Integrated Services Digital Broadcasting-Terrestrial Research Articles

Fixed Reception Performance of FDM-based Transmission System for Advanced ISDB-T

With the aim of improving the quality and expanding the functions of digital terrestrial television broadcasting services, we have been developing an advanced transmission system that inherits key features of the current Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) system, which employs hierarchical transmission based on frequency division multiplexing (FDM) and a segment structure. The advanced ISDB-T system has a new signal frame structure that enables bandwidth to be flexibly allocated to multiple services for different reception scenarios, such as fixed reception and mobile reception, compared with ISDB-T. By introducing transmission technologies such as the latest forward error correction and modulation scheme, this specification has high spectral efficiency and transmission robustness, i.e., the transmission capacity increases by about 10 Mbps for the same required carrier to noise ratio (CNR) in comparison with the current ISDB-T system, or the required CNR can be reduced by about 7 dB for the same transmission capacity. We describe the channel coding scheme and evaluated the performance of bit-interleaved coded modulation (BICM) in simulations. This paper provides a BICM selection guideline based on the simulation results for fixed reception scenarios toward the practical application of advanced ISDB-T.

A Statistical Evaluation of Detection Response of an Electric Field Probe Loaded With Nonlinear Diodes for Modulated Signals

To improve the calibration uncertainty of an electric field probe loaded with diodes to modulated signals, an approximate method for evaluating the detection response using the probability density function (pdf) of the envelope amplitude of an actually transmitted modulated signal waveform is proposed. In this article, we focus on the high-strength modulated signals and evaluate the effect of the nonlinearity of the transmission system on the probe gain. First, the equivalent circuit parameters of an electric field probe are estimated using an unmodulated signal and then used to simulate the probe gain for the amplitude-modulation (AM) signal. The probe gain for the modulated signal deviates considerably from that for the unmodulated signal, depending on the modulating frequency and modulation index of the AM signal, especially when a large incident voltage is applied to the equivalent circuit simulating the probe. Moreover, we propose two approximate expressions using the pdf to obtain the fluctuation range of the detection response of the modulated signal. One is an approximate expression that considers the equivalent circuit parameters of the probe. The other one is an approximate expression for the modulated signal with slow envelope variation. These two expressions are found to give a good approximation of the asymptotic value of the probe gain for an AM signal with fast and slow envelope variations, respectively. By applying these approximate expressions, the upper and lower limits of the gain variation of the probe for the AM signal are obtained. As an application to actual communication signals, integrated services digital broadcasting terrestrial (ISDB-T) signals and single-carrier frequency-division multiple access (SC-FDMA) signals are demonstrated as examples. It is shown that the probe gain in the saturation region increases as the signal bandwidth or peak-to-average-power ratio (PAPR) increases, which can be understood similar to the probe response to AM signals.

Efficient Weighted Least-Squares Frequency Synchronization Scheme for Digital Terrestrial Broadcasting System

The integrated services digital broadcasting-terrestrial (ISDB-T) system provides the interesting advantages of hierarchical transmission and partial reception using band segmented transmission orthogonal frequency division multiplexing scheme. In ISDB-T, the hierarchical configuration varies depending on whether a segment is modulated coherently or differentially. Thus, it is important to accomplish frequency synchronization regardless of segment type. For this purpose, an effective weighted least-squares (WLS) carrier frequency synchronization method is presented using transmission and multiplexing configuration control (TMCC) and auxiliary channel (AC) in a blind manner. Thus, the proposed estimation scheme is performed without resorting to a priori knowledge on segment type that can be known after correct TMCC decoding. To eliminate bias caused by using non-uniformly distributed TMCC and AC subcarriers, an appropriate subset is selected to form the basis of robust WLS estimation. Extensive simulations are conducted to verify the efficiency of the proposed WLS estimation method and compare its performance with that of the conventional WLS estimation scheme.

