Seung W. Yoo

Fuzzy bin packing problem

This paper deals with the fuzzy bin packing problem that is a packing problem of non-rigid rectangles into an open rectangular bin. This problem is different from the conventional bin packing problem, which considers only rigid rectangles. The goal of the fuzzy bin packing problem is to minimize both the height of a packing and the extra cost due to the reduction of each piece. The total cost of the problem is represented as the sum of the height cost and the extra cost due to reductions of the pieces, which is called reduction cost. Because the conventional bin packing problem itself is an NP-hard problem, the presented optimization method assumes that an initial packing for non-reduced pieces has already been found. A closed form solution is presented for fuzzy bin packing problems, in which fuzzy numbers are triangular and the reduction cost is given by a quadratic function.

Tree-Based classification algorithm for heterogeneous unique item ID schemes

For RFID-based applications, the uniqueness of ID assigned to each RFID tag should be guaranteed. Several research/standard organizations such as EPCglobal, ISO/IEC, Ubiquitous ID Center, and so on, have developed their own Unique Item ID (UII) specifications. The existence of various UII schemes may cause interoperability problems between applications using different UII schemes when those applications are operated on future global Internet network environment. In addition, it is expected that the traffic for UII query will be increased ten-times higher than that for DNS query in the current Internet. In order to overcome these problems, this paper proposes a fast tree-based classification algorithm applicable for various UII schemes, which can make it efficient to construct global directory lookup services for RFID applications with various UII schemes. Since the proposed scheme can be operated on readers, it can not only distribute traffic loads for UII queries, but also global RFID networks.

A Novel Detection Methodology of Network Attack Symptoms at Aggregate Traffic Level on Highspeed Internet Backbone Links

In this paper, we investigate the network attack traffic patterns appeared on Internet backbone links. Then, we derive two efficient measures for representing the network attack symptoms at aggregate traffic level. The two measures are the power spectrum and the packet count-to-traffic volume ratio of the aggregate traffic. And, we propose a new methodology to detect networks attack symptoms by measuring those traffic measures. Unlike existing methods based on individual packets or flows, since the proposed method is operated on the aggregate traffic level, the computational complexity can be significantly reduced and applicable to high-speed Internet backbone links.

Wireless Sensor Networks for integrated search and rescue efforts for disaster hit areas

The recent research and development in the domain of Wireless Sensor Networks (WSNs) have opened up tremendous opportunities and applications in many different scenarios. If we take into account the aftermaths of disaster, we certainly need to build up a mechanism to gather the data for the disaster hit area in which there is minimum delay and protocol we use should be energy efficient. This can be achieved by using wireless sensor network as they are energy efficient and can broadcast the data efficiently. The use of WSNs for search and rescue efforts is an evolving concept and numerous architectures have been studied and developed lately. This paper presents a conceptual design of a WSN based system aimed at aiding search and rescue missions in disaster hit area e.g. tsunami. People living in danger zone switch on their personal issued sensors after a warning is issued by relevant authorities. During and after disaster, this WSN is used to track and identify survivors, coordinate search efforts and assess on ground situation in real time.

Instant graph routing: lightweight graph generation scheme

Wireless Sensor Networks (WSNs) is one of the famous researching fields. There are many applications like Smart Grid, Automation Systems, etc. Especially, the ISA100.11a standard that is adapted to the wireless industrial monitoring and control system is most famous sensor network application. In this standard they are suggest a simple and reliable routing mechanism called by graph routing. However the graph routing is a static routing that mean it is hard to change routing route and not flexible. In this paper, we propose a routing path stored graph for instant able. The proposed scheme can overcome the problems of non-flexible graph routing mechanisms. It is shown that the proposed method can provide graph generation efficiency without system manager.

Handoff Delay Performance Comparisons of IP Mobility Management Schemes Using SIP and MIP.

In this paper, we analyze and compare the handoff delays for several architectures such as MIP-only, SIP-only, MIP/CIP and SIP/CIP, which are expected to be most promising solutions to support IP mobility management. For the analysis, we make the detailed message flows of those architectures in handoffs, and then make an analytical model to compute the handoff delay for each scheme. Numerical results showed that the SIP/CIP outperforms other schemes in the viewpoints of the handoff delay.

Optimizing time schedule of key updates in ISA100.11a

Wireless Industrial Sensor Networks (WISN) has many challenges like low-resources, harsh environmental conditions, QoS, integration with other wireless technologies and security. In particular, security is the most important to protect the information of critical infrastructure. ISA100.11a is an industrial standard of WISN, includes key update protocol in its standard in order to protect key exposal. In this paper, we analyze the key update problems of ISA100.11a and investigate the way of calculating optimal key update interval for efficiency. Finally we suggest the algorithm that is for organizing time schedule of key updates using calculated interval and evaluate the performance of proposed algorithm by simulations.

Energy-Saving cluster formation algorithm in wireless sensor networks

In this paper, we propose an efficient energy-saving cluster formation algorithm (ECFA) with sleep mode. ECFA can achieve energy efficient routing with the following two properties. First, ECFA reconfigures clusters with fair cluster formations, in which all nodes in a sensor network can consume their energies evenly. In order to achieve fair cluster regions, ECFA does not require any information on the location and energy of nodes. Second, by letting nodes very close to just elected cluster head be in sleep mode, ECFA can reduce unnecessary energy consumptions. Performances of ECFA are compared with LEACH and LEACH-C in the cases of the static and mobile nodes.

A novel traffic control architecture against global-scale network attacks in highspeed internet backbone networks

In this paper, we propose a global traffic control architecture to isolate network attacks from normal traffic in the backbone networks designed to serve normal traffic only. Unlike existing methods based on individual packets or flows, the proposed traffic control methods are operated on the aggregate traffic level, so the computational complexity can be significantly reduced, and they are applicable to develop a global defense architecture against attacks to network infra-structure. Experimental results show that the proposed scheme can detect the network attack symptoms very exactly and quickly, and protect the network resources as well as the normal traffic flows very efficiently.

Energy-Efficient cluster reconfiguration with fair cluster formations in sensor networks

In cluster-based schemes such as LEACH, cluster reconfiguration algorithm is one of the most critical issues to achieve longer lifetime of sensor networks. In this paper, we propose a new energy efficient cluster reconfiguration algorithm, called EECRA. EECRA does not require any location or energy information of sensors, and can configure clusters with fair cluster regions such that all the sensors in a sensor network can utilize their energies equally. The performances of EECRA have been compared with LEACH and LEACH-C. We also show that EECRA can be well applied to the environments that sensors are moving.