Terrestrial Digital Multimedia Broadcasting System Research Articles

제한수신 기능 기반 T-DMB 시스템

ABSTRACT Current terrestrial Digital Multimedia Broadcasting (T-DMB) is conducting .the emergency alert broadcast, or can view a variety of broadcasting. However, propagation shadow area is a situation where the service is limited due to limitations of facilities investment. In addition, there is the problem of T-DMB broadcasting is for viewing only a restricted area and a mobile device because the mobile is also T-DMB viewing device impossible. In this paper, it receives a T-DMB broadcasting as a way to solve the problems of the T-DMB system, which was studied the re transmission to the mobile device. Accordingly, by receiving the broadcast may be watched in the mobile device the T-DMB reception impossible. Also provides a one-way/two-way authentication mechanism using a conditional access function, and the system was configured so that the user can watch only the registered broadcasting. 키워드 : 멀티미디어 방송, 제한수신, 지상파 방송, T-DMB Key word : Multimedia Broadcasting, Reception Function, Terrestial Broadcasting, T-DMB

Narrowband Interference Cancelation Based on Priori Aided Compressive Sensing for DTMB Systems

In this paper, a novel narrowband interference (NBI) cancelation scheme based on priori aided compressive sensing (CS) for digital terrestrial multimedia broadcasting systems is proposed. The repeated training sequences in the transmitted symbols are exploited by differential measuring to acquire the CS measuring vector of the NBI, and for joint acquisition of the NBI support priori. Using the proposed priori aided sparsity adaptive matching pursuit algorithm, the sparse high-dimensional NBI can be accurately reconstructed from the measuring vector of much smaller size obtained through the proposed CS-based differential measuring method. It is verified by theoretical analysis and simulations that the proposed method outperforms conventional anti-NBI methods under multipath broadcasting channels.

Improving the Reception Performance of Legacy T-DMB/DAB Receivers in a Single-Frequency Network with Delay Diversity

This paper describes a simple delay diversity technique for terrestrial digital multimedia broadcasting (T-DMB) and digital audio broadcasting in a single-frequency network (SFN). For the diversity technique, a delay diversity scheme is adopted. In the delay diversity scheme, a non-delayed signal is transmitted in the first antenna, and delayed versions of the signal are transmitted in each additional antenna. For an SFN environment with multiple transmitters, delay diversity can be executed by controlling the emission times of the transmitters. This SFN delay diversity scheme does not require any hardware changes in either the transmitter or receiver, and perfect backward compatibility can be acquired. To evaluate the performance improvement, laboratory tests are executed with various types of commercial T-DMB receivers as well as a measurement receiver. The improvement in the bit error rate performance is evaluated using a measurement receiver, and an improvement of the threshold of visibility value is evaluated for commercial receivers. Test results show that the T-DMB system can obtain diversity gain using the described technique.

A Generalized Analytical Solution to Channel Estimation With Intersymbol Interference Cancelation and Co-Channel Interference Cancelation for Single Input Single Output/Multiple Input Single Output Digital Terrestrial Multimedia Broadcasting Systems

A novel generalized channel estimation scheme without the need of matrix inversion or iterative operations is proposed for single input single output (SISO)/multiple input single output (MISO) digital terrestrial multimedia broadcasting (DTMB) system, adopting the time-domain synchronous orthogonal frequency division multiplexing technology. Simultaneously exploiting time domain correlation channel estimation and the constant coefficients of the imperfect autocorrelation of m-sequence, a simple and generalized closed-form solution related to each channel tap can be acquired by solving the constructed linear equations. On the basis of the specified frame head structure for the SISO DTMB system, quasi-orthogonal frame head sequences over multiple antennas are designed by employing different cyclic shifts of m-sequence. In addition, in order to effectively recover the transmitted signal in the frequency domain, the tail cancelation and cyclic reconstruction process is elaborated primarily for MISO systems. It is shown that, for the SISO DTMB system, the implementation complexity of the intersymbol interference cancelation (ISIC) of the proposed approach is reduced by approximately 90% over the existing iterative scheme, and for the MISO DTMB system, the implementation complexity of the proposed scheme with the co-channel interference cancelation (CCIC) and ISIC dramatically decreases compared with the existing scheme. Simulation results validate that the proposed channel estimation scheme can achieve almost the same performance as the existing channel estimation methods, but with a significant reduction in computational complexity in both SISO and MISO DTMB systems.

