Jeongsik In

A design and implementation of wireless sensor gateway for efficient querying and managing through World Wide Web

Wireless sensor networks consisting of hundreds to thousands of nodes are expected to find increasing deployment in coming years, as they enable reliable monitoring and analysis of physical worlds. These networks have unique features that are very different from traditional networks, e.g., the large number of nodes, limitation in power. Due to these unique features of wireless sensor networks, their management including querying becomes a challenging problem. In general, it is widely accepted that Web-based management should be used for managing and querying sensor networks. In this paper, we present the architecture of the sensor gateway for Web-based management and its implementation details. We assume that wireless sensor networks have 3-level regional hierarchy, but our gateway is flexible enough to cooperate with other type sensor networks. In addition, to make our gateway process users query dynamically without intervention of user, a back socket is opened using Java applet. For this purpose, Java script code is embedded in Web page to link Java applet code.

Distributed dynamic shared tree for minimum energy data aggregation of multiple mobile sinks in wireless sensor networks

Sink mobility creates new challenges for several sensor network applications. In mobile sink environments, each sink must propagate its current location continuously, through a sensor field, in order to keep all sensor nodes updated with the direction of data forwarding. This method consumes large amounts of energy. Although several protocols, such as DD, TTDD, and SEAD, have been proposed, in order to solve mobile sink problems, no existing approaches provide both a low delay and energy-efficient solution to this mobile sink problem. In this paper, a distributed dynamic shared tree for minimum energy data aggregation with low delay in highly mobile sink environments, is proposed. In the proposed protocol, the tree is shared with the other slave sinks. Through simulations it is shown that the DST is an extremely energy-efficient, robust protocol with relatively low delay, when compared to DD, TTDD, and SEAD.

Dynamic sink oriented tree algorithm for efficient target tracking of multiple mobile sink users in wide sensor field

In this paper, we introduce an efficient target tracking scheme through a dynamic sink oriented tree (SOT) algorithm for multiple mobile sinks. The SOT is maintained by the partial link reversal algorithm to adapt to the mobile sink environment. The main objective of our proposed algorithm is to efficiently deliver location information of targets to the multiple mobile sinks. Since our protocol can construct and dynamically maintain the SOTs although the sinks moves continuously, data aggregation from target nodes to sink can be efficiently achieved through the SOT, and also, in-network processing of the aggregation process is naturally achieved. In addition, the tracking coverage of each mobile sink is wider by dynamically merging each sinks SOT. Also, we evaluated our protocol in terms of how robust it is by examining the packet loss rate with respect to the sink speed.

Novel Sink-Oriented Approach for Efficient Sink Mobility Support in Wireless Sensor Networks

Mobile sinks pose several challenges for network protocol design. While moving, a sink should continuously update its topological position information in the sensor nodes to maintain paths. This may require large signaling overhead, resulting in excessive energy consumption. Various schemes have been proposed to reduce the path management overhead. In many of these schemes, the sinks only maintain paths from active sources to reduce the overhead. While reducing the path management overhead, this approach introduces other problems. In this paper, a novel path management scheme, Net Cast Routing (NCR), is proposed. NCR provides ceaseless connection from every sensor node to every sink in an efficient manner. Since it does not distinguish active sources from other sensor nodes, its performance is not affected by the number or movement of the sensing targets. In addition, unlike multicast based schemes [2,3,4], NCR does not require any subscription procedure to active sources.

Minimum TCP throughput guarantee on minimum rate guaranteed networks

The performance of Transmission Control Protocol (TCP) entirely depends on the network traffic conditions. It will be greatly advantageous if the throughput of the TCP is always maintained above a certain level. However, it is difficult to guarantee minimum throughput for each TCP connection even when enough bandwidth is reserved for it. This is because the TCP congestion control algorithm makes its transmission rate fluctuate so that, in some cases, the connection cannot fully utilize the portion of the bandwidth reserved for it. We propose a slightly modified traffic shaper that can help maintain the TCP transmission rate. It normally regulates traffic just as the conventional shapers, but when necessary, it adjusts its transmission rate depending on its own state, namely its queue length and packet-receiving rate, without explicit notification of the network conditions. It only requires a simple modification of the conventional shapers. However, this simple modification can improve TCP performance significantly and help guarantee minimum throughput when the network guarantees minimum bandwidth for the connection. Simulation results are presented for performance evaluation. The proposed scheme is practical in that it does not require end-host modifications. Also, it has scalability since it requires per-flow management only in the network access routers and not in the core routers.

Data rate adaptive route optimization for sink mobility support in wireless sensor networks

Mobile sinks pose several challenges for network protocol design. While moving, a sink should continuously update its topological position information in the sensor nodes to maintain paths. This may require large signaling overhead, resulting in excessive energy consumption. Various schemes have been proposed to reduce the path management overhead. In many of these schemes, the sinks only maintain paths from active sources to reduce the overhead. While reducing the path management overhead, this approach introduces other problems. In this paper, Data Rate Adaptive Route Optimization (DRARO) scheme is proposed. DRARO provides a method for adjusting the route optimization level depending on the amount of data traffic, to minimize overall energy consumption. In addition, DRARO provides ceaseless connection for every sensor nodes and its performance is not affected by the number or movement of the sensing targets.

Lightweight real-time embedded systems for scalable ubiquitous networks

In this paper, we present real-time system software architecture, composed of an event-driven operating system called the embedded lightweight operating system (ELOS) including fault tolerant self-configuration combined with a multi hop ad hoc routing protocol suite. In the ELOS, a conditional preemptive FCFS scheduling method with a guaranteed time slot is designed for efficient real-time processing. For more elaborate configurations, we reinforce fault tolerance by supplementing semi-auto configuration using wireless agent nodes. The developed hardware platform is also introduced, which is a scalable prototype constructed using off-the-shelf components. Finally, to verify real-time processing ability under the various traffic patterns, the performance of ELOS system on a ubiquitous network test-bed is evaluated. The result shows that the ELOS is more suitable for tiny ubiquitous networked systems with real-time constraints.