WO1994010769A1 - Reglage silencieux d'un telephone sans fil a codage adpcm - Google Patents

Reglage silencieux d'un telephone sans fil a codage adpcm Download PDF

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Publication number
WO1994010769A1
WO1994010769A1 PCT/DE1993/000966 DE9300966W WO9410769A1 WO 1994010769 A1 WO1994010769 A1 WO 1994010769A1 DE 9300966 W DE9300966 W DE 9300966W WO 9410769 A1 WO9410769 A1 WO 9410769A1
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WO
WIPO (PCT)
Prior art keywords
adpcm
signals
burst
sequence
word
Prior art date
Application number
PCT/DE1993/000966
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German (de)
English (en)
Inventor
Christoph Wedi
Christoph Euscher
Original Assignee
Siemens Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Priority to AU51068/93A priority Critical patent/AU5106893A/en
Publication of WO1994010769A1 publication Critical patent/WO1994010769A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/02—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation
    • H04B14/06—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation using differential modulation, e.g. delta modulation
    • H04B14/066—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation using differential modulation, e.g. delta modulation using differential modulation with several bits [NDPCM]
    • H04B14/068—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation using differential modulation, e.g. delta modulation using differential modulation with several bits [NDPCM] with adaptive feedback
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13098—Mobile subscriber