Robust Blind Detection of Integer Carrier Frequency Offset for Terrestrial Broadcasting Systems Using Band Segmented Transmission

In the integrated services digital broadcasting-terrestrial (ISDB-T) system, the combination of digital terrestrial transmission and MPEG-4 advanced video coding (MPEG-4 AVC) has offered ways to provide a variety of digital high-definition television (HDTV) programs. Using band segmented transmission orthogonal frequency division multiplexing (BST-OFDM), the delivery of innovative video-on-demand and HDTV services is supported. To take full advantage of the attractive benefits of BST-OFDM, it is important to estimate integer frequency offset (IFO) without a priori knowledge on the segment type that is transmitted over transmission and the multiplexing configuration control (TMCC) signal. To address this issue, an efficient IFO detection method is proposed for the ISDB-T system employing BST-OFDM. To enable IFO detection independent of the segment type, information-bearing TMCC signals that are asymmetrically distributed in the frequency domain are used as pilot symbols. Numerical analysis is performed to present the relationship between error probability and design parameter. We show via the numerical results that the multiple transmitted TMCC information is efficiently used for blind estimation of the IFO, achieving robust estimation in the presence of the fractional frequency offset.

Suboptimal Maximum Likelihood Detection of Integer Carrier Frequency Offset for Digital Terrestrial Television Broadcasting System

The integrated services digital broadcasting-terrestrial (ISDB-T) system adopts band segmented transmission orthogonal frequency division multiplexing (BST-OFDM) to support different services using hierarchical transmission. In the ISDB-T system, in particular, a hierarchical configuration depends on modulation type used in OFDM segment, which has to be decoded at the receiver. Therefore, it is necessary to detect integer carrier frequency offset (IFO) before decoding the modulation type carried through transmission and multiplexing configuration control (TMCC) signal. To address this issue, an effective IFO estimation scheme is presented for the ISDB-T system, considering information-carrying TMCC signal as pilot symbol without any need of additional pilots. In order to verify the performance of the proposed estimation scheme, theoretical detection error rate is derived. It is shown from simulation results that the redundantly transmitted TMCC signal can be efficiently utilized for IFO detection, offering an approximate performance of maximum likelihood detection.

Method for Determining Broadcaster Advised Emergency Wake-up Signal for ISDB-T Digital Television Receivers

There is a way to automatically wake up television receivers when a broadcaster sends out an emergency alert. In the Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) digital television standard, the emergency wake-up procedure is called an Emergency Warning System (EWS). In ISDB-T, the special signal is embedded in a control message known as transmission and modulation configuration control (TMCC). However, improper identification of the wake-up signal, often encountered in mobile reception, leads to unnecessary wake ups. In this paper, a method of reliably determining a wake-up signal is proposed by assuming that broadcasters will not change the TMCC message except for the wake-up signal when the broadcaster sends out an emergency alert. A change in the wake-up bit leads to variation parity, and the proposed method also relies on such variations. Mutual information to be obtained by the wake-up receiver is evaluated using the memoryless binary asymmetric channel model. Results showed that the proposed method provided mutual information even at a Eb/N₀ being lower than 10 dB. Mutual information of the proposed method with intermittent reception is also analyzed as a function of the duty ratio of the intermittent receiver.

Passive bistatic radar using digital video broadcasting-terrestrial receivers as general-purpose software-defined radio receivers.

We investigate the use of low-cost digital video broadcasting-terrestrial (DVB-T) receivers as general-purpose software-defined radio (SDR) receivers for passive bistatic radar (PBR) applications. Two DVB-T receivers are synchronized using a common clock to perform coherent measurements. By exploiting the direct-path signal in the surveillance channel, we use the cross-correlation process to estimate the time offset between the data streams of reference and surveillance channels caused by the universal serial bus communication. We demonstrate the detection of static and moving targets as well as short-range targets, including a landing airplane at 8 km, multiple ships with different velocities, and vehicles within 20 m from the receiver acquiring at a 2 MHz bandwidth, by using Japan's Integrated Services Digital Broadcasting Terrestrial digital TeleVision (TV) signal broadcast. We also propose to improve the range resolution of the designed PBR system by combining multiple SDR receivers tuned to different carrier frequencies. The designed system and proposed method can be used for various applications, such as airplane navigation, harbor protection, and traffic density monitoring.

