Digital satellite radio
The Digital Satellite Radio ( DSR ) was in Germany , the first radio broadcast digitally to the listener. In contrast to today's digital broadcasting methods, DSR did not focus on increasing the number of programs, but on improving the transmission quality.
history
The Telefunken company presented the first prototype of a receiver for DSR from August 20 to 26, 1982 at the HIFIVIDEO'82 trade fair in Düsseldorf. In autumn 1984, after a cable pilot project in the same year, the decision was made to use this system. On the occasion of the international radio exhibition in Berlin, Federal Post Minister Christian Schwarz-Schilling officially started digital satellite broadcasting on August 24, 1989. A package with 16 radio programs could now be received nationwide via the two satellites DFS 1 Kopernikus , TV SAT 2 and the cable network of Deutsche Bundespost Telekom. A special DSR receiver was required for reception, which initially cost well over DM 1000. A small flat antenna with an edge length of only 30 cm was also required for satellite reception. At the end of 1994, broadcasting via satellite TV SAT 2 was switched off. As a result, the program could only be received via the Kopernikus satellite or by means of a special receiver via Telekom's cable television .
Rumors about the shutdown and the expiry of the contracts between Telekom and program providers in 1996 meant that from 1995 prices for DSR receivers fell to around DM 200. In total, around one to two hundred thousand DSR radio sets were sold. The "round table" for the development of cable television, convened at the invitation of the DTAG boss at the time, Ron Sommer, decided on May 20, 1997 that the special channels S2 and S3 occupied by the DSR urgently need to be cleared for analog TV broadcasting. That should be done by the end of 1998. On January 16, 1999 at 12:01 am, DSR was switched off despite protests from many listeners. Receivers bought after 1996 received compensation from Telekom.
Until recently, 16 radio stations were broadcast via DSR on 118 MHz (special channels 2 and 3) in the Telekom cable.
- K 01: Bayern 4 Classic
- K 02: SWF 2 / SDR 2, from 1991 S2 Kultur , from August 30, 1998 Südwestrundfunk 2
- K 03: Radio Bremen 2 , 1991 alternating with Deutsche Welle
- K 04: Hessischer Rundfunk 2
- K 05: NDR 3 , from October 8, 1997 NDR Radio 3
- K 06: Star * Sat Radio, from 1997 Deutschlandfunk xtra (mono)
- K 07: Deutschlandfunk
- K 08: West German Broadcasting 3
- K 09: RIAS 1, from 1994 Germany Radio Berlin
- K 10: SR 1 (Europawelle Saar)
- K 11: Radio Belcanto / Antenne Bayern , from 1991 Antenne Bayern, 1992–1993 German broadcaster culture , from 1994 Rhineland-Palatinate Radio 2
- K 12: From 1991 classic radio
- K 13: From 1991 radio ffn , from 1994 RTL Radio
- K 14: From 1991 Radioropa Info , from 1996 Radio Melodie
- K 15: From 1992 RTL Radio , from 1994 MDR Sputnik
- K 16: From 1992 Radio Xanadu , from 1994 Energy Munich
In an endless loop that continued well beyond January 16, 1999, Deutsche Telekom explained the setting of DSR in the following words:
"At the end of January 15th, the operation of DSR has been stopped, as already announced several times. You can obtain further information on the free telephone number 0800 3738393. "
In Switzerland, the DSR was still active for a few years in some cable networks (e.g. Cablecom ) under the name DigitSuperRadio . At times there were two packages there, a German and a Swiss, with a total of 32 channels. The Swisscom Broadcast finally stopped broadcasting on December 31, 2003. At last 15 stations could be received.
The successor to DSR
The radio stations originally broadcast using DSR were broadcast via satellite as an alternative to ADR for analog transponders and DVB-S for digital transponders .
Up to March 1999, except for SWR 2 and SR 1, all former DSR stations of public broadcasting could be received digitally as DVB-C on Telekom's cable television in the ARD and ZDF bouquets. The bit rate of the now compressed digital mode was 192 kbit / s.
To receive these offers, however, new hardware was required (e.g. d-box II) because the DSR tuners are not suitable for receiving ADR or DVB-S signals. However, ADR itself was shut down on April 30, 2012, together with the shutdown of analog television and radio programs.
On August 19, 2005, two weeks before the radio exhibition in Berlin, virtually all ARD radio programs in DVB-S standard could be received via the Astra 19.2 ° East satellite. The bit rate of the stereo programs distributed in MP2 is 320 kbit / s, of which at least 256 kbit / s are used for audio data. The rest can (but does not have to) be used for additional data (RDS-like features, Radio Screen Show RaSS). Although, in contrast to DSR, the MP2 transmission is psychoacoustically data-reduced, at least theoretically a very high sound quality is guaranteed at 320 kbit / s. Coding artifacts are present due to the principle involved, but should not be acoustically noticeable when implemented properly at the very high bit rates. In addition, selected programs on some of the ARD culture waves are also offered in Dolby 5.1 - something that was not possible with DSR. The dynamics processing (“sound processing”) is significantly more moderate or even absent at individual stations on the 5.1 track, so that here there is an even better sound quality transmission path.
