• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.1023-1032
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• 2004

It is generally known that handoff delay degrades the QoS by packet drop, packet delay and jitter. Moreover. handoff highly effects on QoS in beyond 3G system because not only micro cells for achieving high capacity and fast moving nodes induce the frequent handoff but also hard handoff must be carried out in OFDM system. Therefore, study on a handoff algorithm for guaranteeing QoS is required. Related works on handoff for beyond 3G system mainly focused on reducing the L3 handoff delay or packet loss. That is, these schemes try to compensate L2 delay rather directly eliminate it. However, remained 1.2 delay degrades QoS, especially delay-sensitive realtime traffic. Therefore, we proposed the seamless handoff algorithmwhich can minimize the L2 handoff delay.

• The KIPS Transactions:PartC
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• v.11C no.5
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• pp.659-670
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• 2004

Handoff is one of the most important features for the user's mobility in a wireless cellular communication system. It is related to resource reservation at nearby cells. Resource reservation to the new connection point should occur prior to handoff to enable the user to receive the data or services at the new location, at the same level of service as at the previous location. For the efficient resource reservation, mobility prediction has been reported as an effective means to decrease the call dropping probability and to shorten the handoff latency in a wireless cellular environment. A recently proposed algorithm, ZMHB, makes use of the history of the user's positions within the current cell to predict the next cell. But, the prediction of the ZMHB algorithm is found to be 80∼85% accurate for regular and random movements. In this paper, we propose a new improved ZMHB mobility prediction algorithm, which is called Detailed-ZMHB that uses detailed-zone-based tracking of mo-bile users to predict user movements. The effectiveness of the proposed algorithm is then demonstrated through a simulation.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.701-708
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• 2005

The mobility prediction algorithm and the channel reservation scheme have been reported as an effective means to provide QoS guarantees and the efficient resource reservation in wireless networks. Among these prediction algorithms, the recently proposed Detailed-ZMHB algorithm makes use of the history of the user's positions within the current cell to predict the next cell, which provides the better prediction accuracy than the others. The handoff prioritizing schemes are proposed to provide improved performance at the expense of an increase in the blocking probability of new calls. In the soft handoff of the CDMA systems, a mobile can communicate via two adjacent cells simultaneously for a while before the actual handoff takes place. In this paper, we propose a new channel reservation scheme making use of the user mobility pattern information in order to reduce the call dropping probability. Our results show that the proposed scheme gives about 67.5-71.1$\%$ lower call dropping probability, compared to the existing scheme.

• Journal of Advanced Navigation Technology
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• v.13 no.2
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• pp.208-213
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• 2009

This paper presents an adaptive call admission control(CAC) algorithm based on a target handoff call dropping probability in mobile wireless environments. This method uses a neural network for predicting and reserving the bandwidth demands for handoff calls and new calls. The amount of bandwidth to be reserved is adaptively adjusted by a target value of handoff call dropping probability(CDP). That is, if the handoff CDP exceeds the a target CDP value, the bandwidth to be reserved should be increased to reduce the handoff dropping probability below a target value. The proposed method is intended to prevent from increasing handoff call dropping probability when bandwidth to be reserved is not enough for handoff calls due to an uncertain prediction. Our simulations compare the handoff CDP in proposed CAC with that of an existing CAC. Results show that the proposed method sustains handoff call dropping probability below our target value.

• 한국ITS학회:학술대회논문집
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• v.2007 no.10
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• pp.1-6
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• 2007

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.746-754
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• 2007

In this paper, we propose a fast handoff algorithm for micromobility management enhancement in HMIPv6 networks, which eliminates the DAD procedure involved in the regular HMIPv6 in order to o decrease handoff latency and increase the resource utilization efficiency. In the proposed scheme, the MAP is designed to guarantee the uniqueness of MN's interface identifier within a MAP domain as long as the MN moves in a MAP domain, so that the MN configures the new address without the DAD procedure resulting in the decreased handoff latency significantly When the MN resides in a subnet, MIPv6 is used adaptively as a mobility management protocol, which is to reduce bandwidth waste from the IP packet header overhead of IP-in-IP tunneling from the regular HMIPv6. We evaluate the performance of the proposed handoff micromobility algorithm in terms of handoff delay and packet loss thru computer simulation. Thru various computer simulation results, we verified the superior performance of the proposed scheme by comparing with the results of other schemes, MIPv6 and HMIPv6.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.11
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• pp.2817-2827
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• 1996