Effective Blind Frequency Offset Estimation Scheme for BST-OFDM Based HDTV Broadcast Systems

The integrated services digital broadcasting-terrestrial (ISDB-T) system is designed in order to accommodate high-quality video/audio and multimedia services, using band segmented transmission orthogonal frequency division multiplexing (BST-OFDM) scheme. In the ISDB-T system, the pilot configuration varies depending on whether a segment uses a coherent or differential modulation. Therefore, it is necessary to perform a joint estimation of carrier frequency offset (CFO) and sampling frequency offset (SFO) independent of the segment format in the ISDB-T system. The goal is to complete those synchronization tasks while considering an information-carrying transmission and multiplexing configuration control (TMCC) signal as pilot symbols. It is demonstrated through numerical simulations that the differential BPSK-modulated TMCC information can be efficiently used for a least-squares estimation of CFO and SFO, offering an acceptable performance.

An Efficient Frequency Offset Estimation Scheme for Band Segment Transmission OFDM Systems

The integrated services digital broadcasting-terrestrial (ISDB-T) system is designed to individually configure transmission parameters of each orthogonal frequency division multiplexing (OFDM) segment using band segmented transmission OFDM (BST-OFDM). Since the pilot configuration relies on whether a segment is a differential or coherent modulation, it is important to develop the frequency-offset estimation scheme that conforms to the segment-dependent pilot structure in the BST-OFDM system. This paper proposes an efficient sampling frequency offset (SFO) in the ISDB-T system using BST-OFDM. Extensive simulations are conducted not only to verify the effectiveness of the proposed SFO estimation scheme but also to compare the new scheme with the conventional scheme. It has confirmed that the performance of the proposed SFO estimation algorithm is better than that of the existing algorithm at a reduced computational cost.

A Low-Complexity Hardware Implementation of Compressed Sensing-Based Channel Estimation for ISDB-T System

Compressed sensing (CS) is one of the hottest research topics in the sparse signal reconstruction problem. But CS implementation has a drawback of high computational complexity due to calculation between large size of matrices. In this paper, we will propose a low-complexity CS hardware realization for channel estimation in the integrated services digital broadcasting-terrestrial (ISDB-T) system using several optimization methods to reduce the implementation complexity of CS usage. Since the ISDB-T is based on orthogonal frequency division and multiplexing system, the measurement matrix of CS computation is a truncated discrete Fourier transform (DFT) matrix. We can exploit the symmetrical property of this DFT matrix to significantly reduce its multiplication complexity and random access memory usage. To achieve fast reconstruction period, this paper also provides a hardware architecture for the proposed method and its realization in field programmable gate array. The simulation results show that the proposed methods can achieve lower complexity CS-based channel estimation with almost the identical system performance with the conventional method. Moreover, the realized hardware can achieve the fastest execution time compare to that of other existing methods.

Low-Complexity Compressed Sensing-Based Channel Estimation With Virtual Oversampling for Digital Terrestrial Television Broadcasting

This paper proposes a low-complexity compressed sensing (CS)-based time domain channel estimation with virtual oversampling for OFDM-based DTTB system. CS technique is first applied to sparse channel estimation in integrated services digital broadcasting-terrestrial (ISDB-T) system. Unfortunately, the CS-based time-domain channel estimation suffers from a performance degradation under the existence of fractional delay. Fractional delay is a common issue in time domain-based channel estimation due to sampling imperfection of channel delay time. Therefore, we propose virtual oversampling to deal with the fractional delay without increasing the signal bandwidth. Furthermore, exploiting the fact that the rate of change of path delay is slower than the path gain, a modified orthogonal matching pursuit is also proposed to reduce computational complexity. Numerical analyses of bit error rate and computational complexity are given to verify effectiveness of the proposed scheme.

A Proposal for the Next Generation of ISDB-TB using FBMC in a SDR Implementation on GNU Radio Environment

Digital TV standards are continuously evolving in order to provide users with livelier experiences. Nowadays, the trend in digital TV is to investigate the evolution of present systems to enable the transmission of 8K video programs. In order to do so, the physical layer of the system has to be adapted to be able to transmit the required bit rate. On the other hand, the modulation technique Filter Bank Multi Carrier (FBMC) has been widely studied in many communication systems, like 5G and WiMax, as a viable alternative to Orthogonal Frequency Division Multiplexing (OFDM). This fact stems from the better utilization of bandwidth and more robustness to interferences in FBMC. This paper presents a study of the use of FBMC in Integrated Services Digital Broadcasting Terrestrial B (ISDB-TB), developing a complete software radio model on GNU Radio, and accomplishing comparisons with the OFDM system. The GNU Radio has been an important tool in order to simulate communications system, due to fact that it is a free and open source software, that allows analyzes and measurements in real time.

