Lubomir Dobos

Mobile Ad-Hoc Networks Connection Admission Control Protocols Overview

A mobile ad-hoc network (MANET) is kind of self-configuring wireless network. Mobile terminals move freely, randomly, organize themselves arbitrarily hence network topology changes rapidly and unpredictably. Due to these properties quality of service (QoS) of MANETs changes frequently. To solve this problem, connection admission control (CAC) algorithms are applied. These algorithms are trying to hold QoS in order to be able transmit one or more data flows without disruptions. This article will overview some CAC algorithms, which are trying to ensure QoS.

Cooperation between Trust and Routing Mechanisms for Relay Node Selection in Hybrid MANET-DTN

Today’s mobile networks require integration of the different networks in order to transport data between mobile devices. The main problems of all networks occur if the communication paths are disconnected for a short time. The hybrid MANET-DTN is an evolution of the Mobile Ad Hoc Networks (MANET) and Delay/Disruption Tolerant Network (DTN) and it gives the possibilities of data transport between the disconnected islands of the nodes. The key problem is how to select reliable and secure nodes to transport messages between isolated islands with limited connectivity. The selection of the relay nodes is a critical factor because the data are transported via these devices in hostile environments. Two algorithms for a relay node selection based on trust are introduced. These algorithms are activated if the connections are disrupted. The selected relay nodes transport data across the disconnected environment via store-carry-forward mode. The proposed algorithms enable selecting reliable relay nodes based on collecting routing information and contact history. We introduce the network performance analyses of these algorithms. The main idea of the analyses is studying how the algorithms can affect the behaviour of the routing and forwarding mechanisms in the simulator OPNET modeler.

Statistical models based password candidates generation for specified language used in wireless LAN security audit

The purpose of this article is to describe a new method which is proposed to be the best practice for creating a very effective password candidate lists for specified language, which could be then also used to test the security level of wireless networks protected by WPA/WPA2 PSK standards. The main principle of this technique is to create the statistical model of the new target language which could be used for password candidates generation in controlled order for security audit of the wireless network. It means that the list starts with more probable combinations, going to the less probable ones, so it can be said that this approach means sorting the Brute-force candidates according to specified language, or predicting the usage of letter combinations according to the specified language statistics. The tests have shown that this approach of generating more probable combinations as first, could improve the procedure since it is about 15 times faster in finding about 70% of passwords than common Brute-force attack, comparing to about 20% effectiveness of old dictionary attacks.

Hybrid MANET–DTN and a New Algorithm for Relay Nodes Selection

In this paper, a new way to a selection of the secure relay nodes in hybrid MANET–DTN networks based on the cooperation between routing, trust and game theory mechanisms is introduced. The hybrid MANET–DTN enables delivering the data or messages in the situation when communication paths are disconnected or broken and also in the emergency situations. We focus on the situations when MANET routing protocol cannot establish the end-to-end connection between source and destination nodes. In this situation, it is necessary to select relay nodes, that will be able to transport data or messages between isolated islands of mobile terminals with limited connectivity to other terminals. The proposed algorithm enables to select the relay nodes, that will come into contact with other mobile nodes located in different network areas with regards to trust and game theory. The parameter trust is computed for all mobile nodes and relies on a parameter obtained during routing and data transport processes. The game theory provides a powerful tool to select one candidate from a number of possible nodes with respect to confidence and security. Moreover, we propose a new mechanism to compute and select the trusted node, that can be used for transportation of the secure data in this hostile and disconnected environment. In order to verify the functionalities of this mechanism, we implement this mechanism into the OPNET modeler simulation environment and introduce performance analysis.

MOBILTEL - Mobile Multimodal Telecommunications Systems and Services

In this paper the project MobilTel is presented. The communication itself is becoming a multimodal interactive process. The MobilTel project provides research and development activities in multimodal interfaces area. The result is a functional architecture for mobile multimodal telecommunication systems. The MobilTel communicator is a multimodal Slovak speech and graphical interface. The other possible modalities are pen-touch screen interaction, keyboard, and display on which the information is more user friendly presented (icons, emoticons, etc.), and provides hyperlink and scrolling menu availability. We describe the method of interaction between mobile terminal (PDA) and MobilTel multimodal PC communicator. We also present the graphical examples of services that enable users to obtain information about weather or information about train connection between two train stations.

