Digital Television Terrestrial Multimedia Broadcasting Research Articles

Channel-Aided Transmission Parameter Signalling Detection for DTMB-A

For reliable synchronization and transmission parameter signalling (TPS) detection, the preamble based on distance detection (PBDD) is adopted in the digital terrestrial television multimedia broadcasting - advanced (DTMB-A) standard. However, the conventional signalling detection methods do not take the channel information into consideration and will undergo severe performance loss over frequency-selective channels, especially those with strong and long delay echos. In this paper, a novel two-stage TPS detection method is proposed based on the preamble for DTMB-A system, which utilizes the channel information to enhance the detection accuracy. After coarse distance evaluation, the equalization will be performed on the possible candidate subcarriers to reconstruct the OFDM signalling block, hence a more reliable correlation statistic can be obtained to achieve more accurate signalling detection. As demonstrated in the simulations, the detection accuracy can be improved remarkably by compensating the impact of the transmission channel compared with the traditional detection schemes, while the increment of the computational complexity is acceptable.

Carrier Phase Ranging with DTMB Signals for Urban Pedestrian Localization and GNSS Aiding

China developed its Digital Television (DTV) standard in 2006, known as Digital Television Terrestrial Multimedia Broadcasting (DTMB), which employs time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) as the modulation method. In contrast to Global Navigation Satellite Systems (GNSSs), DTV signals have higher transmitting power, wider coverage, larger bandwidth, and fixed transmitter location. This paper explores the positioning performance of DTMB signals, and the potential to improve GNSS positioning accuracy in urban environments. Specifically, a solution is proposed, and a software-defined radio receiver is developed for wireless localization. Without changing the current signal structure, the pseudorandom noise (PN) sequences in the signal are used for signal acquisition and carrier phase ranging. The carrier phase of the first arrived path is extracted by the least squares matching pursuit method. Both static and dynamic field tests were conducted to verify the proposed ranging and positioning method. Centimeter-level ranging accuracy was achieved in the static scenario, while meter-level ranging accuracy was achieved in the dynamic scenario. As one possible application, the proposed ranging method was combined with GPS pseudorange measurements to achieve higher accuracy position results in an urban pedestrian scenario, especially when there is only a limited number of visible satellites.

Spectrum Sensing for DTMB System: A CNN Approach

Spectrum sensing for the Digital Television Terrestrial Multimedia Broadcasting (DTMB) system is considered in this paper. A novel method, which contains a preprocessing method of partition and averaging, a convolutional neural network (CNN) and a threshold chosen scheme, is proposed to solve this problem. In the spectrum sensing process, the received signal is firstly preprocessed by a scheme of partition and averaging. Then it is fed into the well-trained CNN. The posterior probability of the signal being noise is output. Based on the Neyman-Pearson theorem, a threshold can be chosen by the Monte Carlo method. The result of spectrum sensing can be obtained by comparing the posterior probability with the threshold and the complexity of the proposed method is also analyzed. Through computer simulations, the advantage of the proposed method is demonstrated. At a low signal-to-noise ratio (SNR), the proposed method can achieve a satisfactory detection probability. Besides, the proposed method is robust to different SNRs and has good generalization performance under different noise assumptions. When the proposed method is transferred to sense DTMB signal under time dispersive channels, the performance does not deteriorate and even can be better, which shows the robustness of the proposed method to the time dispersive channels.

Spectrum Sensing for DTMB-A System Using Accumulated Autocorrelation

The digital terrestrial television multimedia broadcasting - advanced (DTMB-A) system demands an accurate and reliable spectrum sensing method for its implementation. In this paper, an effective method based on weighted autocorrelation of the frame headers is proposed for single-node spectrum sensing in DTMB-A. The decision threshold, lower bounds and miss detection rate of the proposed method are researched in detail. Simulation results indicate that the proposed method shows better sensing accuracy and robustness compared with the existing methods under various channels, while the cost of its higher complexity is acceptable. Furthermore, by using piecewise-weighted information fusion, the proposed method is extended into cooperative spectrum sensing to overcome the problems of shading and hidden terminals in networking. Our work ensures the efficiency of spectrum sensing and contributes to the better use of DTMB-A system in future applications.

