• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.45-51
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• 2010

The main issue in mobile cloud computing is how to support a seamless service to a mobile mode. Mobile IPv6 (MIPv6) is a mobility supporting protocol which is standardized by the Internet Engineering Task Force (IETF). Mobile IPv6 fast handovers (FMIPv6) is the extension of MIPv6 which is proposed to overcome shortcomings of MIPv6. Recently, fast handovers for Mobile IPv6 over IEEE 802.16e which is one of broadband wireless access systems has been proposed by the IETF. It was designed for supporting cross-layer fast handover. In this paper, we propose an enhanced cross-layering mobile IPv6 fast handover over IEEE 802.16e networks. In our scheme, a new access router generates a new address for the mobile node by using a layer 2 trigger. We utilize a layer 2 message which is sent from a new base station to the new access router in order to inform the new access router of information of the mobile node. A previous access router sends a binding update message to the mobile node's home agent when it acquires the new address of the mobile node. We evaluate the performance of the proposed scheme compared with the existing schemes in terms of the signaling cost and the handover latency. From the results, we observe that the proposed scheme can support fast handover effectively over IEEE 802.16e networks than existing schemes.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06d
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• pp.234-237
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• 2007

IEEE 802.16 광대역 무선 접속망에서 QoS 보장을 위한 스케줄링 기법은 매우 중요하고 활발히 연구되고 있는 분야중 하나이다. 현재 IEEE 802.16 표준에 QoS 보장을 위한 메커니즘들이 정의되어 있지만 실제로 이것에 대한 시스템 구현은 설계자의 몫이다. 또한 기존에 제안 되었던 메커니즘은 각 커넥션들이 요구하는 서비스 품질을 만족시키지 못 하고 있다. 특히 딜레이에 민감한 rtPS 서비스 플로우에 대한 특성화된 스케줄링 매커니즘의 필요성이 대두되고 있다. 따라서 본 논문은 IEEE 802.16 표준에 정의된 4가지 QoS Class들중 실시간 서비스 및 멀티미디어 서비스 클래스인 rtPS 클래스에 대하여 각각의 커넥션이 높은 QoS를 만족할 있도록 ACK 정보를 이용한 스케줄링을 제안한다. 최종적으로 NS-2 시뮬레이터를 이용한 실험결과를 통해 성능 향상 시키는 것을 확인할 수 있었다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.1
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• pp.92-101
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• 2009

In this paper, we propose a dynamic bandwidth provisioning method based on traffic forecasting in IEEE 802.16e packet core network. The traffic is categorized as 4-different classes and the traffic amount of each class is forecasted by the Box-Jenkins method. To increase the service provider's revenue we provision the bandwidth of 4-different classes dynamically using greedy algorithm. The simulation results show that the number of packet drops is reduced and the level of QoS is improved compared with two different the methods - no priority considering and static provisioning.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.134-141
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• 2010

In this paper, we propose a scheduling algorithm to improve the performance of IEEE 802.16 based wireless mesh networks using directional antenna. The performance is presented in terms of throughput of system and delay between each node by varying number of users. The result show that proposed scheduling algorithm improving the performance by reducing the delay of mesh network system. Our work may be useful as a guideline to control the fairness between SSs for multi-hop systems such as multi-hop relay and mesh networks.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.7
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• pp.6-11
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• 2012

A mobile station(MS) in an 802.16e network manages its limited energy using the sleep mode operation. An MS can power down its physical operation components during the unavailability interval of the sleep mode. To reduce energy consumption by increasing the unavailability interval, this paper proposes an enhanced power saving mechanism(ePSM) when both activated Type I and Type II power saving classes(PSCs) exist in an MS. A performance evaluation confirms that ePSM results in the improved performance in terms of the unavailability interval as well as the energy consumption than conventional schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5C
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• pp.326-335
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• 2011

In this paper, we evaluate the performance of multi-antenna techniques adopted for the IEEE 802.16m standard. Base station is equipped with 4 or 8 antennas, and each mobile station (MS) has 2, 4, 8 antennas. The number of MSs is 4, and MIMO modes 0, 1, and 4 are evaluated. For each mimo mode, various number of data streams can be implemented, and the selected number of streams in the paper corresponds to the parameters adopted for hardware implementation. The error performance of various mimo modes presented in this paper was used as reference performance to verify successful hardware implementation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.666-673
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• 2006

In this paper, we evaluated the performance of 4 types of ARQ algorithms that have been adopted to offer reliable transmission between MAC layers. First of all, we implemented IEEE 802.16 ARQ algorithms with NS-2 network simulator and then evaluated the performances in various channel states. We used two performance measures to evaluate those performances. First, we used the total number of ARQ block in bytes that have been received without error. Second, we used ACK_Efficiency that is newly defined in this paper. From the results of simulation, we could be aware that each ARQ algorithm has different performance in a various channel states. For improving the transmission data rate in a specific channel state, we have to choose the right ACK interval as well as a suitable ARQ algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.2
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• pp.191-200
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• 2013

In this paper, we propose a new estimation method of time offset, frequency offset, and signal to interference plus noise ratio (SINR) using the synchronization channel preamble to provide IEEE 802.16.1a based talk-around direct communications (TDC). The proposed scheme estimates the time offset and frequency offset both in the time domain and in the frequency domain considering the preamble structure. In addition, it improves the estimation accuracy by combining the estimated values in two domains taking into account TDC synchronization scenarios. Through numerical simulations in the TDC channel environments, the performance of the proposed algorithm is compared with those of existing techniques such as the time domain estimation and the frequency domain estimation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1140-1144
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• 2012

In this paper, we propose a timing offset estimation scheme for initial ranging of IEEE 802.16e systems. The conventional scheme estimates the timing offset by using the cross-correlation between the local and received signals only. On the other hand, this paper proposes a timing offset estimation scheme with additional cross-correlations accumulated on the conventional cross-correlation. The additional cross-correlations are obtained by using the ranging signal with a repetitive structure. Numerical results show that the proposed scheme provides the better timing offset estimation performance compared with that of the conventional scheme.

• Journal of the Korea Society of Computer and Information
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• v.14 no.12
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• pp.119-126
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• 2009

In this paper propose a method to reduce data for collision resolution. It is to reduce a damage of the back off algorithm to apply in both wire and wireless networks. Double back off size can be work in the first and the last movement point service as a same time in IEEE 802.16. It propose of the algorithm to be suited to IEEE 802.16 for increasing network access percentage in increase a data treat, delay error range and random access over fuller condition. In the result of the computer simulation, the proposal algorism give a increasing speed more than under the this paper. From this computer simulation result, we can get the confirmation of the small loss in saturated and saturated could be a longer in last network.