DE19706749C1 - Transmission error detection in method GSM mobile radio system - Google Patents

Abstract

The method involves detecting errors in radio data blocks, whereby the processing at a receiver is inverse with respect to the processing at a transmitter. A data compression of the information signals is performed at the transmitter, whereby the produced compressed signals are replaced by in bits, and additionally redundancy bits are inserted. A receive demodulates the signals, and a correction with reference to the redundancy bits is performed, whereby the redundancy bits are removed. If the redundancy bits are recognized as correct with respect to their position and value, the corresponding radio data block is accepted by the receiver.

Description

The invention relates to a method and a device for Detection of radio blocks (bursts) with transmission errors when transmitting information in a radio commu nication system, for example a GSM mobile radio (MF) - System.

In such a radio communication system in the Processing device in which the channel coding, the ver Interleaving, the radio block (burst) formatting and the encryption (cyphering) is done, normal generates bursts that z. B. in the GSM-MF system from a 26 bit Training sequence in the middle of a radio block, one out of 2 × 58 bit existing, encrypted payload sequence symmetrical to the training sequence and from 2 × 3 tail bits as a pre or post sequence followed by one protection period (GP: Guard Period approx. 30.46 µs) stand. The training sequence is both in the transmitter and in the Known receiver and is used to the channel impulse response capture and thus equalize the transmitted signals.

From US 4,829,526 is a method for coding Nutzin formation known in the course of data compression Bits for error detection introduced in the data stream and be evaluated at the receiving end. From WO 95/30 282 A1 furthermore a method for the detection of defective frames a radio transmission known.

The invention has for its object a method and to provide a facility with the radio blocks with Transmission errors detected in the payload sequence a so-called defect frame detection (Bad  Frame indication), whereby faulty radio blocks are filtered out can be.

The methods according to the invention are used to achieve this object ren characterized in the manner specified in claim 1, while the device according to the invention in claim 10 is marked.  

In a method according to an advantageous embodiment game of the invention for a GSM mobile radio system, the Invention on GSM-type radio communication systems, e.g. B. the DCS or PCS mobile radio systems, or other radio systems with blockwise transmission is also applicable initially a Da in front of the transmitter-side GSM processing device reduction, for example by one, two or more bits performed. So that in the of the GSM processing device created normal burst a corresponding number free of bits into which redundancy after GSM processing Additional bits, for example security or synchronization bits, which can then be inserted in the air interface lenburst can also be transmitted. After demodulation and equalization of the air interface burst on the receiver On the other hand, this signal is checked to see whether the Red andanz additional bits at the corresponding point with the respective current value are available. If so, this will be reviewed additional security over the proper Receive air interface burst transmission. If not, is indicated by the fact that when the burst an error has occurred so that the corresponding burst can be discarded. The quality level of the Bursts improved.

In an alternative method according to an advantageous one Embodiment of the invention is in front of the transmitter GSM processing device a data reduction, for example play for one, two or more bits, and Redun danz additional bits, for example security or Synchronization bits inserted. This modified language signal is then added to the GSM processing device, then modulated and then over as an air interface burst carry. After demodulation / equalization of the air interface lenbursts on the receiver side, this signal is the GSM Subjected to processing and then checked whether the additional redundancy bits at the appropriate point with the  respective value are available. If so, through this Checking additional security for proper ß transmission of the air interface burst received. If no, is indicated by the fact that when the Bursts an error has occurred, so the corresponding one Burst can be discarded. So that the quality level of the burst improved.

If several redundancy Additional bits are available if they are distributed in this way be that the best possible efficiency in the evaluation the quality of the bursts is possible, for example through egg ne regular distribution over the burst.

Another alternative for arranging the redundancy Additional bits consist of the redundancy additional bits made a quasi-midampling sequence and in the payload sequences is housed.

In advantageous embodiments of the Ver will drive the data compression of the speech signals only in the Areas made in the context of the Nutzsignalinformati on less important or less important or less significant bits are present. If at the data compress sion errors occur and possibly one or more Bits are disturbed or lost, so this affects in the quality of the eventual emp after the transmission caught signal less disadvantageous.

