Jongwon Choe

Mobile Multicast Method Using the Habitude of Movement

This paper presents the new mobile multicast method using a habitude of movement that can reduce the total number of the graft and join by making the network including to the habitude be active. The proposed mechanism can provide a multicast service in the mobile environment with the less service delay and not too excessive overhead efficiently. Furthermore, numerical results show that our scheme compared to other mechanisms reduces a delay efficiently until the receipt of multicast service but it has a few overheads.

A load-balancing approach in Ad-hoc networks

In the case of link congestion, most of the existing ad hoc routing protocols like AODV and DSR do not try to discover a new route if there is no change in the network topology. Hence, with low mobility, traffic may get concentrated on some specific nodes. Since mobile devices have low battery power and low computing capability, traffic concentration on a specific node is not a desirable phenomenon. Therefore, in this paper, we propose a new routing approach called SLAR (Simple Load-balancing Ad hoc Routing) which resolves the traffic concentration problem by letting each node check its own load situation and give up its role as a packet forwarder gracefully in the case of high traffic load. We compare the performance of SLAR with that of AODV and DSR in terms of the forwarding traffic distribution.

An efficient multi-channel MAC protocol for wireless ad hoc networks

IEEE 802.11 MAC is designed for single channel and based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The throughput of network is limited by the bandwidth of the single channel and the CSMA-based MAC protocol with omnidirectional antennas can cause the serious unfairness or flow starvation. By exploiting the multiple channels and using the directional antennas, nodes located in each others vicinity may communicate simultaneously. This helps to increase the spatial reuse of the wireless channel and thus increase the network performance. In this paper, we propose a Multi-channel MAC protocol with Directional Antennas (MMAC-DA) that adopts IEEE 802.11 Power Saving Mechanism (PSM) and exploits multiple channel resources and directional antennas. Nodes have to exchange control packets during the Announcement Traffic Indication Message (ATIM) window to select data channels and determine the beam directions which are used to exchange data packets during the data window. The simulation results show that MMAC-DA can improve the network performance in terms of aggregate throughput, packet delivery ratio, energy efficiency and fairness index.

Multi-channel MAC protocol with Directional Antennas in wireless ad hoc networks

IEEE 802.11 Distributed Coordination Function (DCF) is based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). However, the CSMA-based access protocol with omnidirectional antennas can cause the serious unfairness or flow starvation. By exploiting the multiple channels and using the directional antennas, nodes located in each others vicinity may communicate simultaneously. This helps to increase the spatial reuse of the wireless channel and thus increase the network performance. In this paper, we propose a Multi-channel MAC protocol with Directional Antennas (MMAC-DA) that adopts IEEE 802.11 Power Saving Mechanism (PSM) and exploits multiple channel resources and directional antennas. Nodes have to exchange control packets during the Announcement Traffic Indication Message (ATIM) window to select data channels and determine the beam directions which are used to exchange data packets during the data window. The simulation results show that MMAC-DA can improve the network performance in terms of aggregate throughput, packet delivery ratio and energy efficiency.

A novel coding scheme to implement signature based IDS in IP based Sensor Networks

In signature based IDS (Intrusion Detection Systems), if incoming packet header matches a certain set of rules, its payload is scrutinized against a set of known patterns (also called signatures). As the number of patterns could range up to thousands, pattern matching consumes not only the storage but also the most of the CPU cycles to execute the complex pattern matching algorithms. Therefore, so far there is no signature based IDS which can work on resource constraint sensor nodes. This paper presents a dynamic coding mechanism, which helps in implementing a distributed signature based IDS (Intrusion Detection System) in IP-USN (IP based Ubiquitous Sensor Networks). The proposed scheme also allows building of lightweight IDS in terms of storage, messaging and energy consumption, which make it appropriate for resource constrained sensor devices.

Research and implementation on the security scheme of industrial wireless network

Industrial Wireless communications is emerging technology after the Fieldbus in industrial field. For industrial control application with wireless industrial technologies, the WIA-PA standard defines the protocol suite, system management, gateway, and security for low-data-rate wireless connectivity with fixed, portable, and moving devices supporting the limited power consumption requirements. In this paper we summary the security provision in the current standards. Then we present a new security architecture and security protocol based on WIA-PA standard. Furthermore, we design and implement the security communication services. Finally, the security test results illustrate that these security scheme may enhance the security reliability of the WIA-PA network communication.

A Reflective Approach to Dynamic Adaptation in Ubiquitous Computing Environment

To provide users with persistent services in distributed ubiquitous environments, it is required for applications and middleware to be aware of the frequent and unpredictable changes in users requirements as well as environmental conditions, also to be able to adapt their behaviour as such changes. One of the main limitations of current approaches for supporting adaptability is that applications themeselves are responsible for triggering and adaptive mechanism when the underling infrastructure notifies them about any changes. Hence, we design an adaptive middleware framework using reflection and propose the meta-meta-level to support a policy-based adaptation. We implement mobile agents (adaptation, context and meta agents) to adapt user-level and application-level changes dynamically for mobile users and applications.

A router-assisted session tree configuration mechanism for reliable multicast

A session tree based mechanism provides an efficient method to avoid well-known feedback implosion. However, it is not easy to configure an efficient session tree for IP multicast because it does not provide any explicit membership and routing topology information to the upper layer protocol. Incongruity between a session tree built on the transport layer and the corresponding routing tree on the network layer would incur large cost to handle control messages. This problem can be solved if a router that knows the information of routing topology can support the configuration of a session tree. Thus this letter proposed a router-assistant mechanism which minimizes the change of router functions and allows the routers to assist in providing a reliable multicast transport service.

A measurement model for trustworthiness of information on social network services

Due to the spread of unreliable online information on social network services (SNS), the users are faced with a difficult problem for determining if the information is trustworthy or not. At present, the users should make a decision overall by themselves for trustworthiness of information. Therefore, we need a way to systematically evaluate trustworthiness of information on SNS. In this paper, we design a trust metrics, called TII (Trust Index for Information on SNS), as a criterion for measuring the trust degree of information on SNS. Using TII, the users are readily able to determine whether the information is trustworthy. Consequently, we can estimate the social trust degree based on the variation of TII. This paper derives the various factors affecting trust from the properties of SNS, and proposes a model to evaluate the trustworthiness of information that is directly produced and distributed over the online network. Quantifying the trust degree of the information on SNS allows the users to make efficient use of the social network.

Design and Implementation of NEMO Based ZigBee Mobile Router for Healthcare System

In this paper, we focused on the scheme which supports mobility for ZigBee sensor nodes. We adopt NEMO protocol to provide mobility for low power ZigBee sensor nodes. Therefore, we propose NEMO based ZigBee Mobile Router architecture and operations to support the network mobility of ZigBee network. Also, we present the design and implementation of the ZigBee Mobile Router for healthcare system. The architecture is particularly useful to manage patient’s mobility where each patient is equipped with ZigBee sensor nodes.