Omnet++ Research Papers

In this paper we analyze one technique for web caching in MANET. MANET stands for Mobile Ad HocNetwork which is an evolving concept. There are many emerging researches focused on MANET aspects such as routing and caching. Among them, the lack of efforts done on MANET web caching is acknowledged. As the node in MANET is moving, the web caching is difficult task.

The paper reviews the traditional web caching techniques to improve the performance of MANET. In previous techniques, Better Approach to Mobile Ad-Hoc (B.A.T.M.A.N.) is a web caching protocol which is implemented for MANET. The overall performance of B.A.T.M.A.N. is more time consuming. The proposed technique improves the performance of web application in MANET by reducing internet bandwidth. Also preserves the energy consumption. This peer to peer web caching concept purely focused on web applications in MANET.

Low delivery latency and high delivery ratio are two key goals in the design of routing schemes in Vehicular Ad Hoc Networks (VANETs). The existing routing schemes utilize real-time information (e.g., Geographical position and vehicle density) and historical information (e.g., Contacts of vehicles), which usually suffer from a long delivery latency and a low delivery ratio. Inspired by the unique features of bus systems such as wide coverage, fixed routes and regular service, we propose to use the bus systems as routing backbones of VANETs. In this work, we present a Community-based Bus System (CBS) which consists of two components: a community-based backbone and a routing scheme over the backbone.

We collect real traces of 2515 buses in Beijing and build a community-based backbone by applying community detection techniques in the Beijing bus system. A two-level routing scheme is proposed to operate over the backbone. The proposed routing scheme performs sequentially in the inter-community level and the intra-community level, and is able to support message delivery to both mobile vehicles and specific locations/areas. Extensive experiments are conducted on the real trace data of the Beijing bus system and the results show that CBS can significantly lower the delivery latency and improve the delivery ratio. CBS is applicable to any bus-based VANETs.

This paper presents the first study on scheduling for cooperative data dissemination in a hybrid infrastructure-to-vehicle (I2V) and vehicle-to-vehicle (V2V) communication environment. We formulate the novel problem of cooperative data scheduling (CDS). Each vehicle informs the road-side unit (RSU) the list of its current neighboring vehicles and the identifiers of the retrieved and newly requested data. The RSU then selects sender and receiver vehicles and corresponding data for V2V communication, while it simultaneously broadcasts a data item to vehicles that are instructed to tune into the I2V channel.

The goal is to maximize the number of vehicles that retrieve their requested data. We prove that CDS is NP-hard by constructing a polynomial-time reduction from the Maximum Weighted Independent Set (MWIS) problem. Scheduling decisions are made by transforming CDS to MWIS and using a greedy method to approximately solve MWIS. We build a simulation model based on realistic traffic and communication characteristics and demonstrate the superiority and scalability of the proposed solution. The proposed model and solution, which are based on the centralized scheduler at the RSU, represent the first known vehicular ad hoc network (VANET) implementation of software defined network (SDN) concept.

Mobile Ad-hoc Networks (MANETs) have been investigated deeply during the recent years due to their success in both civilian and military applications. MANETs are formed dynamically by an autonomous system of mobile nodes that are connected via wireless links without using an existing fixed network infrastructure or any centralized administration. The nodes organize themselves randomly and are free to move anytime, anywhere; thus, the network’s wireless topology may change hastily and arbitrarily.

In this paper, a comparison between two well-known routing protocols have been evaluated. The two routing protocols are Ad-hoc On-demand Distance Vector AODV and Destination-Sequenced Distance-Vector DSDV. The simulation results show that AODV routing protocol has performed better than DSDV routing protocol in term of throughput, delivery ratio.

With the proliferation of new wireless service, scarce wireless resources is expected to become a critical issue. For this reason, cognitive radio mobile ad hoc networks (CogMANET) are being developed as a promising solution to this problem. However, in CogMANET, channel switching is inherently necessary whenever a primary user with a license appears on the channel. Allowing secondary users to choose an available channel from among a wide spectrum range thus enables reliable communication in this context, but communication characteristics such as bottleneck bandwidth and RTT will change with channel switch.

In response to this change, TCP has to adaptively update its congestion window (cwnd) to make an efficient use of the available resources. For this purpose, TCP CRAHN was proposed for CogMANET. In this paper, TCP CRAHN is first evaluated in cases where bottleneck bandwidth and RTT drastically change. Based on these results, TCP CoBA is proposed to further improve the throughput of the above use cases. TCP CoBA updates the cwnd based upon the available buffer space in the relay node upon channel switch, as well as other communication characteristics. Through simulations, we show that compared with TCP CRAHN, TCP CoBA improves the throughput by up to 200 percent.

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.