Field Trials of UHDTV Broadcasting over DTMB-A System

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Digital terrestrial television broadcasting (DTTB), the most fundamental infrastructure for audio/video transmission networks, can support multimedia information services, targeting lots of audiences within a wide area in an efficient way. The advanced version of digital television/terrestrial multimedia broadcasting (DTMB-A), one of the second-generation DTTB standards of the International Telecommunication Union, provides higher spectrum efficiency and better transmission reliability compared with DTMB. By adopting a more flexible frame structure, advanced forward error correction coding, and improved constellation mapping, it is confirmed that the transmission capacity of DTMB-A is around 30% higher than that of DTMB under the same conditions carried out in laboratory tests and field trials on DTMB-A. In this paper, the trial network and the measurement results focusing on ultrahigh-definition television (UHDTV, both UHD-1/4K and UHD-2/8K) and the single-frequency network (SFN) are presented in detail. The preliminary work on the Integrated Communications and Broadcasting Network (ICBN) concept using both DTMB-A and fifth-generation (5G) networks for UHDTV delivery is also highlighted</i> .

Using DTMB-Based Passive Radar for Small Unmanned Aerial Vehicle Detection

There is inevitable polarization angle deviation between the target echo signal and the direct path signal of illuminator of opportunity (IO) in passive radar. In order to investigate the potential performance loss in target detection induced by the random deviation, small unmanned aerial vehicle (UAV) detection experiments with digital television terrestrial multimedia broadcasting- (DTMB-) based passive radar are conducted in this paper. Experimental results show that the polarization angles of the clutter signal and target echo signal are inconsistent. When the polarization diversity technology is used to suppress the clutter signal, the processing performance of the target echo signal may be reduced. On the premise that clutter is effectively suppressed by the processing algorithm, polarization synthesis can maximize the target echo signal processing gain. The effectiveness of the target localization algorithm combining time difference of arrival (TDOA) and direction of arrival (DOA) is also verified with polarization diversity reception in this paper.

TDS-OFDM based Digital Television Terrestrial Multimedia Broadcasting Standards

As the most popularly utilized broadcasting network, digital terrestrial television broadcasting (DTTB) can provide multimedia information coverage for the broad audience in a very efficient way because of its characteristic of wide-range coverage and mobile reception ability. After promulgating the first generation DTTB standard, digital terrestrial/television multimedia broadcasting (DTMB), in 2006, China began to research and develop the next generation DTTB standard, namely DTMB-advanced (DTMB-A), aiming to support higher spectrum efficiency and further improve transmission reliability. In 2019, DTMB-A was accepted by ITU as the second generation international DTTB standard (as System C). Similar to DTMB, time-domain synchronous - orthogonal frequency division multiplexing (TDS-OFDM) based multi-carrier modulation scheme is adopted by DTMB-A. Thanks to the more flexible frame structure, advanced error correction coding and improved constellation mapping, DTMB-A offers 30% higher transmission capacity than DTMB under the same transmission conditions. Thus, DTMB-A can support both fixed and mobile reception more efficiently, and provide users with higher quality services such as ultra-high definition television (UHDTV). This paper first gives details of key technologies at the transmitter of DTMB/DTMB-A and introduce core algorithms at the receiver. Both laboratory test and field trial results will then be provided and analyzed, especially for the application of 4K UHDTV and single frequency network (SFN).

