Byoung-Gi Kim

Performance Evaluation for A closed loop power control using An Efficient Channel Estimation in SAT-CDMA

This paper presents an efficient closed-loop power control algorithms for the next generation mobile satellite systems. Although we could not see any active role of a satellite system in the 3G networks, satellite system will provide strong advantages in future systems for certain applications. Because a satellite link has longer round trip delay than a terrestrial link, we need time delay compensation- and efficient channel estimation algorithms that would make the satellite component especially efficient. After presenting the satellite radio interface of the 3G system, we suggest powerful power control which need to be considered in the beyond 3G systems

Advanced Power Control and Handover Algorithms for Mobile Satellite Communications Systems with Ancillary Terrestrial Component

In this paper, modified power control algorithms are proposed for a satellite mobile communications system with ancillary terrestrial component (ATC). In order to increase system capacity and reduce the transmitting power of the users equipment, we propose the modified power control scheme consisting of the modified closed-loop and open-loop power control. The modified closed-loop power control (CLPC) 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 round-trip delay (RTD). 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 open-loop power control (OLPC) algorithms using an efficient pilot diversity is mainly applied to the link between the users 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 geostationary earth orbit (GEO) satellite system with ATC.

Analysis of satellite WCDMA systems applying space-time codes with imperfect channel estimation

In this paper, we investigate a satellite WCDMA system combined with space-time code. Generally, space-time codes have been hardly considered in satellite systems because we assume a prevailed line of sight (LOS) condition. However, in a mobile satellite communication channel, space-time codes could play an important role to provide economic and high quality services. We applied Alamoutis space time transmit diversity (STTD) scheme to the satellite WCDMA system, and extensively demonstrate the simulation results on a mobile satellite channel. The simulation results investigated in this paper reveal that the STTD scheme in mobile satellite system could provide much better performance to the one in terrestrial system in reasonable range of signal to noise ratio.

Feasibility Study of 32 Trellis-Coded OFDM Waveform for Tactical Information Communication

In this paper, the applicability of 32 trellis-coded OFDM waveform is studied for the tactical information communications system in NCW (Network Centric Warfare). In order to reduce received SNR in BER 1.0E-6 conditions, we proposed a 32-TCM. We also applied OFDM technologies such as timing recovery, carrier recovery, and equalizer, in order to reduce robust channel impairments caused by non-LOS environments where a signal is not received from another system. Simulation results show that coding gain of a 32 trellis-coded OFDM waveform has about 7 dB and 2 dB, compared to single-carrier 16-QAM waveform and OFDM (16QAM) waveform in tactical communication environments, respectively.