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WO1993015559A1 - Silencieux commande par les taux d'erreurs sur les bits - Google Patents

Silencieux commande par les taux d'erreurs sur les bits Download PDF

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Publication number
WO1993015559A1
WO1993015559A1 PCT/US1993/000511 US9300511W WO9315559A1 WO 1993015559 A1 WO1993015559 A1 WO 1993015559A1 US 9300511 W US9300511 W US 9300511W WO 9315559 A1 WO9315559 A1 WO 9315559A1
Authority
WO
WIPO (PCT)
Prior art keywords
ber
signal
received signal
communication device
threshold value
Prior art date
Application number
PCT/US1993/000511
Other languages
English (en)
Inventor
Tony R. Branch
Chin P. Wong
Original Assignee
Motorola, Inc.
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 Motorola, Inc. filed Critical Motorola, Inc.
Publication of WO1993015559A1 publication Critical patent/WO1993015559A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal

Definitions

  • This invention relates generally to communication devices and more particularly to squelch circuits used in communication devices.
  • a noise squelch circuit to disable the receiver's audio amplifier after the radio frequency (RF) carrier is no longer being received by the radio.
  • the squelch circuit prevents noise from being heard at the receiver's speaker during normal radio operation.
  • the basic purpose of a noise squelch circuit is to detect the change in the discriminator output noise as the received carrier strength changes. As the RF carrier strength increases, the discriminator noise decreases. Because the higher frequency noise falls or "quiets" more rapidly than low or mid-range noise and provides faster response time, it is used in most noise squelch circuits to determine the squelch decision (whether to squelch or unsquelch the receiver).
  • the received signal may have an acceptable high frequency noise floor yet be low in audio quality, because of digital bit corruption.
  • the use of typical squelch circuits result in diminished performance and would permit low quality voice signal to reach the receiver's audio amplifier.
  • a need is therefore felt for a squelch circuit that can be effectively used with digitized voice receivers in preventing low quality voice signals from reaching the audio amplifier, and hence the speaker.
  • a radio communication device having an audio output device.
  • the communication device also includes a receiver for receiving a signal and a means for calculating the bit error rate (BER) of the received signal.
  • BER bit error rate
  • Also included in the communication device is a comparator means for comparing the calculated BER with a threshold value and determining if the calculated BER is above the threshold value.
  • a means for muting the received signal is also provided for muting the audio output device when the BER is above the threshold value.
  • FIG. 1 shows a block diagram of a communication device in accordance with the present invention.
  • FIG. 2 shows a block diagram of the components of a Digital Signal Processor (DSP) in accordance with the present invention.
  • DSP Digital Signal Processor
  • FIG. 3 is an information packet received by the communication device of the present invention.
  • FIG. 4 is a flow chart of the operation of the communication device in accordance with the present invention.
  • Communication devices used in the communication of analog or digital signals utilize a variety of squelch techniques to prevent undesired noise from reaching the speaker. In general, this occurs when the quality (e.g., received signal strength) of the received signal is of such low level that would impair the receivers' ability to properly decode the received information.
  • These squelch techniques are met with a predicament, when apphed to digitized voice receivers. Since the quality of a received digitized voice signal depends both on the signal strength and the quality of the bit stream, the present squelch techniques find shortcomings in successfully distinguishing between desired and undesired received signals.
  • the principles of the present invention provide for a squelch technique that prevents undesired signals in a digitized voice communication system from reaching the speaker.
  • FIG. 1 shows a block diagram of a communication device 100 in accordance with the present invention.
  • the communication device 100 includes an antenna 102 where radio frequency signals are received and applied to a receiver 104.
  • Received signals are coupled to an Analog to Digital Converter (ADC) 106 where they are converted from analog to digital and presented to a digital signal processor (DSP) 110 where they are further processed.
  • ADC Analog to Digital Converter
  • DSP digital signal processor
  • the received signal comprises digitized voice.
  • DSPs is well known in the art.
  • a DSP 56001 is used to provide the demodulation and decoding of the received signal along with a host of other functions.
  • the DSP 110 is in constant communication with a controller 112, which among other things, receives data components of the received signal from the DSP 110 and upon further decoding presents them to the user on a display 108.
  • Voice components once again from the DSP 110, are coupled to an audio gate circuit 114 via a Digital to Analog Converter (DAC) 118.
  • the DAC 118 converts the error-corrected digital signal to analog and couples it to the audio gates circuit 114.
  • the analog signals are then gated from the audio gates 114 to a speaker 116 under the control of the controller 112.
  • the DSP 110 performs Bit Error Rate (BER) measurements in order to determine the quality of the decoded digitized voice.
  • BER Bit Error Rate
  • a signal is communicated to the controller 112, informing it of the BER calculation.
  • the controller 112 compares the calculated BER with a threshold and unmutes the audio gates 114 when the BER is below that threshold.
  • Methods of calculating BER are well known in the art and are available in several varieties.
