• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7B
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• pp.710-720
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• 2009

The Future Generation Networks(FGNs) are proposed to integrate various heterogeneous access technologies, and further expected to support both vertical and seamless handovers. In this motivation, the IEEE 802.21 specifies Media Independent Handover(Mlli) services to enhance the mobile user experience by optimizing handovers between heterogeneous access networks. Additionally, Fast handover for MIPv6(FM1Pv6) is introduced to provide transparent host mobility and to improve handover performance by reducing handover delay as well. This paper focuses on the coordination of FMIPv6 and MIH, and introduces an enhanced mobility management framework suited for FGN. This novel framework replaces handover signaling messages used in wireless networks with novel MIH messages and local primitives. Moreover, Serving Access Router(SAR) performs most of handover processes instead of Mobile Node(MN). Therefore, the proposed mobility management framework reduces handover latency, packet loss, and signaling overhead significantly. We further evaluate the performance of the proposed framework by using both numerical analysis and network simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6B
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• pp.430-439
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• 2008

In this paper, we propose a sender-based TCP congestion control scheme for downward vertical handover (DVHO), in which mobile node moves from a cellular network to a wireless LAN. DVHO can give rise to severe performance problems in TCP throughput because it causes a drastic change of link characteristics. Particularly, TCP executes falsely congestion control by packet reordering, which is occurred from link delay difference between a cellular link and a wireless LAN link. Therefore, the congestion window is reduced. And unnecessary retransmissions wastes bandwidth. To solve these problems, we propose a method using estimated round-trip time in cellular link to process duplicated ACKs from reordering. Furthermore, the duplicated ACKs are used to the control congestion window size. Simulation result shows that the proposed scheme can solve problems. Moreover, the proposed scheme can have better performance than TCP New Reno and nodupack.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.239-246
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• 2014

In the context of wireless sensor networks, one of major issues is energy conservation. For low power communication, by utilizing our experimental results for the relation between clock drift and synchronization interval, we designed a new protocol which can support a wide range of duty cycles for applications with very low traffic rate and insensitive delay. The transmission (TX) node in the protocol synchronizes with the reception (RX) node very before transmitting a packet, and it can adaptively estimate the synchronization error size according to the synchronization interval from minutes to hours. We conducted simulations and a testbed implementation to show the efficacy of the proposed protocol. We found that our protocol substantially outperforms other state-of-the-art protocols, resulting in order-of-magnitude increase in network lifetime over a variety of duty cycles.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.26-33
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• 2012

Please WBAN(Wireless Body Area Networks) is wireless communication of within 3 m radius from inside and outside of the body. WBAN is many uses IEEE 802.15.4 MAC protocol for WBAN MAC protocol requirements. IEEE 802.15.4 MAC protocol applies GTS(Guaranteed Time Slot) allocation scheme for guarantee packet delivery of application which requests QoS(Quality of Service). However, GTS allocation scheme of IEEE 802.15.4 MAC protocol uses FIFS(First In First Service) queueing. So it reduces data transmission reliability and has many problems. Therefore, IEEE 802.15.4 applies not WBAN MAC protocol for emergency data transmission. In this paper, we proposes a priority based MAC protocol for emergency data transmission in wireless body area networks. the proposal MAC protocol sets priority the data. So GTS reqeuest throughput of emergency data increasing and GTS allocation delay of emergency data decreasing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6B
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• pp.387-395
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• 2005

In this paper, we propose an end-to-end mobility management and TCP flow control scheme which considers different link characteristics for vertical handover environments. The end-to-end mobility management is performed by using SIP protocol. When a mobile node moves to a new network, it informs its movement of the correspondent node by sending SIP INFO message containing a new IP address which will be used in the new network. And then the corresponding node encapsulates all packets with the new IP address and sends them to the mobile node. in general, RTT of WLAN is shorter than RTT of cdma2000. when the MN moves from WLAN network to cdma2000 network, TCP retransmission timeout will be occurred in spite of non congestion situations. Thus, TCP congestion window size will be decreased and TCP throughput will be also decreased. To prevent this phenomenon, we propose a method using probe packets after handover to estimate a link delay of the new network. We also propose a method using bandwidth ratio of each network to update RTT. It is shown through NS-2 simulations that the proposed schemes can have better performance than the previous works.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10B
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• pp.947-956
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• 2003