Definitions

  • the invention relates to a method for reducing the disruptive effects of poor voice transmission quality in a radio connection which consists of one of a plurality of selectable radio channels, including a base station part, for a cordless mobile telephone part, criteria being determined in each of these subunits in each case provide a certain statement about the quality of the connection and the coded information between them, which correspond to each other in the context of the speech connection, in coded information, among others, according to the DECT standard the bursts containing ADPCM-encoded voice information are transmitted as radio signals and the subunits each have a processor and devices for deriving the respective criteria.
  • DECT Digital European Cordless Telecommunication
  • the digital radio transmission method allows multiple mobile terminals to be operated by means of one radio part as part of a time ultiplex method. 24 time channels are defined in a time multiplex frame of 10 ms, for example. There are 12 channels assigned to each frequency that can be used, so that 12 mobile telephone parts of a DECT system can be used in the frequency band. You can work in duplex mode at the same time.
  • a time slot of approx. 417 ⁇ s is assigned to the time channels. This time slot then indicates the time in which information that is combined in a certain way to form a burst constructed according to the DECT standard is transmitted.
  • the chronological sequence of the transmitted bursts defines a channel (the so-called physical channel) with a data throughput of 420 bits / 10 ms.
  • the PCM values obtained from the analog voice information are additionally compressed, for example, by the so-called adaptive difference PCM method (ADPCM method).
  • ADPCM method adaptive difference PCM method
  • the difference between two successive samples is encoded. This difference between the last and the new sample no longer has the amplitude fluctuations, such as, for example, the original signal. To encode this reduced amplitude, significantly fewer bits are required than with normal PCM encoding.
  • An adaptive algorithm is also used insofar as the quantification levels continue to be dynamically adapted to the respective average level. A further bit rate reduction is then achieved.
  • the resulting words can then in addition to the usual PCM words of z.
  • B. 8-bit width can be summarized. This information then includes, for example, two ADPCM words.
  • the speech or LF signal is distorted disadvantageously. This is particularly critical in the case of so-called cordless transmissions, particularly in the area of the range limit. It is the object of the invention to provide a method in which the interference reduction can be carried out in such a way that it leads to the least possible loss of speech information.
  • this is achieved in that a program assigned to the processor is designed in such a way that in the subunits, when a burst is received, at least one with respect to each of the criteria is dependent on the detected excess fixed error limit value for temporarily suppressing the speech transmission of the unit carrying out the ADPCM coding of the speech signals, a sequence of identical ADPCM signals is fed in on the input side, so that, as a result of this, a continuous reduction of the speech level to the idle level er ⁇ follows and that this supply is carried out until a value has been reached that has been properly defined with respect to the respective criterion.
  • the speech channel is "muted" (mute) for the duration of the disturbances, likewise defined by certain criteria. If a constant sequence of the same ADPCM signals is supplied to the unit performing the ADPCM coding, there are no differences between the individual values of the supplied signals, so that the speech level is continuously reduced to the idle level. This muting occurs whenever the quality of the connection is judged to be so poor on the basis of the criteria assessed in a certain way during the channel monitoring that a muting of the voice connection makes more sense than the background noise caused, for example, by bit errors arise to tolerate.
  • the individual criteria to be considered can only be evaluated individually or in a predetermined combination.
  • the error limit values to be determined for the individual criteria are programmed in such a way that - based on the respective circumstances of the disruptive effects - an optimized reception situation for the conversation participants is achieved.
  • Test words are formed as a criterion for transmissions according to the DECT standard for error detection. As a rule, more than one test word is derived from the data or information stream. Furthermore, by assessing the synchronization word contained at the beginning of a burst, the information is available as to whether the burst was received correctly.
  • the conditions under which a burst is detected can be varied. It is Z. B. possible a bit error allow in the synchronization word so that a burst is always considered not received if more than one bit error occurs in this synchronization word. With respect to the check words, checksum monitoring can be carried out. The burst is considered faulty if e.g. B. n of the test words are incorrect. If more than one test word is contained in a burst, the predetermined number n results from the summation of each incorrect test word in the successive bursts.
  • An error in the synchronization word can be assigned priority when initiating the muting. If this synchronization word is deemed to be lost, the data still contained in the burst cannot be evaluated. A subsequent correct synchronization word can cause the mute to be switched back in the same way as the test word recognized as correct.