Reference Signal Reconstruction Under Oversampling for DTMB-Based Passive Radar

The robust reconstruction of the reference signal is one of the key technologies in passive radars. This paper investigates the reference signal reconstruction problem for digital television terrestrial multimedia broadcasting (DTMB)-based passive radar. The conventional digital signal processing for the DTMB signal is usually based on the assumption of the equal bandwidth sampling (EBS) in which the sampling rate is equal to the nominal bandwidth 7.56 MHz defined in the DTMB standard. But we reveal that the high-frequency subcarriers of the DTMB signal are aliased under the EBS, which will degrade the reconstruction performance. Thus we suggest the oversampling approach for the DTMB-based passive radar. The least squares (LS) channel estimation under oversampling is thoroughly analyzed. Moreover to solve the problem that the LS algorithm cannot estimate the time-domain response of the channel under oversampling, we propose two modified LS channel estimation algorithms, namely the Tikhonov regularization LS and reduced rank approximation LS. The advantages of the reference signal reconstruction under oversampling over that under EBS are validated by both the simulation and field experimental data.

Cochannel Interference in DTMB-Based Passive Radar

This paper discusses the situation with cochannel interferences in the digital television terrestrial multimedia broadcasting (DTMB)-based passive radars. The cochannel interference comes from the station that works in the same frequency with the adopted illuminator of opportunity (IO), but broadcasts different contents. Based on the frame structure of the DTMB signal, the features of the cochannel interference are elaborated. Analyses show that several interfering peaks present in the range-Doppler map when the cochannel interference has the same frame header with the IO. These interfering peaks can be used to identify the existence of cochannel interferences. In addition, to eliminate the influences of the cochannel interference on the target detection, we propose a method that can effectively remove the interfering peaks. The simulation and field experimental results verify the effectiveness of the proposed method.

Indoor positioning using public FM and DTMB signals based on compressive sensing

Location-Based Services have become an indispensable part of our daily life, the sparsity of location finding makes it possible to estimate specific position by Compressive Sensing (CS). Using public Frequency Modulation (FM) broadcasting and Digital Television Terrestrial Multimedia Broadcasting (DTMB) signals, this paper presents an indoor positioning scheme, which is consisted of an offline stage and an online stage. In the offline stage, the Received Signal Strength (RSS) at the Reference Points (RPs) is measured, including the average and variance of public FM broadcasting and DTMB signals. In the online stage, the K-Weighted Nearest Neighbor algorithm is used to fulfill coarse positioning, which is able to narrow the selection scope of locations and choose partial RPs for accurate positioning. Then, the accurate positioning is implemented through CS. Experiment shows that the average positioning error of the proposed scheme is 1.63m. What's more, a CS-based method has been proposed in this paper to reduce the labor cost when collecting data. Experiment shows the average positioning error is 2.04m, with the advantage of a 34% labor cost reduction. Experiment results indicate that the proposed system is a practical indoor positioning scheme.

PN Signal as a New Illuminator of Opportunity for Passive Radar Applications

In this letter, we use the known pseudorandom noise (PN) signal in the digital television terrestrial multimedia broadcasting (DTMB) system as a new illuminator of opportunity for the passive radar. We propose a computationally efficient signal processing method for the PN-based passive radar (PNPR). The proposed method takes advantage of the distinctive structure of the PN signal and constructs a locally remapped PN signal. The circular cross-correlation between the remapped PN signal and the original PN signal is an ideal impulse function. Thus, the PNPR even does not need to do the clutter cancellation. The proposed method is validated via both the simulated and experimental data.

Indoor positioning using public FM and DTMB signals based on compressive sensing

Location-Based Services have become an indispensable part of our daily life, the sparsity of location finding makes it possible to estimate specific position by Compressive Sensing (CS). Using public Frequency Modulation (FM) broadcasting and Digital Television Terrestrial Multimedia Broadcasting (DTMB) signals, this paper presents an indoor positioning scheme, which is consisted of an offline stage and an online stage. In the offline stage, the Received Signal Strength (RSS) at the Reference Points (RPs) is measured, including the average and variance of public FM broadcasting and DTMB signals. In the online stage, the K-Weighted Nearest Neighbor algorithm is used to fulfill coarse positioning, which is able to narrow the selection scope of locations and choose partial RPs for accurate positioning. Then, the accurate positioning is implemented through CS. Experiment shows that the average positioning error of the proposed scheme is 1.63m. What's more, a CS-based method has been proposed in this paper to reduce the labor cost when collecting data. Experiment shows the average positioning error is 2.04m, with the advantage of a 34% labor cost reduction. Experiment results indicate that the proposed system is a practical indoor positioning scheme.

