Dae-Seung Yoo

A modified AOMDV routing protocol for maritime inter-ship communication

In maritime communication, QoS problem caused by routing is very important. In this paper, we propose a method based on AOMDV protocol providing a route recovery mechanism when a link breaks in an active route to reduce lost packets. The results show that the proposed method can reduce packet loss ratio and delay time compared with the AOMDV.

The Modified Proportional Fair Packet Scheduling Algorithm for Multimedia Traffic in LTE System

The Long Term Evolution (LTE) system is already able to provide a various background of media to mobile users, including multimedia services such as audio, video, data. In fact, the High Speed Downlink Access plus (HSPA+) solution within LTE can greatly enhance bit rates on downlinks. However, the supporting for multimedia applications with different QoS requirements is not devised yet. Hence, in this paper we present an effective packet scheduling algorithm based on proportional fairness (PF) scheduling algorithms for LTE. We optimize traffic class weightings and instantaneous user data rates that are central to packet prioritization approach of packet scheduling. Finally, we evaluated and showed the performance of optimized scheduling algorithm through simulation of multimedia traffics being currently transmitted to users the over LTE links in a multi-cell environment.

Implementation of MariComm bridge for LTE-WLAN maritime heterogeneous relay network

In this study, we shortly introduce MariComm bridge of MariComm (Maritime Broadband Communication) project to provide broadband internet/multimedia services available at a rate of 1 Mbps or more on the sea. MariComm bridge enables MariStations to form the maritime heterogeneous relay networks. Thanks to this bridge function, MariStation can act as a gateway node or a relay node according to the connection possibility of a terrestiral base station. And finally, marine performance tests of this noble maritime communication system on 4 vessels in the Korean southern sea are introduced.

A two-channel level-order pipelined transmission protocol for over-the-air programming in wireless sensor networks

This paper presents an efficient and reliable protocol that enables a pipelined transmission using two channels in wireless sensor networks. Nodes in the network form a tree originating from a sink node. A sharable slot is allocated to each tree level and one unique channel is assigned to every other level in the tree. Data transmission is performed from the lowest level to the highest level, allowing two simultaneous transmissions. The level-order data transmission using a sharable slot also increases the reliability of data reception greatly because every node has multiple chances of receiving the same data while it reduces competition for data transmission. Using the simulator Cooja on Contiki OS, we showed that the proposed approach far outperformed the Deluge protocol in terms of completion time and control overhead.

A novel antenna tracking technique for maritime broadband communication (MariComm) system

Maritime communication is internationally protected because closely related to the maritime safety, and it has evolved slower than terrestrial communication technologies. However, with the recent rapid advances in communication technology, maritime communications have become faster and increasingly modernized. A maritime broadband wireless data communication (MariComm) system was developed to make two-way high-speed internet/multimedia services available at a rate of 1 Mbps or more on the sea by extending the communication coverage of terrestrial wireless communications networks to sea areas. The MariComm system uses high-gain directional antennas to extend the transmission range and has multiple directional antennas to cover 360 degrees in azimuth. In this paper, we introduce a directional antenna tracking technique and apparatus using received RF signal and ship location information in the MariComm system.

A Study of Presence Services in SIP-Based Group Communication Systems

As the Presence Service provides users with dynamic information such as status and availability of their contacts increases the likelihood for success of the user’s communications, and enhances user satisfaction. Currently the Presence Service is used importantly in VoIP and Instant Messaging Service. However, in the systems that a real-time property is required, presence service should be provided limitedly and efficiently because it is in the trade-off relation with a real-time property. In this paper, we propose more effective Presence Service in the Group Communication System based on SIP. As the Presence Service of in this paper extracts the presence information from the normal SIP messages and sends minimal changed presence information to previously defined watchers instead of the OMA defined SIMPLE framework which consists of complex presence messages such as REGISTER, SUBSCRIBE, PUBLISH and NOTIFY it can be provided more efficiently in the Group Communication System.

A Modified AOMDV Routing Protocol for Maritime Inter-ship Communication

In maritime communication, QoS problem caused by routing is very important. In this paper, we propose a method based on AOMDV protocol providing a route recovery mechanism when a link breaks in an active route to reduce lost packets. The results show that the proposed method can reduce packet loss ratio and delay time compared with the AOMDV.