Seung-Joon Seok

Flow based 3G/WLAN vertical handover scheme using MIH model

Vertical handover is to change the local interface or the access network of mobile node in the middle of communications. IEEE 802.21 Media Independent Handover (MIH) model can provides mobile nodes with necessary information for handover. This paper proposes a MIH vertical handover model which is consists of event messages, vertical handover procedure, and handover decision algorithm for 3G/WLAN vertical handover. In the proposed model, 3G base station, Wi-Fi WLAN access point, and vertical handover decision agent (VHDA) exchange event messages each other. VHDA finally decides the vertical handover for each flow according to our decision algorithm and sends the result to the mobile node. The flow based vertical handover decision algorithm is based on flow quality and cost functions. This paper evaluates the proposed algorithm through simulation experiments. The simulation results show that our algorithm may increases network efficiency.

A transmission control SCTP for real-time multimedia streaming

Multimedia streams over the Internet have a strict playback delay time, i.e., multimedia data arriving after the playback time cannot be played by the receiver and they are discarded. In this paper, we introduce a transmission control SCTP (TC-SCTP) which has a transmission control sub-layer (TCSL) in which the multimedia streaming server determines whether data can be played in the receiver before sending the data and decides whether to send data messages or not. In addition, TCSL employs differentiated retransmission policy depending on the type of multimedia. We evaluate the performances of SCTP, partial reliability (PR)-SCTP, and TC-SCTP via ns-2 simulator. The simulation results demonstrate that the TC-SCTP protocol can decrease the amount of transmissions and increase the video decodable ratio, compared with other protocols.

A Transport-Layer Based Simultaneous Access Scheme in Integrated WLAN/UMTS Mobile Networks

The integration of UMTS cellular network and wireless LANs enables users to achieve both the broad coverage of UMTS cellular network and the higher data rate of WLANs. In this paper, we present a transport-layer based simultaneous access scheme which enhances throughput by efficient use of these networks. Two representative transport protocols in the Internet, UDP and TCP, show significantly different behaviors against end-to-end delay and packet losses, and UMTS cellular network and WLANs have different packet losses and end-to-end delay characteristics. After prediction of UDP and TCP throughput in each network, each transport protocol is allocated to the network where total throughput can be maximized. We evaluate the proposed mechanism using NS-2 and show the improvement of the total throughput.

A scheme for enhancing TCP fairness and throughput in IEEE 802.11 WLANs

In this paper, we consider two fairness problems that occur in the infrastructure network (fairness between TCP uplink/downlink flows and fairness between competing TCP uplink flows). A large number of existing works have studied the TCP fairness issues and greatly solved the TCP unfairness problems. However, these solutions suffer from the drawback of TCP throughput degradation even though the TCP unfairness problem can be solved. In order to solve these problems effectively, we propose a scheme that modifies the receiver window size on the basis of maximum window size which is able to maximize link utilization. We have evaluated our scheme with ns-2 simulator and the results demonstrate that our scheme greatly improves both the TCP fairness and total throughput.

Aggregation management design for user-defined network infrastructure.

Recently, OpenFlow and FlowVisor are the most promising architecture components of the software-defined networks (SDNs). The evolution of these components brought the revolution of utilizing network elements for the shared and virtual network infrastructure, however from the aspects of production networks, it still lacks of some key component. For example, policy-based services provisioning for user-defined requirement is an indispensable part. Hence, innovative aggregation management design for virtual network management system framework must be developed and tested. This paper describes an initial design to user-defined network infrastructure in order to make it capable of running policy-based engineering related experiments. We developed the framework regarding the real use cases upon the shared and virtual network in KREONET infrastructure. Moreover, we also presented perflow-user-defined specifications which include max rate limiter and dynamic priority assignment strategy to enhance the validation performance of our system for production networks.

