• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.314-323
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• 2002

The routing protocols designed for wired networks can hardly be used for mobile ad-hoc networks due to limited bandwidth of wireless transmission and unpredictable topological change. Recently, several routing protocols for mobile ad-hoc networks have been Proposed. However, when theme protocols are applied to support real time services like multimedia transmission, they still have problems in ad-hoc networks, where the topology changes drastically. In this paper, we propose a new route selection algorithm which selects the most reliable route that is impervious to route failures by topological changes by mobile hoots. For reliable route selection, the concept of virtual zone (stable zone and caution zone) is proposed. The zone is located in a mobile node'transmission range and determined by mobile node's mobility information received by Global Positioning System (GPS). The proposed algorithm is applied to the route discovery procedure of the existing on-demand routing protocol, AODV, and evaluated by simulation in various traffic conditions and mobility patterns.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.224-232
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• 2002

The routing protocols designed for wired networks can hardly be used for mobile ad-hoc networks due to limited bandwidth of wireless transmission and unpredictable topological change. Recently, several routing protocols for mobile ad-hoc networks have been proposed. However, when these protocols are applied to support real time services like multimedia transmission, they still have problems in ad-hoe networks, where the topology changes drastically. In this paper, we propose a new route selection algorithm which selects the most reliable rouse that is impervious to route failures by topological changes by mobile hosts. For reliable route selection, the concept of virtual zone (stable lone and caution zone) is proposed. The lone is located in a mobile node's transmission range and determined by mobile node's mobility information received by Global Positioning System (GPS). The proposed algorithm is applied to the route discovery procedure of the existing on-demand routing protocol, AODV, and evaluated by simulation in various traffic conditions and mobility patterns.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.4
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• pp.44-51
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• 2000

Wireless ATM is the next-generation technology which can provide broadband services for mobile multimedia terminals. Proposed in this paper is a method of enabling fast handover by forming one cell group with the cell having the mobile terminal (MT) at present and six adjacent cells and storing information on COS which is to perform re-routing between new cell to which MT is moved when handover occurs and adjacent cells to which the MT can be handed over in new cells in advance. And the order of data cells is guaranteed by using the in-band marking cell during handover. Also the handover delay is analyzed and compared to the conventional handover method without COS reservation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2847-2856
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• 2014

It is necessary for maritime multi-band networks, which provide ships with diverse and seamless multimedia services, to perform vertical handover. As IEEE 802.21 WG has standardized vertical handover technologies for terrestrial wireless networks that do not consider VHF, HF, satellite networks, they cannot be directly applied to maritime multi-band networks. In this paper, the vertical handover framework for use in maritime mutlti-band networks is proposed, which includes the logical architecture, the communication reference model, re-defined handover primitives, and the handover process. The proposed vertical handover for maritime multi-band network can be applied in the ocean alone, as well as to the heterogeneous wireless networks which embrace both terrestrial and maritime networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10B
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• pp.1182-1191
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• 2011

In this paper, we propose a network-based IP mobility management scheme, called Access Independent Mobile Service with IPv4/IPv6 Dual Stack (AIMS-DS), which can provide high-quality multimedia services to IPv4/IPv6 dual-stack mobile nodes (MNs) without any interruption over various wireless/wired access networks. The proposed scheme provides an MN with a fast and reliable mobility service among heterogeneous wireless access networks through the network-based control, the complete separation method of control and data plane, the cross-layer (layer2 and layer3) interworking method for handover control acceleration, etc, In addition, the proposed AIMS-DS can provide seamless mobility service to an MN under the environments of IPv4/IPv6 coexisting networks through the home address mobility support and transport network support. Through performance evaluation with computer simulations, we have shown the superiority of the proposed AIMS-DS in terms of handover latency, packet 1085 and packet delivery latency.

• Journal of IKEEE
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• v.17 no.2
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• pp.96-103
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• 2013

Since multimedia data takes large part of realtime transmission in wireless communication environments such as IEEE 802.11, QoS issues became one of the important problems with network performance. 802.11e MAC provides differentiated services based on priority schemes to solve existing 802.11 MAC problems. The TXOP is an important factor with the priority to improve network performance and QoS because it defines the time duration in which multiple frames can be transferred at one time for each station. In this paper, therefore frame sizes, TXOP Limit, and Priority values in accordance with the number of stations are experimented and derived for best network performance and QoS. Using 802.11e standard parameters, simulation results show the best throughput when the number of stations is 5 and TXOP Limit value is 6.016ms. For fairness, the best result is achieved at 3.008ms of TXOP Limit value and 15-31 of CW(Contention Window) that is lower priority than CW 7-15.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.498-508
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• 2009

In wireless mobile environments, large bandwidth and high QoS (Quality of Service) are recently required to support the increased demands for multimedia services. LTE (Long Term Evolution) is one of the promising solutions for the next generation broadband wireless access systems. To efficiently use downlink resource and effectively support QoS, packet scheduling algorithm is one of the important features in LTE system. In this paper, we proposed DAPS (Delay-Aware Packet Scheduling) algorithm to consider QoS requirements of delays for various traffic classes as well as channel condition and fairness. To reflect delay experiences at scheduling instance, DAPS observes how queue waiting time of packet is closed to maximum allowable delay. The simulation results show that the DAPS algorithm yields better performance for delay experience by increasing the number of transmitted packets with satisfying the required delay time compared with existing scheduling algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.909-917
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• 2004

Mobility support is one of the most important functions to provide seamless data transfer for real-time multimedia services in wireless networks. In this paper, we analyze and compare the handoff delay performances for several architectures such as MIP-RO, SIP, MIP-RO/CIP and SIP/CIP, which are expected to be a promising solution 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 approach outperformed other schemes in the viewpoints of the handoff delay.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.1-8
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• 2010

Wireless multimedia service through the access to mobile telephone network or data network is a vital part of contemporary life, and the demand for frequency spectrum for new services is expected to explode as the ubiquitous computing proliferate. Cognitive radio is a technology, which automatically recognizes and searches for temporally and spatially unused frequency spectrum, then actively determines the communication method, bandwidth, etc. according to the environment, thus utilizing the limited spectrum resources efficiently. In this paper, we investigate the effects of imperfect sensing, misdetection and false alarm, on the primary and secondary users' spectrum usage through the analysis of continuous time Markov Chain. We analyzed the effects of the parameters such as sensing error, offered load on the system performance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.3
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• pp.155-160
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• 2011

IPTV functions not only as media player that does play the broadcasting industry's contents, also as the gateway is guaranteed of QoS(Quality of Service). This is for free contents-sharing that device stores contents using home network circumstance, and is for watching with seamless network service. Also this have required next QoS model that can handle stably as it may contain more data of the small computing device in next generation home system. We need ubiquitous-oriented QoS's design and development project that focuses on internal and external media service, not the existing QoS nor one-sided QoS of media sevice industry. This paper focuses on network module development. This supports IPTV in media industry and two-way capability of QoS highlighting multimedia service in network industry. In additional, this can handle stably the multiplex signal of USN/RFID as the representative ubiquitous and home network that services high-speed wire and wireless interface, and support the seamless u-QoS.