We Measured and Have Expanded the Space for More Services in Digital Television

Digital TV stations transmissions can be configured so that the useful bit rate can accommodate a variable amount of information. We observed that the ISDB-Tb (Integrated Services Digital Broadcasting Terrestrial, version B) bit rate is not fully utilized by the broadcasters. Hence, services can be added beyond to the content of television without this being hindered.

Spectrum Sensing System in Software-defined Radio to Determine Spectrum Availability

Spectrum sensing is an integral part of cognitive radio, which seeks to address the perceived spectrum scarcity that is caused by inefficient utilization of the available spectrum. In this paper, a spectrum sensing system using energy detection for analog TV and FM broadcast transmitters as well as modified Integrated Services Digital Broadcasting Terrestrial (ISDB-T) signals is implemented on a software-defined radio platform using GNU’s Not Unix (GNU) radio and the N200 Universal Software Radio Peripheral (USRP). Real-time implementation and experimental tests were conducted in Metro Cebu, a highly urbanized area in the southern part of the Philippines. Extensive tests and measurements were necessary to determine spectrum availability, particularly in the TV band. This is in support of the Philippine government’s efforts to provide internet connectivity to rural areas. Experimental results have so far met IEEE 802.22 requirements for energy detection spectrum sensing. The designed system detected signals at -114 dBm within a sensing time of 100 ms. Furthermore, the required PSUBd/SUB(≥ 90) and PSUBfa/SUB(≤10) of the standard were also achieved with different thresholds for various signal sources representing primary users.

Feasibility Study on Aircraft Positioning by Using ISDB-T Signal Delay

This letter is concerned with experimental results of aircraft positioning by using terrestrial digital broadcasting signal delay. Passive bistatic radar (PBR) is expected to be a conventional primary surveillance radar alternative, and it can also achieve expanding coverage area of the conventional radar. The PBR sensors allow the detection and tracking of noncooperative targets illuminated by transmitters of opportunity such as communication systems [digital terrestrial television broadcasting (DTTB), AM/FM, 3G/LTE base stations, etc.] or conventional radar system. Especially, the DTTB signals are the most expected radio waves. In this letter, we show experimental results of aircraft positioning by using the signal delay profile of DTTB whose type is Integrated Services Digital Broadcasting–Terrestrial (ISDB-T) used in Japan. It will be shown that the ISDB-T signal delays are useful surveillance systems.

On Enhancing the Pilot-Aided Sampling Clock Offset Estimation of Mobile OFDM Systems

Sampling Clock Offset (SCO) estimation is an important issue in Orthogonal Frequency-Division Multiplexing (OFDM) systems because sampling frequency mismatch between the transmitter and the receiver may severely degrade the system performance due to the loss of orthogonality between the subcarriers. SCO estimation in mobile environment is quite challenging since channel variation leads to an additional phase rotation that masks the SCO effects. However, most of the existing techniques rely on the assumption of a time-invariant channel and become considerably inaccurate in a mobile environment. In this paper, we propose an improvement to an existing pilot-aided SCO estimator aiming to provide robustness against channel variations. Performance was evaluated through simulations in an ISDB-T (Integrated Services Digital Broadcasting Terrestrial) compliant system and the results have shown a considerable improvement for all ranges of signal-to-noise ratios, specially for higher Doppler spread.

Implementation of Compact Polyphase Channel-Select Filters for Multistandard Broadcasting

An 8th-order fully electronically programmable complex filter based on current amplifiers for multistandard mobile TV applications is presented. Its center frequency, pole frequency, and gain are electronically programmable to accommodate both Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) and Terrestrial Digital Multimedia Broadcasting (T-DMB). The proposed solution avoids employing capacitor and resistor arrays leading to a compact design (0.51 $\mathrm{mm}^{2}$ ). It adopts minimum number of amplifiers for maintaining relatively low power consumption (2.55 mW). The experimental results obtained from a 0.18- $\mu $ m digital CMOS process show that the proposed design achieves spurious-free dynamic range (SFDR) of better than 65 dB and image rejection ratios of more than 38 dB.

