Sharif Digital Repository

Prevention of unauthorized access to services in mobile ad hoc networks is a more sophisticated problem than access control in other networks, due to interconnection facilities and lack of any fixed network infrastructure in such networks. Therefore regarding the nature of these networks, controlling access to services should be in a decentralized manner providing good performance and preserving network security. In this paper, we propose a decentralized Cooperation Enforcement Based Access Control (CEBAC) framework for mobile ad hoc networks. CEBAC comprises several groups of Service Authorizers, each issuing Credentials for access to a specific kind of services. The User Authorization for... 

A mobile ad hoc network is a collection of mobile hosts forming a temporary network on the fly, without using any fixed infrastructure. Characteristics of mobile ad hoc networks such as lack of central coordination, mobility of hosts, dynamically varying network topology, and limited availability of resources make QoS provisioning very challenging in such networks. In this paper, we introduce a fuzzy QoS traffic conditioner for mobile ad hoc networks. The proposed traffic conditioner consists of fuzzy admission control (FAC), fuzzy traffic rate controller (FTRC), and fuzzy scheduler (FS). The proposed FAC monitors the delay and available bandwidth and decides whether to accept or reject the... 

Mobile Ad Hoc Networks (MANETs) are networks with selforganizing capabilities and without a fixed infrastructure. Wireless nodes communicate among themselves using multi-hop radio relaying, without requiring the packets to pass through a central access point or a base station. In a highly mobile and infrastructure-less scenario, pre-configuration of addresses is not possible. Therefore node addresses need to be configured dynamically with minimum delay and packet loss. Existing solutions for IP address auto-configuration do not address security issues. In this paper we propose a secure address autoconfiguration for Mobile Ad hoc Networks (MANET) based on Virtual Address Space Mapping [1].... 

Today sending spams has turned to be a major problem in the Internet. In last 20 years, the Internet and mobile communication growth in parallel. So the spams are also born on the mobile phones as the form of SMS (Short Message Service) spams. In this paper a new method is proposed for filtering SMS spams using CAPTCHA (Completely Automatic Public Turing Test to Tell Computer and Human Apart) systems. CAPTCHA systems are used to distinguish between human users and computer programs automatically. In this method, the picture of an object is sent as an SMS picture message. Also name of that object and name of three other objects are written in the SMS as a multiple-choose question. The user... 

In this paper, we propose a concept of relaying named symetric relaying strategy for two relay network. In our strategy, we have two relays in the network and both relays can completely decode the message transmitted by the other relay. The proposed rate is shown to subsume the previously proposed rate for feed-forward relay network based on decodeand- forward. © 2008 IEEE  

One of the most important challenges in mobile Ad-hoc networks is simulation. The simulation of these networks based on the accessible simulation techniques, which are based on packet, is a demanding and time-consuming task. Moreover, with the complexity of the network and the increase in the numbers of the nodes, it is likely to take a long time. This is because these simulators, one by one, regard the acts of all moving packets in one part of the network, and process these acts as a series of events. Since the number of the events is high in this method, the simulation takes time. Nowadays, in wired networks, several methods have been suggested to lessen the time of simulation; one example... 

The track fusion combines individual tracks formed by different sensors. Tracks are usually obtained by Kalman Filter (KF), since it is suitable for real-time application. The KF is an optimal linear estimator when the measurement noise has a Gaussian distribution with known covariance. However, in practice, some of the sensors do not have these properties, and the traditional KF is not an optimal estimator. In this paper, a novel adaptive Kalman filter (NAKF) is proposed. In this approach, the measurement noise covariance is adjusted by using an introduced simple mathematical function of one variable, called the degree of matching (DoM), where it is defined on the basis of covariance... 

In this paper, a combination of fuzzy clustering estimation and sliding mode control is used to control a chaotic system, which its mathematical model is unknown. It is assumed that the chaotic system has an affine form. At first, the nonlinear noninput part of the chaotic system is estimated by a fuzzy model, without using any input noise signal. Without loss of generality, it is assumed that chaotic behavior is appeared in the absence of input signal. In this case, the recurrent property of chaotic behavior is used for estimating its model. After constructing the fuzzy model, which estimates the noninput part of the chaotic system, control and on-line identification of the input-related... 

A Mobile Ad Hoc Network (MANET) is an infrastructure-less network composed of mobile devices. In order to meet the foresight of newly developing MANETs, a method of maintaining a real-time flow despite dynamic topology and random movement of users is required. Mobility prediction is one of the keys to successful design of efficient protocols to find stable and reliable routes in MANETs. An important characteristic of a MANET is the distribution of the link distance between communicating users. In this paper a novel mobility model is developed for users of a MANET wandering in an unlimited area and is used to derive an analytical framework to approximate the communication links distance... 

Overlay multicast has gained much attention in recent years as an alternative method to network layer multicast, especially for mobile ad hoc networks (MANETs). In this paper, we propose a new overlay multicast protocol to achieve simplicity of deployment, rapid adaptation of overlay structure when nodes move, and reduced delay. In our algorithm, to join or leave a multicast group, it is only sufficient for a member node to inform its first upstream member node. This updates the tree structure more rapidly when nodes move. In addition, join and leave delays are reduced and this makes the protocol suitable for multimedia multicasting in MANETs. Simulation results compared to that of ODMRP and... 