Intelligent channel assigning in CR-MANET based on spectrum sensing

This paper is focusing on the technology of cognitive radio (CR), which is implemented in Mobile Ad-hoc network (MANET). Different problems which are accrued in CR-MANET network are described. Two of them, spectrum sensing and channel assigning are the main area of the research. Spectrum sensing is oriented on the frequency gaps finding when Wi-Fi, as a wireless technology was used. Mobile devices used some intelligent and non-intelligent techniques for selection and assigning possible channels between them. In the paper is presented one intelligent method, fuzzy logic, which tries to solve a problem with effective channel assigning. Results from spectrum sensing are the main inputs arguments for the fuzzy logic process, which gives the recommendation of channels assigning for every mobile node. This introduced problem was simulated and compared to the set of nodes in CR-MANET network. Non-intelligent and intelligent methods of channel assigning were used and compare their effectivity.

Proposal of simple metrics for evaluation of socialties in mobility models for MANET networks

In this paper, simple metrics for evaluation of social ties in mobility models for MANET networks are described as a proposal of the new evaluation method. In general, Mobile Ad Hoc NETwork (MANET) are networks, where a group of wireless mobile devices communicate wirelessly without fixed infrastructure. In the real world, mobile devices of these networks are carried by humans. Thus, it is useful if simulation tools such as mobility models used to verify functionality and correctness of network protocols are using mobility and behaviour of humans. Peoples are the social creatures so they live and move in social groups. Therefore, we adapt Louvain method for community detection to solve assignment of nodes into social communities based on the movement in mobility models. From performed simulations of mobility models evaluated by proposed metrics along with other common used metrics, it is possible to say if used mobility model shows signs of social ties among nodes.

A brief comparision of fundamental routing methods for Mobile Multihop Networks (MANET)

In this paper are proposed three basic approaches for providing and keeping communication in Mobile Multihop/Ad-Hoc Network (MANET). There are three approaches for solving communication in these networks. Standard approach represented by MANET routing protocols, Opportunistic approach used in Delay Tolerant Networks (DTN) represented by opportunistic routing protocols, and Hybrid approach represented by hybrid (standard and opportunistic) routing protocols. MANET consists from mobile devices, which have different features and can create diverse type of mobile environment. Not all of basic approach can work efficient to provide and keep communication in such environments. From this reason, in this paper are compared three representatives of this approaches (Dynamic Source Routing - DSR, Social Based Opportunistic Routing - SBOR and Hybrid Social Based Routing - HSBR) and verified their usability and affectivity for given MANET environment for simulations. All methods are simulated with different level of mobile nodes velocity. Theoretical assumptions of increasing success of delivery by combination of advantages from MANET and DTN solutions are verified and confirmed based on simulations.

Contact table splitting impact on performance of hybrid MANET-DTN SCaTR

While current on-demand routing protocols are optimized to take into account unique features of mobile ad hoc networks (MANETs) such as frequent topology changes and limited battery life, they often do not consider the possibility of intermittent connectivity that may lead to temporary partitions. In this work is introduced the Space-Contentadaptive-Time Routing (SCaTR) framework and one of its modification: contact table modification, which was created due to increasing its performance. SCaTR takes advantage of past connectivity information to effectively route traffic towards destinations when no direct route from the source exists by proxy nodes, which transfer information closer to destination. We introduce our proposal of improvement for SCaTR protocol. AODV, SCaTR and mSCaTR were simulated and its performances were compared and concluded.

How to simulate DTN in OPNET modeler

Delay Tolerant Networks (DTN) with store and forward architecture are able to operate in environment with considerable delays and intermittent connectivity. Evaluation of such networks and protocols requires reliable simulation tool as is OPNET (Optimized Network Engineering Tool) modeler. One drawback of the OPNET is missing implementation of the wireless DTN protocols and models, therefore we developed bundle protocol extension and the forwarding algorithm based on the history of past encounters PRoPHET (Probabilistic Routing Protocol using History of Encounters). Protocol enables communication between participating nodes in an intermittently connected network where at least few of the nodes are mobile nodes. The implementation details of the PRoPHET are presented in article.