Pastry Based Sensor Data Sharing

With research effort of Ubiquitous computing development, Wireless Sensor Networks have also been studied and deployed in many places. Recently various works for sharing the existing sensor data have been tried. In this paper we propose a P2P based system for sharing sensor data. It uses a structured P2P - Pastry to provide DHT based routing without server and has been deployed in KOREN. We classify the sensor data into real-time data and past data, and Scribe in Pastry is applied to multicast the real-time data and PAST in Pastry is used to store and provide the past data. Also as Pastry itself does not provide the search function, we propose to use PAST for providing search function using keywords.

New service differentiation model for end-to-end qos provisioning in wireless ad hoc networks

In this paper, a new QoS model is presented for end-to-end service provisioning in wireless ad hoc networks. Many previous works focus on the packet scheduling mechanism using multiple service classes implemented for traffic prioritization based service differentiation. However, this paper concentrates on a scheme for dynamically selecting a proper one among several forwarding classes that perform different service rate according to service requirements. There service requirements include low delay, high throughput, and low loss. The proposed solution is a new QoS provisioning model called Dynamic Hop Service Differentiation (DHSD). This model supports soft QoS provisioning to reduce network overhead and wireless PHB (WPHB) to achieve the end-to-end QoS required by applications. The proposed QoS model is evaluated using OPNET simulation. We show that this model outperforms both best-effort and strict priority service models in wireless ad hoc network environments.

multiFIA Multi-dimensional future Internet architecture

Rapid growth in Internet of Things (IoT) has resulted in the need for effective management and provisioning of resources in an IoT-based system. The resource may be an entity (virtual or physical) that constitutes the IoT system, such as network elements, gateways, cloud data stores, and sensors. The dynamic and constantly changing nature of request by a typical user for resource allocation demands end-to-end slices of an IoT system. In order to meet such requests, end-to-end slices need to be integrated, ultimately making it necessary to control and aggregate diverse types of resources from IoT, cloud infrastructures, and network functions. To that end, in this paper, we propose a framework for IoT resources management and provisioning. Our proposed approach enables to automate resource management and provisioning for users across IoT, clouds, and network functions by virtualizing access to underlying IoT resources and utilizing APIs to employ those resources. Furthermore, our proposed approach aims to establish and manage end-to-end slices of various types of resources from distributed and diverse infrastructure. In this paper, we present multiFIA — multi-dimensional Future Internet Architecture — which permits IoT system designers to accommodate multiple user demands by establishing end-to-end slices of the overall IoT network. We outline multiFIA components and layers and also describe our approach to an implementation of multiFIA.

A Two-Tier Routing Algorithm Based on Geographical Zone in VANET

VANET Routing configures a data transmission path between vehicles sending and receiving message by using car node as relay node. Since car node is of mobility, it is difficult to maintain communication connectivity between two neighbor vehicles. A lot of studies have addressed VANET routing for improving communication qualities so far. This study proposes GZTR Protocol fit to VANET environment to tackle the difficulty. The essence of the protocol is to divides urban space into zones, selects one zone with high geographical conditions as next zone, operate relay node selection algorithm for forwarding packets to the next zone. The performance test of this system turned out to be superior to that of existing protocol.

An implementation of P2P system for sharing sensory information

So far, numerous wireless sensor networks have been deployed indepedently and restrictly used for specific services as isolated islands. Recently it is considered to exploit the sensor networks already deployed by others or open its sensor networks for sharing the sensor data. In this paper, we introduce our empirical development of a P2P system for sensor information. We design a gateway node which includes a sink function for sensor nodes and plays a role of a peer node of the proposed P2P system. And we modify an open P2P framework of Pasty for adopting sensor, sensor network and sensor information. This P2P system is referred to as sensor P2P. To test the utility of our sensor P2P system, we deploy this system in KOREN (KOrea advanced Research and Education Network) and develop an application using which a user can search a sensor network with key words, find the position of the sensor network on the digital map and receives sensor data from the sensor network.