routers in VANETs

Vehicular Ad hoc Networks, also known as VANETs, enable vehicles that are not necessarily within the same radio transmission range to communicate with each other. VANETs also allow vehicles to connect to Roadside Units (RSUs). The latter are connected to the Internet, forming a fixed infrastructure that offers them the capability of communicating with each other and with roaming vehicles. RSUs support cooperative and distributed applications in which vehicles and RSUs work together to coordinate actions and to share and process several types of information. RSUs have so far been used for different roles such as data disseminators, traffic directories, location servers, security managers, and service proxies. In this paper, we focus on routing; namely we exploit RSUs to route packets between any source and destination in the VANET. To our knowledge, this is the first attempt to use the RSU backbone to efficiently route packets to very far locations in VANETs by using geographic forwarding. We evaluate the RSU backbone routing performance via the ns2 simulation platform. We compare our scheme to existing solutions and prove the feasibility and efficiency of our scheme in terms of query delay, packet success delivery ratio, and total generated traffic.

A Framework for Secure and Efficient Data Acquisition in Vehicular Ad Hoc Networks

Intervehicular communication lies at the core of a number of industry and academic research initiatives that aim at enhancing the safety and efficiency of transportation systems. Vehicular ad hoc networks (VANETs) enable vehicles to communicate with each other and with roadside units (RSUs). Service-oriented vehicular networks are special types of VANETs that support diverse infrastructure-based commercial services, including Internet access, real-time traffic management, video streaming, and content distribution. Many forms of attacks against service-oriented VANETs that attempt to threaten their security have emerged. The success of data acquisition and delivery systems depends on their ability to defend against the different types of security and privacy attacks that exist in service-oriented VANETs. This paper introduces a system that takes advantage of the RSUs that are connected to the Internet and that provide various types of information to VANET users. We provide a suite of novel security and privacy mechanisms in our proposed system and evaluate its performance using the ns2 software. We show, by comparing its results to those of another system, its feasibility and efficiency.

Finding a STAR in a Vehicular Cloud

The strong capabilities that exist in a Vehicular Ad hoc Network (VANET) has given birth to the concept of Vehicular Clouds, in which cloud computing services are hosted by vehicles that have sufficient resources to act as mobile cloud servers. In this paper, we design a system that enables vehicles in a VANET to search for mobile cloud servers that are moving nearby and discover their services and resources. The system depends on RSUs that act as cloud directories with which mobile cloud servers register. The RSUs share their registration data to enable vehicles to discover and consume the services of mobile cloud servers within a certain area. We evaluated the proposed system using the ns2 software and demonstrated through comparing the results to another mechanism the feasibility and efficiency of our system in terms of service discovery and service consuming delays and packet success ratio.

SSUM: Smart Server Update Mechanism for Maintaining Cache Consistency in Mobile Environments

This paper proposes a cache consistency scheme based on a previously proposed architecture for caching database data in MANETs. The original scheme for data caching stores the queries that are submitted by requesting nodes in special nodes, called query directories (QDs), and uses these queries to locate the data (responses) that are stored in the nodes that requested them, called caching nodes (CNs). The consistency scheme is server-based in which control mechanisms are implemented to adapt the process of caching a data item and updating it by the server to its popularity and its data update rate at the server. The system implements methods to handle disconnections of QD and CN nodes from the network and to control how the cache of each node is updated or discarded when it returns to the network. Estimates for the average response time of node requests and the average node bandwidth utilization are derived in order to determine the gains (or costs) of employing our scheme in the MANET. Moreover, ns2 simulations were performed to measure several parameters, like the average data request response time, cache update delay, hit ratio, and bandwidth utilization. The results demonstrate the advantage of the proposed scheme over existing systems.

