• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.850-857
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• 2012

A moving network is the usage model that provides the mobile stations to the communication service via the mobile relay deployed in the high-speed vehicle. The mobile relay periodically performs the signal strength measurement of the neighbor base stations to select the target base station during the handover procedure. The mobile stations experience the service disruption during the measurement of the mobile relay. In this paper, we propose the estimation based scanning method to overcome the service disruption of the mobile stations connected via the mobile relay. In the proposed method, mobile stations subordinated in the mobile relay periodically measure the signal strength of neighbor base stations in order to perform handover. The measured signal strength is used to estimate the signal strength between the mobile relay and the neighbor base station. We performed simulations in order to evaluate the performance of the proposed method in terms of the estimation accuracy and the overhead due to the exchange of channel information. By the simulation result, The estimation error is less than 4dBm when more than 6 mobile stations are used for the estimation. The overhead caused by the proposed method is less than that caused by the direct measurement of the mobile relay when the data rate is more than 8Mbps.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.10
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• pp.775-784
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• 2013

Mobile operators are considering a variety of technical measures to cope with the explosion of data while reducing TCO(Total Cost of Ownership) of their networks. In this paper, to investigate the possibility about one of such technical measures, system level simulation to evaluate the performance of the capacity and mobility was performed in cloud base station structure to apply coordinated multi-point transmission and reception. As a result, we find out that system capacity and mobility performance may be improved according to the scale and application area of cloud base station with the operation of coordinated multi-point transmission and reception, and these mutual causality can provide practical guidelines to mobile network's operation.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.2
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• pp.43-50
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• 2022

As the use of mobile data increases, the proportion of video content is increasing steeply. In order to solve problems that arise when mobile users receive data from geographically remote cloud servers, methods of caching data in advance to edge servers geographically close to the users are attracting lots of attention. In this paper, we present a caching policy that stores data on Small Cell Base Station(SBS) to effectively provide content files to mobile users by applying a delayed offloading scheme in a cellular network. The goal of the proposed policy is to minimize the size of data transmitted from Macro Base Station(MBS) because the delayed offloading scheme requires more cost than when downloaded from MBS than from SBS. The caching policy is proposed to determine the size of content file and which content file to be cached to SBS using the probability of mobile users' paths and the popularity of content files, and to replace content files in consideration of the overlapping coverage of SBS. In addition, through performance evaluation, it has been proven that the proposed policy reduces the size of data downloaded from MBS compared to other algorithms.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.247-256
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• 2002

In a wireless multicasting when a mobile host moves to the new bate station being in the same multicast group it needs to exchange information about data delivery between base stations to receive data from the new base station at once. However it is inefficient to use the existence schemes because it takes too much time to exchange information and many overheads. The next, a mobile host moving to the base station not being in the same multicast group, the old base station will pre-forward data to neighboring base stations to avoid transmission delay. However, if other mobile hosts move at short interval, the old base station may retransmit the same data to the same neighboring base stations. In this paper we proposed called Information Exchange Scheme (IES). In IES in the same multicast grope the base stations exchange information locally so it takes the minimum time and overheads to use IES. Also in IES the neighboring base stations delay to delete data for continuous moving of other MHs. We also present how our scheme is efficient by producing cost ad simulating.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.15-22
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• 2006

In OFDMA system, even if the number of allocated sub-channel in mobile station varies from one to the whole sub-channel as in base station, while because of mobile station's transmit power is lower than that of base station, therefore full loading range(FLR) constraint occurs where whole sub-channel can be used and the conventional open-loop power control scheme can not be used beyond FLR. We propose a new scheme that limits the maximum sub-channel allocation number and uses power concentration gain(PCG) depending on location of mobile station, which is based on ranging in OFDMA system. Simulation results show that the proposed scheme provides solutions for optimum utilization of radio resource depending on the location of mobile station and enables open-loop power control beyond FLR without extra hardware complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.804-811
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• 1997

In the CDMA mobile communication system, reverse power control can be used to minimize the interference level for a good quality of the voice channel, and used to maxmize the system capacity. In this paper, we have analyed the environment of the K-parameter and the access procedure for the mobile station, and proposed a new algorithm for the access probe procedure of the station. K-parameter is determined according to the environment of the base station and access probe can adaptively control the power according to the position changes of the mobile station or the rapid and various state changes of the channel. Simulation results in the limited test environment show that it can increase the system capacity and decrease the power comsumption of the mobile station while maintaining the good and stable quality of the voice channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1223-1230
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• 2000

In this paper, we proposed a handoff decision method based on signal-to-interference ratio(SIR) of the pilot channel in order to perform a handoff more effectively and to complement disadvantages - deterioration quality of a call, decreasing capacity of the system, and wasting power of the mobile station - which is caused when handoff is performed by the classical method that execute a handoff based on received signal strength. Moreover, when we change that the minimum threshold, the cell loading which is defined active traffic channels to total traffic channels ratio, and the fraction of the transmit power from base station allocated to the pilot channel on the forward link of a DS-CDMA system, we analyzed mean numbers of handoff depending on hysteresis level during the mobile station moving from one base station to another base station.

• Journal of KIISE:Information Networking
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• v.27 no.1
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• pp.39-47
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• 2000

This paper is to propose an efficient and reliable control procedure of Base Station Controller of mobile communication system for bulk input messages which was delivered instantaneously. We divided the input messages that are processed by the base station controller of the mobile communication system into two things ; they are messages related to call connection and o&m(operation and maintenance). In addition, we analyzed the properties of the input messages and then performed computer simulation on each input message by using M/M/1/K queueing model in term of the following viewpoints : the loss probability of input messages, the average queue length, the utilization of process controller(server),the average waiting time in queue. And we compared the performance of the two input messages in the overload controlling which was caused by the congested input messages.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.14-20
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• 2012

CoMP(Coordinated Multi-Point transmission and reception) refers to a cooperative transmission strategy to control the interference from adjacent base stations in cellular mobile communication systems, which efficiently enhances the data throughput of the systems. As the number of the base stations participating in cooperative transmission increases, however, a larger amount of information exchange to carry the CSI(Channel State Information) of the mobile terminals is required. In this paper, we propose a partial CoMP transmission method for systems under the constraint of finite feedback information data. This method selects candidates of base stations which can provide high efficiency gain when they participate in the CoMP set. To achieve this, the cooperative base station combination is constructed by considering the preferred base stations of users. The cooperative base station combinations are dynamically applied since the preferred base station combinations of users may be different. We perform computer simulations to compare performance of the non-CoMP, full-CoMP and partial CoMP in terms of the average throughput using finite feedback and demonstrate the performance improvement of the proposed method.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.110-114
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• 2017

Using a small mobile wireless network as a supplement to the disaster safety network can be useful for eliminating small radio shadowing areas, reducing traffic overloads in disaster areas, and quickly building a disaster communication network in difficult access areas. Potable base station is needed to build a small mobile wireless network, and the portable base station using TVWS(TV White Space) is effective in terms of utilization of radio frequency resources and construction cost of wireless networks. In this paper, we design and implement a power amplifier for portable base station operating in TVWS. The implemented power amplifier operates at 470 ~ 698MHz. The gain of the implemented amplifier is more than 20.1dB, the input/output return loss is more than 11.4dB, and the isolation is more than 39.9dB when the output is off. The IMD characteristic of the power amplifier has characteristics of 61.0dBc with 18.8dBm output at 470MHz, 59.3dBc wih 18.6dBm output at 550MHz and 56.5dBc with 19.0dBm output at 690MHz. The power amplifier implemented in this paper can be used as a power amplifier for portable base station.