• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.3D
• /
• pp.307-315
• /
• 2008

The aim of this study is to develop travel time estimation model by using Self-Organized Neural network(in brief, SON) algorithm. Travel time data based on vehicles equipped with GPS and number-plate matching collected from National road number 3 (between Jangji-IC and Gonjiam-IC), which is pilot section of National Highway Traffic Management System were employed. We found that the accuracies of travel time are related to location of detector, the length of road section and land-use properties. In this paper, we try to develop travel time estimation using SON to remedy defects of existing neural network method, which could not additional learning and efficient structure modification. Furthermore, we knew that the estimation accuracy of travel time is superior to optimum located detectors than based on existing located detectors. We can expect the results of this study will make use of location allocation of detectors in highway.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.12A
• /
• pp.962-970
• /
• 2009

This paper proposes a self-organizing scheme which collects the information of neighboring cells, and then assigns a Physical Cell Identifier (PCI) for a newly deployed cell in LTE systems. The number of PCIs are limited, so the reuse of PCIs in different cells is unavoidable. In a dense urban environment where many small cells such as Pico/Femto cells are deployed under macro cells, it is expected that the number of PCIs becomes more limited. Therefore, the limited number of PCIs needs to be allocated very efficiently. We propose a PCI allocation scheme for a newly deployed cell that can autonomously select a PCI to increase PCI reuse efficiency by utilizing the levels of received signal strength from neighboring cells. To evaluate the performance of the proposed scheme, simulations have been developed and performed with two scenarios on the coverage types of newly deployed cells. When the proposed scheme is applied, the simulation results show that the number of PCIs required for the operation of the system can be saved so that PCIs can be efficiently reused.

• Journal of KIISE:Information Networking
• /
• v.34 no.2
• /
• pp.88-99
• /
• 2007

P2P systems are distributed data sharing systems, and each node in them plays the role of client as well as server. There are several studies using Distributed Hash Table, such as Chord, CAN, Tapestry, Pastry, but these systems don't consider the physical latency, therefore they have a weakness of difficulty to guarantee stable performance. To improve this problem, we present the TP2P system. This system is a self-organizing hierarchical overlay system and it uses Chord routing mechanism for lookup data. This system is organized by several subnets, each subnet is organized by physically close nodes, and global network organized by all nodes. In each subnet, one node finds a data, it saves in a node in the subnet, therefore it has higher probability to reduce physical lookup latency than Chord system. And each node has global information of some nodes in its subnet, and it is used to lookup data, therefore the number of hops decrease about 25% as well as the physical lookup latecy are reduced.