• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.4
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• pp.171-183
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• 2008

Nowadays, wireless packet data services are provided over Wireless MAN (WMAN) at a high data service rate, while 3G cellular networks provide wide-area coverage at a low data service rate. The integration of mobile WiMAX and 3G networks is essential, to serve users requiring both high-speed wireless access as well as wide-area connectivity. In this paper, we propose a cross-layer optimization scheme for a vertical handover between mobile WiMAX and 3G cellular networks. More specifically, L2 (layer 2) and L3 (layer 3) signaling messages for a vertical handover are analyzed and reordered/combined, to optimize the handover procedure. Extensive simulations using ns-2 demonstrate that the proposed scheme enhances the performance of a vertical handover between mobile WiMAX and 3G networks: low handover latency, high TCP throughput, and low UDP packet loss ratio.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.3
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• pp.91-99
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• 2009

Development of high-speed Internet services and the increased supply of mobile devices have become the key factor for the acceleration of ubiquitous technology. WiBro system, formed with lP backbone network, is a MBWA technology which provides high-speed multimedia service in a possibly broader coverage than Wireless LAN can offer. Wireless telecommunication environment needs not only mobility support in Layer 2 but also mobility management protocol in Layer 3 and has to minimize handover latency to provide seamless mobile services. In this paper, we propose a fast cross-layer handover scheme based on signal strength prediction in WiBro environment. The signal strength is measured at regular intervals and future value of the strength is predicted by Exponential Smoothing Method. With the help of the prediction, layer-3 handover activities are able to occur prior to layer-2 handover, and therefore, total handover latency is reduced. Simulation results demonstrate that the proposed scheme predicts that future signal level accurately and reduces the total handover latency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.666-671
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• 2007

EPON is proposed to be used in an infrastructure of the next generation wireless network. EPON can reduce fiber deployment cost and easily decrease the occurrence of layer-3 handover by introducing group cell concept. An EPON-based layer-2 handover algorithm is suggested for fast handover. The time-delay of the control signals are examined using simulation.

• Journal of information and communication convergence engineering
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• v.8 no.2
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• pp.168-172
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• 2010

The Network-based handover still has problems such as the transmission delays and the packet losses in the case of macro mobility, though technological advances have been made in the wireless and mobile communication. For end-to-end handover, the link bandwidth has been reduced in the wireless network due to its burst errors and congestion control. To overcome such problems, we propose a new scheme of the macro handover according to the protocol layer. The proposed macro handover is implemented on the network layer to partially substitute wired signaling for wireless signaling, to flexibly employ buffers, and on the transport layer to postpone its retransmission time. We have performed extensive simulation using ns-2 and the result shows that our proposed scheme outperforms the other existing schemes in terms of transmission delay, packet loss, and data transfer rate during the handovers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2A
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• pp.113-123
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• 2009

Wireless mesh networks have been studied as the next generation technology to solve problems of conventional wireless networks. Particularly, mobile WiMAX based wireless mesh networks are noticed due to many advantages. In this paper, we propose a layer-2 handover scheme for mobile WiMAX based wireless mesh networks. A layer-2 handover scheme based on mobile WiMAX causes many handover failures over mobile WiMAX based wireless mesh networks because it does not consider the characteristics of wireless mesh networks. The proposed scheme does not bring about packet losses achieving lower handover latency than a conventional handover scheme. Simulation results show that the proposed scheme achieves loss-free and low handover latency during the layer-2 handover.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.4015-4033
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• 2015

The future mobile networks consist of hyper-dense heterogeneous and small cell networks of same or different radio access technologies (RAT). Integrating mobile networks of different RATs to provide seamless and smooth mobility service will be the target of future mobile converged network. Generally, handover from high-speed networks to low-speed networks faces many challenges from application perspective, such as abrupt bandwidth variation, packet loss, round trip time variation, connection disruption, and transmission blackout. Existing inter-RAT handover solutions cannot solve all the problems at the same time. Based on the high-layer convergence sublayer design, a new receiver-aided soft inter-RAT handover is proposed. This soft handover scheme takes advantage of multihoming ability of multi-mode mobile station (MS) to smooth handover procedure. In addition, handover procedure is seamless and applicable to frequent handover scenarios. The simulation results conducted in UMTS-WiMAX converged network scenario show that: in case of TCP traffics for handover from WiMAX to UMTS, not only handover latency and packet loss are eliminated completely, but also abrupt bandwidth/wireless RTT variation is smoothed. These delightful features make this soft handover scheme be a reasonable candidate of mobility management for future mobile converged networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8B
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• pp.1129-1140
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• 2010

Wireless mesh networks have been widely studied as the next generation technology to solve the problems of conventional wireless networks. Particularly, Mobile WiMAX based wireless mesh networks are noticed due to many advantages. Mobile WiMAX standard provides two kinds of layer-3 handover schemes: Mobile IP and Proxy Mobile IP based handover schemes. MIP based handover scheme has a problem in that it incurs the long handover latency because mobile nodes generate a lot of handover messages. On the other hand, PMIP based handover scheme decreases the handover latency by reducing the number of handover messages, because mobile nodes do not participate in handover procedure. Therefore, layer-3 handover for Mobile WiMAX should be designed based on PMIP. However, conventional PMIP based handover still has latency overhead, because of many message exchanges between PBU and PBA after completing the layer-2 handover. Hence, in this paper, we propose a fast layer-3 handover scheme that achieves the lower handover latency for Mobile WiMAX based wireless mesh networks. Proposed scheme has advantages in terms of handover latency. Simulation results show that proposed scheme achieves low handover latency during the layer-3 handover.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.2
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• pp.91-99
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• 2009

Mobile WiMAX is an emerging technology that can provide ubiquitous Internet access. To provide seamless service in mobile WiMAX environment, delay or disruption in dealing with mobility must be minimized. However offering seamless services on IEEE 802.16e networks is very hard due to long handover latency both in layer 2 and 3. In this paper, we propose a fast cross-layer handover scheme based on prediction algorithm. With the help of the prediction, layer-3 handover activities are able to occur prior to layer-2 handover, and therefore, total handover latency can be reduced. The experiments conducted with system parameters and propagation model defined by WiMAX Forum demonstrate that the proposed method predicts the future signal level accurately and reduces the total handover latency.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.75-78
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• 2007

Mobile IP provides hand-held devices with mobility which allows the user to do work over the network. However, handover time due transfer between access routers causes network delays and data loss. L2Trigger Handover expects this handover to take place, and executes L3 handover before L2 handover takes place, thereby reducing overall handover latency, although it still is an issue since handover latency between AR is not completely eliminated in L2 trigger handover. In this paper took into consideration where MIH is used in MIPv4 and using MIH Table when handover is about to occur in MN(Mobile Node), thereby pre-fetching data needed by Handover. In this way, when the handover is estimated, it improves the init time that L2trigger had. Furthermore we can find that we can execute the handover with shorten init time in smaller and narrow overlap length

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.8
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• pp.499-509
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• 2014

In this paper, we propose that a FDL(Freeze DeadLine) Algorithm to solve handover problems in heterogeneous wireless networks. Many previous studies concentrated on low level layer to solve handover problems. In this paper, however, we concentrate on high level handover problems such as network layer and transport layer. We analyze handover's problems of transport layer in Heterogeneous wireless network, propose the FLD algorithm for better performance than others studies. The Proposed method is analyzed by theoretical frames and we verify that the propose method using the NS-2(Network Simulation - 2).