Eyuphan Bulut

Exploiting Friendship Relations for Efficient Routing in Mobile Social Networks

Routing in delay tolerant networks is a challenging problem due to the intermittent connectivity between nodes resulting in the frequent absence of end-to-end path for any source-destination pair at any given time. Recently, this problem has attracted a great deal of interest and several approaches have been proposed. Since Mobile Social Networks (MSNs) are increasingly popular type of Delay Tolerant Networks (DTNs), making accurate analysis of social network properties of these networks is essential for designing efficient routing protocols. In this paper, we introduce a new metric that detects the quality of friendships between nodes accurately. Utilizing this metric, we define the community of each node as the set of nodes having close friendship relations with this node either directly or indirectly. We also present Friendship-Based Routing in which periodically differentiated friendship relations are used in forwarding of messages. Extensive simulations on both real and synthetic traces show that the introduced algorithm is more efficient than the existing algorithms.

Friendship Based Routing in Delay Tolerant Mobile Social Networks

Routing in delay tolerant networks (DTN) have attracted a great interest recently. Increasingly popular type of DTNs are mobile social networks (MSN) also called pocket switched networks. Hence, analyzing accurately social network properties has become an important issue in designing efficient routing protocols for MSNs. In this paper, we first introduce a new metric for detecting the quality of friendships accurately. Using the introduced metric, each node defines its friendship community as the set of nodes having close friendship with itself either directly or indirectly. Then, we present Friendship Based Routing in which temporally differentiated friendships are used to make the forwarding decisions of messages. Real trace-driven simulation results show that the introduced algorithm achieves better delivery rate while forwarding fewer messages than the existing algorithms.

Energy Efficient Collision Aware Multipath Routing for Wireless Sensor Networks

Multipath routing can reduce the need for route updates, balance the traffic load and increase the data transfer rate in a wireless sensor network, improving the utilization of the limited energy of sensor nodes. However, previous multiple path routing methods use flooding for route discovery and transmit data with maximum power regardless of need, which results in waste of energy. Moreover, often a serious problem of collisions among multiple paths arises. In this paper, we propose an energy efficient and collision aware (EECA) node-disjoint multipath routing algorithm for wireless sensor networks. With the aid of node position information, the EECA algorithm attempts to find two collision-free routes using constrained and power adjusted flooding and then transmits the data with minimum power needed through power control component of the protocol. Our preliminary simulation results show that ECCA algorithm results in good overall performance, saving energy and transferring data efficiently.

Cost-effective multiperiod spraying for routing in delay-tolerant networks

In this paper, we present a novel multiperiod spraying algorithm for routing in delay-tolerant networks (DTNs). The goal is to minimize the average copy count used per message until the delivery while maintaining the predefined message delivery rate by the given deadline. In each period, some number of additional copies are sprayed into the network, followed by the wait for message delivery. At any time instance, the total number of message copies distributed to the network depends on the urgency of achieving the delivery rate by the given deadline for that message. Waiting for early delivery in the initial periods with a small number of copies in existence decreases the average number of copies sprayed in the network till delivery. We first discuss two- and three-period variants of our algorithm, and then we also give an idea of how the presented approach can be extended to more periods. We present an in-depth analysis of the algorithm and validate the analytical results with simulations. The results demonstrate that our multiperiod spraying algorithm outperforms the algorithms with a single spraying period.

Distributed energy-efficient target tracking with binary sensor networks

Target tracking is a typical and important cooperative sensing application of wireless sensor networks. We study it in its most basic form, assuming a binary sensing model in which each sensor returns only 1-bit information regarding targets presence or absence within its sensing range. A novel, real-time and distributed target tracking algorithm is introduced. The algorithm is energy efficient and fault tolerant. It estimates the target location, velocity, and trajectory in a distributed and asynchronous manner. The accuracy of the algorithm is analytically derived under an ideal binary sensing model and extensive simulations of ideal, imperfect, and faulty sensing models show that the algorithm achieves good performance. It outperforms other published algorithms by yielding highly accurate estimates of the targets location, velocity, and trajectory.

