• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.19-23
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• 2015

In this paper, we present the return link ACM method to improve the link availability and system throughput for satellite communication service. Also, we describe the optimization of an algorithm for channel prediction using the LMS (Least Mean Square) adaptive filter and the MODCOD (Modulation & Code rate) decision. The simulation results show that the optimized filter taps and step-size of adaptive filter are 2 and 0.00026, respectively. And also confirms the required SNR margin for minimization of MODCOD decision error is 0.3dB.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.748-751
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• 2005

This paper introduces the testbed configuration for telematics wireless communications using terrestrial digital multimedia broadcasting (T-DMB) network. The testbed for telematics wireless communications is consisted of indoor laboratory testbed and outdoor field testbed. As a result of research, are derived testbed configurations for individual function verification at the indoor laboratory and performance test at the outdoor test road. In addition, a return channel configuration is described for interactive protocol as necessary for telematics services using T-DMB.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.139-142
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• 2006

Digital TV 환경에서, Advanced Television System Committee(ATSC) 표준을 채택한 지상파 방송 사업자들은 자기 채널 정보만을 전송하기 때문에, 시청자가 타 채널 편성정보를 검색하기 위해서는 채널 튜닝(Tuning) 후 정보를 받아볼 수 있다. 이러한 이유는 방송 사업자의 송출 대역폭(Bandwidth)의 부족 및 사업자간의 이해관계가 원인이 될 수 있다. 본 논문에서는 ATSC 의 데이터방송 규격인 Advanced Common Application Platform(ACAP) 기반에서 자기 채널 편성 정보는 현재 수신되고 있는 PSIP 규격을 이용하여 디스플레이 하고, 타 방송사 채널 편성 정보 및 장르 정보, 양방향 데이터방송 정보 등은 리턴 패스(Return Path)를 이용하는 통합 편성 정보 서비스(Integrated Scheduling Information Service, ISIS) 구현 방법을 제시하여 문제점을 해결하였다.

• Journal of Broadcast Engineering
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• v.11 no.3 s.32
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• pp.311-319
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• 2006

Platform operators adopted ATSC standard send only their own channel program schedule information, so in order for the viewer to see other channel information, they have to tune the channel to the other. This issue arises from the operators' lack of bandwidth and the business interest conflicts between the platform operators. This paper guides how ATSC standard could be used within Xlet based application to display other channel information through the ISG (Integrated Scheduling Guide) technology via interactive return channel services. Its own channel information can be displayed by using on-air PSIP (Program and System Information Protocol) data.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.3
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• pp.1-9
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• 2003

We analyze the performances of MC-CDMA and MC-DS/CDMA systems on quasi-synchronized mobile satellite return link. Quasi-synchronization is considered that chip offset between user terminals is within a few chips. Since the transmitted signals of MC-CDMA and MC-DS/CDMA systems have non-constant envelop, they are easily distorted by nonlinearity of transmit amplifier. Since the nonlinear amplifier input signal level of MC-CDMA system using Walsh code to employ frequency domain spreading is lower than that of MC-DS/CDMA system, performance of single user in MC-CDMA system is respectively 2.3dB and 1dB better than that of MC-DS/CDMA system when amplifier input backoff is 0dB and 6dB. However, since interference of MC-DS/CDMA is less than that of MC-CDMA with many subcarriers in quasi-synchronization and AWGN channel, MC-DS/CDMA system is much better than MC-CDMA system as the number of users increases.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.14-24
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• 2006

The terrestrial-DMB (T-DMB) provides one-way broadcasting service in intial phase and two-way interactive data services through a return channel of mobile communications network are commercialized recently. The possible evolution of the T-DMB will be fully convergence between the T-DMB and other communication services such as telematics, RFID and so on. From this evolution point of view, a framework should be defined for supporting telematics and RFID applications on T-BMB platform. In this paper, we propose an integrated service model that could support RFID application services on the interactive T-DMB. To realize the model, we design a service scenario, a network reference model, functionalities of each entity, a data transmission mechanism messages, and coding rules. The service model could allow users to support the identical RFID application services over the T-DMB network even if T-DMB terminal doesn't have RFID reader capability. In addition, in the case for providing the interactive TTI(Traffic and Travel Information)service, users could utilize the current location based RFID application service using by the TPEG-Location application that forms the basis of user location referencing. The messages structure is designed by following TPEG standardization

