• 한국IT서비스학회지
• /
• 제7권2호
• /
• pp.181-195
• /
• 2008

The rapid growth of mobile communication technology has provided the expansion of mobile internet services, particularly mobile realtime transaction takes much weight among mobile fields. There is an increasing demand for various mobile applications to process transactions in a mobile computing fields. Thus, During transmission in wireless networks a base station failure inevitably causes data loss of the base station buffer. It is required to compensate the loss for communication. The existing methods for a base station failure are not adequate because they all suffer from too much overhead and resolve only the link failure. In this paper, we study an efficient recovry systems for a mobile DBMS. We propose SLL (Segment Log List) that enables the mobile host to compensate data loss efficiently in the case of base station failure. In SLL, a base station deliveries an output information of data cells to a mobile host. when a base station fails, the mobile host can retransmit just next data cells. We also prove the efficiency of new method.

• 한국통신학회논문지
• /
• 제35권4A호
• /
• pp.341-349
• /
• 2010

본 논문은 차세대 이동통신 기술로 주목받고 있는 IEEE 802.16 기반의 Mobile WiMAX (또는 WiBro) 시스템에서 여러 가지 채널환경조건 및 기지국의 조건을 고려하여 기지국의 출력파워를 최적으로 설계하는 방법에 관한 것이다. 본 논문에서는 다양한 환경조건에서 Mobile WiMAX 시스템의 상/하향 링크버짓(link budget)을 산출하여, 이로부터 Mobile WiMAX 기지국의 최적 출력파워를 도출하는 방법에 대해 정리하였다. 본 논문에서는 MIMO(multiple input multiple output) 기술이 적용된 기존의 2Tx-2Rx 기지국과 여기에 수신단의 감도를 높이기 위해 수신단의 안테나 개수를 4개로 늘린 2Tx-4Rx 기지국과 성능을 향상시키기 위해 새롭게 빔포밍(beamforming) 기술이 적용된 4Tx-4Rx 기지국의 경우 등 총 세 가지 경우에 대하여 최적 출력파워를 도출하였다.

• 한국측량학회:학술대회논문집
• /
• 한국측량학회 2010년 춘계학술발표회 논문집
• /
• pp.311-313
• /
• 2010

This study is on the adapting vehicle-based mobile mapping system to the frequent unscheduled revision of 1:5000 scale national base map. We analyzed map layers which could be built by vehicle-based mobile mapping systems and studied surveying methods for each layers. Also, the methods of maintain surveying accuracy to satisfy accuracy standards of national base map were suggested. The maps of Yeouido, Hyangnam, and Suwon area were revised by vehicle-based mobile mapping system on a trial bases and possibility of utilizing vehicle-based mobile mapping system for map revision was analyzed. As a results it was revealed that vehicle-based mobile mapping systems were adequate for a irregular revision of national base map.

• ETRI Journal
• /
• 제19권3호
• /
• pp.141-168
• /
• 1997

The base station (BS) in the CDMA Mobile System (CMS) connects calls through the radio interface and is designed to provide mobile subscribers with high quality service in spite of mobile subscribers motions. The BS consists of multiple base station transceiver subsystems (BTSs), a base station controller (BSC) and a base station manager (BSM). This paper is concerned with the BSC and the BSM. The BSC is located between the BTSs and the mobile switching center (MSC) connected with the public network, and to mobile subscribers via the BTSs. The BSM provides operator-interfaces per the BS and takes responsibility of operation and maintenance (OAM) of the BS. Design of the BSC is based on two module types: functional module and unit module. The functional module is used to support new services easily and the unit module to increase the system capacity economically. Both modular types are easily achieved by inserting the corresponding modules to the system. Particularly, in order to efficiently support the soft handover which is one of CDMA superior advantages, the BSC adopts a large high-speed Packet switch connecting up to 512 BTSs, and thus mobile subscribers can be provided with soft handover in high probability. The BSM is based on a commercial workstation to support OAM functions efficiently and guarantee high reliability of the functions. The BSM uses graphical user interface (GUI) for efficient OAM functions of the BS.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제49권2호
• /
• pp.74-80
• /
• 2000

