Due to limitations in computing resources of mobile NODES, Mobile Ad-hoc Networks (MANETs) are very fault-prone. So far, redundancy at different levels of the network has been considered an efficient strategy to enhance the fault-tolerance of networks. Indeed, ad-hoc networks are extremely redundant; therefore, natural redundancy to fault tolerance enhancement has a great impact on the network performance. In this paper, a fault tolerant algorithm for MANETs has been proposed that by assigning BACKUP node(s) to each node tries to increase in fault-tolerance. For this reason, the proposed algorithm chooses the BACKUP NODES from among those NODES having the same movement route. The NODES movement route can be determined or predicted through the BACKUP NODES table. Choosing BACKUP NODES is done based on the time of NODES adjacency. Experimental results taken from NS-2 simulator indicated that in comparison to other algorithms, the proposed algorithm increases by 1) the package delivery rate in relation to the percentage of fault, and 2) the package delivery rate in relation to various mobile NODES’ pause time.

In this paper, an efficient fault-tolerant routing algorithm for Mobile Ad-hoc Networks (MANETs) is presented. The proposed algorithm increases the network fault-tolerance using natural redundancy of Ad-hoc networks. This algorithm is carried out in two stages; 1) the selection of BACKUP NODES 2) the selection of BACKUP route(s). In the first stage, the proposed algorithm chooses NODES with the same path as BACKUP NODES. Prediction and diagnosis of NODES paths is performed through BACKUP tables. Since the selection of BACKUP NODES is fulfilled, the proposed algorithm begins fault-tolerance routing. For this purpose, initially the proposed algorithm provides the main route between each pair of source & destination NODES based on DSR routing algorithm. Then, from a destination node towards a source node, the BACKUP route(s) is established between the chosen BACKUP NODES in the first stage. Experimental results taken from NS-2 simulator demonstrate that in comparison with previous methods the proposed increases; 1) 10% the package delivery ratio against the percentages of faulty NODES and, 2) 22% package delivery ratio against the pause time of various mobile NODES.

Different types of contact, including contact between node pairs, any-contact of NODES, and contacts of the entire network, are used to characterize social relations in mobile social networks. Different modes of routing, from the point of view of message delivery semantics, encompass unicasting, multicasting, any-casting, and broadcasting. Studies have shown that using probability distribution functions of contact data, which is mainly assumed to be homogeneous for NODES, improves the performance of these networks. However, there exists an important challenge in studies on distributions. A lot of works apply the distribution of one type of contact to other types. Hence in routing applications, it causes to use of the distribution of one type of contact for any mode of routing. This study provides a complete solution to model each type of homogeneous contact data distribution and to use them in different modes of routing. We propose a routing algorithm that uses this new model. Results show that our solution improves the average latency of comparing methods Epidemic, TCCB, and DR about 3.5-times, 30%, and 45%, respectively. It achieves a delivery rate of about 5% and 6%, and average latency about 6% and 8% better than that of DR and TCCB, respectively.

In recent years, performance of the Mobile Ad-Hoc Network (MANET) has become an important research area in the wireless networks community. MANET consists of clusters of Mobile NODES (MNs) on the access network that could be connected to other clusters through a fixed backbone of routers. The access link contention can severely constrain the end-to-end throughput of the path between a pair of source and destination MNs connected through the backbone. In this paper, we propose an integrated routing system for MANET that includes the backbone paths and the ad-hoc paths formed as a result of direct communication among MNs without going through the backbone. In our proposed routing system, an alternative ad-hoc path can be used only when the primary backbone path is severely constrained due to access links contention. We also propose a scheme for making the MN aware of link quality measures, and incorporate throughput metric in the core of AODV. We implemented the proposed routing system in the OPNET simulator, and evaluated the performance of our scheme under a variety of conditions. Simulation results show that the alternative ad-hoc path is effective in delivering higher throughput when the backbone path is severely constrained.

The notion of strong arcs in a fuzzy graph was introduced by Bhutani and Rosenfeld in [1] and fuzzy end NODES in the subsequent paper [2] using the concept of strong arcs. In Mordeson and Yao [7], the notion of "degrees" for concepts fuzzified from graph theory were defined and studied. In this note, we discuss degrees for fuzzy end NODES and study further some properties of fuzzy end NODES and fuzzy cut NODES.

Wireless Sensor Networks need primal information like location of the NODES to start working and sending environment data. One method for setting a sensor network in a battlefield is to drop them from helicopter or to fire from artillery. It will cost a lot to Equip all network NODES with GPS. So to reduce these costs, only a few of NODES called anchor NODES are equipped with gps. Location of NODES are estimated by using belief propagation algorithm with measuring distance between NODES (with use of recieved signal strength) and location information of anchor NODES. Since the cost of anchor NODES is reletively high, their number is important. also position of anchor NODES affects algorithms error. In this paper, by using multi-objective algorithms with two objectives of error reduction and anchor NODES number reduction, position and number of anchor NODES are determined. results show that by using this methond, a few solutions are provided which are better than similar algorithms in terms of error reduction and energy consumption.

In this paper we consider the reverse BACKUP 2-median problem with variable coordinates of vertices in Rk. Let n points be given, then in the reverse BACKUP 2-median problem we want to change the coordinates of these points with a limited budget such that the two given points become the BACKUP 2-median. We present a mathematical model for this problem and then solve a spatial case of this problem by a meta-heuristic method.