• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.10
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• pp.39-46
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• 1999

In this paper, we propose new hardware architecture of a fast searcher for an initial code acquisition in wideband CDMA wireless local loop systems. The proposed searcher uses double-dwell serial search algorithm and has N active correlators for the high performance code acquisition. Since the N active correlators are designed with pipelined architecture, it is possible to reduce the hardware complexity with only one energy calculation. Our architecture is designed using VHDL to meet wideband CDMA wireless local loop standard and verified under JTC wideband channels. Average code acquisition time of the proposed fast searcher which has 16 correlators is about 40 seconds in case of initial installation and 0.16 seconds when a base station is known. The verified fast searcher is synthesized with in $0.6\mu\textrm{m}$ LG library. The synthesized searcher has 15.8K rates when the number of 4he correlators is 16.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.209-216
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• 2005

This paper generally relates to the field of wireless local area networks(WLANs), and more particularly, to AP selection and association methods for the performance of a station. In these days, IEEE 802.11 Wireless LAN network is widely deployed and used as an emerging service to connect high-speed Internet in the public wireless environment. But, if there are many users in hot spot area, they suffer a severe decrease of performance. Thus it needs an association and access control mechanism especially when it is used in the public environment. In this paper, we suggest a selection and association method using Beacon or Probe Response frames based IEEE 802.11. Station selects AP using the information of the capacity area in a Beacon or a Probe Response frame. According to the present paper, an association method for a public WLAN service, which includes a WLAN user terminal and an AP for relaying WLAN communications to and from the user terminal, includes the steps of the user terminal asking the AP's states for access to a radio channel; and the station selects and associates with the AP According to the above-described selection in a high speed wireless Internet service based on public WLAN technologies that are currently in operations. Further, it is possible to improve the efficiency of network management.

• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.149-155
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• 2003

This paper generally relates to the field of wireless local area networks(WLANs), and more particularly, to AP selection and association methods for the performance of a station. In these days, IEEE 802.11 Wireless LAN network is widely deployed and used as an emerging service to connect high-speed Internet in the public wireless environment. But, if there are many users in hot spot area, they suffer a severe decrease of performance. Thus it needs an association and access control mechanism especially when it is used in the public environment. In this paper, we suggest a selection and association method using Beacon or Probe Response frames based IEEE 802.11. Station selects AP using the information of the capacity area in a Beacon or a Probe Response frame. According to the present paper, an association method for a public WLAN service, which includes a WLAN user terminal and an AP for relaying WLAN communications to and from the user terminal, includes the steps of the user terminal asking the AP's states for access to a radio channel; and the station selects and associates with the AP. According to the above-described selection in a high speed wireless Internet service based on public WLAN technologies that are currently in operations. Further, it is possible to improve the efficiency of network management.

• The KIPS Transactions:PartC
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• v.17C no.6
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• pp.471-484
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• 2010

In the wireless communication systems, the power consumption of a mobile device is very important issue due to its battery limitations. Hence most of the standards for wireless networks including a mobile WiMAX system are supporting their own power saving mode in way that a mobile device is able to reduce its energy usage while in the mode. However, those standards just define the arrangement of special time intervals, called a paging listening interval, during which the device needs to receive the paging-related control messages, and they do not specify how to effectively reduce the power in many different network environments. This means the amount of power spent by the device is very dependent on the implementations of individual device-vendors, and undesirable paging loss may happen according to the channel conditions. To reduce unnecessary power usage and the risk of paging loss, this paper proposes the effective frequency/BS selection algorithm applicable to a mobile device operating in the power saving mode, which serves the device with better BS based on the tracking for channel variation. This algorithm consists of the channel estimation phase during each paging listening interval, the tracking phase for the measured results, the frequency reselection phase based on the tracking activity, and the preferred BS reselection phase. Thus the proposed method can improve the paging performance while the device is moving in the network. Also the simulation result shows that the presented scheme is superior to other candidates in energy efficiency due to the channel-adaptive frequency/BS selection.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.102-105
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• 2011

2008년 처음 IPTV 서비스가 시작된 이후 IPTV 콘텐츠 호환성 확보와 단말 이동성 확보를 통한 IPTV 서비스 활성화 및 전체적인 비용 절감을 위해 많은 표준화 이슈들이 있었고 현재까지 표준화가 일부 완료 및 진행중이다. IPTV는 짧은 시간에 급격히 발전하였고 사업이 활성화 되었기 때문에 표준의 적용을 위한 준비 기간이 짧고 표준의 검증이 이루어지지 않은 상태이다. 그래서 표준을 적용한 시스템에 문제가 생길 수 있고 이는 많은 자원 낭비와 콘텐츠 호환성과 단말 이동성이 점점 늦어지는 원인이 되고 있다. 이에 본 논문은 표준을 적용한 플랫폼과 솔루션들이 상용화 되기전에 표준 적용 개발 제품의 표준 적합성을 시험해보고 표준 기술을 검증하여 표준을 정립하기 위하여 국내 IPTV 표준 중 "IPTV 서비스 탐색 및 전송방식 표준[3]"을 적용한 플랫폼과 솔루션을 검증하기 위한 시험 환경을 구축하고 시험규격을 개발하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.176-179
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• 2013