MDPF: Minimum Distance Packet Forwarding for Search Applications in Mobile Ad Hoc Networks

This paper introduces a message forwarding algorithm for search applications within mobile ad hoc networks that is based on the concept of selecting the nearest node from a set of designated nodes. The algorithm, which is called Minimum Distance Packet Forwarding (MDPF), uses routing information to select the node with the minimum distance. The goal of the proposed algorithm is to minimize the average number of hops taken to reach the node that holds the desired data. Numerical analysis and experimental evaluations using the network simulation software ns2 were performed to derive the lower and upper bounds of the confidence interval for the mean hop count between the source node of the data request, on one hand, and the node that holds the desired data and the last node in the set of search nodes, on the other hand. In the experimental evaluation, the performance of MDPF was compared to that of Random Packet Forwarding (RPF) and Minimal Spanning Tree Forwarding (MSTF). The results agreed with the numerical analysis results and demonstrated that MDPF offers significant hop count savings and smaller delays when compared to RPF and MSTF.

DSDM: A Distributed Service Discovery Model for Manets

Service discovery is indispensable to ad hoc networking where establishing a stand-alone and self-configurable communication environment is the main objective. This paper concentrates on designing a distributed service discovery model for service sharing among diverse mobile devices in mobile ad hoc networks. This model is built on top of the network layer of the TCP/IP stack and benefits from the up-to-date routing information enabled by proactive routing protocols that attempt to keep the information in the routing tables of the mobile nodes current. The designed system is based on storing service descriptions in selected nodes that are searched in accordance to a proposed Minimum Distance Packet Forwarding (MDPF) algorithm. In addition to identifying and analyzing the design parameters of the system, this paper studies the delay and traffic performance using analytical derivations and experimental evaluation based on the ns-2 network simulation software. The system is intended to be used in a collaborative mobile ad hoc network environment whereby a mobile node can consume services, share them, or facilitate such sharing by helping other nodes find them.

A Cluster Based Service Discovery Model for Mobile Ad Hoc Networks

Mobile ad hoc networks, as a typical example of self-organized networks, represent an emerging and promising communication paradigm. Not only the variety of devices but also the diversity of services is continuously increasing. Such services must be provisioned in a flexible and distributed way without a central infrastructure. The discovery of such services is an involved task since it must cope with the high level of mobile device heterogeneity, degree of mobility, and take the limited device resources into account. In this paper, we propose a decentralized and scalable service discovery and invocation framework for ad hoc networks of clustered mobile devices. The basic idea is to use the clusterheads as service directory nodes to assist mobile nodes in the network in finding desired services. In addition to storing the descriptions of services that fall in their clusters, clusterheads also cache descriptions of services that are retrieved from other clusters as they are requested. Experimental analyses are conducted to study the performance of the proposed architecture and to compare it with the broadcast-based model that has been extensively studied in the literature.

REACT: Secure and efficient data acquisition in VANETs

Vehicular ad hoc networks (VANETs) enable vehicles that are not necessarily within the same radio transmission range to communicate with each other and with roadside units (RSUs). The success of data acquisition and delivery systems in VANETs depends on their ability to defend against the different types of security and privacy attacks. The security of safety messages (like emergency and traffic information) has been the concern of VANET security researchers, and very few works dealt with the security of data messages exchanged between users and the infrastructure. This paper introduces a system that takes advantage of the RSUs that are connected to the internet and provide various types of information to VANET users. We provide a suite of novel security and privacy mechanisms in our proposed system, and evaluate its performance using the ns2 software. We demonstrate through comparing its results to those of another system its feasibility and efficiency.

CODISC: Collaborative and distributed semantic caching for maximizing cache effectiveness in wireless networks

In wireless mobile ad hoc networks (MANETs), a mobile node would normally acquire data from a data server through an access point by sending the server a request each time it needs data. To reduce the high costs normally associated with accessing remote servers (i.e., outside the MANET), data caching by the mobile nodes can be employed. Several caching techniques for MANETs have been proposed and implemented, including a cooperative scheme that we recently introduced. It employs a directory-based approach in which submitted queries are cached in the MANET to be used subsequently as indexes to corresponding data items (results). When a request is issued, nodes cooperate to find its answer (if it exists) and send it to the requesting node. In this paper, we extend this scheme by semantically comparing each submitted request with all cached queries. The semantic analysis process includes trimming the request into fragments and joining the answers of these fragments to produce the answer of the request. We study the performance of the proposed system both analytically and experimentally, and prove the advantageous features of the system relative to others in terms of query response time, generated traffic, and hit ratio.