Frame Head Mode Detection and Symbol Detection Scheme for Digital Terrestrial Multimedia Broadcasting Systems

As an effective technique for combating multipath fading and for high-bit-rate transmission over wireless channels, orthogonal frequency division multiplexing (OFDM) is extensively used in modern digital television terrestrial broadcasting (DTTB) systems to support high performance bandwidth-efficient multimedia services. Chinese digital television terrestrial broadcasting standard recommends three kinds of Frame Head mode with PN420/PN595/PN945 as training sequences for the time domain synchronous OFDM (TDS-OFDM) based Digital Terrestrial Multimedia Broadcasting (DTMB) systems. At the receiver side, Frame Head mode detection and symbol detection should be done before subsequent synchronization and channel estimation. In this paper, a Frame Head mode detection and symbol detection scheme robust to carrier frequency offset is proposed for the TDS-OFDM based DTMB systems. Performance studies under different channel situations are used to verify the efficiency of the proposed scheme.

Frame Synchronization for the DTMB Systems with the Multiple-Antenna Receivers

Faced with the challenges of modern communication, high data throughput requirements, extensive research has been paid to broadband modulation. The multi-carrier modulation is one of the most important wide band modulation techniques. Orthogonal frequency division multiplexing (OFDM) is an effective blow to the broadcast channel multipath fading and high bit rate transmission multi-carrier modulation technology of wireless channels, it is widely used in modern digital television terrestrial broadcasting (DTTB) system to support performance bandwidth-efficient multimedia services with the aid of inverse fast Fourier transform and fast Fourier transform operation. Multiple-antenna transmitter and receiver technology allows several times to achieve data transmission rates and spectrum efficiency and the use of multiple transmit antennas and multiple receive antennas through spatial processing. The Digital Terrestrial Multimedia Broadcasting (DTMB) system with the multiple-antenna receiver is considered in this paper. Digital Terrestrial Multimedia Broadcasting (DTMB) has three kinds of Frame Head mode with PN420/PN595/PN945 as training sequences for the time domain synchronous OFDM (TDS-OFDM). At the receiver side with multiple antennas, Frame Head mode detection should be done. In this paper, the frame synchronization scheme is proposed for the DTMB systems with the multiple-antenna receiver. System performance studies under different channel situations are used to verify the efficiency of the proposed scheme for the DTMB systems with the multiple-antenna receiver.

Interference Cancellation Techniques for Digital On-Channel Repeaters in T-DMB System

Digital on-channel repeater (DOCR) is regarded as a desirable solution to effectively build a wide-area network of mobile terrestrial-digital multimedia broadcasting (T-DMB) services. On the other hand, the DOCR mainly suffers from interference effects caused by a strong feedback signal and a time-varying channel dispersion. In this paper, we propose a novel DOCR for use in the T-DMB system in order to mitigate effectively both interference effects. First, we present an energy equalizer using the scarce pilot structure of T-DMB system to estimate a channel state information on every OFDM symbol. An optimum frequency domain channel estimation (FDCE) algorithm is then derived for the energy equalizer. In addition, a moving average filter (MAF) is employed to mitigate the phase distortion of truncated equalizer coefficients in deep null channel. Finally, in the performance evaluations, it is shown that the optimum FDCE outperforms a perfect FDCE. It is also shown that the DOCR equipped with the proposed interference cancellation can solve the problems caused by a limited channel information update, a phase distortion of the equalizer, and a residual feedback signal.

Feedback Cancellation for T-DMB Repeaters Based on Frequency-Domain Channel Estimation

This paper presents a novel feedback canceller for a terrestrial digital multimedia broadcasting (T-DMB) on-channel repeater (OCR). There is a crucial requirement for an OCR that the isolation between the transmitter and the receiver antennas should be sufficiently secured to prevent unwanted oscillation. The required isolation, however, may not be satisfied by some physical or technical limitations. In order to overcome these obstacles, undesired feedback signals have been usually reduced by feedback cancellation techniques based on pilot-aided frequency-domain channel estimation (FDCE). In case of the T-DMB system, however, there are no pilot symbols except for the phase reference symbols (PRSs), which are transmitted only once every 76 OFDM symbols. Consequently, the convergence speed and the tracking capability of the FDCE-type feedback cancellers may not meet the required robustness in coping with dynamic feedback channels. To improve the immunity to time-varying channels, we increase the usable number of updates in our feedback canceller, where the PRS is divided into several sub-PRSs during the PRS period and pseudo pilots are generated by decision-directed estimation in the data-symbol duration. Simulation results show that the proposed methods do improve the convergence speed and the tracking capability of the conventional method in both static and dynamic feedback channels.

Backward-compatible terrestrial digital multimedia broadcasting system for multichannel audio service

In this paper, a Terrestrial Digital Multimedia Broadcasting (T-DMB) system for a multichannel audio service is proposed. The multichannel audio information on the T-DMB system proposed in this paper consists of a stereo audio signal coded by BSAC and additional multichannel side information coded by MPEG surround. These two types of information are conveyed through two elementary streams (ES), respectively. To control two elementary streams, two object descriptor (OD) streams are exploited, each of which transmits OD commands, including ObjectDescriptorUpdate and ES_DescriptorUpdate, related to a stereo audio signal and additional multichannel side information, respectively. With this method, the proposed system can convey multichannel side information while guaranteeing backward compatibility for the legacy T-DMB terminals, and moreover makes it possible to provide various advanced service scenarios with outstanding extensibility.

