DK163089B - PROCEDURE FOR TRANSMISSION AND RECEIVING DIGITAL INFORMATION SIGNALS - Google Patents

Description

DK 163089 B

The invention relates to a method for transmitting and receiving information signals, in particular for digital audio transmission over satellites, according to the preamble of claim 1.

5 With satellite stereo radiophony, it is known, through a transmission path, to transmit several different programs, any of which can be selectively selected on the receiving side. The transfer occurs e.g. in time multiplex. In this case, within a so-called frame, i.e. a specific period of time, successive bit words for the left channel of the first program, the right channel of the first program, the left channel of the second program, the right channel of the second program, the left channel of the third program, etc. After the execution of such a frame, the sequential transfer resumes with the left channel of the first program, etc.

In the digital information transmission over satellites, only statistically distributed single bit errors 20 (Gauss's case) occur, as stated in "British Telecommunications; OTS and Digital" Television Transmission Investigations of Error Statistics Relevant to the Design of Error Correctors for Television (20.11.80 ) ".

For the correction of statistically distributed errors, cyclic 25 codes are particularly suitable.

It has been proposed (DE patent application no.

P 31 34 831.9), to use a BCH code 63/44 for error detection and correction. With this code, by means of a suitable decoder coupling, e.g. find 30 five errors, both of which can be corrected using the code. The three additional errors found are interpolated with an appropriate coupling.

In phase difference modulation, at the output of the demodulator, predominantly double-bit errors occur, which inadvertently limit the error detection or error correction with block codes. Already three transfers

DK 163089 B

In some circumstances, two ring errors are no longer detected by this code, and two transfer errors cause an error finding instead of a complete correction.

Due to the exploitation of the difference, a counterfeit bit on the transmission line, namely in the demodulator, leads to two false statements: first, this false bit is assigned to a preceding real bit, and secondly the subsequent correct bit is assigned to the preceding false bit.

The invention aims to provide an improvement in error detection and error correction by a method according to the preamble of claim 1, in particular by using block code 63/44 and phase difference modulation.

This is achieved according to the invention by a method according to the characterizing part of claim 1.

Suitable further developments of the method according to the invention are set out in the subclaims.

The method according to the invention is distinguished by the fact that the information bits in a first information on spreading are separated by the bits in other information.

This is achieved by interleaving the data rows in two or more BCH blocks by the single-bit multiplex method. For example, if instead of 25 single-bit errors occurring only double errors, while so far only two double errors and one double error could be corrected, with a spread of two BCH blocks, five double errors can be recognized and interpolated or two double errors corrected. In this example, a block error of up to ten bits is possible.

Interleaving the entire subframe (four BCH blocks) increases security against block failure. A disadvantage, however, is an increased probability of occurrence of the occurring errors. The interleaving of only two BCH blocks therefore constitutes a favorable compromise.

In the original frame without interlacing, a processing speed of the demodulator of a 3

DK 163089 B

data rate of 10.24 MHz. When interleaving two BCH blocks, the data rate drops to 5.12 MHz. At the halved processing speed, a demo modulator in the MOS technique can conveniently be constructed.

It is proposed to transmit the digital signal from the transmitter to the receiver in the form of 4-phase angular changes or differences of the carrier. This is done in that in the transmitter a four-stage phase difference modulation is carried out and in the receiver a corresponding difference demodulation, as stated in "Nachrichtentechnische Zei-tung, 29 (1976), booklet 5, pages 390-394". In another demodulation method to which the present invention may also be applied, coherent demodulation with differential decoding is used. The more favorable system conditions obtained by this method are obtained at the expense of a larger supply.

In contrast to a completely coherent modulation, where the clarity of the 4-phase switching on demodulation is to be eliminated by appropriate coupling means, as proposed in DE Patent Application No. P 31 25 894.8, this clarity is no longer present at phase difference modulation or decoding. The information lies in the difference between two successive bits. Passage difference modulation is particularly suitable for digital audio transmission during the off periods of a television signal. Since the carrier is not to be diverted into the demodulator, in the television multiplexing method of transmitting a digital television audio signal during the off periods by the differential modulation of the signal, only the bit rate must be derived. Continuous verification of whether the received frame is properly synchronized will lapse.