본 연구는 최근 활성화된 스마트폰 내비게이션의 교통정보를 이용 시 상대적으로 품질이 취약한 지방지역의 빠른길 및 통행시간 정확도를 개선하는 방안에 대한 연구이다. 본 연구에서는 Hadoop기술을 이용하여 교통데이터에 대한 방대한 양의 데이터를 분석 처리한다. 특히, 실시간 교통정보가 제대로 수집되지 않는 지역의 도로 속도 정보에 대한 개선 방안으로 고객 단말로부터 올라오는 위치 데이터를 실시간으로 수집하여 전자지도 기본 속성값을 실시간 통계 데이터로 교체 반영하여 상대적으로 취약한 지방지역의 경로 품질 및 경로 탐색을 개선하는 방안을 제시하였다. 단말로부터 올라오는 많은 양의 GPS 위치정보등 대용량 데이터 처리를 위해 오픈소스프로젝트인 Hadoop플랫폼 환경에서 빅데이터 처리용 오픈소스를 활용하여 고가의 RDBMS를 대체하는 효과와 시간 단축의 효과를 기대할 수 있게 되었다.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.11b
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• pp.487-490
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• 2003

본 논문에서는 적은 메모리 공간을 가진 이동 단말 장치와 같은 임베디드 시스템에서 많은 메모리를 필요로 하는 비디오 디지털 신호처리 알고리즘이 동작될 수 있도록 움직임 검출을 효율적으로 구현하는 방법을 제시한다. 즉, 움직임 검출 알고리즘을 구현할 때 현재의 매크로 블록과 다음의 매크로 블록간의 참조 탐색 영역의 중복성이 존재함을 인지하여, 필요 메모리의 데이터 이동을 최소화시켜 내부 메모리를 효율적으로 이용하려 한다. 이렇게 움직임 검출에서 적은 내부 메모리를 이용함으로써 내부 메모리를 다른 용도로 사용할 수 있는 가용성을 증대시키고, 내부 메모리에서 보다 많은 연산을 수행하게 함으로써 빠른 성능으로 복잡한 MPEG-4 비디오 부호화 알고리즘의 구현이 가능하도록 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.126-129
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• 2015

Device-to-device (D2D) communications, a subset of Proximity-based Services that enables direct communication between LTE network subscribers, is gaining popularity. It is well underway to be adopted in cellular communication systems for pedestrian and connected-vehicles alike. In this paper, we briefly present our model of an Evolved Packet Core Network-assisted device discovery simulator and show the applicability of Proximity-based Services for Vehicular Ad-hoc Networks. Through the performance evaluation based on the developed simulation environment, it is shown that in case when users gather in the same vicinity, as in public transportation, LTE network data can be efficiently offloaded and multicasted through Wi-Fi for e.g. delivering traffic-related information and for the benefit of infotainment service consumers.

• The KIPS Transactions:PartC
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• v.19C no.2
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• pp.149-152
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• 2012

In the roaming case, the cost of using the visited network is larger than that of home network. So, if a mobile terminal is connected to the visited network, even though it actually came back to the home network, the user may unduly pay for communication. Such a problem frequently occurs when many networks are overlapped in the same region, as shown in the case of Poland. In this paper, we propose a network search algorithm to support the fast comeback to home network in the roaming environment. In the proposed scheme, which is based on the 3GPP specification, the mobile terminal tries to search the home network by using a database of network information, as fast as possible. For performance evaluation, we construct a virtual testbed with real terminal and network equipment to emulate the service providers in Poland. From the experimental results, we can see that the proposed scheme can reduce the time of comeback to the home network by 3~60 minutes, compared the existing 3GPP scheme.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.941-947
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• 2018

Station transfers for smart card based railway networks refer to transfer pedestrian movements that occur at the origin and destination nodes rather than at a middle station. To calculate the optimum path for the railway network, a penalty for transfer pedestrian movement must be included in addition to the cost of within-car transit time. However, the existing link label-based path searching method is constructed so that the station transfer penalty between two links is detected. As such, station transfer penalties that appear at the origin and destination stations are not adequately reflected, limiting the effectiveness of the model. A ghost node may be introduced to expand the network, to make up for the station transfer penalty, but has a pitfall in that the link label-based path algorithm will not hold up effectively. This research proposes an optimal path search algorithm to reflect station transfer penalties without resorting to enlargement of the existing network. To achieve this, a method for applying a directline transfer penalty by comparing Ticket Gate ID and the line of the link is proposed.