In most cable networks, the ARD-DVB radio programs are now also offered in the DVB-C standard, so that extensive coverage (satellite and cable) with high-quality digital radio is guaranteed. The advantages over DSR are above all the significantly greater variety of programs, the possibility of 5.1 surround sound and the direct digital recording option on USB storage media connected to suitable receivers or directly on hard drives built into receivers (PVR). The advantage that results from the use of a sampling rate of 48 kHz is of a more “academic” nature. While with DSR (sampling rate 32 kHz) there was an upper audio cut-off frequency of approx. 15 kHz, at 48 kHz sampling rate an upper cut-off frequency of 20 to 22 kHz is possible, so that the programs are provided accordingly and the sound is not processed.
For a long time, with the exception of a single, very expensive DVB radio receiver, there were no pure DVB receivers on the market that could be set up, maintained and programmed without a connected screen. DSR tuners were always fully operable on the device with the aid of its display, the first DVB receivers, primarily designed for TV use, always required an image output for menu operation. When the analog signal in the cable was switched off, the situation improved and DVB tuners appeared that can be operated and set independently of an image output.
The disadvantage compared to DSR is the use of psychoacoustic data reduction with the associated artifacts.
technology
Compared to ADR , DAB or DVB , which work with data reduction, DSR has done without this. The playback quality of DSR is comparable to that of an audio CD . 16 radio programs were bundled into a package and broadcast digitally via a satellite transponder and broadcast on the Deutsche Telekom cable network on 118 MHz (cable channel S2 / 3).
Additional data was transmitted parallel to the music: There was a speech / music bit that the receivers could use to set the volume for speech and music separately. The station identification and the type of program such as classical music, pop music or cultural program were also transmitted.
A sampling rate of 32 kHz was chosen for the transmission , as this corresponds to the internationally agreed sampling frequency for digital audio program transmission lines. This enabled audio signals up to 15 kHz to be transmitted.
When DSR was being planned, the Deutsche Bundespost was just setting up its digital network. Combining 30 telephone channels ( primary rate connection ) resulted in a bundle with a transmission rate of 2048 kbit / s (DS2). These smallest bundles could be combined to form higher order bundles with 8448 (DS8), 34368 (DS34) or 137472 kbit / s (DS140).
Since three channels result in 1632 kbit / s with 16 bits including parity bit per channel, the remainder of 288 kbit / s would be waste. By reducing the word length to 14 bits, the channel bit rate was optimally used. The net bit rate of a stereo signal (2 × 14 bits × 32 kHz = 896 kbit / s) reached almost half the net bit rate (992 kbit / s) of the DS2 bundle. Half the gross bit rate 1024 kbit / s (DS1) was chosen for the stereo signal. It also made sense to use a similar frame structure with 256 bits.
A 256-bit block consisted of 8-bit frame identification, followed by 4 × 30-bit music data, further 8-bit additional information and another 4 * 30-bit music data. 8000 of these blocks were transmitted per second on a DS2 line.
The 30 bits of a sample consisted of 14 bits for the left channel and 14 bits for the right channel for a stereo signal or two mono channels and a 15th parity bit each. This was offset against the 3-bit scale factor that was also transmitted in this bit. The word length of 14 bits, which was specified by the full utilization of the mail delivery routes, was also retained for the radio transmission. Only the DSR receiver restored the 16-bit audio signal.
When specifying the DS1 interface, an attempt was made to achieve a new quality of audio signal transmission. Quote: "With the agreement between the broadcasters and the DBP to use the DS1 audio channel technology with digital signal transmission for higher-quality audio connections in the future, a new era of audio line technology has certainly begun."
The coding
With a 10 dB safety margin and a linear quantization curve, 14 bits result in a signal-to-noise ratio of 76 dB for a sinusoidal signal due to the quantization noise . Since you wanted to keep the dynamic range of 98 dB from 16 bits, you had to encode the signal. For this purpose, the signal was broken down into eight 6 dB wide sections. The maximum value was taken from 64 consecutive samples and a 3-bit scale factor was calculated for this block. This scale factor was transmitted within the parity bits, 21 times per block. When decoding in the receiver, it was determined by majority decision. A scale factor bit of 1 inverted the parity bit of the corresponding word.
Losses only occurred at full output (0 dB - scale factor 0). In this case the least significant or the two least significant bits were not transmitted. This was negligible, however, because the upper levels were used for headroom and it was assumed that they rarely occur. So the 16 bits of the original PCM signal could be transmitted. This 16/14-bit floating point representation could be expanded for a transmission of up to 18 bits per sample.
On the satellite route, this data stream was channel- coded using the BCH code in order to maintain the redundancy for error detection and error correction. 44 bits of useful signal were coded into a 63-bit block with corresponding redundancy information and combined in frames with a length of 512 bits.
This bit stream was modulated on the RF carrier by means of digital phase modulation , which can transmit two bits per transmission symbol (4-PSK). The bandwidth of 27 MHz corresponded to that of a television channel. In addition to the music, information was transmitted at 11 kB / s per stereo channel.
Individual evidence
- ↑ Information brochure for digital radio on radio satellites from the Federal Minister for Research and Technology (BFMT), page 31
- ↑ Information brochure for digital radio via broadcasting satellites from the Federal Minister for Research and Technology (BFMT)