  • the same signals can be supplied according to the invention as constant ADPCM words, which either represent the binary value "zero” or the binary value "one". Furthermore, the last ADPCM word transmitted before the requested muting can be repeated continuously in order to then actually effect the muting. The repetition of a constant arbitrary received ADPCM-coded word can also be carried out.
  • FIG. 1 shows a receiving or transmitting device in which the method according to the invention is implemented
  • the device shown in FIG. 1 is formed, for example, by the base station of a cordless telephone. It is assumed that for this cordless telephone, which can also be referred to as a mobile telephone part, the
  • the DECT standard is implemented.
  • the device is basically divided into three function blocks, namely the transceiver part HF-T, which contains a transmitter device SEN in connection with the receiver device EE.
  • This transmitting or receiving device is connected to an antenna A.
  • the FM unit is used to determine whether a channel is occupied. This is registered by measuring the field strength (minimum field strength of received signals). Furthermore, information about the respective field strength of the received signals can take place in this unit, in which case these measurement results are used for certain subsequent functions.
  • the unit ST-T forms a further function block, which is essentially responsible for the implementation of the DECT method in the transmitting and receiving device.
  • a processor Dect-C is provided, which controls the processes via the interface Sn.
  • Storage units for example the units RAM, ROM and E 2 PROM, are assigned to this processor.
  • the third functional unit LT-T represents a line part represents, which can be constructed in the same way as the telephone line parts of known cordless telephone systems (Wolf, Klaus: “Even without a cord on wire” - Telcom Report 10, 1987, Issue 2, pages 130 ff.).
  • this unit there are coding devices or decoding devices ADPCM-CODEC, which are followed by corresponding internal subscriber circuits ANi or an external connection / extension connection ANe for wired telephony equipment, for example FeAp, which are connected to an external line ALtgg or also to one a branch line leading line are connected.
  • ADPCM-CODEC are used to convert the voice information arriving via the line ALtg or from the telephone set FeAp into corresponding ADPCM words which are then fed to the unit TSC via the serial interface S1-ADPCM. In the opposite direction, the information is fed via the interface SO to the ADPCM-CODEC, which converts the compressed digital information back into analog voice information.
  • the serial ADPCM data from the CODEC are stored in the ADPCM memory ADPCM-MI as parallel 8-bit data.
  • the TSC (Time Switch Control) unit for example over a period of 10 ms, which is based on a data throughput of 42 kbit / s, samples from the speech information for the transmission direction in a - as already mentioned - 417 ⁇ s long burst summarized or these bursts are received in relation to the direction of reception and forwarded via the ADPCM-CODEC.
  • this unit TSC also switches several connections using the time-division duplex method (TDMA method).
  • the processor Dect-C of the functional unit ST-T also takes on control tasks for other components, for example for the units in the transceiver part HF-T.
  • the data which form the so-called A field of a burst are stored in the memory unit CB1 (control buffer) by the processor Dect-C, which is formed by a programmable microprocessor or possibly also a hardware structure. This is shown in the same way as the other contents of a burst in FIG.
  • Such an A field contains internal control information, for example the necessary identifier for a base station part and the information that this station is connected to a specific mobile part
  • connection is established.
  • the information can also be introduced that, based on certain monitoring results of the established radio connection, the change to another channel is to take place.
  • This A field which is responsible for information accompanying the connection, can consist, for example, of a 64-bit data block.
  • the information assigned to the B field of the burst represents that in the case of a line-bound connection (connection with FeAp or connection via an outside line device ALtg) in the time-division multiplex frame of 10 ms obtained ADPCM values of the speech information. As already mentioned, these are stored in the memory ADPCM-M.
  • This voice information of the B field is taken from the memory SM (switch memory) in a connection that exists between two mobile telephone parts, in which it has been stored in the meantime.
  • the SB (switch board) unit sets the course from which of these named memories the information for the B field of the burst is taken.
  • the data forming the A field and the B field are read out of the memories and fed to the SOL (Serial Out Line) unit.
  • a serial data stream is generated. This is passed through the unit PR1 in order to form a test word from the data of the A field as well as from the data of the B field, which is then used as the ACRC or XCRC data block for the A field or the B Field is added in the respective burst.
  • the unit PR1 contains, in the same way as the unit PR2 for the reception direction, for example so-called FIFO (first-in-first-out) stages, which form a shift register and which are then interconnected in a very specific arrangement. Individual transfer information points are then formed on the basis of this predetermined interconnection.
  • the check word is generated in this shift register according to a very specific algorithm. This results, for example, in a 16-bit ACRC check word for the data block of the A field; the data stream of the B field of a burst is in turn determined by a certain predetermined algorithm, e.g. B. a 4-bit XCRC check word.