Sleep scheduling with expected common coverage in wireless sensor networks

Sleep scheduling, which is putting some sensor nodes into sleep mode without harming network functionality, is a common method to reduce energy consumption in dense wireless sensor networks. This paper proposes a distributed and energy efficient sleep scheduling and routing scheme that can be used to extend the lifetime of a sensor network while maintaining a user defined coverage and connectivity. The scheme can activate and deactivate the three basic units of a sensor node (sensing, processing, and communication units) independently. The paper also provides a probabilistic method to estimate how much the sensing area of a node is covered by other active nodes in its neighborhood. The method is utilized by the proposed scheduling and routing scheme to reduce the control message overhead while deciding the next modes (full-active, semi-active, inactive/sleeping) of sensor nodes. We evaluated our estimation method and scheduling scheme via simulation experiments and compared our scheme also with another scheme. The results validate our probabilistic method for coverage estimation and show that our sleep scheduling and routing scheme can significantly increase the network lifetime while keeping the message complexity low and preserving both connectivity and coverage.

Impact of Social Networks on Delay Tolerant Routing

Delay Tolerant Networks (DTNs) are wireless networks in which at any given time instance, the probability of having a complete path from a source to destination is low due to the intermittent connectivity between nodes. Several routing schemes have been proposed for such networks to make the delivery of messages possible despite the intermittent connections. In this paper, in addition to intermittent connectivity which impacts routing most strongly, we also analyze the effects of underlying social structure over the communication network. In a social network, nodes interact in diverse ways so that some nodes meet each other more frequently than others. In the paper, we first propose a new network model to reflect the underlying social structure over the network nodes, then we study the effects of this model on the performance of multi-copy based routing algorithms. We also analyze the performance of routing and validate our analysis with simulations.

A Distributed Cooperative Target Tracking with Binary Sensor Networks

Target tracking is a typical and important cooperative sensing application of wireless sensor networks. We study it in its most basic form, assuming the binary sensing model in which each sensor can return only 1-bit information regarding targets presence or absence within its sensing range. A novel, real-time and distributed target tracking algorithm is proposed. The algorithm reduces the uncertainty of the target location from a two-dimensional area into a one-dimensional arc and estimates the target velocity and trajectory in a distributed and asynchronous manner. Extensive simulations show that our algorithm achieves good performance by yielding highly accurate estimates of the targets location, velocity and trajectory.

Conditional shortest path routing in delay tolerant networks

Delay tolerant networks are characterized by the sporadic connectivity between their nodes and therefore the lack of stable end-to-end paths from source to destination. Since the future node connections are mostly unknown in these networks, opportunistic forwarding is used to deliver messages. However, making effective forwarding decisions using only the network characteristics (i.e. average intermeeting time between nodes) extracted from contact history is a challenging problem. Based on the observations about human mobility traces and the findings of previous work, we introduce a new metric called conditional intermeeting time, which computes the average intermeeting time between two nodes relative to a meeting with a third node using only the local knowledge of the past contacts. We then look at the effects of the proposed metric on the shortest path based routing designed for delay tolerant networks. We propose Conditional Shortest Path Routing (CSPR) protocol that routes the messages over conditional shortest paths in which the cost of links between nodes is defined by conditional intermeeting times rather than the conventional intermeeting times. Through trace-driven simulations, we demonstrate that CSPR achieves higher delivery rate and lower end-to-end delay compared to the shortest path based routing protocols that use the conventional intermeeting time as the link metric.

Cost Efficient Erasure Coding Based Routing in Delay Tolerant Networks

Routing in delay tolerant networks (DTNs) in which most of the nodes are mobile and intermittently connected is a challenging problem because of unpredictable node movements and lack of knowledge of future node connections. To ensure reliability against failures and increase the success rate of delivery, erasure coding technique is used to route messages in DTNs. In this paper, we study how the cost of erasure coding based routing protocols can be reduced. Specifically, we analyze the effects of different spraying algorithms, right parameter selection and splitting spraying phase on the cost of message delivery. We also perform simulations to evaluate the proposed approaches and demonstrate that the cost of erasure coding based routing can be reduced considerably with the proposed strategies while maintaining the delivery rate and delay objectives.