• Journal of Information Processing Systems
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• v.7 no.1
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• pp.43-52
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• 2011

Whether it is crosstalk, harmonics, or in-band operation of wireless technologies, interference between a reference system and a host of offenders is virtually unavoidable. In past contributions, a benchmark has been established and considered for coexistence analysis with a number of technologies including FWA, UMTS, and WiMAX. However, the previously presented model does not take into account the mobility factor of the reference node in addition to a number of interdependent requirements regarding the link direction, channel state, data rate and system factors; hence limiting its applicability for the MBWA (IEEE 802.20) standard. Thus, over diverse modes, in this correspondence we analytically derived the greatest aggregate interference level tolerated for high-fidelity transmission tailored specifically for the MBWA standard. Our results, in the form of benchmark indicators, should be of particular interest to peers analyzing and researching RF coexistence scenarios with this new protocol.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.154-163
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• 2008

In a mobile broadband wireless access (MBWA) network, many users access a base station (BS), which relays data transferred from high-speed wired network to low-speed wireless network. For this difference of their data rate, a BS suffers from the lack of its buffer space when many users run multiple applications at the same time, and thus packet losses occur. TCP, which guarantees end-to-end reliability, is used as transport protocol also in wireless networks. But TCP lowers their transmission rate incorrectly and frequently whenever packet losses occur. And they increase their transmission rate differently with each other; finally TCP throughput of each TCP flow varies largely, and then TCP fairness goes worse. In this paper, a scheme that controls packet transmission rate adaptively according to TCP flows' transmission rate, that prevents buffer overflows at BS, and that guarantees TCP fairness at a certain degree is proposed. As it is analyzed by simulations, the proposed scheme enhances TCP fairness by maintaining TCP throughput of each TCP sender similarly with each other.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3A
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• pp.261-270
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• 2007

The Delay Threshold-based Priority Queueing (DTPQ) scheme has been shown useful for scheduling both real-time (RT) and non-real-time (NRT) service traffic in mobile broadband wireless access (MBWA) systems. The overall system capacity can be maximized subject to their QoS requirement by the DTPQ scheme, which takes the urgency of the RT service into account only when their head-of-line (HOL) packet delays exceed a given delay threshold. In practice, the optimum delay threshold must be configured under the varying service scenarios and a corresponding traffic load, e.g., the number of RT and NRTusers in the system. In this paper, we propose an adaptive version of DTPQ scheme, which updates the delay threshold by taking the urgency and channel conditions of RT service users into account. By evaluating the proposed approach in an orthogonal frequency division multiple access/time division duplex (OFDM/TDD)-based broadband mobile access system, it has been found that our adaptive scheme significantly improves the system capacity as compared to the existing DTPQ scheme with a fixed delay threshold.

• 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.31 no.11A
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• pp.1101-1112
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• 2006

With the recent growth in demand for high-data rate multimedia services in the wireless environments, the Mobile Broadband Wireless Access (MBWA) technologies, such as WiBro (Wireless Broadband internet) system, are gradually coming into the spotlight. Unlike the conventional mobile communication networks based on cellular system, the WiBro system basically consists of IP based backbone networks that will be ultimately deployed by Ipv6 (IP version six) based backbone networks according to the All-IP trend for the network evolution. In such wireless mobile environments, it is needed to support the mobility management protocol on network layer as well as physical layer and Medium Access Control (MAC) layer in WiBro system. Accordingly, in this paper, we propose a fast handover scheme for improving the handover performance in IPv6 based WiBro system and show that the proposed scheme achieves loss-free and low handover latency during inter-subnet movement of the mobile stations through the simulation.

• The Magazine of the IEIE
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• v.30 no.8
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• pp.64-64
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• 2003

국내외적으로, 2.3GHz 대역의 휴대 인터넷 서비스와 이동 고속 무선 패킷 데이터 MBWA(Mobile Broadband Wireless Access) 서비스를 위한 기술 개발 및 표준화 작업이 진행중이며, 이들 기술 표준에서는 데이터 속도의 고속화를 달성하기 위하여 AMC(Adaptive Modulation and Coding)를 요구하고 있다. AMC방식 무선 패킷 시스템은 서비스 지역 내에서 SNR(Signal to Noise Ratio)의 값에 연동하여 가변적인 데이터 서비스 속도를 제공하게 되고, 사용자가 서비스 지역을 이동하면서 제공받는 서비스 품질은 물리 채널의 서비스 속도 변화에 대응하여 변화되므로, 서비스 사업자는 서비스 사용자의 속도 품질을 일정하게 유지하고 관리 제어할 수 있도록 하는 서비스 품질 설계 기준이 필요하다. 따라서, 본 기고문에서는 이들 AMC 방식의 고속 무선 패킷 서비스 시스템 기술의 표준화에 병행하여 공중망 무선 패킷 서비스 시스템의 망 구축 설계시 고려되어야 할 가입자 수용용량과 서비스 품질 등을 산정하고 관리하기 위한 파라미터로서 기지국의 평균 데이터 공급 용량 MDT(Mean Data Throughput), 평균속도 공유 패킷 링크 MSPL (Mean Shared Packet Link) 그리고 서비스 Uniformity 지수 UI(Uniformity Index) 등을 제안하고자 한다.

• The Magazine of the IEIE
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• v.30 no.8
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• pp.844-852
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• 2003

국내외적으로, 2.3GHz 대역의 휴대 인터넷 서비스와 이동 고속 무선 패킷 데이터 MBWA(Mobile Broadband Wireless Access) 서비스를 위한 기술 개발 및 표준화 작업이 진행중이며, 이들 기술 표준에서는 데이터 속도의 고속화를 달성하기 위하여 AMC(Adaptive Modulation and Coding)를 요구하고 있다. AMC방식 무선 패킷 시스템은 서비스 지역 내에서 SNR(Signal to Noise Ratio)의 값에 연동하여 가변적인 데이터 서비스 속도를 제공하게 되고, 사용자가 서비스 지역을 이동하면서 제공받는 서비스 품질은 물리 채널의 서비스 속도 변화에 대응하여 변화되므로, 서비스 사업자는 서비스 사용자의 속도 품질을 일정하게 유지하고 관리 제어할 수 있도록 하는 서비스 품질 설계 기준이 필요하다. 따라서, 본 기고문에서는 이들 AMC 방식의 고속 무선 패킷 서비스 시스템 기술의 표준화에 병행하여 공중망 무선 패킷 서비스 시스템의 망 구축 설계시 고려되어야 할 가입자 수용용량과 서비스 품질 등을 산정하고 관리하기 위한 파라미터로서 기지국의 평균 데이터 공급 용량 MDT(Mean Data Throughput), 평균속도 공유 패킷 링크 MSPL (Mean Shared Packet Link) 그리고 서비스 Uniformity 지수 UI(Uniformity Index) 등을 제안하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.6 s.336
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• pp.33-40
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• 2005

In this paper, we analyzed the DRMA(Dynamic Reservation Multiple Access) protocol with Rayleigh fading, shadowing, and capture effect for the Broadband fireless Access System. We consider the TDMA-based protocols, since these are based on the standard for IEEE 802.16 WMAN, IEEE 802.20 MBWA, and ETSI HIPERLAN//2. The results of analytical model will be apply the development of collision resolution algorithm, scheduling algorithm and the dynamic change of system parameters.