  • the data block of the B field is "scrambled" in the unit SCI.
  • Such encryption then prevents longer sequences of a binary "one” or a binary "zero” from being contained. Such an equally long data sequence would not be favorable for the HF-T functional unit.
  • the frame synchronization takes place in the unit SY1 and the synchronization word is placed in front of each transmission burst and transmitted. As can be seen in FIG. 2, this synchronization word Syne forms the beginning of each burst to be sent.
  • the data formed into the burst packet are fed to the transmitter SEN via the output DA and transmitted to a mobile telephone part via the air interface by means of an antenna A on the radio path.
  • a check relating to the data of the A field and the B field can then be carried out in the receiving part in order to determine whether this data has been transmitted correctly.
  • certain subsequent functions can then be initiated. These subsequent functions are then carried out in the same way in the base station part shown in FIG. 1 with respect to each burst received.
  • the serial data stream transmitted over the radio path is received by the mobile telephone part corresponding to the base station part and the individual bursts, which are received every 10 ms according to the time-division multiplex frame, are registered by the receiver EE and transmitted via the Data input DE supplied to the unit TSC. These are the digital data converted in the functional part HF-T from the received frequency-modulated data.
  • the frame synchronization is carried out in the unit SY2 and the sampling phases are determined.
  • the bit position In order to maintain synchronism with the remote station, the bit position must be detected. Thus, for example, the end of a synchronization word contained in the beginning of the burst and thus the beginning of the A field following in the burst can be detected.
  • a bit counter is set to the relevant value and the first and the following can then be used Bits of the A-field data block are correctly assigned. It is also checked in the unit SY2 for the presence of the synchronization word. If this word has been received without any errors, then it is recorded in a so-called sta p byte that information was transferred in a time slot and which of the total possible time slots concerned this.
  • test words namely the test words ACRC for the A field and XCRC for, are made from the data stream relating to the A field and the B field of a burst in the receive direction by the unit PR2, again in the same way as described for the send direction the B field formed.
  • These respective check words are compared with those which have been inserted in the received burst in each received burst and in this burst each follow the data block of the A field or the data block of the B field.
  • these test words are thus formed in the mobile telephone part in the manner described for the base station part and are introduced into the data stream. If, when comparing the test words formed on the receiving side from the two data fields with the test words already transmitted in the burst, it is found that there is a deviation and thus an incorrect transmission, this fact is stored in the memory SC.
  • Voice channel hand-over or an antenna change can be initiated.
  • Another possibility is to perform a so-called muting of the voice channel on the basis of the evaluation of these stored test word errors or the errors in the synchronization word.
  • the corresponding slot number is then entered in the relevant memory.
  • the memory or the register SC can be read out by the processor Dect-C via the interface Sn.
  • the processor can use this to determine whether a slot has been received and whether there is an error in the test words.
  • he can query the errors which have also been stored therein and have occurred in a synchronization word of a burst. In the event that everything has proceeded properly, the memory or .
  • Register CB2 (Control Buffer) stores the data of the A field in the burst for further processing for the Dect-C processor.
  • the digital voice information in the B field is stored in the ADPCM-M2 unit in the case of an outside line or a wired internal connection, for example to the FeAp telephone set. If there is a connection between two mobile telephone parts, the digital voice information of the B field is stored in the memory unit SM (switch memory). This voice data for the readout of the burst going out in the transmission direction, as already described. This selection is made by the unit SB (switch board).
  • the ADPCM-M2 (RAM memory) contained in the ADPCM-M2 unit is converted into a serial data stream by the SO-ADPCM unit and forwarded to the ADPCM-CODEC.
  • analog signals are then formed from the digital information, which are applied to the corresponding line via the respective interface units ANi or ANe.
  • the call connection is disturbed if there are bit errors in the synchronization word SYNC of the burst and / or if errors are found during the check of the test words described.
  • the checks which are assessed as incorrect are numerically stored, for example, in the unit SC.
  • a rough estimate of the strength of the disturbances is possible.
  • Another criterion for a disturbance can be the level of the field strength, which is measured in the functional part HF-T by the unit FM. If this field strength falls below a certain value, the quality of the connection is no longer sufficient.
