Hosung Park

Mobile Geocasting to Support Mobile Sink Groups in Wireless Sensor Networks

Traditionally, geocasting has been known as the appropriate scheme for providing effective data dissemination from a source to all nodes in a geographically restricted region. However, since the geocasting typically assumes the restricted region is stationary, it is hard to directly adopt the traditional geocasting in order to offer effective data delivery to mobile sink groups that have geographically collective mobility. Hence, this letter proposes a novel geocasting, called M-Geocasting (Mobile Geocasting). M-Geocasting provides the representative location information of a sink group to sources. The location information contains information with respect to a restricted region in which all member sinks of the group exist. A source disseminates data to the closest node in the region; then, the node restrictedly floods the data only within the region. Also, to support local movement of member sinks toward out of scope of the region, some nodes on boundary of the region maintain the data and offer it to member sinks out of scope of the region.

A Cluster-Based Continuous Object Tracking Scheme in Wireless Sensor Networks

Due to the severe resource constraints of sensor hardware, energy efficiency is a principal factor for detecting and tracking the movement of the large-scale phenomena such as wild fire, poison gas and hazardous bio-chemical material, denoted by continuous objects. In order to save the energy, the selective wakeup approach is effective way in the wireless sensor networks. However, most previous researches concentrated on individual objects such as intruders, tanks, and animals cannot be applied to the continuous object tracking because it is hard to expect that the diffusion of continuous object has the uniform velocity or acceleration. Recently, a prediction-based selective wakeup algorithm, denoted by PRECO is proposed. Nevertheless, this mechanism is still not acceptable. First, its prediction result is very inaccurate because a sensor node calculates next boundary line with only a few data while the continuous objects are pretty flexible and vicissitudinous. Second, its prediction tasks among current boundary nodes should be operated at the same time but it is a hard problem for the nodes to have synchronization in the wireless sensor networks. Therefore, we propose a novel prediction and selective wakeup scheme for energy efficient and accuracy continuous object tracking by using structured clustering. Hence, when objects are detected in some specific area, appointed areas where the target may move activate to keep guard without any complex calculations. Moreover, our scheme is asynchronous so that it is suitable for the sensor networks.

Multicast Protocol for Real-Time Data Dissemination in Wireless Sensor Networks

Real-time data dissemination to a multicast group is data delivery to each member in the multicast group within the desired time deadline. The hardest aspect of this mission is to enforce the real-time constraint in the communication between a source and the furthest member since an end-to-end delay is proportional to a physical distance in wireless sensor networks. We call it the critical distance. The critical distance should be most important constraint for real-time multicasting. That is, the delivery distance from a source to each member should not be longer than the critical distance even by any reason. However, since the traditional multicast protocols lay the strong emphasis only on the overall communication cost rather than delivery distance to each member, they may violate the real-time constraint related to the critical distance. In this letter, we propose a novel multicast protocol for real-time data dissemination.

Selective wakeup discipline for continuous object tracking in grid-based wireless sensor networks

A principal issue for wireless sensor networks is energy efficiency, which is necessary for prolonging applications to track continuous object, such as wild fire and poison gas. Selective wakeup approach is an effective way to save energy in such networks. However, most previous studies on selective wakeup schemes have concentrated on individual objects, such as intruders and tanks, and they cannot be applied for tracking continuous objects. This is because the continuous object is pretty flexible and dynamic due to its sensitiveness to surrounding natural effects so that movable area cannot be correctly estimated by the just spatiotemporal mechanism. Therefore, we propose a grid-based protocol for applying the efficient and accurate selective wakeup technique to tracking continuous objects. When an object is detected in some specific area which tightly surrounds the object, a pre-designated area where the target may move is activated to prepare the target without any complex calculations. Moreover, our protocol is simple and asynchronous, which makes it more suitable for wireless sensor networks.

Quality-based event reliability protocol in wireless sensor networks

For reliable event detection in wireless sensor networks, a sink requires collective information reported by sensor nodes sensing an event. In other words, the sink has to receive a certain amount of data dealing with the event for reliable event detection. Existing studies propose quantity-based event reliability protocols that improve event reliability by increasing the number of data successfully transmitted by controlling transport process. These studies present diverse schemes to successfully transmit as many reporting data as possible such as diversification of routing path for congestion avoidance and control of data reporting frequency rate for transport error compensation. However, since it frequently happens that wireless sensor networks with restricted capacity cannot deliver more than required amount of data due to data collision and congestion, the quantity-based event reliability protocols have limitation to raise the possibility of event detection. In this paper, we proposes a Quality-based Event Reliability Protocol (QERP) utilizing a property that the reporting data from sensor nodes are different in the contribution degree (CD) for event detection according to their environmental conditions. QERP selects sensor nodes to send their reporting data according to CD, and differentially transports them by CD-based buffer management and load balancing. Simulation results show that QERP detect more reliably and energy-efficiently an event than quantity-based event reliability protocols.