The current IP Routing Protocolspacket networks also need to provide the network QoS based of DiffServ, RSVP, MPLStraffic model which is standardized as IETF reference model for NGN. The first topic of this paper is to propose Traffic-Balanced Routing Protocol(TBRP) to process existing best effort traffic. TBRP will process low priority interactive data and background data which is not sensitive to dealy. Secondly Hierarchical Traffic-Traffic-Scheduling Routing Protocol(HTSRP) is also proposed. HTSRP is the hierarchical routing algorithm for backbone and access networkin case of fixed-wireless convergence network. Finally, HTSRP_Q is proposed to meet the QoS requirement when user want interactive or streaming packet service. This protocol will maximize the usage of resources of access layer based on the QoS parameters and process delay-sensitive traffic. Service classes are categorized into 5 types by the user request, such as conversational, streaming, high priority interactive, low priority interactive, and background class. It could be processed efficiently by the routing protocolstraffic model proposed in this paper. The proposed routing protocolstraffic model provides the increase of efficiency and stability of the next generation network thanks to the routing according to the characteristic of the specialized service categories.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.463-468
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• 2009

In VANET(Vheicle Ad hoc Network), the researches based on the wireless LAN are conducting and the method based on 802.11a is being adapted in IEEE 802.11p WAVE(Wireless Access in Vehicular Environments). However, wireless LAN which uses a single channel in a competition can cause transmission delays because of a frequent collision and a use of CSMA/CA to avoid competition in VANET requiring a fast access. In this paper, we designed CMMP (Clustering based Multi-channel MAC protocol) adequate to VANET and then confirmed the appropriate channel conditions in a V2V communication on the basis of this protocol. The simulation results showed that a packet collision and a transmission delay by the use of an existing single channel based on the contention decreased more than 60% by CMMP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2B
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• pp.83-89
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• 2007

In this paper, we have proposed the power detection (PD)-based TDM-PON architecture, which is implemented with a hardware-based decentralized DBA (Dynamic Bandwidth Allocation) algorithm among ONUs, without OLT's intervention. Of particular importance in the proposed approach is that the hardware-based power detection scheme is used to manage the distributed MAC algorithm without any complex, time-consuming and costly software-processing elements for DBA in ONUs and OLT. We evaluate the performance of average packet end-to-end delay in a statistical analysis and numerical analysis. In addition, through simulations with various traffic models, we verified the superior performance of the proposed approach by comparing with the results of other E-PONs.

• Journal of Communications and Networks
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• v.15 no.1
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• pp.61-70
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• 2013

The increasing number of mobile users and the popularity of real-time applications make wired-wireless integrated network extremely attractive. In this case, quality of service (QoS) adaptability is particularly important since some important features of the integrated network call for QoS adaptability, such as mobility, bursty applications and so on. Traditional QoS schemes include integrated service (IntServ) and differentiated service (DiffSev) as well as their variants. However, they are not able to balance well between scalability and QoS granularity. For example, IntServ faces the scalability problem, while DiffServ can only provide coarse granular QoS. In addition, they are also unable to efficiently support QoS adaptability. Therefore, a per-packet differentiated queueing service (DQS) was proposed. DQS was originally proposed to balance between scalability and QoS granularity in wired networks and then extended to wireless networks. This paper mainly discusses how to use DQS to support QoS adaptability in wired-wireless integrated networks. To this end, we propose a scheme to determine dynamic delay bounds, which is the key step to implement DQS to support QoS adaptability. Simulation studies along with some discussions are further conducted to investigate the QoS adaptability of the proposed scheme, especially in terms of its support of QoS adaptability to mobility and to bursty real-time applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.807-810
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• 2005

Constructed network test environment of wireless base for confidentiality guarantee of data and safe transmission that is transmited at Mobile node of Wireless Network environment in this paper. And, progressed research about IKEv2's Multiple-Key Exchange mechanism for efficient security transmission that use IPSec that is built-in to basis to IPv6 of Mobile environment. Have several key to single terminal to solve that is seam at hand off packet transmission process of Mobile Node in Wireless Network and Re-setting for Key and Re-exchange problem that happen frequently and studied technology that move. Key exchange protocol that is used for an experiment loads basically in MIPv6 and used IKEv2 protocol that is used for management and distribution of reliable encryption key between both end. Using network simulator of SSFNet(Scalable Simulation Framework Network Models) in this paper Key exchange delay value of IKEv2's security transmission analyzing comparison Performance measure and studied about problem and improvement way accordingly.