Sub-Peaks Suppression for DTMB Signal Based Passive Detection Systems

Passive detection is an effective way to monitor the security of the low-altitude airspace. Tsinghua University’s independently developed Digital Television Terrestrial Multimedia Broadcasting (DTMB) signal enjoys a high coverage in China, whereas few studies have addressed the passive detection based on this kind of signal in detail. Ambiguity function is utilized to detect the targets, however there exists sub-peaks caused by the frame format of the DTMB signal. In this paper, we propose a sub-peaks suppression scheme based on DTMB. The influence of the repeated PN sequence and the power difference on sub-peaks generation are analyzed. To tackle the sub-peaks problem, sampled Linear Frequency Modulation signal with the same power of the frame body is adopted to replace the original PN sequence in DTMB reconstruction. The experimental results show that our proposed method can effectively mitigate the sub-peaks problem.

Indoor localization using FM radio and DTMB signals

AbstractIndoor localization systems based on Wi‐Fi signal strength fingerprinting techniques are widely used in office buildings. However, a general problem of these systems pertains to Wi‐Fi signal degradation due to the environmental factors. And also, these systems cannot be used in the environments not covered with Wi‐Fi signals or the environments with only a single Wi‐Fi access point. In this paper, a new indoor location fingerprinting system using both FM radio and Digital Television Terrestrial Multimedia Broadcasting (DTMB) signals is proposed. First, the indoor location fingerprinting using FM radio and DTMB signals is theoretically analyzed to confirm its feasibility. Then, a specially designed combined strength fingerprinting location algorithm is proposed for the location system, which is achieved on the USRP2 platform. Finally, the system is tested in a typical indoor environment. The theoretical analysis and the tests show that the indoor location fingerprinting system using FM radio and DTMB signals has a similar localization accuracy to the Wi‐Fi signal strength fingerprinting location system, while it has a wider coverage area, a lower maintenance cost, and more stable signal strength, which makes it a practical indoor positioning method.

Backward Compatible Multiservice Transmission Over the DTMB System

In this paper, a backward compatible multiservice transmission scheme over the digital television terrestrial multimedia broadcasting (DTMB) system is proposed, which is based on embedded constellation and bit division multiplexing. With the proposed scheme, simultaneous transmission of original services and multiple augmented services can be supported in the DTMB system in a backward compatible manner. No additional RF spectrum is required and no additional complexity is introduced to the legacy DTMB receivers. Two schemes over the DTMB system are proposed toward two different requirements, which are maintaining the transmission rate of original services and maintaining the reception SNR-threshold of original services, respectively. Average mutual information analysis and bit error ratio simulations are performed. In both schemes, the increment in the throughput of the DTMB system can be over 7.6 Mb/s in typical mode.

Reception Quality Prediction in a Single Frequency Network for the DTMB Standard

Single frequency network (SFN) is an attractive scheme for the digital television terrestrial broadcasting (DTTB) coverage with efficient utilization of the spectral resources. In this paper, a method featuring low complexity and low workload is proposed to estimate the reception quality under the SFN environment with the maximum delay spread of the artificial multipath no longer than the guard interval. Based on the analysis of error probability and channel capacity, this method supports an unambiguous prediction of the signal-to-noise ratio (SNR) threshold according to the parameters of received signals, which is thus meaningful for system evaluation. We applied this method to the digital television/terrestrial multimedia broadcasting (DTMB) systems, and carried out the laboratory measurements for performance verification. The predicted results show a satisfactory match with the measured results, validating the accuracy and effectiveness of the proposed method.