A Radio-disjoint Geographic Multipath Routing in Wireless Sensor Networks

Geographic multipath routing is one of the most appropriate approaches which can improve the end-to-end reliability via multiple paths for the wireless sensor networks that have frequent network dynamics such as both node and link failures. It has been focused on how to construct a node-disjoint multipath that an intermediate node should be belonged by only a single path. It is because that if two or more paths share one intermediate node, the node may be congested by multiple traffics. Even it might bring multiple path failures if the shared node fails. However, if the node-disjoint multipath schemes are used, there might be another significant problem such as transmission failure or corrupted packet reception due to collisions between adjacent paths. Therefore, we propose a radio-disjoint geographic multipath scheme to avoid the collisions, which allow multiple paths to keep a certain distance between each other. Unfortunately, this simple idea still remains inevitable interference regions, i.e., both source side and destination side. So we eliminate the interferences in these regions by using local scheduling algorithms. We demonstrate that the proposed protocol shows better performance than the previous studies via extensive simulation in terms of end-to-end packet delivery ratio and the end-to-end delay.

Sink Location Service via Inner Rectangular in Wireless Sensor Networks

Geographic routing has been considered as an efficient, simple, and scalable routing protocol for wireless sensor networks since it exploits pure location information instead of global topology information to route data packets. Geographic routing requires the source nodes to be aware of the location of the sink nodes. How source nodes efficiently obtain the sink location information has been merely studied yet. In this paper, we propose a Sink Location Service via Inner Rectangular in Wireless Sensor Networks. A source node and a sink node send location queries and location announcement messages to specified direction respectively by geographic routing; thus, a sink location query path and a sink location announcement path is generated. The node located on a crossing point of these two paths informs the source node about the sink location information. Then the source node sends data to the sink node by geographic routing. The proposed scheme constructs a virtual restricted linear flooding zone inside the network to guarantee the existence of the crossing point. Simulation results show that proposed scheme is reliable and efficient than the existing protocols.

Region-Based Collision Avoidance Beaconless Geographic Routing Protocol in Wireless Sensor Networks.

Due to the lack of dependency on beacon messages for location exchange, the beaconless geographic routing protocol has attracted considerable attention from the research community. However, existing beaconless geographic routing protocols are likely to generate duplicated data packets when multiple winners in the greedy area are selected. Furthermore, these protocols are designed for a uniform sensor field, so they cannot be directly applied to practical irregular sensor fields with partial voids. To prevent the failure of finding a forwarding node and to remove unnecessary duplication, in this paper, we propose a region-based collision avoidance beaconless geographic routing protocol to increase forwarding opportunities for randomly-deployed sensor networks. By employing different contention priorities into the mutually-communicable nodes and the rest of the nodes in the greedy area, every neighbor node in the greedy area can be used for data forwarding without any packet duplication. Moreover, simulation results are given to demonstrate the increased packet delivery ratio and shorten end-to-end delay, rather than well-referred comparative protocols.

Strategy for real-time data dissemination to mobile sinks in wireless sensor networks

In wireless sensor networks, with respect to a desired time deadline real-time data dissemination schemes achieve that by a spatiotemporal communication approach forwarding data from a source to a destination with a delivery speed. The delivery speed is typically obtained from both the static distance from the source to the destination and the interval of the time deadline. However, in case of real-time routing to a mobile sink, since the mobile sink randomly moves around, the distance from a source to the mobile sink would be dynamically changed. Hence, we propose a new real-time routing scheme considering the dynamic distances by the mobile sink. In the scheme, the source calculates an expected area of the mobile sink by the moving speed of the sink; then, the data delivery speed is obtained from the worst case distance from the source to the farthest position on the area. The source transmits data to expected area with the delivery speed, and the first sensor node within the area then floods in the area to deliver the data to the mobile sink that is dynamically located within the area.

IoT routing architecture with autonomous systems of things

This article presents a future-driven routing architecture for Internet of Things (IoT). This IoT is a novel concept involving a new concept regarding a set of things with the same routing and service polices, denoted by an autonomous system of things (ASoT). In IoT, an ASoT would be connected not only to the others but legacy autonomous systems (ASs) for the Internet in a wide variety of scenarios. Hence, this article firstly addresses classification of diverse features of ASoTs, and then explores new challenges especially on inter-domain routing.