The invention is explained in more detail below with reference to the schematic drawing, in which fig. 1 shows the structure of an interlacing of two 35 BCH blocks; FIG. 2 shows the construction of a half-frame for 4-phase switching; and 4

DK 163089 B

FIG. 3 shows a link to the BCH block selection.

FIG. 1 shows the structure of an interlacing of two BCH blocks, At 8 stereo channels in one half frame, a letter L characterizes a left channel and a letter R 5 a right channel of a stereo program. Li is e.g. the left channel in a first stereo program and R3 the right channel in a third stereo program. A scan value consists of 14 bits divided into 11 high-value bits, briefly referred to as MSB, and three low-value bits, briefly referred to as 10 LSBs. Two stereo programs are combined into one BCH block. A first BCH block consists of stereo programs 1 and 2, a second BCH block of stereo programs 3 and 4. The first 22 bits are MSB from LI and L3. A first bit is bit number 1 in LI, a second bit is bit 15 number 1 in L2 and then follows as third e bit, bit number 2 in LI, as fourth bit, bit number 2 in L2, etc. Then they follow 22 MSB in R2 and R4. Each of the two BCH blocks includes 19 sample bits Fl-2 and F3-4. They join the 88 MSB in LI to R4.

20 As proposed in DE patent specification 31 26 880, the semi-frame contains information bits in the form of characteristic bits for the program type and program number. To the sample bits F1-2 / F3-4 of the two BCH blocks, a characteristic bit of a BCH block in this frame according to the invention is joined. Following these characteristic bits Kl-2, K3-4, a total of 24 LSBs follow for the two BCH blocks, namely LSB for L1 / L3, then R1 / R3, as well as L2 / L4 and R2 / R4.

This structure is then repeated until the end 30 of the half frame of the stereo programs 5-8 so that a total of 2 x 152 bits are intertwined. At the beginning of a half-frame, 16 bits are reserved for a synchronous word and / or special service. In total, this half frame has a length of 320 bits. The structure of the second half frame for control programs 9 to 16 is identical.

FIG. 2 shows a complete half-frame for the 4-phase switch. The half frame starts with 16 not in each other.

Claims (11)

A method for transmitting and receiving digital information signals, in particular for digital audio transmission over satellites in which data rows in a frame are arranged in succession, characterized in that an error correction system with block formation over two stereo channels or four mono channels is used, and that the data rows in each subframe of a 4-phase switched signal (4-PSK) are so intertwined over at least two blocks by a single-bit multiplex method that two consecutive bits for each sensing value for each subframe at least separated by a bit associated with another scan value. Method according to claim 1, characterized in that the high-value bits (MSBs) for each of four DK 163089 B scan values are summarized in a cyclic block code. Method according to claim 1 or 2, characterized in that a bit row consists of a cyclic block code, the corresponding low value bits and a bit for additional information. Method according to claim 3, characterized in that two bit rows are interleaved in a single bit multiplex method. Method according to claim 1, characterized in that the frame consists of two subframes with 320 bits each. Method according to claim 1 or 5, characterized in that a subframe contains 16 sensing values associated with eight stereo channels or 16 mono channels or a combination of stereo and mono channels. Method according to claim 6, characterized in that a scanning value consists of 14 bits, 20 divided into 11 high-value bits (MSB) and three low-value bits (LSB). Method according to claim 1 or 2, characterized in that the first 16 bits of a subframe are reserved for special services and / or for a synchronous word. Method according to claim 5, characterized in that a 63.44 BCH code is used as a cyclic block code. Method according to claim 1, characterized in that the digital information signals are transmitted from the transmitter to the receiver in the form of four phase angle changes or differences of the carrier. Method according to claim 10, characterized in that in the receiver a phase difference demodulation or a coherent demodulation is performed with subsequent differential decoding of the received signal.