  • This muting is controlled by the processor Dect-C, which reads out the content of the register SC. This is done in addition to a number of other tasks performed by him, such as Connection setup / clearing down, channel selection, channel change, data flow and antenna switching. It can be specified, for example, that this muting is activated when the sum of the erroneous test words found in the check mentioned in the individual successive bursts reaches a certain numerical value n. This numerical value n can be specified, for example, with "10". When this counter reading for the incorrect test words, which the processor Dect-C stores from the register SC, is reached, this muting is then carried out in the manner to be described.
  • a burst is considered to have been received correctly if the synchronization word leading it has been detected. by virtue of With this synchronization word, the data can be inserted into the bit pattern. This possible assignment is questioned or impossible if a bit shift in the data sequence has arisen due to incorrect bits. This misinterprets the data. In the event of a bit error, there is usually still the possibility of synchronization. The muting is therefore only effected if there is more than one bit error in the synchronization word. As already mentioned, these faulty states in the synchronization word determined by means of the unit SY2 are stored in the memory SC and can be processed by the processor Dect-C in the same way as the number of faulty test words be asked.
  • the errors occurring in the bit word are therefore given absolute priority for muting.
  • the field strength could be used as a further criterion.
  • These individual criteria can now not only be considered individually, but basically any mixtures with the limit values adapted for the individual criteria are also conceivable. For example, the presence of a certain number of test words and falling below a certain reception field strength could lead to muting. It could also be provided that if only one bit error occurs in the synchronization word, this error is evaluated as if one or more test words were incorrect, so that the count of this relevant error counter is then increased by the corresponding value.
  • the burst loss caused by bit errors in the synchronization word can be weighted such that the muting is initiated in the case of a predetermined number of errors, regardless of the state of the test words.
  • information representing either the binary value "zero” or information representing the binary value "one” can be applied to the data bus.
  • the unit TSC feeds the respective data and a "clock" to the ADPCM-CODEC via the serial interface SO, with which it scans this data. If, for example, a permanent high signal is applied to the data bus, then this CODEC is supplied with ADPCM word "1" representing the binary value "one” on the basis of the sampling performed.
  • the last ADPCM word read before a muting could also be stored and repeated continuously to implement the muting.
  • Muting can be canceled, for example, if there is no bit error or only a bit error in the synchronization word. This is because the conditions under which a burst is still "recognized" can be variably specified with these limit values. For example, 1 errors in the synchronization word are permitted. If it is determined that the two test words ACRC and XCRC are correct, this information can immediately lead to the muting being withdrawn.
  • the cycles required for the individual functions, which are necessary for the individual components, are generated in the unit TE. They can basically be derived from a master clock. Bit and slot counting devices can also be implemented in this unit TE. These counters are from. Processor initialized or synchronized.
  • the functional part HF-T and ST-T shown in FIG. 1 as a digital DECT part are essentially contained in the same way in the mobile telephone part.
  • a functional unit is then included, which also contains an ADPCM-CODEC and is also equipped, inter alia, with the earpiece, the microphone and a call organ, each of which is then provided with an amplifier circuit. can be arranged.
  • the mobile telephone part there are batteries, identification contacts, LED displays, key detectors and the so-called folding switch.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Dans les liaisons téléphoniques établies entre une station de base et des terminaux mobiles, la voix est transmise sous forme codée ADPCM, selon la norme DECT. Lors de cette transmission ADPCM numérique, les erreurs sur les bits génèrent des grésillements et des bruits parasites intenses. Pendant la durée de ces bruits parasites, le canal vocal est rendu silencieux. Dans la transmission opérée selon la norme DECT, deux mots de contrôle sont formés pour la détection d'erreurs. Ces mots de contrôle (ACRC, XCRC) permettent d'évaluer l'intensité des bruits parasites. L'estimation du mot de synchronisation (Sync) précédant une salve permet de savoir si la salve a été parfaitement bien reçue. Si tel n'est pas le cas ou si un certain nombre (par exemple 10) des mots de contrôle des salves successives ne sont pas justes, une séquence de mots ADPCM constants est acheminée à la branche ADPCM. Cette séquence peut par exemple consister en signaux ADPCM à 4 bits similaires, représentant la valeur binaire 'zéro' ou 'un'. Il peut également y avoir une répétition continue du dernier mot ADPCM transmis avant le réglage silencieux. Ainsi, le niveau de la voix est lentement abaissé, jusqu'à ce que le niveau de repos soit atteint, ce qui évite le phénomème de grésillement pouvant intervenir lorsque le canal vocal est subitement coupé. Le réglage silencieux est suspendu lorsque le mot de synchronisation ne présente plus un nombre d'erreurs sur les bits dépassant un nombre donné ou lorsque les mots de contrôle sont corrects.
PCT/DE1993/000966 1992-10-26 1993-10-12 Reglage silencieux d'un telephone sans fil a codage adpcm WO1994010769A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU51068/93A AU5106893A (en) 1992-10-26 1993-10-12 Muting of a cordless telephone with adpcm coding

