Sungchol Cho

P-LEACH: An Efficient Cluster-Based Technique to Track Mobile Sinks in Wireless Sensor Networks

For a wireless sensor network (WSN) with a large number of inexpensive sensor nodes, energy efficiency is the major concern in designing network structure and related algorithms. If network collects sensor data using mobile sinks, object tracking mechanism must consider the energy efficiency of sensor nodes in the networks as a whole. Recently research works on WSNs with mobile sinks apply prediction techniques for sink tracking in order to improve tracking precision while keeping the number of active nodes to the minimum. In this paper, we analyze existing works for sink tracking in WSN and propose P-LEACH that is cluster-based prediction technique for WSN with mobile sinks. Simulation results show that P-LEACH performs better than previous techniques in terms of energy saving of sensor nodes and data transmission performance.

Design and implementation for reducing zapping time of IPTV over overlay network

The QoE improvement provides improvement in the speed of internet service. If we can reduce one second of the delay of internet service, there will be a big improvement for the QoE. There is the same situation with IPTV service. Reducing zapping time is the linchpin in the QoE of the IPTV service. The main reason of the zapping time occurrence is the latency when user joins IGMP group. The second causation is the latency of transporting video, and the third one is latency that a settop box takes to encode the video. In this paper, we mainly research how to reduce the latency when the user joins into the IGMP[2] group. In IPTV, each user must join the group according to the IGMP group. We are proposing to tie join messages of the same IPTV groups users together and after send to the server. With this way we can reduce the latency of the joining to the IGMP. In this paper, we analyzed zapping time problem about IPTV service, and we also addressed network performance and user management. We tested our solution in the overlay multicast testbed and analyzed the results of test.

Performance optimization of media distribution in overlay networks using OpenFlow

Throughout the last decade, overlay multicast is a hot issue for media distribution services. High bandwidth consumption and multi-source multicasting in widely distributed networks is a critical issue for a wide range of applications including video conferencing, multi-party games, content distribution etc. A number of research projects have explored to use multicast as an efficient and scalable mechanism to deal with group oriented communications. However, there are still some limitations, such as long latency, duplicated packet transmission at certain points and lack of network equipment functionality support. With the appearance of Software Defined Networking, represented by OpenFlow devices, network control and management becomes possible to remote administrators. With the support of OpenFlow, it is possible to do some optimizations of existing media distribution mechanisms in overlay networks. In this paper, we proposed a novel method to improve the traditional overlay multicast relay networks with available limited number of OpenFlow devices, to cut down the bandwidth expenditures and perform a good control and management of media distribution services.

Reconnection of the Pre-assigning Peers in the Seamless Video Streaming

The main idea of this paper is using a manager server on the top of the tree-based P2P network construction for smartly providing alternative parent peers to reconnect in a case, when the downloading parent is down or crashes. The solution for these issues is considered to use minimum reconnection time for the parent change and solving the problem as lack in alternative peers. This is one of the main demands in the peer-to-peer video streaming system, as seamless streaming is one of the main issues in the P2P network.

Establishment and traffic measurement of overlay multicast testbed in KOREN, THaiREN and TEIN2

Nowadays not only many of research works with various international networks are increasing more and more but also commercial works are increasing with different international networks. In this paper, we have constructed the overlay multicast testbed with KOREN and TEIN2 network, and then we also analyze and research many works with the data got from the testbed experiments, and research works for speed of transmission and transmission security when the data is forwarded to several various international network. We work out the process of problem based on several data of experiments. We analyze these problems and propose the research way to other researchers in overlay multicast area, and we also provide these useful results to other researchers in this area.

Effective sensing movement of objects in ring sensor networks

A sensor uses nearby sensors to collect information and sends the information to sinks. Then, the sink forwards this collected information to users. However, if the purpose of these sensors is not to collect general data but to sense the movement of movement objects, it is difficult to sense fast moving objects with a clustering technique, which is used to collect general data. In this paper we propose a ring cluster technique that is an extended method from the basic cluster method, and this method is suitable for sensing of moving objects movement.

QoS-Adaptive Router Based on Per-Flow Management over NGN

In the present paper, we designed a specific router which provides the required level of QoS over NGN(Next Generation Network) by controlling data flows. We called this router QoS-Adaptive router, which consists of two parts, a legacy routing part and a QoS guarantee routing part. In order to provide differentiated services, QoS-Adaptive router enables data taking broad bandwidth or data requiring high-level QoS to be processed immediately and not to be affected by other services. And, we used the definition of flow for per-flow management, and assigned new service types to the flow label field of IPv6 header so as to provide differentiated services according to the packet type. By doing this, we designed a distinguishing mechanism in order to adapt to NGN that concentrates upon QoS. We built not only a small network to test QoS-Adaptive router but also a simulation environment called OMNeT++, and we could verify the performance of QoS-Adaptive router supporting QoS based on subscriber and service levels.

Design of User Bandwidth Management in Transport Layer of NGN

Current networks are evolving to NGN (Next Generation Network) which supports guaranteed quality of broadband multimedia services that are integrated with communication, broadcast and the Internet. In NGN environment should enable various services which are requiring high-level quality of service like real-time services to be provided seamlessly even though users use many kinds of communication networks and terminals. This paper proposes not only a solution for a problem that a user networks bandwidth is so insufficient that all services cannot be supported, but also a mechanism that tries to improve services efficiency for the user network over NGN by designing the user bandwidth control function, named UBCF (User Bandwidth Control Function).

Overlay Multicast Mechanism Supporting Differentiated QoS According to Service Level and User Environment over NGN

ABSTRACT NGN(Next Generation Network) is a communication network which can make use of broadband and QoS-enabled transport technologies. One of the main service issues over NGN is a multimedia service, such as IPTV, using a multicast method. And overlay multicast technology is one of the promising solutions instead of traditional multicast technology which has a few problems, and supports flexibility and scalability for multicast services. Also, the main controversial topic in NGN and overlay multicast is QoS. In the present paper, we designed an agent in each receiver’s network, and a manager which is in a source network and which manages the whole multicast network. Both of them are communicating with each other and applying resource policies to their multicast network. This mechanism enables overlay multicast to support QoS, focusing on RACF(Resource and Admission Control Functions) in NGN QoS architecture.Keywords:NGN(Next Generation Network), Overlay Multicast, QoS, Differentiated Service, Resource Management, RACF(Resource and Admission Control Functions)