Development of depth-image-based three-dimensional mobile broadcasting system in terrestrial digital media broadcasting

We present a 3-D mobile broadcasting system based on a depth-image-based rendering (DIBR) technique in terrestrial digital multimedia broadcasting (T-DMB). It is well known that a 3-D mobile broadcasting service based on the DIBR technique can be one of the solutions to meet service requirements, because the required bit rates of depth images in DIBR schemes are less than additional video bit rates of other 3-D formats, while keeping good 3-D quality and guaranteeing backward compatibility with conventional broadcasting systems. We propose an implementation of a DIBR-based 3-D T-DMB system that supports real-time rendering with good image quality and realistic depth effect at the receiver, verifying that it could be perfectly applicable in mobile broadcasting. Specifically, the proposed 3-D T-DMB receiver adopts a look-up table (LUT)-based simultaneous method to accomplish the real-time implementation of DIBR algorithms, including warping, hole filling, and interleaving. Moreover, we establish the parameter values that are needed for generating the LUT based on theoretical analysis. The verification is accomplished through objective and subjective evaluations, based on simulation and real-time implementation of the system under actual service conditions.

Novel Equalization On-Channel Repeater with Feedback Interference Canceller in Terrestrial Digital Multimedia Broadcasting System

In this paper, we propose a novel equalization on-channel repeater (OCR) with a feedback interference canceller (FIC) to relay terrestrial digital multimedia broadcasting signals in single frequency networks. The proposed OCR not only has high output power by cancelling the feedback signals caused by insufficient antenna isolation through the FIC, but also shows better output signal quality than the conventional OCR by removing multipath signals existing between the main transmitter and the OCR through an equalizer. In addition, computer simulations and laboratory test results demonstrate that the proposed OCR successfully cancels feedback signals and compensates channel distortions and provides a higher quality transmitting signal with higher output power than conventional OCRs. Keywords: T-DMB, single frequency network (SFN), on-channel repeater (OCR), equalizer, feedback interference canceller (FIC).

A Higher Data-Rate T-DMB System Based on a Hierarchical A-DPSK Modulation

Hierarchical modulation can be effectively used to enhance terrestrial digital multimedia broadcasting (T-DMB) or digital audio broadcasting (DAB) systems in response to both the demand for higher data-rate and the need to be backward compatible with legacy receivers. QAM-type modulations are well-liked for hierarchical transmission but require coherent detection based on pilot symbol aided channel estimation. In the T-DMB or the DAB system using DQPSK modulation, however, any available pilot symbols except for the phase reference symbol do not exist. Differential amplitude phase shift keying (DAPSK) modulation is easily applied to the T-DMB system for a hierarchical modulation but may be susceptible to fast fading. As a good candidate for a hierarchical modulation of T-DMB to solve the above problems, we propose an amplitude differential phase shift keying (A-DPSK) modulation which is robust to fast fading by estimating only amplitude coefficients of the channel transfer function with the use of amplitude pilots. To raise the accuracy of channel estimation, we arrange the amplitude pilots in a come-type and introduce a noise-reduction scheme of averaging estimated channel coefficients. Simulation results show that the proposed A-DPSK provides a good choice for achieving a higher data-rate over other possible modulation schemes for advanced T-DMB or DAB systems.

Equalization On-Channel Repeater for Terrestrial Digital Multimedia Broadcasting System

This paper presents technical requirements of on-channel repeaters (OCRs) to broadcast the terrestrial digital multimedia broadcasting (T-DMB) signals in single frequency network (SFN) environment. In order to meet such requirements, the configuration and implementation method of the equalization OCR are proposed. The proposed equalization OCR does not have only short processing delay, but also provides high quality transmitting signals with high power because of the rejection capability of a feedback signal introduced by incomplete antenna isolation and multipath signals existing between a main transmitter and the OCR. Computer simulations and laboratory tests results are provided to figure out performance of the proposed equalization OCR.

Design of the Channel Estimation Algorithm for Advanced Terrestrial DMB System

This paper describes a channel estimation algorithm for the advanced terrestrial digital multimedia broadcasting (T-DMB) transmission system which is fully backward compatible with the conventional T-DMB standard. The advanced T-DMB has enhanced features which provide higher transmission data rate for increasing program channel capacity and better multimedia A/V service quality than the conventional T-DMB system by adopting a hierarchical modulation and scalable audio/video CODEC. To support the higher data rate transmission for the advanced T-DMB, high performance channel estimation and equalization techniques should be adopted into the advanced T-DMB receivers. In this paper, we propose a new channel estimation technique for the Advanced T-DMB to compensate channel distortion under dynamic multipath environment.