Further advantageous embodiments of the invention result itself from the subclaims.

Exemplary embodiments are now based on the enclosed Described drawings. Show it:

Fig. 1 is a block diagram of an embodiment of an inventive GSM-MF system;

Fig. 2 is a block diagram of another game Ausführungsbei an inventive GSM-MF system;

Fig. 3 is an air interface with a first burst at proper of redundancy overhead bits;

Fig. 4 shows an air interface burst with a different arrangement of additional redundancy bits.

The device according to FIG. 1 has a speech encoder 2 , to which a digital, linear PCM signal of 104 kbit / s is supplied, which is derived from the standard 64 kbit / s PCM signal by expansion of the nonlinear quantization (8 bit / A law) is obtained. In the language coder, the bit rate is reduced to 13 kbit / s, and voice data blocks with a length of 260 bits are defined every 20 ms. Such source coding is possible due to the redundancy of the language, i.e. the time invariance and linearity in the ms range.

The speech signal blocks delivered by the speech encoder 2 arrive at a data compressor 4 , in which the coded speech signal is reduced by n bits by means of digital data compression. Depending on the data compression setting, 1, 2, 3 .... n bits can be saved. If the signal to be processed contains higher significant (important) bit areas, the data compression is carried out in the area of the less significant bits.

The compressed voice signal is then fed to a GSM processing device 6 in which the channel coding, interleaving, burst formatting and cyphering is carried out, as is provided in the GSM system.

A modified normal burst is emitted at the output of the GSM processing device 6 , since the speech information in the data compressor 2 has been reduced. The modified normal burst is fed to a mixing device 8 , in which n additional redundancy bits are inserted into the modified normal bursts, according to a pattern, as will be described. At the output of the mixing device 8 , an air-cut burst is thus emitted, which again has the prescribed total number of bits. This air interface burst is then modulated in a modulator 10 and transmitted over the air interface.

The air interface burst is received and demodulated or equalized in a demodulator / equalizer 12 and fed to a test device 14 , in which the air interface burst is checked with regard to the additional redundancy bits, i.e. it is determined whether the additional redundancy bits have the correct values ( 0 or 1) at the corresponding positions (digits, location number) in the air interface burst. If the check leads to a positive result, the air interface burst is passed on, otherwise it is discarded.

The passed air interface burst is processed in a GSM processing device 16 in the opposite sense to that in the GSM processing device 6 , so that the compressed voice signal is recovered.

The compressed voice signal is fed to a data decompressor 18 , in which the data decompression is carried out in an inverse manner to the data compression. The signal emitted by the data decompressor 18 is fed to the speech decoder 20 and from there converted into the speech signal in a manner known per se.

Digital data compression is known per se, and one the so-called Lempel-Ziv- Algorithm with which compression factors of approximately 2 are possible are. When using such an algorithm, a  correspondingly large number of additional redundancy bits inserted and transmission security can be improved.

The device according to FIG. 2 has a language encoder 22 which corresponds to the language encoder 2 described above. The speech signal blocks emitted by the speech encoder 22 arrive at a data compressor 24 , in which the coded speech signal is reduced by n bits by means of digital data compression. Depending on the setting of the data compression, 1, 2, 3, ... n bits can be saved, the data compression being carried out in the areas with less significant bits, as in the example of FIG. 1.

The compressed speech signal is then supplemented in a mixing device 26 by n additional redundancy bits. At the output of the mixing device 26 , a modified speech signal is thus emitted, which again contains as many bits as were present before the data compression. This voice signal is then fed to the GSM processing device 28 , the output signal of which is fed to a modulator 30 , the output signal of which is transmitted via the air interface.

The air interface burst is received and demodulated or equalized in a demodulator / equalizer 32 and supplied to a GSM processing device 36 , in which the air interface burst is processed in the reverse sense of the GSM processing device 28 , so that the modified voice signal is recovered.

