Tae Chul Hong

Capacity of the WCDMA System Using High Altitude Platform Stations

In this paper, we provide a method to estimate the capacity of the wideband code division multiple access (WCDMA) scheme using High Altitude Platform Stations (HAPS), and demonstrate the results. This is to validate that the HAPS system is one of the most effective solutions to provide high quality wireless communication services, such as IMT-2000 services. We use a practical system model which describes the HAPS system most appropriately, and this leads to realistic estimation results. We estimate the reverse and forward link capacity of the HAPS WCDMA system and compare it to that of the terrestrial system. The estimation results show that the capacity of the HAPS WCDMA system is about 1.2–1.67 times larger than that of the terrestrial system.

A satellite radio interface for IMT-Advanced system using OFDM

In this paper, we introduce a new satellite radio interface technology to provide efficient IMT-Advanced services. Maximizing the commonalities with the terrestrial system is one of the most important factors for cost-effective service delivery, which will finally bring successful deployment of the system. For this purpose, we adopt an OFDM based radio interface. At the same time, the interface should be tailored in order to compensate a long round trip delay of satellite systems. In this paper, we present a number of satellite specified techniques which was developed for this purpose, including frequency reuse technique, uplink synchronization technique, random access technique, and interleaving technique combined with adaptive modulation and coding.

Analysis of interference and availability between satellite and ground components in an integrated mobile-satellite service system

Summary An integrated mobile-satellite service (MSS) system is one of the most promising infrastructures for the efficient use of satellite frequency, and the satellite coverage can be extended by reusing the satellite frequency in its ground components. However, the co-channel interferences caused by the frequency reusing technique may lead to the performance degradation. This paper presents the interference analysis for an integrated MSS system that is composed of a multi-beam satellite, complementary ground components (CGCs), and mobile earth stations, by using statistical simulations. These statistical results are then used to evaluate the availability of the system. Our simulation results reveal that the satellite frequency reuse in the CGCs of the integrated MSS system can increase efficiency of satellite spectrum utilization with a tradeoff between CGC network capacity and intra-system interferences. Copyright

Forward link capacity of the WCDMA system using high altitude platform stations

High Altitude Platform Station (HAPS) system is considered as one of the most effective solutions to provide high quality wireless communication services, such as IMT-2000 services. In this paper, we provide a method to estimate the reverse link capacity of the wideband code division multiple access (WCDMA) system using HAPS, and demonstrate the results. HAPS would be located at 17 km to 22 km above sea level with a multi-beam antenna system and it leads to considering new channel conditions and system design criteria different from those of the conventional terrestrial system. Therefore, we use a practical system model which represents the HAPS system most appropriately, and it leads to realistic estimation results. We estimate the reverse link capacity of the HAPS WCDMA system considering a multi-cell and multi-HAPS model and compare it to that of the conventional terrestrial system. The estimation results show that the capacity in the border cells is decreased and the capacity of the HAPS WCDMA system is about 1.2 to 1.67 times larger than that of the conventional terrestrial system.

Adaptive buffering scheme for streaming service in intersystem handover between terrestrial and satellite systems

In this paper, we propose an adaptive buffering scheme for streaming service during inter-system handover. In general, the buffering scheme of streaming service is used to compensate for delay jitter of networks. By the way, the terminal, which is served from wireless communication systems, can explore the discontinuation of receiving streaming packets during handover. Especially, in case of inter-system handover, the discontinuation of receiving packets is longer than that of intra-system handover. Therefore, existing buffering schemes cannot fully compensate for the degradation of QoS. The proposed method of this paper is an additional buffering scheme before handover. Using this method, we can prevent the discontinuation of streaming service during handover. This method is validated through simulations.

Inter-System Handover Analysis in Integrated Terrestrial and GEO Satellite Communication Networks for Seamless Mobility

In this paper, we propose the handover decision method for inter-system handover between satellite communication system and terrestrial communication system. The characteristics of signal of satellite communication system are not different from those of terrestrial communication system. Therefore, we analyze the characteristics of satellite signal, and we design the handover decision method to reflect those characteristics. The performance of proposed method is validated through simulations. The proposed method decreases the unnecessary handovers more than that of existing handover method which considers only hysteresis margin.

Call Admission Control Scheme with Bandwidth Borrowing in Integrated Services Network

In this paper, we propose the bandwidth borrowing scheme to improve the performance of call admission control schemes and demonstrate the results. In general, the target transmission rates of communications and streaming services are fixed, but data services do not have the target transmission rates. Therefore, we can control the transmission rates for data services flexibly according to the situation. The bandwidth borrowing scheme is implemented by the transmission rates control of data services through the packet scheduler. We make the queuing model for our system model. However, it is difficult to get the analytic solution, so we demonstrate the results through the simulations. The simulation results show that there is a 8.7-35.2 dB gain at the total blocking probability according to the use of bandwidth borrowing scheme

HARQ–ARQ interaction method for LTE‐based mobile satellite communication system

SUMMARY Hybrid automatic repeat request (HARQ) and automatic repeat request (ARQ) of the terrestrial long-term evolution (LTE) system are designed considering the very short propagation delay of terrestrial environment. Therefore, when HARQ and ARQ are applied to the LTE-based mobile satellite communication system, the inefficiency is caused by the long propagation delay of satellite environment. This paper proposes the interaction method between HARQ and ARQ for the decrease of inefficiency in the LTE-based mobile satellite communication system. The existing concept of layered architecture about HARQ and ARQ is also maintained in our interaction method. Simulation results reveal that our proposed scheme can provide the larger spectrum efficiency than that of the non-interaction scheme in all environments. The performance improvement can be up to 2.04 times through the interaction method. Copyright

Efficient utilization of an adaptive modulation and coding for mobile satellite systems using LTE-Advanced

One of the most important features of the IMT-Advanced system is to utilize adaptive modulation and coding (AMC) in order to counteract time and/or frequency varying channel conditions. Due to increasing importance of integrated satellite and terrestrial networks, a satellite system specification needs to be designed by considering compatibility with terrestrial systems. In this paper, we propose an efficient utilization of AMC scheme for mobile satellite systems compatible with the LTE-Advanced. Due to a long round-trip delay (RTD) of a satellite system, the adaptation strategy of a satellite system should be quite different from that for the terrestrial system. In our scheme, a variable margin is allocated along with AMC in a comparatively slow fading condition such as open environment, while a long time interleaver is utilized along with AMC in a comparatively fast fading condition such as sub-urban area.

Reverse link capacity of the WCDMA system using high altitude platform stations

The high altitude platform station (HAPS) system is considered as one of the most effective solutions to provide high quality wireless communication services, such as IMT-2000 services. In this paper, we provide a method to estimate the reverse link capacity of the wideband code division multiple access (WCDMA) system using HAPS, and demonstrate the results. HAPS would be located at 17 km to 22 km above sea level with a multi-beam antenna system and it leads to a consideration of new channel conditions and system design criteria different from those of the conventional terrestrial system. Therefore, we use a practical system model which represents the HAPS system most appropriately, and it leads to realistic estimation results. We estimate the reverse link capacity of the RAPS WCDMA system considering a multi-cell and multi-HAPS model and compare it to that of the conventional terrestrial system. The estimation results show that the capacity in the border cells is decreased and the capacity of the HAPS WCDMA system is about 1.2 to 1.67 times larger than that of the conventional terrestrial system.