Digital Radio Mondiale System Research Articles

DRM DIGITAL BROADCASTING SYSTEM AUDIO PATH QUALITATIVE CHARACTERISTICS

The Digital Radio Mondiale (DRM) digital broadcasting system is the only ITU-approved digital broadcasting system for the LF, MF and HF bands. Numerous theoretical and field studies, as well as operating experience over the past 20 years, have allowed a good study of digital broadcasting networks organization according to this standard. However, some of the issues related to the audio path formal characteristics were not considered. The article discusses the audio coders used in the DRM system and the available data rates in various immunity modes. A set of test signals for instrumental measurements and listening has been developed. The results of experimental measurements for various data rates are presented. It is shown that the range of modulating frequencies in 7 modes of immunity is not narrower than for FM transmitters. In another 5 modes of noise immunity, the range of modulating frequencies is narrower than for FM transmitters, but wider than for AM transmitters. It is confirmed that at data rates of more than 16.5 kbps, the DRM transmitter signal quality becomes no worse than AM signal transmitter quality. Above 24 kbps, the DRM transmitter signal quality becomes comparable to that of an FM transmitter.

Improved Frequency Offset Estimation Based on the DRM System

In this paper, an improved frequency offset estimation algorithm is proposed. It can effectively utilize pilot symbols in orthogonal frequency division multiplexing (OFDM) signals based on the Digital Radio Mondiale (DRM) system. In order to reduce the computational difficulty, the difference values of adjacent pilot symbols in the DRM system are sequentially combined into a pilot difference set. The pilot difference set is analyzed by inductive statistics so that the frequency offset estimator has higher calculation efficiency and accuracy. Through the induction statistics of multiple groups of symbols, the contingency of results can be effectively avoided. By comparing the performance of the proposed frequency offset estimator with that of the traditional estimators, the proposed algorithm has higher frequency offset estimation accuracy.

Joint Estimation of Symbol Timing and Sampling Frequency Offset for CDD-OFDM-Based DRM Systems

In this paper, an efficient symbol timing offset (STO) and sampling frequency offset (SFO) estimation scheme is proposed in an orthogonal frequency division multiplexing-based digital radio mondiale system using cyclic delay diversity. By using a periodic nature of channel transfer function, cyclic delay and pilot pattern with a maximum channel power are chosen, which aids to enable a robust estimation of STO and SFO against frequency selectivity of the channel. As a performance measure, the mean squared error of the proposed scheme is theoretically derived and is verified through simulations. By simulation results, the proposed estimation scheme is proved to profit from properly selected cyclic delay and pilot pattern, with a superior performance over the conventional estimation scheme.

Application of Digital Radio Mondiale System in Medical Signal Transmission.

In order to study the application of digital radio mondiale (DRM) broadcasting system in medical signal transmission, taking sinusoidal signal as an example, the transmission format is designed, and the data transmission function of the system channel is verified and applied to the transmission of medical information. Taking the traditional electrocardiogram signal and magnetic resonance image as examples, the two kinds of medical information are successfully transmitted according to the appropriate transmission format. As the simplest and easiest to deploy communication mode, the system will provide the fastest and timeliest information and emergency communication function for disaster relief and rescue, which is a practical and valuable application.

On the efficiency of PAPR reduction schemes deployed for DRM systems

Digital Radio Mondiale (DRM) is the universally, openly standardized digital broadcasting system for all frequencies including LW, MW, and SW as well as VHF bands. Alongside providing high audio quality to listeners, DRM satisfies technological requirements posed by broadcasters, manufacturers and regulatory authorities and thus bears a great potential for the future of global radio. One of the key issues here concerns green broadcasting. Facing the need for high-power transmitters to cover wide areas, there is room for improvement concerning the power efficiency of DRM-transmitters. A major drawback of DRM is its high peak-to-average power ratio (PAPR) due to the applied transmission technology based on Orthogonal Frequency Division Multiplexing (OFDM), which results in non-linearities in the emitted signal, low power efficiency, and high costs of transmitters. To overcome this, numerous schemes have been investigated for reducing PAPR in OFDM systems. In this paper, we review and analyze various technologies to reduce PAPR providing that the technical feasibility and DRM-specific system architecture and edge conditions regarding the system performance in terms of modulation error rate, compliance with frequency mask, and synchronization efficiency are ensured. All evaluations are carried out with I/Q signals which are monitored in real operation to present the actual performance of proposed PAPR techniques. Subsequently, the capability of the best approach is evaluated via measurements on a DRM test platform, where achieved transmit power gain of 10 dB is shown. According to our evaluation results, PAPR reduction schemes based on active constellation extension followed by a filter prove to be promising towards practical realization of power-efficient transmitters.

A Robust SFO Estimation Scheme for OFDM-Based DRM with Non-Symmetric Distributed Pilots

This paper proposes a robust sampling frequency offset (SFO) estimation scheme in an orthogonal frequency division multiplexing based digital radio mondiale system with non-symmetrically distributed pilots. In particular, a post fast Fourier transform SFO estimation method is suggested to provide an unbiased estimate of SFO in the presence of frequency selectivity of the channel as well as non-symmetrically distribution of pilot symbols. In order to verify the performance of the proposed frequency-offset estimation scheme, a closed-form expression for the mean square error (MSE) is derived. We show via simulations that the proposed estimation scheme achieves a remarkable robustness against frequency selectivity fading and the theoretical MSE analysis is proven accurate.

