• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.68-73
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• 2013

In recent years, the developments in 3D technologies have initiated the commercialization of 3D services on mobile devices. For this purpose, stereoscopic 3D technology is used, which enables 3D TV on mobile devices including smartphone with glasses-free 3D viewing. As a result, the issues related with stereo imaging have been spotlighted greatly. Especially, three MPEG coding standards are provided for mobile 3D services, namely H.264/AVC with and without SEI message and H.264/MVC. In this respect, this paper presents an overview of developments in stereoscopic technologies for mobile devices to gain some perspective on the changes and progress. in this paper, we verified the availability of android based stereoscipic 3D technology related with mobile 3D TV and Smartphone with special emphasis on 3D video format and 3D features by various technollogy characteristics analysis.

• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.22-28
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• 2013

In this paper, new LBS (location based service) are proposed using conventional DMB (digital multimedia/mobile broadcasting) system. LBS applications are proposed that can be suitable for the subway and ground transportation based on S-DMB (satellite-DMB) and T-DMB (terrestrial-DMB) respectively. In the shaded area such as subway, the broadcasting signal transmitted from the satellite of S-DMB system should be retransmitted by the earth repeater called the gap filler and each gap filler has its own identification value called the gap filler ID which introduces the area in which the gap filler was installed. Therefore, the LBS can be implemented by using the gap filler ID of S-DMB on the subway in which the GPS (global positioning system) can't be received. Unlike the LBS on the subway, the combination of T-DMB and DGPS (differential GPS) will be introduced as a way for ground transportation. Generally, DGPS has been designed to compensate the position value calculated from the GPS signal so that positioning error of about 1 meter can be obtained by using DGPS information. T-DMB system transmitting DGPS signal will be expected to be commercial in Korea and, if using DGPS information transmitted through T-DMB network, LBS with more precise positioning than GPS alone can be implemented in the ground vehicles.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.129-133
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• 2008

In this paper, modified power control algorithms are proposed for a satellite mobile communications system with ATC (ancillary terrestrial component). In order to increase system capacity and reduce the transmitting power of the user's equipment, we propose the modified power control scheme consisting of the modified closed-loop and open-loop power control. The modified CLPC (closed-loop power control) algorithm, combining the delay compensation algorithms and pilot diversity, is mainly applied to the ATC link in urban areas because it is more suitable to the short RTD (round-trip delay). In the case of rural areas where ATCs are not deployed or a signal is not received from ATCs, combining monitoring transmitting power equipment and OLPC (open-loop power control) algorithms using an efficient pilot diversity is mainly applied to the link between the user's equipment and the satellite. Two power control algorithms are applied equally to the boundary areas where two kinds of signals are received in order to ensure coverage continuity. The simulation results show that the modified power control scheme has good performance compared to conventional power control schemes in a GEO (geostationary earth orbit) satellite system with ATC.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.64-72
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• 2013

Blind equalization is a technique that equalizes the received signals without the training sequence. Because of the absence of training sequence, we can increase the bandwidth efficiency due to the blind equalization system. And we must use the blind equalization for removing the ISI in mobile satellite communication receiver. ISI occurs due to mobility of users in mobile satellite communications. Blind equalization is suitable for the mobile satellite communication channels. In this blind equalization, it's very important to improve BER performance to apply the mobile satellite communication system. In this paper, we propose the blind beamforming equalization system using the beamforming, MUSIC algorithm and coordinate change method. We were confirmed by the simulation that the proposed system improves the BER performance.

• Journal of Satellite, Information and Communications
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• v.8 no.1
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• pp.31-34
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• 2013

This paper deals with the interfering audio noise caused by LTE(Long Term Evolution) UE(User Equipment) which is 4th generation mobile communications on audio devices. At first, we realized that the interfering signal of the LTE UE is determined by the transmit power of the LTE UE through analysis and measurement. Then, we performed to measure audio noise level according to the variation of transmitting power level and separation distance between the LTE UE and an audio device. As a result, it is required that minimum separation distance should be 25 cm and above in order to protect audio device from the interference noise of the LTE UE with the maximum transmit power level of 22 dBm.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.127-130
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• 2015

ITU-R has conducted a studies for the frequency allocation to the maritime mobile satellite service (MMSS) in the 7375 - 7750 / 8025 - 8400 MHz under WRC-15 agenda item 1.9.2. In order to allocate a certain frequency bands to the new service, compatibility between new service and the existing services is ensured taking into account protecting the existing services form interference of new service. In this paper, we present current studies results of the frequency sharing studies between new allocation to MMSS and the existing services in the ITU-R. In addition, some proposals for allocating the 7/8 GHz frequency bands to MMSS are also considered for efficient spectral utilization with respect to preparing WRC-15.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.7
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• pp.1224-1233
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• 1994

The error performance of BPSK and QPSK signals in mobile satellite channel is investigated considering nonlinearity of TWTA (Traveling Wave Tube Amplifier) in the presence of AWGN(Additive White Gaussian Noise) on the uplink and downlink paths. It is assumed that the fading on the downlink path forms a Rician distribution. The Rician distribution is approximated by discrete probability values. The values are firstly found by Classical Moment Technique. Finally, the error probability is evaluated using approximate discrete values of Rician distribution and the Gaussian Quadrature Formula.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2261-2270
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• 2015

GIS(Geographic Information System) based Positioning technique uses geographic information to predict which satellites are visible or invisible. GPS positioning has poor positioning accuracy in dense urban area where tall buildings block the satellite signals. In this paper, we proposed GIS based Advanced Positioning technique of Mobile GPS to resolve this problem. Particularly, this technique improves positioning accuracy in dense urban area. It is consist of ephemeris and GIS server. We will inversely estimate pseudorange by using NMEA-0183 output data of mobile GPS. After that, we can find more accurate position by using ephemeris and GIS information.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.42-46
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• 2012

This paper analyses technical and economical conditions which activate the use of mobile communication spectrum not to limit the growth of mobile broadband service because of mobile big data traffic and proposes the method which activate the use of mobile communication spectrum. To activate new mobile communication spectrum the expenditure and income of investment should be balanced. The activation of new mobile communication spectrum to process mobile big data traffic depends on technical and economical conditions, internal and external factors of service provider. The investment expenditure is relate to CAPEX, OPEX which is internal factors of service provider and to spectrum price which is external factor of service. The investment income is relate to tariff system which is internal factors of service provider and to spectrum neutrality which is external factor of service provider. The activation of new mobile communication spectrum can be implemented when the investment expenditure and investment income meet the balance including the spectrum price in the investment expenditure and the tariff system which is able to extend network and the income based on traffic increase by external contents in the investment income.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.111-116
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• 2014

Thanks to diffusions of mobile devices and advances of network technologies, demands for mobile app have been increased dramatically. It has resulted in mobile app industries as well as mobile app authoring tools are facing a crisis over subordinate to specific OS and platform such as iOS, Android and Apple App Store. Because these particular OS and platforms are obstacles to overcome for supporting interoperability and compatibility. In this study, we have conducted expert interviews and surveys to analyze status of mobile app markets and needs for mobile app user and developer. As a result, mobile app based on HTML5 leads to interconnect various mobile devises without additional efforts. Thereby, mobile app user and developer take a positive view of HTML5. However, mobile app developers tend to have the technical path dependence, they especially in venture and small enterprises need to government support for professional manpower training.