The modified speech signal is fed to a test device 36 , in which the modified speech signal is checked with regard to the additional redundancy bits in order to determine whether the additional redundancy bits have the correct values (0 or 1) at the corresponding locations (location number) in the modified speech signal available. If the check leads to a positive result, the speech signal is processed further, otherwise it is discarded. A modified speech signal classified as acceptable is fed to a data decompressor in which the data compression is carried out in a manner inverse to the data compression. The signal emitted by the data decompressor 38 is fed to the speech decoder 20 and from there converted into the speech signal in a manner known per se.

FIG. 3 shows an air interface burst with 3 tail bits (lead or lag), 2 × 58 voice data bits and 26 training sequence bits. Of the 58 speech signal bits in each case, 2 bits are taken up by the additional redundancy bits, which are arranged schematically at positions 20 and 36 starting from the respective end of the training sequence and have the logic state 1. If four bits are saved in the data compressor 4 (n = 4), two additional redundancy bits can be arranged in the two speech signal sequences of the normal burst.

Figure 4 shows another way in which the security bits can be arranged in the speech data sequence. Here the Da tenkompressor is set so that 6 bits are free, so that 2 × 3 bits are available for the two voice data sequences. In this case, the additional redundancy bits can be combined into groups of three and, for example, at positions 19 to 21 , calculated from the end of the training sequence, can be occupied by addition. An example of the values of the additional redundancy bits is indicated in FIG. 3 as 1, 1, 0 for the left speech data sequence and 0, 1, 1 for the right speech data sequence. Quasi-mid-sample sequences of this type provide increased security when recognizing the security bit sequences.

The particular embodiment described above relates focus on the transmission of language. The invention relates however, generally relates to the transmission of digital or digitized information.

Claims (13)

1. Method for the detection of radio blocks with transmission errors in a useful information transmission in a radio communication system, the processing being carried out on the receiver side inversely to the processing on the transmitter side, on the transmitter side

• 1. a data compression of the useful information signals is carried out, compressed signals shortened by n bits being generated,
• 2. - Additional redundancy bits are inserted into the compressed signals, and on the receiver side
• 3. the signals of a demodulation and equalization are checked with regard to the additional redundancy bits, the additional redundancy bits being removed,
• 4. if the additional redundancy bits are recognized as correct during the check in position and value, the corresponding radio block is accepted,

characterized in that a number n additional redundancy bits are inserted into the compressed signals on the transmission side, which essentially corresponds to the number of n bits saved by the compression. 2. The method according to claim 1, characterized in that the transmitter side

• 1. - digital useful information signals are subjected to a data processing according to funkstan standard processing, with information signals being shortened by n bits, compressed useful information signals being generated that
• 2. - The compressed useful information signals are subjected to the radio processing according to standard in order to produce modifi ed normal radio blocks that
• 3. - n redundancy additional bits are inserted into the modified normal radio blocks in order to generate air interface radio blocks which are modulated and transmitted,

and that on the receiver side

• 1. - the air interface radio blocks are demodulated / equalized that
• 2. - The demodulated equalized air interface radio blocks are checked with regard to the redundancy additional bits and the redundancy additional bits are removed in order to recover the modified normal radio blocks
• 3. - the modified normal radio blocks are subjected to inverse radio standard processing in order to recover the compressed useful information signals, and that
• 4. - the compressed useful information signals are subjected to an inverse data compression in order to recover the digital useful information signals.

3. The method according to claim 1, characterized in that the transmitter side

• 1. - The data compression is carried out before a radio-standard processing, whereby compressed, useful information signals shortened by n bits are generated
• 2. - n redundancy additional bits are inserted into the compressed useful information signals in order to generate modified useful information signals that
• 3. - The modified useful information signals are subjected to the radio processing according to standard to produce modifi ed normal radio blocks that are modulated and transmitted, and that on the receiver side
• 4. - the air interface radio blocks are demodulated / equalized that
• 5. - The demodulated / equalized air interface radio blocks are subjected to inverse radio standard processing in order to recover the modified useful information signals that
• 6. - The modified useful information signals are checked with regard to the additional redundancy bits and the additional redundancy bits are removed in order to recover the compressed useful information signals, and that
• 7. - the compressed useful information signals are subjected to an inverse data compression in order to recover the digital useful information signals.