Multiple-site investigation of the properties of an HF radio channel and the ionosphere using Digital Radio Mondiale broadcasting

The Digital Radio Mondiale (DRM), one of the new digital radio broadcasting standards, has been designed to overcome typical short wave radio channel difficulties, such as the multipath propagation and fast temporal changes of the received signal level, both related to the properties of the ionosphere along the path of propagation. In particular, some of the RF carriers used in the applied COFDM transmission technique serve to estimate the current state of the radio channel to enable the proper demodulation of the received signal. We have been detecting such RF carriers on select frequency channels (standard DRM broadcast) using a network of recording stations located in different parts of Poland in order to collect data on the HF radio channel. We have been also evaluating the usefulness of this procedure in providing information on the current state of the ionosphere in the refraction region between the transmitter and receivers. When the DRM system becomes more widespread, this method can supplement data that comes from the ionosondes, since it does not require much financial resources and the receivers can be easily scattered over a large area. This paper presents a set of experimental data and its analysis.

Improved and low-complexity sampling frequency offset estimation scheme for DRM systems

In this letter, an improved sampling frequency offset (SFO) estimation scheme is proposed for an orthogonal frequency division multiplexing based digital radio mondiale (DRM) system. An analytical closed-form expression of the mean square error is derived for the proposed SFO synchronization scheme. The new scheme is demonstrated and verified under simulations carried out within the framework of DRM systems.

Low-overhead sampling clock frequency synchronization for OFDM-based DRM systems

In this paper, an improved and low-complexity sampling clock frequency offset (SFO) estimation scheme is proposed for orthogonal frequency division multiplexing (OFDM) based digital radio mondiale(DRM) systems. In order to devise the low-complexity SFO estimator, some modifications on the conventional estimator are highlighted with an emphasis on the selection of pilot subcarrier.

Synchronization Receiver for OFDM-Based FM Broadcasting Systems

The digital radio mondiale (DRM) consortium is now preparing to test and verify the design of DRM plus, prior to standardization, produce a revision to the existing DRM system specification. This p...

Robustness Mode Detection Algorithm in the DRM System

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> To extract parameters of the received signal correctly in the Digital Radio Mondiale (DRM) system, robustness mode detection must be accomplished in time domain. Based on the cyclic prefix (CP), this paper presents a robustness mode detection algorithm in the DRM system. Using the system parameters of each robustness mode separately, the linear-weighted correlation and global maximum correlation-value searching algorithm is applied to detect the robustness mode. Simulations show that the proposed correlation operation in the presented algorithm has a better detection performance than the other correlation operations, making the algorithm accurate under flexible parameter choice. The proposed algorithm overcomes the disadvantage of the existing algorithms that can not detect the mode A signal, and the detection accuracy can exceed 99% for each mode at signal-noise-ratio (SNR) no less than 8 dB. When SNR decreases to 0 dB, the accuracy can also achieve 97%. </para>

Design of a mixed prime factor FFT for portable digital radio mondiale receiver

To achieve better sound quality and to improve data reception, digital radio mondiale (DRM) offers a worldwide initiative to bring analog amplitude modulation (AM) radio into the digital era. DRM systems use coded orthogonal frequency division multiplexing (COFDM) modulation with a multilevel coding scheme to get high resistance to the multipath padding and interference. The bandwidth of a DRM passband signal is less than 20 kHz and the number of carriers used in orthogonal frequency division multiplexing (OFDM) modulation is relatively small. For this reason, DRM systems use non-power-of-two Fast Fourier Transforms (FFT) for OFDM demodulation, such processing gives way to more speed and power consumption in critical paths in DRM receivers. In this paper, we propose a mixed radix-2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> and prime factor FFT algorithm for portable DRM receivers. Using the proposed architecture, we can reduce the processing time and energy consumption compared to conventional digital signal processor (DSP) based DRM receivers.

Estimation of Inchannel-Interference to Digital Radio Mondiale (DRM) Signals During Operation

This paper presents two novel interference measurement estimators for the DRM (Digital Radio Mondiale) system. They are based on the PSD (Power Spectral Density) estimation of the received spectrum, and provide interference estimation whilst the DRM transmitter is in operation. The first estimator provides successful detection of in-channel narrowband interference. If the interferer is an AM co-channel signal, the second estimator takes advantage of the specific characteristics of the DRM modulation to provide accurate measurement of the signal-to-interference ratio value. This allows protection ratio calculus and failure detection caused by interference.

Performance evaluation of low density parity check codes for Digital Radio Mondiale (DRM) system

In Digital Radio Mondiale (DRM) system, achieving good audio quality becomes a challenge due to its limited band-width of 9 or 10kHz and the very bad fading channels. Therefore, DRM needs highly efficient channel coding schemes. This paper, proposes the schemes which use the Low-Density Parity-Check (LDPC) coded Bit-Interleaved Coded Modulation (BICM) schemes for the implementation of DRM systems. Simulation results show that the proposed system is more efficient than the Rate Compatible Punctured Convolutional (RCPC) coded DRM system on various broadcast channels, and may be recommended as a coding technology for Digital Amplitude Modulation Broadcasting (DAMB) systems of China.

Medium Wave DRM Field Test Results in Urban and Rural Environments

This paper presents the results of the first Spanish field trial carried out to analyze a DRM (Digital Radio Mondiale) system in the medium-wave band. A 4-kW average power omni directional ground-wave experimental DRM transmission at a frequency of 1359 kHz was surveyed by means of a measurement vehicle for fixed and mobile reception. Several radial routes starting from the transmitter site provided rural and suburban behavior features of the system. Urban reception trials were performed in several dense and open streets of Madrid, within the expected coverage area. Field strength threshold values were determined for the tested transmission configurations and compared with the AM ground-wave ITU model predictions. Reliability versus distance from the transmitter is stated in this paper for different transmission configurations and the causes of dropouts for different reception conditions are explained. This analysis took into account subjective quality features of each configuration, providing practical planning parameter values.