In this paper, we present a control method of mobile power assist systems. Most of mobile power assist systems have a heavy base for preventing easy tumbling, so continual movement of the base during operations causes high energy consumption and gives the high risk of human injury. Furthermore, the slow dynamics of the base limits the frequency bandwidth of the whole system. Thus we propose a cooperation control method of the mobile base and manipulator, which removes the unnecessary movements of the base. In our scheme, the mobile base does not move until the center of gravity(C.G) of the system goes outside a safety region. When C.G. reaches the boundary of the safety region, the base starts moving to recover the manipulator's initial configuration. By varying the parameters of a human impedance controller, the operator is warned by a force feedback that C.G. is on the marginal safety region. Our scheme is implemented by assigning a nonlinear mass-damper-spring impedance to the tip of the manipulator. Our scheme is implemented by a nonlinear mass-spring impedance to the tip of the manipulator. The experimental results show the efficacy of the proposed control method.

• Journal of information and communication convergence engineering
• /
• 제2권4호
• /
• pp.209-213
• /
• 2004

With the commercialization of CDMA 2000-1x late in 2000, a high-speed wireless Internet, based on a mobile communication networks, appeared in Korea. This will develop into the next-generation of mobile communications(4G) in the future and the new cell layout will be required the cellular configuration of 4G. We would need the legislation with respect to base-stations and to building the mobile communication networks, as well as the optimization of mobile communication systems. In this study, in order to provide 4G, I examined and analyzed that the current laws & regulations related to licensing and operating a mobile communication base-stations in KOREA.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2004년도 ICCAS
• /
• pp.834-839
• /
• 2004

In this paper, we investigate the optimal base position and joint configuration of a planar wheeled mobile manipulator in terms of manipulability measure. Taking into account the level of coordination between a manipulator and a platform, both local and global optimization problems are considered. First, based on the kinematic models of a mobile manipulator, the manipulability measures are expressed along with the analysis of the configurational dependency. Second, the geometric symmetry of a mobile manipulator in view of manipulability measure is analyzed, and for some base positions, the best and worst joint configurations are determined, Third, with reverence to the maximum, minimum, and average manipulability measures, the optimal base positions are determined, and the percent improvements due to the base relocation are discussed considering the relative scales among the platform size, the wheel radius, and the link length.

• 한국IT서비스학회지
• /
• 제9권2호
• /
• pp.163-177
• /
• 2010

In this paper, we consider a channel ordering problem that seeks to maximize the service quality in mobile radio communication systems. If a base station receives a connection request from a mobile user, one of the empty channels belonging to the base station is assigned to the mobile user. In case multiple empty channels are available, we can choose one that incurs least interference with other channels assigned to adjacent base stations. However, note that a pair of channels that are not separated enough generates interference only if both channels are assigned to mobile users. That is, interference between channels may vary depending on the channel assignment sequence for each base station and on the distribution of mobile users. To find a channel assignment sequence that seems to generate minimum interference, we develop an optimization model considering various scenarios of mobile user distribution. Simulation results show that channel assignment sequence determined by the scenario based optimization model significantly reduces the interference provided that scenarios and interference cost are properly generated.

• ETRI Journal
• /
• 제26권5호
• /
• pp.493-496
• /
• 2004

An effective paging strategy is essential for improving the utility of radio channels. This paper proposes a two-step paging strategy which involves using base station paging agents to page a single cell at each paging. An analytical model is used to evaluate the performance of the proposed strategy. The proposed strategy is compared with the traditional simultaneous paging strategy and a recent proposal using the base station paging agents. The numerical results showed that the proposed strategy proficiently reduces paging cost on radio channels compared with other paging strategies.

• ETRI Journal
• /
• 제25권1호
• /
• pp.55-58
• /
• 2003

We propose a new paging strategy to reduce paging cost by adding paging agents at base stations. When a mobile-terminated call occurs, the base stations look up the paging agents to determine if terminal paging is actually to be made. An analytical model based on a Markov chain is used to evaluate the performance of the proposed strategy. The numerical results show that the proposed strategy significantly reduces the paging cost compared with the simultaneous paging strategy.