• Journal of Broadcast Engineering
• /
• v.16 no.2
• /
• pp.360-371
• /
• 2011

T-DMB hybrid data service provides advanced data services while maintaining backward compatibility with legacy T-DMB receivers by using hybrid BIFS technology enabling distributed delivery of scene description information and object description information. This paper presents the hybrid service authoring framework implementing hybrid BIFS technology for creating contents for distributed delivery, and the results of experiments by using it. Hybrid service authoring framework is comprised of service creation system, service management system, and contents offering system. It enables the creation of combined hybrid data service and the splitting of the contents into two parts for ecah delivery network, data for broadcasting network and the data for mobile network. It also enables the managements of the contents. The feasibility of advanced data services while maintaining backward compatibility with the legacy T-DMB receiver has been proved by the contents created by using the hybrid authoring framework presented in this paper.

• Journal of Broadcast Engineering
• /
• v.13 no.4
• /
• pp.501-515
• /
• 2008

Recently, as users' requests for high quality mobile multimedia services are rapidly increasing and additional bandwidth can be provided by adopting the hierarchical modulation transmission technology, the research on the Advanced Terrestrial DMB (AT-DMB) service using the SVC (Scalable Video Coding) scheme is being actively studied. But, in order to realize a compatible video service and to accelerate the successful standardization and commercialization, it is necessary to simplify the compatible encoder structure. In this parer, we propose a fast mode decision method by constraining the redundant coding modes in the spatial scalable encoder that keeps the current T-DMB video in base layer. The proposed method is based on the statistical characteristics of each coding mode at both base and enhancement layers, inter-layer predictions, which are derived by investigating macroblock-layer coding modes of the spatial scalable encoder's functional structure. Through computer simulations, it is shown that a simplified encoder model that reduces the heavy computational burden can be found, while keeping the objective visual quality very high.

• The Journal of the Korea Contents Association
• /
• v.7 no.12
• /
• pp.254-261
• /
• 2007

In this paper, we propose a blind equalization method for advanced terrestrial digital multimedia broadcasting (AT-DMB) systems which use hierarchical modulation. The AT-DMB system adopts hierarchical 16-ary quadrature amplitude modulation (16-QAM) to ensure backward-compatibly with the differential quadrature phase shift keying (DQPSK) signal of the legacy terrestrial digital multimedia broadcasting (T-DMB) systems and to support higher transmission rate. Due to the hierarchical modulation, the conventional T-DMB signal and the additional signal have different error rate at same signal to noise ratio (SNR). By weighting the decided symbols differently according to the reliability of the symbols, i.e., high priority symbol with low error rate and low priority symbol with high error rate, we can improve the channel estimation accuracy. In this paper, we analyze SNR loss by hierarchical modulation and confirm it through simulations. Moreover, through simulations, we verify that the proposed weighting method improve BER compared to the no-weighting method.

• ETRI Journal
• /
• v.33 no.4
• /
• pp.629-632
• /
• 2011

This letter presents a hybrid conditional access system (CAS) for advanced terrestrial digital multimedia broadcasting (AT-DMB). The proposed architecture is characterized by its use of a unified CAS channel and various communication networks for CAS message transmissions. We implement a prototype CAS based on the hybrid architecture, which improves the CAS message transmission efficiency greatly compared to the existing T-DMB CAS standard and supports various AT-DMB interlayer services more easily and efficiently.

• Proceedings of the KIEE Conference
• /
• 2008.04a
• /
• pp.83-85
• /
• 2008

현행 지상파 DMB(Digital Multimedia Broadcasting)에서는 최대 CIF급 해상도의 동영상을 384 Kbps 정도의 비트율로 압축하여 비디오 CD급의 화질을 제공한다. 따라서 큰 화면을 통해 DMB 방송을 시청할 경우 해상도 부족 등으로 인한 화질 열화를 느낄 수 있다. 이와 같은 문제를 해결하기 위한 방안으로 계층적으로 부호화된 비트스트림을 서로 다른 채널로 전송하는 고품질 AT-DMB 시스템이 연구되고 있다. 더불어, 계층변조 기술을 이용하여 추가적인 전송대역폭을 확보하고, 계층적 비디오 부호화 기술을 이용하여 고품질 이동 멀티미디어 방송을 제공하는 고품질 T-DMB 방식이 개발되고 있다. 이와 같은 AT-DMB 방식으로 사용자에게 안정된 고품질 비디오 서비스를 제공하기 위해서는 계층적 비디오 부호화를 고려한 효율적인 AV다중화 및 동기화 구조에 대한 연구가 필수적으로 요구 된다. 본 논문에서는, 이와 같은 고품질 AT-DMB 시스템을 위해서 각 계층 ES(Elementary stream)을 MPEG-4 over MPEG-2 시스템과 Eureka-147 DAB 시스템을 통해 서로 다른 채널로 전송한다. 계층별 전송으로 인한 시간 지연에 대처하여 수신입력부에서는 각각의 계층으로 전송된 ES들이 동기화 되어 복호화 되도록 SVC의 계층적 비트스트림 구조와 적응적으로 동작되는 다중화 시스템구조를 제작하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2011.07a
• /
• pp.141-142
• /
• 2011