In this paper, the problem of content caching in 5G cellular networks relying on social-aware device-to-device communications (DTD) is investigated. Our focus is on how to efficiently select important users (IUs) and how to allocate content files to the storage of these selected IUs to form a distributed caching system. We aim at proposing a novel approach for minimizing the downloading latency and maximizing the social welfare simultaneously. In particular, we first model the problem of maximizing the social welfare as a many-to-one matching game based on the social property of mobile users. We study this game by exploiting users' social properties to generate the utility functions of the... 

The critical issue in designing correlated data networks like Wireless Sensor Networks is to minimize the total cost of data transmission in the network, and decrease the amount of data flow. The problem of finding optimal aggregation tree for correlated data gathering in single sink network is considered as an NP-Complete problem and hence heuristic methods are usually applied to solve it[1]. In this paper, we apply genetic algorithm (GA) to solve the problem. In our method, we improve the performance of genetic search by selecting proper initial population. This initial population is determined in two ways, by using Prime's algorithm, and shortest path tree. The main issue is to regard... 

A Mobile Ad hoc Network (MANET) is a collection of wireless mobile nodes forming a self-configuring network without using any existing infrastructure. Since MANETs are not currently deployed on a large scale, research in this area is mostly simulation based. Among other simulation parameters, the mobility model plays a very important role in determining the protocol performance in MANET. Thus, it is essential to study and analyze various mobility models and their effect on MANET protocols. In this paper we introduce a new framework for simulation of mobility models in mobile Ad-Hoc networks. This simulator can generate mobility traces in various mobility models. The mobility traces can be... 

In this paper, we propose an analytical framework in order to compute the throughput capacity of a multi-hop ad hoc network with a finite number of mobile wireless nodes. The proposed framework consists of two related queueing networks; a closed BCMP queueing network to represent the mobility model of the wireless nodes and an open BCMP queueing network comprising symmetric M/G/l nodes to represent the multi-hop packet routing process from sources to destinations. In this respect, we consider very simple MAC and routing schemes and then map the related parameters onto several components of the queueing network. By solving the linear traffic equations corresponding to concerned queueing... 

There are two types of scatterers in a multipath propagation environment: fixed and non-fixed scatterers. Fixed scatterers like buildings, mountains and tree stems do not move, while non-fixed (moving) scatterers like cars, people and tree leaves move from their initial positions. In addition to different movements of the mobile station (MS) that cause different kinds of Doppler fading, movements of non-fixed scatterers are also anticipated to generate other kinds of fading/correlation. This fading changes depend on the type of the propagation environment and the type of movements of local surrounding scatterers. In this paper we characterize these effects in terms of temporal correlations.... 

In UMTS mobile networks, there are some circumstances that the International Mobile Subscriber Identity (IMSI) of a user is conveyed in clear-text over the radio interface. Such situations violate the anonymity of users. In this paper, we introduce an Improved User Identity Confidentiality (IUIC) mechanism which attempts to avoid the drawback and makes users more anonymous. We give the role of IMSI to anonymous tickets in such a way that IMSI is never exposed on the radio interface or over any other link. Our IUIC mechanism, employs symmetric cryptography based on the existing network access security features of UMTS. Its implementation, security, and performance issues are also considered.... 

Recently Mobile Learning (M-Learning) has attracted much attention. Due to advantages of SMS (Short Messaging Service) on mobile phones we present a safe and protected method for taking multiple-choice quizzes by using the SMS on mobile phones in this paper. In this method questions of quiz are sent to students along with their answers through some SMS messages. The students will receive their grades immediately after answering the questions and this grade is also sent to the instructor or professor along with the student's answers through an SMS Picture Message. Answers of questions and the student's grade are hidden in SMS picture message through stenography and then they are sent. The... 

A Mobile Ad hoc Network (MANET) is a collection of wireless mobile nodes forming a self-configuring network without using any existing infrastructure. Network nodes in a mobile Ad-hoc network move in some motion patterns called mobility models. The mobility models play a very important role in determining the protocol performance in MANET. Thus, it is essential to study and analyze various mobility models and their effect on MANET protocols. If we can recognize the mobility pattern of motion of mobile nodes in our environment we can customize our network protocols to deal with that existing mobility model. In this paper we introduce a new method for classification and pattern recognition of... 

The short message service, abbreviated to SMS, is one of the services used in mobile phones and has been warmly welcomed by the public throughout the world, esp. in Asia and Europe. Using this service, individuals can write and send to each other short messages and also black and white pictures. On the one hand, considering the issue of information security and esp. establishing hidden communications, many methods have been presented for hidden communications, among which steganography is a relatively new one. Combining steganography of data in picture and using pictures in SMS messages, this article proposes a method for hidden exchange of information. The main focus of this article is on... 

Usually the digital phase shifters are used to steer the beam of a phased array antenna, and the accuracy of beam steering and other properties of the radiation pattern is dependent on the number of bits of the phase shifter and its resolution. In this paper the results of simulations, accomplished using a number of phase feeding methods in order to reduce the phase quantization error effects are presented and three new methods are introduced and compared with the previous works. Copyright 2006 IEICE