About Omnet Project Team

The growth of complex software, communication interfaces and the presence of low-cost processors are key factors for designing distributed applications. Distributed computation allows processes to run concurrently, share resources and work independent of one another. Resource sharing is one of the main advantages of distributed computing. Distributed computations that involve sharing of resources require that only one process is allowed to enter critical section (CS) at a time. Therefore, the mutual exclusion issue is to make sure that no more than one process is allowed to access shared resource at a time.

Existing literature consists of different algorithms with varied performance levels to achieve mutual exclusion. These algorithms have been classified as token-based and permission-based. In the paper, we present a quorum-based mutual exclusion algorithm under permission-based category. Our algorithm is message efficient and suitable for mobile ad hoc networks (MANETs). We represent the model of the proposed algorithm along with its assumptions and discuss an application of MANET in which quorum-based mutual exclusion algorithm would be applied.

A wireless ad-hoc network is a collection of nodes that are dynamically and arbitrarily located in such a manner that the interconnections between each node are capable of changing on a continual basis. In this paper, we provide a novel way to improve node interconnects without changing the overall network topology by allowing nodes to have limited mobility.

Received signal strength (RSS) measurements are recorded from neighboring nodes as the node makes small changes in position. This allows the node to move out of fades due to multi-path or shadowing, and is a form of selection diversity that requires only a single antenna. This algorithm is tested using a full 3-D ray tracing propagation model as well as physical measurements in an indoor scenario.

In a mobile  ad hoc network (MANET), communication between mobile nodes occurs without centralized control. In this environment the mobility of a node is unpredictable; this is considered as a characteristic of wireless networks. Because of faulty or malicious nodes, the network is vulnerable to routing misbehavior. The resource constrained characteristics of MANETs leads to increased query delay at the time of data access.

In this paper, AntHocNet+Security (ANTSEC) framework is proposed that includes an enhanced cooperative caching scheme embedded with artificial immune system. This framework improves security by injecting immunity into the data packets, improves the packet delivery ratio and reduces end-to-end delay using cross layer design. The issues of node failure and node malfunction are addressed in the cache management.

This paper proposes a modified version of vehicular ad hoc network media access control (VeMAC) protocol for further increased throughput. In the modified VeMAC, an additional bit is appended to the field for each time slot in the header used in VeMAC as the collision flag. Upon detecting a collision for a time slot, a node sets the collision flag for that time slot without changing the ID field and sends its packet in its acquired time slot. By receiving the packet with the collision flag, nodes notice a collision happen in the time slot. One of the nodes involved in the collision knows from its ID field that it is the node itself that is supposed to use the time slot, and therefore it continues to use the time slot.

The other nodes recognize themselves as nodes that should not use the time slot because their IDs are not included in its ID field of the packet. Consequently, they release the time slot and begin by acquiring new time slots. Since not all nodes involved in the collision release the time slot in our modified VeMAC, the possibility that access collisions following the merging collision happen is reduced, compared to the original one. Simulation results show that our modified one outperforms the original one in terms of the average number of collisions and throughput.

In a mobile ad hoc network (MANET), effective prediction of time-varying interferences can enable adaptive transmission designs and therefore improve the communication performance. This paper investigates interference prediction in MANETs with a finite number of nodes by proposing and using a general-order linear model for node mobility. The proposed mobility model can well approximate node dynamics of practical MANETs. In contrast to previous studies on interference statistics, we are able through this model to give a best estimate of the time-varying interference at any time rather than long-term average effects.

Specifically, we propose a compound Gaussian point process functional as a general framework to obtain analytical results on the mean value and moment-generating function of the interference prediction. With a series form of this functional, we give the necessary and sufficient condition for when the prediction is essentially equivalent to that from a binomial point process (BPP)network in the limit as time goes to infinity. These conditions permit one to rigorously determine when the commonly used BPP approximations are valid. Finally, our simulation results corroborate the effectiveness and accuracy of the analytical results on interference prediction and also show the advantages of our method in dealing with complex mobilities.