4. The method of claim 1, wherein the normal radio blocks egg ne training sequence in the middle of the normal radio blocks and have useful information sequences on both sides, characterized in that at least two additional redundancy bits on both sides and arranged at a distance from the training sequence the. 5. The method according to claim 1, characterized in that the additional redundancy bits for two quasi-midampling sequences are summarized in the payload sequences zen can be arranged. 6. The method according to any one of the preceding claims, characterized in that the redundancy additional bits security bits and / or syn include chronization bits. 7. The method according to any one of the preceding claims, characterized in that data compression with the Lempel-Ziv algorithm follows. 8. The method according to any one of the preceding claims, characterized in that the digital payload signals voice data signals are from a language encoder or speech decoder can be delivered or received. 9. The method according to any one of the preceding claims,  characterized in that the data compression in the areas of less signi fictional or important bits performed becomes. 10. A device for improving the radio block quality in a useful information transmission in a radio communication system according to one of claims 1 to 9, wherein a processing device on the receiver side works inversely to a processing unit on the transmitter side,

• 1. - with a transmitter-side data compressor ( 4 ; 24 ) in which data compression of the useful information signals is carried out, compressed signals shortened by n bits being generated,
• 2. with a mixing device ( 8 ; 26 ) through which additional redundancy bits are inserted into the compressed signals,
• 3. - With a receiver-side test device ( 14 ; 36 ), in which the signals are checked after demodulation and equalization with regard to the additional redundancy bits, the additional redundancy bits being removed, and if the additional redundancy bits are checked at the the right place and with the right value, the corresponding radio block is accepted,

characterized in that the mixing device ( 8 ; 26 ) is designed such that a number n additional redundancy bits are inserted on the transmission side into the compressed signals, which essentially corresponds to the number of n bits saved by the compression. 11. The device according to claim 10, for use in a GSM mobile radio system, characterized by

• 1. - a GSM processing device ( 6 ) upstream data compressor ( 4 ) to generate compressed Nutzin information signals which are given to the GSM processing device ( 6 ) which outputs modified normal radio blocks at its output,
• 2. - A mixing device ( 8 ), in order to insert additional redundancy bits into the modified normal radio blocks in order to generate an air interface radio block which is modulated and transmitted in a modulator ( 10 ), and on the receiving side
• 3. - a demodulator / equalizer ( 12 ) downstream test device ( 14 ), which checks the demodulated air interface radio block with respect to the additional redundancy bits and removes the additional redundancy bits in order to recover the modified normal radio blocks that the GSM processing device ( 16 ) are supplied to recover the compressed useful information signals, and by
• 4. - a data decompressor ( 18 ) to recover the digital useful information signals from the compressed useful information signals.

12. The device according to claim 10, for use in a GSM mobile radio system, characterized by

• 1. - a GSM processing device ( 28 ) upstream data compressor ( 24 ) to generate compressed Nutzin information signals,
• 2. a mixing device ( 26 ) for inserting additional redundancy bits into the compressed useful information signals in order to generate modified useful information signals which are supplied to the GSM processing device ( 28 ),
• 3. - A modulator ( 30 ), to which the output signals of the GSM processing device are supplied, the modulated output signals of the modulator being transmitted as radio blocks, and on the receiver side by
• 4. - a demodulator / equalizer ( 32 ), the output signals of which are fed to a GSM processing device ( 38 ), in order to recover the modified useful information signals, by
• 5. - One of the GSM processing device ( 38 ) downstream test device ( 36 ), which checks the modified useful information signals with respect to the additional redundancy bits and removes the additional redundancy bits in order to recover the compressed useful information signals, and by
• 6. a data decompressor ( 38 ) in order to recover the digital useful information signals from the compressed useful information signals.

13. Device according to one of claims 10 to 12, characterized in that the data compressor ( 4 ) and the data decompressor ( 18 ) work with a Lempel-Ziv algorithm.