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.55-56
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• 2022

긴급재난문자는 재난상황을 전달할 때 가장 선호도가 높은 매체이다. 그러나 전송 채널의 용량이 비교적 작아 텍스트만 보낼 수 있고, 리턴 채널이 없어서 수신자의 응답을 받을 수 없다는 한계가 있다. 이 문제를 해결하기 위해서 다대일 통신 기법 연구가 있었으나 이를 위해서는 5G 표준 개정이 필요하다는 문제가 있다. 본 논문에서는 5G 재난문자환경에서 활용하기 위한 긴급재난문자 답신서비스를 설계하였다. 표준 개정 없이 서비스를 제공하기 위하여 재난문자에 링크를 추가하고 답신서비스 웹페이지에 접근하여 수신자의 상태 또는 재난현장의 상태를 텍스트와 사진으로 신고할 수 있도록 하였다.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.65-74
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• 2012

The QoS guarantee for the forward link in satellite communication networks is very important because there are a variety of packets with multiplexing. Especially, the packets are processed depending on the available bandwidth in satellite network changing the wireless channel state in accordance with weather condition. The DVB-S2 increases the transmission efficiency by applying the adaptive coding and modulation (ACM) techniques as a countermeasure of rain attenuations. However, the channel estimation algorithm is required to support the ACM techniques that select the MODCOD values depending on the feedback data transmitted by RCSTs(Return Channel via Satellite Terminal) because satellite communication networks have a long propagation delay. In this paper, we proposed the channel estimation algorithm using rain attenuation values and reference data and the packet scheduling scheme to support the QoS and fairness. As a result of performance evaluation, we showed that proposed algorithm exactly predicts the channel conditions and supports bandwidth fairness to the individual RCST and guarantees QoS for user traffics.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.5
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• pp.694-702
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• 2022

This paper shows a small and low-powered wireless communication system based on the ATSC broadcasting system using the ISM frequency band that can be used as a PBS(Personal Broadcasting System). It is designed to demonstrate a channel-adaptive CR(Cognitive Radio) system to provide a better service quality in the unlicensed band where co-channel interference exists. And it achieved very reliable communications by a closed-loop active phased array antenna. This ATSC-based personal broadcasting platform can be modified easily with given flexibility by using GNU Radio as an open-source signal processing platform based on USRP and implementing additional functions in FPGA. In addition, the chosen communication frequency resource can be managed and controlled by the return channel that transmits the channel status and communication parameters between transmission and reception in real-time.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.887-890
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• 2003

기존의 아날로그 TV에 비해 새로운 방식의 디지털 TV는 단순한 영상과 음성의 처리뿐만 아니라 데이터를 처리 및 저장해야 한다. 그리고 필요에 따라서 데이터를 요구하기 위한 리턴 채널을 관리해야 한다. 이처럼 많은 기능을 동시에 충족시켜줘야 하기 때문에 디지털 TV시스템에서는 운영체제가 필요하다. 현재 출시되는 디지털 TV 시스템은 고비용의 상용 OS를 사용하므로 가격 경쟁력을 확보하기가 어렵다. 이에 비해 오픈 소스인 임베디드 리눅스를 사용함으로서 가격 경쟁력을 확보할 수 있다. 또한 공개된 장치 드라이버와 응용프로그램을 재사용 가능하며, 오픈 소스 공동체를 통해 문제를 해결할 수 있고, 쉘, 파일 시스템을 이용하여 관리한 개발 환경을 제공해 주는 이점이 있다. 본 논문에서는 디지털 TV 시스템을 위해서 임베디드 리눅스를 재설계하고, 기존 디지털 TV 시스템에 이식하였다.