Dream DRM Receiver 1.6.25 review
DownloadDigital Radio Mondiale, also known as DRM, is a new digital radio standard for the long-, medium- and short-wave ranges
|
|
Digital Radio Mondiale, also known as DRM, is a new digital radio standard for the long-, medium- and short-wave ranges.
The standard was formed by a consortium in co-operation with the International Telecommunication Union (ITU). The new system offers the radio stations and new service providers access to the multimedia age with small bit rates for large target areas and long distances.
The bandwidth of a DRM bandpass signal is less than 20 kHz and the number of carriers used in the OFDM-modulation is relatively small (max. 460). These features motivate a real-time software implementation of a DRM-receiver on a conventional personal computer (PC) using the sound card as the input and output device. A long, medium and short wave front-end with an intermediate frequency (IF) between 5 kHz and 15 kHz is used to receive the DRM signal.
Any commercial front-end with an IF of 455 kHz should be usable by adding a 455 kHz to 12 kHz adaptor (assumed the receiver bandwidth is sufficient for a DRM signal).
With this software project we intend to implement a working software receiver with, at least, the basic features. Since this project is created at a university and the fundamental idea of such an institution is to teach and stimulate the creativity, this source-code is free under the GNU-General Public License (GPL).
Dream is a development project which uses the open source model to improve DRM technology. The main aim of this project is to implement and test new research results on an existing system, whereby the synchronization and channel estimation is of special interest.
The programming-language is C++. The code runs under Microsoft Windows and Linux. Start of the project was June 2001.
Although this software is going to be distributed as free software under the terms of the GPL this does not mean that its use is free of rights of others. The use may infringe third party IP and thus may not be legal in some countries.
The intended audience of the Dream software are people who are interested in how to decode a DRM stream and want to learn from the algorithms used in this software and people who want to help us improving the performance of the receiver and the source code.
Requirements:
FFTW2 or later
FFTW2-devel or later
What's New in This Release:
added reverbration effect for masking audio drop-outs. A switch was added to the evaluation dialog to enable or disable this feature.
added error detection for SDC channel (show yellow light (LED) if SDC data seems to be corrupted)
bug fix: when SDC data was used completley the CRC was read as length of entity data which was wrong. Now, the length of data read is checked whether it has reached the total number of bits available
do not show bit-rate in service selector label if bit-rate is zero
apply hanning window to input spectrum plot
use lower value of Doppler for initialization phase of Wiener filter in time direction (aliasing peaks in impulse response are lower now are re-synchronization)
use shorter filter lengths for Wiener filtering for channel estimation in time direction
improved initialization phase for DRM frame synchronization
Only use DRM frame synchronization based on time pilots since the algorithm based on the impulse response does not perform well in case of a very long IR
added waterfall display for input spectrum
use smaller buffers to speed up audio output after re-synchronization
for long symbol interleaving, try to decode data before the whole interleaver buffer is filled by setting the uninitialized symbols to erasure
bug fix for time-sync-acquisition initialization
moved bandpass-filter and frequency offset correction from OFDM module in Frequency-Sync-Acquisition module,
improved bandpass filter for receiver -> better interfere rejection BUT: under normal conditions, this filter will degrade the performance a little bit since it attenuates the OFDM carriers at the borders a bit
store input data vector which is used for frequency offset acquisition and output entire data vector when acquisition was successful -> speeds up audio output when re-synchronization is needed
fixed problem with high CPU utilization when no DRM signal was received
WINDOWS: make the software more robust against high CPU utilization by other applications by increasing the thread priority of the Dream signal processing thread
bug fix: time sync Hilbert filter must be shifted to virtual intermediate frequency
added informations about robustness mode, MSC scheme, protection levels in log long (a log file which is generated parallel to the standard log file (compatible to the DRM software radio))
display sample rate offset in ppm, too
do not show mode , protection levels and MSC constellation in log long until FAC CRC was correct
resize windows fix for Linux by Andrea Russo
add name of picture in tool-tip (in case a MOTSlideShow picture is shown). The tool-tip is shown when the user moves the mouse over the picture
Journaline pages can be saved as HTML (patch from Andrea Russo)
added preview for stations dialog, thanks to Andrea Russo for his patch! A new menu was added for setting the preview time. If a DRM transmitter will transmit no later than the preview time but is not active, an orange marker is shown next to this transmission (in the list)
improved averaging of estimation of impulse response: the time shift is considered more exactly (sample rate offset estimation should be improved, too)
added new column to stations list showing the days the transmission is active. This code is based on a patch by Andrea Russo
added Weighted Modulation Error Ratio (WMER) and MER calculation based on the MSC cells. The values are shown in the evaluation dialog
added SDC data entity type 3 (information is not used right now) and some more error checking
added SDC data entity type 4 (information is not used right now)
added SDC type 7 (not used right now)
added class for storing alternative frequencies transmitted in SDC type 3
store plot type selection for evaluation dialog
Dream DRM Receiver 1.6.25 keywords