Next-generation digital television terrestrial broadcasting systems: Key technologies and research trends

In the last two decades, digital television terrestrial broadcasting (DTTB) systems have been deployed worldwide. With the approval of the fourth DTTB standard called Digital Television/ Terrestrial Multimedia Broadcasting (DTMB) by International Telecommunications Union (ITU) in December 2011, the research on first-generation DTTB standards is coming to an end. Recently, with the rapid progress of advanced signal processing technologies, nextgeneration DTTB systems like Digital Video Broadcasting-Terrestrial-Second Generation (DVB-T2) have been extensively studied and developed to provide more types of services with higher spectral efficiency and better performance. This article starts from the brief review of the first-generation DTTB standards and the current status of emerging second-generation DTTB systems, then focuses on the common key technologies behind them instead of describing the specific techniques adopted by various standards. The state-of-the-art, technical challenges, and the most recent achievements in the field are addressed. The future research trends are discussed as well. In addition, the scheme of integrating DTTB and Internet is proposed to solve the crucial problem of information expansion.

An Area-Efficient Reconfigurable LDPC Decoder with Conflict Resolution

Based on Turbo-Decoding Message-Passing (TDMP) and Normalized Min-Sum (NMS) algorithm, an area efficient LDPC decoder that supports both structured and unstructured LDPC codes is proposed in this paper. We introduce a solution to solve the memory access conflict problem caused by TDMP algorithm. We also arrange the main timing schedule carefully to handle the operations of our solution while avoiding much additional hardware consumption. To reduce the memory bits needed, the extrinsic message storing strategy is also optimized. Besides the extrinsic message recover and the accumulate operation are merged together. To verify our architecture, a LDPC decoder that supports both China Multimedia Mobile Broadcasting (CMMB) and Digital Terrestrial/ Television Multimedia Broadcasting (DTMB) standards is developed using SMIC 0.13µm standard CMOS process. The core area is 4.75mm2 and the maximum operating clock frequency is 200MHz. The estimated power consumption is 48.4mW at 25MHz for CMMB and 130.9mW at 50MHz for DTMB with 5 iterations and 1.2V supply.

Novel Approach to Support Multimedia Services Over DTMB System

In the conventional digital television terrestrial multimedia broadcasting (DTMB) systems, all the transport streams (TS) from various programs are multiplexed in the level of TS packets, which have the same interleaving, constellation mapping, channel coding, and thus the same quality of service (QoS). Moreover, due to the convolutional interleaving mode, the receivers have to be turned on all the time to obtain the designated data until all the received signals are de-interleaved. In this paper, for DTMB systems, the concept of the physical sub-channel (PSC) in time-frequency domain is proposed, and the scheme to support services with different QoS requirements is also addressed. Based on these techniques, a novel approach to support multimedia services over DTMB systems in a backward compatible manner is proposed and evaluated by computer simulations.

A Novel Scheme of Joint Channel and Phase Noise Compensation for Chinese DTMB System

In broadband wireless communication systems, orthogonal frequency division multiplexing (OFDM) will suffer from severe performance degradation in the presence of phase noise (PHN) especially for the applications with narrow subcarrier spacing to support high bit rate. In the Chinese digital television terrestrial multimedia broadcasting (DTMB) system the time-domain synchronous OFDM (TDS-OFDM) is adopted in which the time-domain pseudo noise (PN) sequences and OFDM data block are combined into a signal frame. Continuous transmission parameter signaling (TPS) symbols are inserted into OFDM data blocks in the frequency domain which can be used for phase noise estimation. In this paper, joint channel estimation and phase noise reduction algorithms are investigated for DTMB systems using the common phase error (CPE) of PN sequences as an intermediate variable of channel frequency response (CFR) during estimation stage and removing it at compensation stage. A simplified channel and phase noise equalization method performed in both frequency and time domain is studied to suppress the distortion. Simulations prove that this proposed scheme has low complexity and works well under additive white Gaussian noise (AWGN) and multipath fading channels.