최근 급격한 모바일 방송 시장의 변화로 인해 사용자 들이 다양하고 고화질의 방송 서비스에 대한 요구가 증대되고 있으며, 지상파 DMB 사업자들도 수익구조를 개선하기 위한 노력을 하고 있다. 이러한 요구와 노력에 맞춰 T-DMB와 역호환성을 유지 하면서 기존의 T-DMB와는 달리 계층변조 방식을 적용해 동일 주파수 내에서 채널의 용량을 증대시키는 AT-DMB 방송 기술을 개발 완료 하였다. AT-DMB의 채널 용량의 증대에 따라 서비스 채널을 늘리거나 SVC를 적용해 고화질 서비스 등 적용 가능한 서비스가 늘어남에 따라 사용자와 DMB 사업자들의 요구를 충족 시켜줄 수 있게 되었다. 이에 상용화 서비스에 앞서 실험방송을 위해 AT-DMB 송신 시스템을 구축하였다. 본 논문은 서론에서 AT-DMB의 배경, 본론에서 AT-DMB 송신 시스템에 대한 간략한 설명, 실험방송을 위해 구축된 송신 시스템 설명 및 예비 테스트 결과를 보여주고 결론을 맺는다.

• ETRI Journal
• /
• v.31 no.1
• /
• pp.65-67
• /
• 2009

We introduce an advanced terrestrial digital multimedia broadcasting (AT-DMB) system that overcomes the limitation of data transmission rates of T-DMB by doubling it with the same frequency bandwidth. In this letter, we propose an efficient algorithm which generates a scalable transport stream in AT-DMB by multiplexing certain types of elementary streams encoded using scalable video coding and an MPEG-surround audio coder for high-quality multimedia services.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.1
• /
• pp.1-9
• /
• 2007

Digital Multimedia Broadcasting is the next generation broadcasting service which enables various digital multimedia contents, i.e., audio and video, and data access for mobile users. However, due to the bandwidth limitation, the spatial resolution is limited to CIF(Common Interleaved Frame). The Advanced Terrestrial DMB (AT-DMB) secures additional bandwidth by adopting hierarchical modulation transmission technology and provides high data rate and quality for mobile multimedia broadcasting services with scalable video coding(SVC). This paper proposes scalable video coding technology for AT-DMB which enables high quality mobile multimedia broadcasting services that exceeds current DMB service's quality and contents capability.

• Journal of Broadcast Engineering
• /
• v.15 no.1
• /
• pp.122-132
• /
• 2010

AT-DMB system has been developed to increase data rate up to double of conventional T-DMB in the same bandwidth while maintaining backward compatibility. The AT-DMB system adopted hierarchical modulation which adds BPSK or QPSK signal as enhancement layer to existing DQPSK signal. The enhancement layer signal should be small enough to maintain backward compatibility and to minimize the coverage loss of conventional T-DMB service coverage. But this causes the enhancement layer signal of AT-DMB susceptible to fading effect in transmission channel. A turbo code which has improved error correction capability than convolutional code, is applied to the enhancement layer signal of the AT-DMB system for compensating channel distortion. However there is a need for other solutions for better reception of AT-DMB signal in receiver side without increasing transmitting power. In this paper, we propose adaptive array antenna system with Eigen-space beamforming algorithm which benefits beamforming gain along with diversity gain. We analyzed the reception performances of AT-DMB system in indoor and mobile environments when this new smart antenna system and algorithm is introduced. The computer simulation results are presented along with analysis comments.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2006.11a
• /
• pp.157-160
• /
• 2006

이 논문에서는 계층변조를 적용하는 AT-DMB (advanced terrestrial digital multimedia broadcasting) 시스템을 위한 자력 채널추정 기법을 제시하고 그 성능을 살펴본다. AT-DMB 시스템은 기존 T-DMB 시스템과의 호환성을 유지하기 데이터 전송채널의 경우 DQPSK 변조를 적용한 각 신호점을 다시 QPSK 변조하는 16-QAM 계층변조 방식을 적용한다. 또 프레임의 동기신호 및 정보채널은 기존 T-DMB 신호와 동일하게 유지한다. 이 신호들을 이용하여 자력 추정을 위한 채널의 초기치를 계산한다. 데이터 신호에 대해서는 일단 판정궤환 모드를 적용하여 채널을 추정한 후 시간 및 주파수 영역에서 인접 심볼 및 부반송파에 걸쳐 평균을 취함으로써 잡음의 영향을 감소시킨다. 모의실험을 통해 제시한 자력 채널추정 방식의 성능을 살펴본다.