차세대 T-DMB 방송의 부가 서비스 제공을 위한 비트 분리 방법 및 Double Binary Turbo 부호 적용 연구

T-DMB(Terrestrial Digital Multimedia Broadcasting) system, is based on the Eureka-147 standard, provides various multimedia data services. However T-DMB system needs upgrades for more various services and better services. Therefore, we proposed advanced T-DMB system using unequal error protection system and hierarchical modulation in this paper while maintaing backward compatibility. And we simulated various bit split methods and double binary turbo code of DVB-RCS standard as method of LP data stream for additional service of advanced T-DMB. As the simulation results, double binary turbo code of proposed advanced T-DMB system have each coding gain of over 2 dB compared to conventional T-DMB.

T-DMB 시스템을 위한 E-OCR에서의 채널추정

This paper proposes noise reduction methods to improve the channel estimation performance in Equalization On-Channel Repeater (E-OCR) for Terrestrial-Digital Multimedia Broadcasting (T-DMB) system. In the E-OCR for T-DMB system, the channel estimation is performed by the pilot signal extraction and the channel coefficient estimation. Since the performance of the channel estimation highly depends on the estimated channel coefficients whose accuracy is associated with the received signal-to-noise ratio (SNR), it is important to reduce noise existing at the estimated channel coefficients. To reduce such noise components, various noise reduction methods of the estimated channel coefficients based on the M -point weighted moving average are proposed. Computer simulations show that the proposed methods improve the estimation performance by more than 2 to 3 dB in terms of the symbol error rate after equalization.

A New Scheme to Predict Erasures for Reed-Solomon Decoder in T-DMB Receiver

In this paper, we introduce a new scheme to improve the performance of the terrestrial - digital multimedia broadcasting (T-DMB) system, which exploits the burst error characteristics at the output of the convolutional decoder and the properties of the Reed-Solomon (RS) decoder to correct more errors by predicting erasures in each RS packet in advance as many as possible before decoding in the RS decoder. Simulation results show that the proposed scheme yields performance gain of around 1 dB at BER of 10-R which can result in the extended coverage area of the T-DMB system.

Field Trials for Terrestrial Digital Multimedia Broadcasting System

This paper presents the field trial results of the terrestrial digital multimedia broadcasting (T-DMB) service in Korea. The T-DMB system, based on the Eureka-147 digital audio broadcasting (DAB) system, provides streaming video, CD-quality audio and data services at speeds of up to 300 km/h using H.264 video codec along with additional channel coding and interleaving schemes. In order to provide seamless high-quality services on various radio channels, we measured the bit error rate (BER), electric field strength (EFS), and subjective video quality using specially-designed mobile test equipment. From the field tests we obtained the required effective EFS (EEFS) for error-free reception and also derived the minimum EFS from the link budget analysis. Furthermore, we present the optimal transmit and receive parameters for constructing the T-DMB networks and also developing T-DMB broadcasting equipment and mobile receivers

Real Time Traffic Information Service Using Terrestrial Digital Multimedia Broadcasting System

The major contribution of this paper is the implementation of real time traffic and traveler information service through the terrestrial digital multimedia broadcasting (T-DMB) system, which are known to be suitable for the mobile data services as well as audio and video services. The implemented system converts the Korean characteristic traffic information into the transport protocol expert group (TPEG) messages, and provides them to the T-DMB system. By testing the service with the TPEG message decoder implemented in the navigation system on PDA and laptop, it has turned out that it can be used as a highly efficient traffic information service system that could be adopted in Korea as well as in European countries

Demonstration of Bidirectional Services Using MPEG-4 BIFS in Terrestrial DMB Systems

Digital broadcasting technology has developed focusing on multi-channel/multi-media, high-definition quality, and mobility-support. Recently, there has been a clear trend toward bidirectional service with the convergence between broadcasting and communication. The broadcasting viewer is no longer simply a passive receptor but has also become an information generator. Currently, the digital multimedia broadcasting (DMB) specifications are the major standard for portable digital broadcasting and have been establishing the overall guidelines for bidirectional service using the MPEG-4 system. While detailed specifications for DMB systems are not well-established for bidirectional service yet, they share the basic concepts underlying the European Eureka-147 Digital Audio Broadcasting (DAB) system. This paper develops key scenarios for bidirectional service in DMB, describes the signal transaction of broadcasting and return channels, and demonstrates typical scenarios using binary format for scenes (BIFS) in the MPEG-4 system.