Seungjin Park

Black hole attack in mobile Ad Hoc networks

The black hole problem is one of the security attacks that occur in mobile ad hoc networks (MANETs). We present two possible solutions. The first is to find more than one route to the destination. The second is to exploit the packet sequence number included in any packet header. Computer simulation shows that compared to the original ad hoc on-demand distance vector (AODV) routing scheme, the second solution can verify 75% to 98% of the route to the destination depending on the pause times at a minimum cost of the delay in the networks.

Fault-tolerant wormhole routing algorithms in meshes in the presence of concave faults

A fault ring is a connection of only nonfaulty adjacent nodes and links such that the interior of the ring contains only faulty components. This paper proposes two wormhole routing algorithms that deal with more relaxed shapes of fault rings than previously known algorithms in the mesh networks. As a result, the number of components to be made disabled would be reduced considerably in some cases. First algorithm, called F4, uses four virtual channels and allows all four sides of fault rings to contain concave shapes. Second algorithm, F3, permits up to three sides to contain concave shapes using only three virtual channels. Both F3 and F4 are free of deadlock and livelock and guarantee the delivery of messages between any pair of nonfaulty and connected nodes in the network.

An efficient reliable one-hop broadcast in mobile ad hoc networks

A reliable one-hop broadcast is a fundamental communication primitive in mobile ad hoc networks in which a message from the source node is guaranteed to be delivered to all nodes within the source nodes transmission range. Despite the importance of it, reliable one-hop broadcast is not easy to accomplish due to collisions in wireless networks known as Hidden Terminal Problem. This paper presents a MAC protocol that not only guarantees reliable one-hop broadcast but also achieves it efficiently by exploring as many simultaneous executions of the communication as possible. In addition to the data packets, the proposed algorithm utilizes the control packets that prevent packet collisions, and at the same time, make the simultaneous communications possible to improve the network throughput. Simulation results show the effectiveness of the proposed algorithm.

All-to-all broadcasting in faulty hypercubes

A new fault-tolerant all-to-all broadcasting algorithm in an n-dimensional hypercube with up to [n/2] faulty links is given. An extension of this algorithm that can tolerate up to [n/2] faulty nodes is also described. These algorithms assume a multiport I/O model, meaning each node can send and receive messages from all its adjacent nodes simultaneously. The total time steps taken by the proposed algorithms are near optimal, and they produce a factor of n less traffic than previously known algorithms.

Reliable one-hop broadcasting (ROB) in mobile ad hoc networks

Although many algorithms are built on the existence of reliable one-hop broadcasting, reliability is very hard to achieve in MANETs due to the node mobility and hidden terminal problem. This paper proposes a new reliable one-hop broadcast algorithm, called Reliable One-Hop Broadcasting (ROB). Unlike other algorithms that consider the collisions as useless, ROB utilizes the collisions as an indication and measurement of completion of the broadcast. Our simulation results using ns-2 show that ROB outperforms unreliable broadcasting by up to 400% in terms of number of retransmissions when network density is high.

A performance simulation for route maintenance in wireless ad hoc networks

A routing protocol in ad hoc wireless networks must take special consideration to link failure and route maintenance in order that the network services will not be interrupted. To decrease the link failure, Anticipated Route Maintenance Protocol (ARM) has been proposed. However, the detailed performance for this protocol has not been evaluated. In this paper, we have compared the performance of two protocols, standard Dynamic Source Routing Protocol (DSR) and a combination of DSR and ARM. The simulation results show how ARM improves the functionality of DSR by preventing the links in the route from breaking. Packets delivery ratio could be increased using ARM maintenance and achieved approximately 100% improvement. The simulations clarify also how ARM shows a noticeable improvement in dropped packets and links stability over DSR, even though there is more traffic and channel overhead in ARM.

Anticipated route maintenance (ARM) in location-aided mobile ad hoc networks

Mobile ad hoc networks are composed of moving wireless hosts which, when within range of each other, form wireless networks. For communication to occur between hosts that are not within each others range, routes involving intermediate nodes must be established; however, since the hosts may be in motion, a host that was part of a route may move away from its upstream and downstream partners, thus breaking the route. Our work shows that by utilizing only local geographic information (now a part of some route finding algorithms), a host can anticipate its neighbors departure and, if other hosts are available, choose a host to bridge the gap, keeping the path connected. We present a distributed algorithm that anticipates route failure and performs preventative route maintenance using location information to increase a route lifespan. The benefits are that this reduces the need to find new routes (which is very expensive) and prevents interruptions in service. Simulation shows that as the density of nodes increase the chance to successfully utilize our route maintenance approach increases, and so does the savings.

Recycled path routing in mobile ad hoc networks

In mobile ad hoc networks, many routing algorithms rely on some form of flooding to accomplish the route discovery process. Flooding, however, consumes many valuable network resources such as time, bandwidth, and power. Most current routing schemes expire valid routes after a time period to account for nodal movement. This paper proposes a new route discovery method, called recycled path routing (RPR), which directs broadcasts toward the destination node even in the absence of location information. The recycled path routing scheme reduces the search space for the destination node by implementing an expired route cache that is utilized by each node in the network. Routes are added to the expired route cache as they expire from the active route cache and remain there until some time interval has passed or a new route has been discovered. Since these expired routes can provide valuable insight into finding new routes, RPR uses them to direct broadcasts toward the destination node. RPR can save a significant quantity of valuable network resources because only nodes near the optimal path will rebroadcast route requests.

Fault-tolerant broadcasting in wormhole-routed torus networks

This paper describes a fault-tolerant broadcast algorithm for wormhole-routed torus networks for which there is only local knowledge of faulty components. This algorithm tolerates tip to k-1 faulty nodes in a k-ary n-cube provided the faults do not cause the network to be disconnected. Based on the fault-tolerant dimension-order unicast communication, this algorithm is deadlock-free and no additional virtual channels are needed. The first stage of this algorithm is itself an optimal broadcast algorithm for a torus if no faults are present. The second stage overcomes the presence of up to k-1 faults with a fixed number of additional message transmissions. Thus, the cost of this algorithm is within a constant factor of the cost of optimal non-fault-tolerant broadcast algorithms.

Efficient data dissemination and aggregation in large wireless sensor networks

In this paper, we investigate an energy-efficient data dissemination scheme that prolongs the lifetime of battery-powered sensors by reducing the amount of communication required. In order to save energy and bandwidth, the proposed scheme constructs and maintains only one grid structure per data type, and sources of same data type share the grid structure to disseminate sensing data. Another novel idea in the proposed scheme is to use a hash function in order to retrieves the position of the nearest grid point. By using a hashing function, a sink can substitute expensive local query flooding with unicasting. Our simulation results show that the proposed scheme consumes much less energy than previously known schemes by sharing grid structures and eliminating local flooding.