Doohyun Ko

Prediction Based Mobile Data Aggregation in Wireless Sensor Network

A wireless sensor network consists of many energy-autonomous micro-sensors distributed throughout an area of interest. Each node has a limited energy supply and generates information that needs to be communicated to a sink node. To reduce costs, the data sent via intermediate sensors to a sink, are often aggregated. The existing energy-efficient approaches to in-network aggregation in sensor networks can be classified into two categories, the centralized and distributed approaches, each having its unique strengths and weaknesses. In this paper, we introduce PMDA (Prediction based Mobile Data Aggregation) scheme which uses a novel data aggregation scheme to utilize the knowledge of the mobile node and the infrastructure (static node tree) in gathering the data from the mobile node. This knowledge (geo-location and transmission range of the mobile node) is useful for gathering the data of the mobile node. Hence, the sensor nodes can construct a near-optimal aggregation tree by itself, using the knowledge of the mobile node, which is a similar process to forming the centralized aggregation tree. We show that the PMDA is a near-optimal data aggregation scheme with mobility support, achieving energy and delay efficiency. This data aggregation scheme is proven to outperform the other general data aggregation schemes by our experimental results.

Geographical location based RFID tracking system

A large number of RFID system support location based service. This RFID Location System based on the general purposed geographic location code supports monitoring of the RFID tags in real time effectively. To identify the RFID tags, we allocate the general purposed geographic location code for each region. Throughout this system, the distribution and services related with RFID can easily manage the objects.

Priority-Based Hybrid Routing in Wireless Sensor Networks

By the wide range of researches on Wireless Sensor Networks (WSNs), various routing schemes with diverse criterion have been introduced. However, techniques that consider the characteristics of the sensed data as definitive parameters in determining the behavior of WSNs are extremely rare. In most monitoring applications, sampled data are not equal in their importance. Unexpected data is more likely to be important. That is, data collected during abrupt changes in the environment are more critical than the others. In this paper, we propose Priority-Based Hybrid Routing (PHR) that provides functions ranging from data priority verification to differentiated services according to different priorities. Data priorities, or importance, are determined by their distinctiveness in relation to past data. Dixons Test, a hypothesis testing method, is adopted for the process. To provide more reliable routing method for high priority data, PHR offers them a novel, diffusion-based forwarding scheme, referred to as Geographic Diffusion. On the other hand, low priority data are delivered by a famous single path routing algorithm, Ad hoc On-demand Distance Vector (AODV). Furthermore, AODV is revised to compensate with the increased traffic caused by Geographic Diffusion. The performance of PHR is evaluated through various simulations.

Enhanced Distributed Address Assignment Scheme for ZigBee-Based Wireless Sensor Networks

ZigBee is a standard that is suitable for wireless sensor networks. In ZigBee, sensor nodes can be connected by a tree topology called Distributed Address Assignment Mechanism (DAAM). It has the merits as follows: 1) it is easy to implement; 2) it simplifies the task of routing. It restricts the number of children and the depth of the network by setting a topological parameter set, which is defined as a topological policy in this paper. While there are many different kinds of geographical distributions, DAAM can have only one topological policy. If the policy in DAAM is unsuitable for the geographical deployment, the utilization of the address pool is very low. Thus, in spite that there is a large address space, some devices cannot join the sensor networks. To overcome the problem, this paper proposes Enhanced Distributed Address Assignment Scheme (EDAAS) based on DAAM; it can separate the node distribution into several simpler elements which can have their own topological policies. The evaluation shows that it can manage address space with more flexibility by using an additional storage.

Research on Anti-Reader Collision Protocols for Integrated RFID-WSNs

Integrated RFID-WSNs (wireless sensor networks) have recently been researched to provide object identities, sensing information, mobile service, and network functionalities. In integrated RFID-WSNs, the reader collision is one of the critical problems. Above all, due to the absence of universally applicable anti-collision protocols and the channel capture phenomenon, the medium access control protocols in integrated RFID-WSNs suffer from reader collision and starvation problems. In this paper, we propose an efficient MAC protocol, called EMP, to avoid the above problems in integrated RFID-WSNs. EMP is a CSMA-based MAC protocol which is compatible with sensor networks operating on integrated nodes which consist of an RFID reader and a senor node. EMP resolves not only the reader collision problem, but also the starvation problem using a power control mechanism. To verify the performance of EMP, we compared it with other anti-reader collision MAC protocols using simulations. As a result, the performance of EMP showed improvements in throughput, system efficiency, and energy consumption compared to the single data channel protocols (CSMA/CA, Pulse, and DiCa) in dense deployment environments.

PR-RAM: The Page Rank Routing Algorithm Method in Ad-hoc wireless networks

This paper presents the Page Rank Routing Algorithm Method (PR-RAM), which is the Ad-hoc wireless networks routing protocol using Page Rank algorithm. Page Rank is the link analysis algorithm used by the Google internet engine that assigns a numerical weighting to each element of World Wide Web (WWW) with the purpose of measuring its relative importance within the WWW. If any web page has a higher rank than other web page, it means that this web page is more important than other web page. In order to measure the relative importance of mobile node in wireless network environments, this paper uses the Page Rank algorithm in Ad-hoc wireless networks. Mobile nodes Page Rank means how many routing paths are included to this node. This paper also uses available every multiple minimum hop-count routing paths to be more efficient on view of variance of entire mobile nodes energy. PR-RAM is guaranteed the access fairness of source node to Access Point (AP) in Ad-hoc networks environments.

Energy-Efficient Tree Routing Algorithm-Based Destination Family Group in ZigBee Networks

This paper solves the hierarchical tree routing’s inefficiency problem by using a neighbor node table, defined by the Zigbee standard, the Zigbee tree architecture, and an address allocation mechanism. This method selects a relay node through hierarchical tree routing, but if it finds a neighbor node, one of the destination family group, which reduces the expense of routing; then, this method selects the neighbor node as a relay node, and so reduces the expense of routing to the destination node.

WiMoS: Wise mobile sensor networks a study on design of infrastructure for supporting mobile WSNs in wide area

We propose a network infrastructure, called wise mobile sensor network (WiMoS), for supporting mobile WSNs in wide area. WiMoS has been developed to integrate conventional WSN systems and provide efficient location based services (LBSs), and has been designed by the open structure which has standard interfaces to support machine to machine (M2M) and internet of things (IoT). This paper introduces the system architecture, functions, implementation, and standardization issues for WiMoS.

ECO: Enhanced Reader Collision Avoidance MAC for Reader-Sensor Networks

Abstract—In recent years, one of alternatives for constructing RFID networks that provide mobile services is using wireless sensor networks (WSN) to enhance network capacity,utility and scalability. Due to absence of compatible reader anti-collision control and channel capture phenomenon, the medium access control protocols as used in the RFID networks lead to reader collision and starvation problem. In this paper, we develop a MAC protocol which is called Enhanced Collision Avoidance MAC (ECO) to avoid reader to reader collisions in an integrated RFID network. ECO is a CSMA-based MAC protocol, and operates on integrated nodes which consist of a RFID reader and a mote. Performance evaluation shows superior results to pure-CSMA protocols under dense deployment environments, both in number of failures and in throughput.