In this paper, we propose a new channel assignment scheme considering traffic characteristics in the CDMA cellular system. The object of proposed method is to reduce the hard handoff of data calls which are very sensitive to transmission errors. In this algorithm, we use three channel assignment policies. First, all of the data calls are assigned to the primary CDMA channel if possible. Second, priority for primary CDMA channel is given to data calls by assigning some primary CDMA traffic channels exclusively for data calls. Third, data calls are assigned to the CDMA channel most served by neighbor cells, when all of the primary CDMA traffic channels are used. A performance analysis shows the minimum soft handoff probability of data calls in handoff which is guarantied any cellconfiguration is increased above 40% by the adopting proposed algorithm.

• The Journal of the Korea Contents Association
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• v.2 no.3
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• pp.119-126
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• 2002

The QoS(Quality of Service) guarantee mechanism is one of critical issues in the wireless network. Real-time applications like VoIP(Voice over IP) in All-IP networks need smooth handoffs in order to minimize or eliminate packet loss as a Mobile Host(MH) transitions between network links. In this paper, we design a new multicasting algorithm using DB(Dynamic Buffering) mechanism for Mobile-IPv6. A key feature of the new protocol is the concepts of the DB and MRA(Multicast Routing Agent) to reduce delivery path length of the multicast datagram. Particularly, the number of tunneling and average routing length of datagram are reduced relatively, the multicast traffic load is also decreased.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.35-57
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• 2014

Multi-criteria decision making (MCDM) algorithms play an important role in ensuring quality of service in an integrated HetNets (Heterogeneous Networks). The primary objective of this paper is to develop a multi-criteria vertical handoff decision algorithm (VHDA) for best access network selection in an integrated Wireless Local Area Network (WLAN)/Universal Mobile Telecommunications System (UMTS)/Worldwide Interoperability for Microwave Access (WiMAX) system. The proposed design consists of two parts, the first part is the evaluation of an Analytic Hierarchy Process (AHP) to decide the relative weights of handoff decision criteria and the second part computes the final score of the weights to rank network alternatives using Simple Additive Weighting (SAW). SAW ranks the network alternatives in a faster and simpler manner than AHP. The AHP-SAW mathematical model has been designed, evaluated and simulated for streaming video type of traffic. For other traffic type, such as conversational, background and interactive, only simulation results have been discussed and presented in brief. Simulation results reveal that the hierarchical modelling and computing provides optimum solution for access network selection in an integrated environment as obtained results prove to be an acceptable solution to what could be expected in real life scenarios.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.10
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• pp.33-51
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• 1997

On ATM-based wired/wireless integrated network, we apply the connection re-routing method[1] which reduced the inter-cluster handoff delay by reserving VPI/VCLs for possible inter-cluster handoff calls in advance. Additionally, we propose wired resource reservation methods, which are ausiliary method and split method, for handoff QoS guarantee of various expected services. The characteristics of these methods reserve wired connection resources based on the information on the possible inter-cluster handoff calls. With mathematical analysis, we also propose each algorithm and cost function for deciding an optimal amount in reserving resources. With numberical examples, we can see that the auxiliary method effectively reduces the cost in all cases(.alpha.>.betha., .alpha.=.betha., and .alpha.<.betha.). The split method has a little cost-reduction effects, when handoffs call does not have priority over new calls (that is, .alpha..leq..betha.) and the total capacity is relatively large. In other cases, the split method, however, has effective cost-reduction effects. The numerical resutls show that these reservation methods ca flexibly cope with the time-variant environment and meet the QoS requriements on the inter-cluster handoff calls.