Juhyun Jung

Communication Scheme to Support Sink Mobility in Multi-hop Clustered Wireless Sensor Networks

In wireless sensor networks, the studies that support sink mobility without global position information exploit a Backbone-based Virtual Infrastructure (BVI) to avoid the routing structure construction per each mobile sink by full network flooding. The BVI approach typically considers one-hop clusters and a backbone structure-based tree configured by the cluster heads (CHs). For data dissemination to a mobile sink, the head of the cluster where the mobile sink exists registers the backbone structure on behalf of the sink, and then source nodes generate the data to their CHs via the tree. Finally, the CHs deliver the data to the mobile sink. However, the one-hop cluster makes the tree organized by too many CHs so that it causes large location registration overhead according to movement of the sink. Moreover, the data delivery via the tree with a large number of CHs might lead to data delivery from source nodes to the sink though detour paths due to always delivering data via the tree. Namely, although the source nodes exist at nearest clusters from the cluster attached by the sink, if they are located in different branch of the tree, the data should be delivered via detour paths on the tree. Therefore, we propose a novel BVI-based communication protocol to support sink mobility without global position information. To reduce the number of CHs, we consider multi-hop clusters. Also, to avoid the location registration of a mobile sink to the whole CHs, we uses a rendezvous CH on which queries of the mobile sink and reporting data of a source node meet. However, such a manner also has data detour problem that the source node sends data packets to the mobile sink via the rendezvous CH. Thus, we present a scheme to find a path with fewer hop-counts between CHs where the source node and the mobile sink are located in. Simulation results show that the proposed protocol is superior to the existing protocols in terms of the control overhead and the data delivery hop counts.

OMLRP: Multi-Hop Information Based Real-Time Routing Protocol in Wireless Sensor Networks

In wireless sensor networks, real-time data delivery schemes typically achieve a desired delivery speed by proactively performing one-hop lookahead. Recently, to reduce the deadline miss ratio against the desired delivery speed, a study has proposed a real-time routing protocol based on proactively performing twohop lookahead. However, the recent study might cause heavy message exchange overhead and high computing complexity to proactively carry out obtainment of two-hop neighborhood speed information in the entire sensor network whether data are delivered or not. Moreover, although multi-hop lookahead provides the least deadline miss ratio, due to the restriction from the overhead and the complexity, the recent study merely adopts the two-hop lookahead manner. In this paper, we propose a novel real-time routing protocol. The proposed routing protocol adopts on-demand neighborhood information obtainment only around data forwarding paths. The on-demand information obtainment is performed in multi-hop lookahead. Hence, the proposed routing protocol is able to provide the least deadline miss ratio to realtime data delivery. Simulation results prove that the proposed routing protocol offers better performances with respect to deadline miss ratio, total communication costs, energy efficiency, and network lifetime.

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.

Real-Time Data Dissemination Based on Reactive and Restricted Zone Search in Sensor Networks

Typical real-time routing data dissemination schemes employ 1-hop transmission speed based on the 1-hop lookahead manner that proactively obtains information of 1-hop neighbor nodes and selects one that satisfies a desired delivery speed as next hop. To improve performance of 1-hop lookahead based real-time routing protocols, THVR (Two-Hop Velocity-based Routing) is proposed. THVR reduces deadline miss ratio that the ratio of the number of data that exceeds the time limit to total number of sending data via routing decision based on 2-hop neighborhood information obtained from the 2-hop lookahead information. However, since the 2-hop lookahead manner makes every sensor node proactively obtain 2-hop neighborhood information whether the sensor node has data to forward or not, THVR carries two inefficiencies: heavy control message exchange overhead and high computing complexity. In this paper, we propose a noble real-time routing protocol based on reactive and restricted zone search. The proposed protocol minimizes the deadline miss ratio and eliminates the two inefficiencies mentioned above by on-demand multi-hop lookahead. In the proposed scheme, reactive multi-hop neighborhood information obtainment is fulfilled only by a small number of sensor nodes within a restricted zone around a data forwarding path from the source to the destination.