Magdy S. El-Soudani

A Survey on Trust and Reputation Schemes in Ad Hoc Networks

The dynamic and cooperative nature of ad hoc networks present substantial challenges in securing these networks. There is a natural incentive for nodes to only consume, but not contribute to the services of the system. Intentional misbehavior can aim at an advantage for the misbehaving node or just constitute vandalism, such as enabling a malicious node to mount an attack or a selfish node to save power. The use of reputation systems in many different areas of IT is increasing because of their widely publicized use in online auctions and product reviews. Reputation systems are used to decide who to trust, and to encourage trustworthy behavior. In this paper we introduce the concept, goals, features and architecture of reputation systems and survey the reputation and trust based security schemes that were proposed for ad hoc networks. Finally we conclude this paper.

Lifetime optimization in hierarchical wireless sensor networks

Wireless sensor networks is a voracious field for research, especially after the great advances in MEMS based sensors. In this paper, environmental monitoring applications are considered where data may be continuously reported with the possibility of urgent alarming if necessary. Hierarchical architecture of the network is assumed in order to overcome the problem of energy constrained sensors. Two algorithms are proposed with the purpose of network lifetime elongation and the maximization of the use of the available energy. The first algorithm is a modification for LEACH-C to enhance its performance. It results in a 25% longer lifetime. The second algorithm is an energy efficient method to ensure full coverage of the network as long as sensors are still working. This achieves 32% longer lifetime than LEACH-C.

Immuning Routing Protocols from the Wormhole Attack in Wireless Ad Hoc Networks

Ad hoc networks can be rapidly deployed and reconfigured. Hence, they are very appealing as they can be tailored to lots of applications. Due to their features they are vulnerable to attacks. A particularly severe security attack, called the wormhole attack, has been introduced in the context of ad-hoc networks. During the attack a malicious node captures packets from one location in the network, and tunnels them to another malicious node at a distant point, which replays them locally. In this paper, we propose a scheme for the wormhole attack prevention in ad hoc networks. The scheme relies on the idea that usually the wormhole nodes participate in the routing in a repeated way as they attract most of the traffic. Therefore, each node will be assigned a cost depending in its participation in routing. The cost function is chosen to be exponential in powers of two such that to rapidly increase the cost of already used nodes. Besides preventing the network from the wormhole attack, the scheme provides a load balance among nodes to avoid exhausting nodes that are always cooperative in routing. In addition, a better network performance has been achieved in terms of traffic

Optimized spectrum sensing algorithms for cognitive LTE femtocells

In this article, we investigate to perform spectrum sensing in two stages for a target long-term evolution (LTE) signal where the main objective is enabling co-existence of LTE femtocells with other LTE femto and macrocells. In the first stage, it is required to perform the sensing as fast as possible and with an acceptable performance under different channel conditions. Toward that end, we first propose sensing the whole LTE signal bandwidth using the fast wavelet transform (FWT) algorithm and compare it to the fast Fourier transform-based algorithm in terms of complexity and performance. Then, we use FWT to go even deeper in the LTE signal band to sense at multiples of a resource block resolution. A new algorithm is proposed that provides an intelligent stopping criterion for the FWT sensing to further reduce its complexity. In the second stage, it is required to perform a finer sensing on the vacant channels to reduce the probability of collision with the primary user. Two algorithms have been proposed for this task; one of them uses the OFDM cyclic prefix for LTE signal detection while the other one uses the primary synchronization signal. The two algorithms were compared in terms of both performance and complexity.

Certification and Revocation Schemes in Ad Hoc Networks Survey and Challenges

Ad hoc networks have many features that make them attractive for the use in many applications. However, there are many unsolved problems in ad hoc networks; securing the network being one of the major concerns. The dynamic and cooperative nature of ad hoc networks present substantial challenges in securing these networks. In this paper, we focus on the role of Certification Authorities (CAs) in securing ad hoc networks communication. We introduce the concept of certification authorities and their selection, we survey and classify the certification schemes and give a brief overview on the revocation schemes. We conclude and end this paper by discussing some challenges and research issues in the certification and revocation in ad hoc networks.

Threshold Cryptography and Authentication in Ad Hoc Networks Survey and Challenges

The dynamic and cooperative nature of ad hoc networks present challenges in securing these networks. There are recent research efforts in securing ad hoc networks. Amongst security approaches, there are threshold cryptography and authentication. In this paper we survey the threshold cryptography based schemes and the authentication schemes that have been proposed to secure ad hoc networks. We conclude this paper and identify the challenges and open research areas associated with each of these approaches.

Energy Balanced Model for Data Gathering in Wireless Sensor Networks with Fixed and Mobile Sinks

Ubiquitous computing is increasingly introduced in our daily life. An emerging application is environmental monitoring in urban areas. Data gathering in such wireless sensor networks can be performed by using uncontrolled mobile sinks besides the fixed sinks in order to reduce the transmission energy. This method can be highly inefficient as the notification of presence by the mobile sink is not guaranteed. An efficient hybrid method for message relaying and load balancing is proposed in low mobility wireless sensor networks. The system uses either a single hop transmission to a nearby mobile sink or a multi-hop transmission to a far-away fixed node depending on the predicted sink mobility pattern. Taking a mathematical approach, the system parameters are adjusted so that all the sensor nodes dissipate the same amount of energy. Consequently, the problem of losing connectivity due to the fast power drainage of the closest node to the fixed sink is resolved. Numerical results showed that the system lifetime outperforms classical methods of message gathering.

Security in Ad Hoc Networks: From Vulnerability to Risk Management

Mobile Ad hoc Networks (MANETs) have lots of applications. Due to the features of open medium, absence of infrastructure, dynamic changing network topology, cooperative algorithms, lack of centralized monitoring and management point, resource constraints and lack of a clear line of defense, these networks are vulnerable to attacks. A vital problem that must be solved in order to realize these applications is that concerning the security aspects of such networks. Solving these problems combined with the widespread availability of devices such as PDAs, laptops, small fixtures on buildings and cellular phones will ensure that ad hoc networks will become an indispensable part of our life. In this paper, we discuss the reasons of vulnerability as well as active and passive attacks on such networks. We present the security measures used to secure ad hoc networks such as authentication, threshold cryptography, trust and reputation, and present a risk management scheme. Concluding remarks are presented at the end of this paper, while mentioning the different open research areas and challenges in the discussed security measures.

WiFi architecture for traffic control using MIPv6

This paper focuses on the wireless communication aspect of the traffic control problem in urban areas. The IEEE 802.11b standard is used and an architecture is developed that produces zero packet loss at vehicle speeds of up to 60 Km/hr. A quantitative comparison is made between the Mobile Internet Protocol v4 (MIPv4) and MIPv6. It is shown that MIPv6 produces much less packet losses than MIPv4. Burst communication is then used to eliminate packet losses completely and the inter-packet and inter-burst intervals are determined. Finally, the effects of the router advertisement interval (RAI) and the mobility detection factor (MDF) are investigated and the optimum parameter values are determined in the context of the traffic control problem.

Elongation of WSN lifetime using a centralised clustering technique

Wireless sensor networks (WSN) is one of the most important fields of research in recent years due to its wide range of applications. Lifetime elongation is the main concern in WSN. This paper focuses on improving the lifetime by using the clustering technique with a centralised algorithm. The optimum number of clusters that maximises the lifetime is obtained and the relation between clusters is investigated. The results prove that the independency of cluster head selection decisions improves the lifetime. Clustering is applied to networks covering large areas and the clustering efficiency is verified. Also, using clustering in applications that do not need data aggregation, is investigated.