  • the preferred BER measurement technique uses BER count with multiple error correction codes. In other words, a variety of error detection techniques may be employed to correct the errors in the received bit stream which includes different segments each being possibly coded with a different error correction routine.
  • the received signal includes an information packet having several portions, segments, or words.
  • FIG 3 shows one such information packet 300.
  • a preamble 302 generally precedes the received information packet followed by a sync word 304.
  • a network ID word 306 follows the sync word and is preceded by a link control segment 308.
  • the final component of the preferred frame is a user voice data segment 310 which is the actual intelligence desired to be received by the receiver 100.
  • each of the segments of the information packet 300 are encoded with different error detection and correction information.
  • the DSP 110 therefore includes circuitries to determine the type of error correction it should use in decoding and correcting each segment of the information packet 300, accordingly.
  • FIG. 2 a block diagram of a portion of the elements of the DSP 110 in accordance with the present invention is shown.
  • Signals from the demodulator 106 are coupled to a frame dis-assembler 202 where the information packet is disassembled into different words and a decision is made as to what segments of the DSP should be retrieved in order to decode and correct the particular frame under evaluation.
  • the demodulated signal is coupled to a buffer 204 and a decoder with error corrector 206.
  • the error corrector 206 proceeds to correct any errors that it can correct that may have occurred during the transmission of the signal.
  • the result of this error corrected signal and the buffered signal of the buffer 204 are compared at a bit comparator 208.
  • the information on the bit comparison is fed into a BER counter 210 where the BER is counted.
  • the BER counts are then coupled to the controller 112 where a decision is made as to whether audio gates 114 should be muted or unmuted.
  • the BER counter 210 is reset periodically to prevent BER overflow.
  • An operating window controls the period of time the counter 210 continues to count. This operating window may be controlled via the DSP 110 or the controller 112.
  • the combination of the buffer 204, the error corrector 206, the bit comparator 208 and the BER counter 210 are repeated for the different frame variations that may be used in the communication of the packet 300.
  • a buffer 212 an error corrector 214 are shown to receive the signal at the output of the frame dis-assembler 202.
  • the output signals of 212 and 214 are compared at a bit comparator 216 and the BER is counted as a counter 218. The result of this count is once again coupled to the controller 112.
  • Elements 212, 214, 216, and 218 represent the Nth circuit of the error detection and correction circuits needed to process the received packet 300.
  • FIG. 4 shows a flow chart of the operation of the DSP 110 and the controller 112. From a start block 402, the DSP calculates the BER, block 404. The output of block 404 is coupled to a condition block 406 where the BER is compared to a threshold. The NO output indicates that the error rate is too high thereby the audio gates 114 are muted, block 408. The output of block 408 is returned to the calculate BER, block 404. The YES output of the condition block 406 which indicates that the BER is lower than the threshold and hence a valid signal is coupled to an unmute audio block 410 where the controller 112 proceeds to unmute the audio gates 114. With the audio gates unmuted, the BER is once again calculated, block 412.
  • the output of block 412 is coupled to another condition block 414 where the BER is once again compared to a threshold and a decision is made as to whether it is higher than the threshold value.
  • a NO output returns the operation to the calculate BER block 412. Note that in this loop the audio remains unmuted until the BER count increase to a level above the threshold. As soon as the BER creeps above the threshold, hence resulting in the condition block 414 having a YES output, the audio gates 114 are muted via a return to block 408.
  • the BER can be used to squelch the receiver.
  • the DSP 110 in combination with the controller 112 decode the demodulated audio and correct the errors in the received frame.
  • the BER is compared to a threshold to determine the quality of the received signal.
  • the controller 112 proceeds to mute or unmute the audio gates 114, accordingly.
  • the principles of the present invention as have been demonstrated, provide for a squelch system for use in digitized voice environments. Thereby overcoming the deficiencies of present squelch systems that work with analog signals.
  • the BER squelch may be used with any modulation technique (i.e., frequency or phase modulation, amplitude modulation, etc.) as opposed to presently available squelch systems which are highly modulation dependent.
  • bit corruption is what determines the voice quality and not the prevailing RF noise.
  • the DSP 110 is only concerned with the quality of the bit stream being received and its ability to successfully retrieve and correct any corrupted bits, rather than the prevailing RF noise.
  • Another benefit of the present invention is that it uses the existing components of a communication device to achieve its objectives in preventing undesired signals from reaching the speaker.
  • a DSP and a controller are essentially required to allow for recovery of digitized voice.
  • These components are used in this invention to provide an additional benefit of determining whether that digitized voice is of high quality or of unrealizable quality, hence preventing unintelligible signals from getting to the speaker.
  • the DSP 110 could be so designed to include the functionality of the controller 112 with a presentation of the components of the communication device 100 is not to imply limitations to the invention and is there merely to provide a preferred embodiment of the present invention.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Noise Elimination (AREA)