Transport Stream Analysis of a ISDB-T Signal Using an Embedded and Reconfigurable System

Quality management is an important criterion to evaluate broadcaster's transmission system integrity, which can be affected by radiofrequency signal impairments and by coding, multiplexing, and/or modulation errors. The international system integrated services digital broadcasting - terrestrial (ISDB-T) was designed to provide a reliable reception, even with interferences inherent to radio wave propagation. However, channel noise, as well as problems in the transmission system, may corrupt the transport stream (TS), causing image failures and, depending on the error level, even a complete loss of signal. This paper presents a supervisory system consisting of an ISDB-T front-end with spatial diversity of four branches, associated with a system-on-chip (SoC) board, in order to analyze the TS of any broadcaster, identifying transmission errors in real-time. The system continuously searches received data for impairments such as cyclic redundancy check - 32 and continuity counter errors, table/section intervals, and program clock reference jitter. The SoC comprises a field programmable gate array that includes a hard-wired processor, used to compute and show the analysis results.

ISDB-T 시스템을 위한 SNR 추정기 구현

본 논문에서는 ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) 시스템을 기반으로 한 동기 방식의 OFDM 시스템에서 방송 시스템에서 중요한 지표가 되는 SNR (Signal to Noise Ratio) 추정기를 구현하고자 한다. 다양한 SNR 추정 방법 중 복잡도가 적어 ASIC 설계에 적합한 MSE (Mean Square Error) 알고리즘을 사용하여 ISDB-T 시스템의 OFDM 세그먼트를 구성하고 있는 요소 중 방송 정보 데이터를 사용하여 SNR을 추정하는 방법과 분산 파일럿 신호를 사용하여 SNR을 추정하는 방법을 각각 RTL(Register Transfer Level)로 구현하였다. 두 방법을 이상적인 채널인 AWGN (Additive White Gaussian Noise) 채널뿐만 아니라 SFN(Single Frequency Network) 채널 및 주파수 선택적 페이딩 채널과 같이 왜곡된 채널에서 모의실험을 통해 성능을 비교하고 RTL 구현을 통해 복잡도를 비교하여 분산 파일럿 신호를 사용하여 SNR을 추정하는 방법의 성능과 구현의 용이함을 보였다. This paper aims to realize a Signal to Noise Ratio Estimator which constitutes a critical index of the broadcasting system in OFDM system with a synchronized type based on ISDB-T system. Of the elements which are comprising OFDM segments of ISDB-T system using the MSE algorithm suitable for ASIC design owing to its low complexity among a diverse SNR estimation methods, SNR estimation method using the broadcasting information data and the SNR estimation method using scattered pilot signal were realized by RTL. These two methods were compared in terms of their performance through simulation test not only in the AWGN channel which is an ideal channel, but also in SFN channel and frequency selective fading channel, which are distorted channels. Complexity of two methods were also compared through RTL realization. As a result of this comparison analysis, it was concluded that the SNR estimation method using scattered pilot signal shows more excellent performance and easiness in realization.

멀티모드 이동 방송용 EWS(Emergency Warning System) 송·수신 시스템 설계 및 구현

This paper presents the design and implementation of a multi-mode mobile broadcasting Emergency Warning System (EWS) transmission and reception system which enables the propagation of disaster information using the encoding and transmission, reception and decoding methods specified in diverse mobile broadcasting standards. The implemented system supports global mobile broadcasting standards such as Terrestrial Digital Multimedia Broadcasting (T-DMB), Digital Video Broadcasting-Handheld (DVB-H), Integrated Services Digital Broadcasting-Terrestrial (ISDB-T), and the Digital Radio Mondiale (DRM) digital radio standard. The system consists of two key part: an encoding/transmission part and a reception/decoding part. The multi-mode mobile broadcasting EWS encoding and transmission system generates EWS data according to each broadcasting specification. The generated EWS data is then transmitted through a channel interface which meets the commercial broadcasting equipment specification. The receiver system receives and decodes the EWS data on a single hardware platform and can display the results on screen. Verification and conformity testing has been carried out on the implemented system by transmitting emergency data for each mode in real-time and displaying the received information in text on the receiver display. 한국통신학회논문지 '12-12 Vol.37C No.12