Most modern metropolitan cities have suffered from increasing traffic accidents and jams. Vehicular adhoc network (VANET), consisting of information collecting, processing and transmitting units embedded in vehicles assisted by roadside infrastructures, has been proposed as one the most promising solution to problems introduced by the increasing number of vehicles in modern cities. To achieve the goal, it is crucial to allow the transportation administration center to collect information about the traffic and road status through VANET. A major obstacle in this scenario is the privacy concern on the vehicles.

To address this issue, this paper proposes a generic privacy-preserving traffic monitoring framework which allows individual vehicle driving status and the road usage information are collected while the privacy of the vehicles is well preserved. This goal is achieved by the novel technology of distinguishing individual vehicles with their spatio-temporal occupations. The continual change of spatio-temporal identities provides privacy for vehicles in a natural way, which remains nonetheless traceable by a trusted authority to prevent misbehaving vehicles from abuse the privacy-preserving mechanism provided by the system.

Ad-hoc network can be defined as a collection of number of mobile nodes which makes a temporary network. Black hole can be defined as a malicious node which on any request of route replies in an incorrect manner as if it has new route to the goal and then it drops all incoming packets. Loss will be very high if malicious nodes work collectively. This attack can be defined as cooperative black hole attack.

This paper gives the analysis of Black Hole ADOV performance by frequently changing number of mobile nodes and by also changing black hole nodes. To analyze this various performance metrics are used which includes average end to end delay, loss of packet and packet delivery ratio and It has been seen that effect on end to end delay is higher that on loss of packet.

In an ad hoc network, selfish nodes do not cooperate in packet forwarding of other nodes to maximise their own welfare. Such nodes will have a negative effect on the performance of the network. In this study, an enhanced node cooperation technique (ENCT) is proposed which is a hybrid technique of reputation-based mechanism and incentive-based mechanism. It evaluates relaying nodes’ behaviour, calculates its reputation and outwitting selfish nodes by utilising receipts submitted by each relaying node in the path to a centralised authority rather than using promiscuous mode.

A mathematical analysis is provided which demonstrates that the expected gain of reputation for a particular node is maximum if it adopts cooperative behaviour. To motivate nodes for cooperation, variable incentives are provided proportionate to their reputation and current behaviour. Simulation results demonstrate modification of reputation and incentive with varying number of selfish nodes, traffic connections, and topology with static and dynamic behaviour of selfish nodes. The result shows that the ENCT is robust, fair and efficient technique.

Public key management scheme in mobile ad hoc networks (MANETs) is an inevitable solution to achieve different security services such as integrity, confidentiality, authentication and non reputation. Probabilistic asymmetric key pre-distribution (PAKP) is a self-organized and fully distributed approach. It resolves most of MANET’s challenging concerns such as storage constraint, limited physical security and dynamic topology. In such a model, secure path between two nodes is composed of one or more random successive direct secure links where intermediate nodes can read, drop or modify packets. This way, intelligent selection of intermediate nodes on a secure path is vital to ensure security and lower traffic volume.

In this paper, subjective logic is used to improve PAKP method with the aim to select the most trusted and robust path. Consequently, our approach results in a better data traffic and also improve the security. Proposed algorithm chooses the least number of nodes among the most trustworthy nodes which are able to act as intermediate stations. We exploit two subjective logic based models: one exploits the subjective nature of trust between nodes and the other considers path conditions. We then evaluate our approach using network simulator NS-3. Simulation results confirm the effectiveness and superiority of the proposed protocol compared to the basic PAKP scheme.

Although some scaling law-based studies have been conducted for describing the asymptotic capacity of Vehicular Ad Hoc Networks (VANETs), the obtained results are not easy to directly use for estimating the actual capacity of a communication link or the entire network. To overcome this drawback, an interference-based capacity analysis is carried out in this letter for the abstracted 1-dimensional VANETs scenario.

For a reasonable and tractable modeling, the classic Car-Following model is applied to represent the dynamic change of the inter-vehicle distance, which strongly affects the power decay of both the signal and interference in the network. Based on that, a series of probability characteristics is derived for the worst-case interfering scenario, which finally leads to the stochastic characteristics for both the link and network capacity.