Abstract

Dispositif (100) de radiocommunications comprenant un dispositif de sortie audio (116), un récepteur (104) de signal et un processeur (110) de signal numérique qui calcule les taux d'erreurs sur les bits (TEB) du signal reçu. Ce dispositif (100) de communication comporte également un comparateur (208) qui compare le TEB calculé à une valeur de seuil et qui détermine si le TEB calculé est supérieur à la valeur de seuil. Le processeur de signal numérique (110) est couplé à des portes audio (114) au niveau desquelles le signal sonore reçu est arrêté et ne peut atteindre le dispositif de sortie audio (116) lorsque le TEB est supérieur à la valeur de seuil.
PCT/US1993/000511 1992-02-03 1993-01-21 Silencieux commande par les taux d'erreurs sur les bits WO1993015559A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US82983092A 1992-02-03 1992-02-03
US829,830 1992-02-03

Publications (1)

Publication Number Publication Date
WO1993015559A1 true WO1993015559A1 (fr) 1993-08-05

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Family Applications (1)

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PCT/US1993/000511 WO1993015559A1 (fr) 1992-02-03 1993-01-21 Silencieux commande par les taux d'erreurs sur les bits

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Country Link
WO (1) WO1993015559A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5615412A (en) * 1995-07-31 1997-03-25 Motorola, Inc. Digital squelch tail system and method for same
FR2753592A1 (fr) * 1996-09-18 1998-03-20 France Telecom Procede de demodulation de signaux numeriques emis par salves robuste aux brouilleurs a bande etroite
US6144936A (en) * 1994-12-05 2000-11-07 Nokia Telecommunications Oy Method for substituting bad speech frames in a digital communication system
EP1381161A3 (fr) * 2002-07-11 2006-03-22 Pioneer Corporation Récepteur de radiodiffusion numérique avec fonctionnement d'élimination de bruits

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4355407A (en) * 1980-03-03 1982-10-19 Siemens Aktiengesellschaft Device for disconnecting the receiver in case of a small signal-to-noise ratio for a digital-modulated radio system
US4450573A (en) * 1981-12-07 1984-05-22 Motorola Inc. Bit data operated squelch
US4630290A (en) * 1983-11-18 1986-12-16 Nec Corporation Squelch signal generator capable of generating a squelch signal with a high reliability
US4922549A (en) * 1988-10-27 1990-05-01 Motorola, Inc. Digital FM squelch detector
US4967413A (en) * 1986-07-26 1990-10-30 Nec Corporation Burst signal detection apparatus
US5187811A (en) * 1989-11-29 1993-02-16 Motorola, Inc. Error detection

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4355407A (en) * 1980-03-03 1982-10-19 Siemens Aktiengesellschaft Device for disconnecting the receiver in case of a small signal-to-noise ratio for a digital-modulated radio system
US4450573A (en) * 1981-12-07 1984-05-22 Motorola Inc. Bit data operated squelch
US4630290A (en) * 1983-11-18 1986-12-16 Nec Corporation Squelch signal generator capable of generating a squelch signal with a high reliability
US4967413A (en) * 1986-07-26 1990-10-30 Nec Corporation Burst signal detection apparatus
US4922549A (en) * 1988-10-27 1990-05-01 Motorola, Inc. Digital FM squelch detector
US5187811A (en) * 1989-11-29 1993-02-16 Motorola, Inc. Error detection

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6144936A (en) * 1994-12-05 2000-11-07 Nokia Telecommunications Oy Method for substituting bad speech frames in a digital communication system
US5615412A (en) * 1995-07-31 1997-03-25 Motorola, Inc. Digital squelch tail system and method for same
FR2753592A1 (fr) * 1996-09-18 1998-03-20 France Telecom Procede de demodulation de signaux numeriques emis par salves robuste aux brouilleurs a bande etroite
EP1381161A3 (fr) * 2002-07-11 2006-03-22 Pioneer Corporation Récepteur de radiodiffusion numérique avec fonctionnement d'élimination de bruits

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