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DEP4236088.9 1992-10-26
DE19924236088 DE4236088A1 (de) 1992-10-26 1992-10-26 Verfahren zur Verringerung störender Auswirkungen schlechter Sprachübertragungsqualität bei einer Fernsprechverbindung mit einem schnurlosen Fernsprechgerät

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WO1994010769A1 true WO1994010769A1 (fr) 1994-05-11

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Cited By (3)

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Publication number Priority date Publication date Assignee Title
EP0712218A1 (fr) * 1994-11-10 1996-05-15 Ericsson Business Mobile Networks B.V. Procédé et dispositif de reconstruction de sous pendant des effacements
EP0858180A2 (fr) * 1997-02-05 1998-08-12 DeTeWe - Deutsche Telephonwerke Aktiengesellschaft & Co. Procédé silencieux pour dispositif d'écoute dans des terminaux de communication mobiles
US6134522A (en) * 1994-08-02 2000-10-17 Siemens Aktiengesellschaft Signal processing method and arrangement for substitution or erroneous signals in a block-coded audio signals of an audio communication system

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DE19501517C1 (de) * 1995-01-19 1996-05-02 Siemens Ag Verfahren, Sendegerät und Empfangsgerät zur Übertragung von Sprachinformation
WO1996022637A1 (fr) * 1995-01-20 1996-07-25 Siemens Aktiengesellschaft Procede de traitement de signaux pour un signal audio a code a blocs dans un systeme de transmission d'informations audio
DE19712047A1 (de) * 1997-03-21 1998-09-24 Deutsche Telephonwerk Kabel Verfahren zur Übergabe einer bidirektionalen Funkverbindung sowie Anordnung
DE19730984A1 (de) * 1997-07-18 1999-02-11 Siemens Ag Funk-Übertragungsverfahren und Schnurlostelefon, insbesondere für DECT-Standard
US6651207B1 (en) * 1999-08-20 2003-11-18 Siemens Information & Communication Mobile, Llc Method and system for improving voice quality in cordless communications
EP2207273B1 (fr) * 2009-01-09 2016-01-06 AKG Acoustics GmbH Procédé et dispositif de réception de données audio numériques

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EP0394493A1 (fr) * 1988-10-24 1990-10-31 Matsushita Electric Industrial Co., Ltd. Circuit demodulateur de signaux audio
EP0486232A2 (fr) * 1990-11-12 1992-05-20 Texas Instruments Incorporated Décodeur MICDA à détection d'erreur

Patent Citations (2)

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Publication number Priority date Publication date Assignee Title
EP0394493A1 (fr) * 1988-10-24 1990-10-31 Matsushita Electric Industrial Co., Ltd. Circuit demodulateur de signaux audio
EP0486232A2 (fr) * 1990-11-12 1992-05-20 Texas Instruments Incorporated Décodeur MICDA à détection d'erreur

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6134522A (en) * 1994-08-02 2000-10-17 Siemens Aktiengesellschaft Signal processing method and arrangement for substitution or erroneous signals in a block-coded audio signals of an audio communication system
EP0712218A1 (fr) * 1994-11-10 1996-05-15 Ericsson Business Mobile Networks B.V. Procédé et dispositif de reconstruction de sous pendant des effacements
US5732356A (en) * 1994-11-10 1998-03-24 Telefonaktiebolaget Lm Ericsson Method and an arrangement for sound reconstruction during erasures
EP0858180A2 (fr) * 1997-02-05 1998-08-12 DeTeWe - Deutsche Telephonwerke Aktiengesellschaft & Co. Procédé silencieux pour dispositif d'écoute dans des terminaux de communication mobiles
EP0858180A3 (fr) * 1997-02-05 2000-11-02 DeTeWe - Deutsche Telephonwerke Aktiengesellschaft & Co. Procédé silencieux pour dispositif d'écoute dans des terminaux de communication mobiles

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AU5106893A (en) 1994-05-24

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