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WO1996004744A1 - Systeme et procede pour mener une teleconference dans un systeme de communications a compression des signaux vocaux - Google Patents

Systeme et procede pour mener une teleconference dans un systeme de communications a compression des signaux vocaux Download PDF

Info

Publication number
WO1996004744A1
WO1996004744A1 PCT/US1995/009935 US9509935W WO9604744A1 WO 1996004744 A1 WO1996004744 A1 WO 1996004744A1 US 9509935 W US9509935 W US 9509935W WO 9604744 A1 WO9604744 A1 WO 9604744A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
signals
sum
remote conferee
participating users
Prior art date
Application number
PCT/US1995/009935
Other languages
English (en)
Inventor
David Almagor
Original Assignee
National Semiconductor Corporation
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 National Semiconductor Corporation filed Critical National Semiconductor Corporation
Priority to KR1019960701711A priority Critical patent/KR960705440A/ko
Publication of WO1996004744A1 publication Critical patent/WO1996004744A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/42—Systems providing special services or facilities to subscribers
    • H04M3/56—Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities
    • H04M3/568—Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities audio processing specific to telephonic conferencing, e.g. spatial distribution, mixing of participants
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/42—Systems providing special services or facilities to subscribers
    • H04M3/56—Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/42—Systems providing special services or facilities to subscribers
    • H04M3/56—Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities
    • H04M3/561—Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities by multiplexing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/40—Applications of speech amplifiers

Definitions

  • the present invention relates to communication systems such as cellular phone systems, and more specifically, to a system and method for cost-effectively conducting conference calls in a communication system which uses voice compression techniques, by reducing the number of data compression stages required
  • Personal communication systems which allow the transmission of information to another person in a distant location are rapidly becoming a common business tool.
  • portable handsets are used to connect users to each other through base stations which are linked to analog, digital, and mobile cellular networks.
  • An example of such a system is a cellular phone system, which is a wireless system used by many people to allow them to place telephone calls while in their cars or away from their home or office.
  • Personal communication systems can also be based on wired or fiber optic cable connections. and are capable of transmitting voice, data, or faxes between users.
  • These communication systems typically transmit digital signals which represent either analog or digital data.
  • Analog information such as voices, is converted to digital form and compressed before it is transmitted over the system.
  • Digital signals are similarly compressed prior to being transmitted over the system.
  • the compression stage is used in order to reduce the memory and bandwidth requirements of the system and to reduce the bandwidth requirements of the communication channel for each user This last aspect allows a communication channel to support a greater number of users for a given bandwidth of the spectrum.
  • Standard compression techniques operate on the data in a non-linear fashion This means that a signal must be decompressed before other operations, such as combining data streams for purposes of carrying out a conference call, can be performed.
  • One of the most intensive data processing operations performed by a base station involves a multi- handset conference call, wherein multiple communication system users are engaged in a conference call with a remote party connected to a standard telephone line.
  • a base station involves a multi- handset conference call, wherein multiple communication system users are engaged in a conference call with a remote party connected to a standard telephone line.
  • data processing stages are described with reference to a wireless communications system, many of the same operations would occur in a wired or fiber optic cable based system.
  • the base station has to decompress the compressed digital signals coming from each of the conferee's handsets, combine them together, compress the combined signal, and then send it out on the telephone line to the remote conferee.
  • a digital-to-analog stage which converts the compressed digital signal to analog form prior to transmission over the phone line may also be required.
  • the station must also provide the conference call to each of the conferees using the wireless communication system, with each conferee receiving the signal from the remote conferee and the other wireless system conferees. However, it is desireable that each wireless system user not receive their own signal to prevent their hearing an echo which would degrade the quality of the received signal. Thus, for each wireless handset conferee, the base station must generate a signal equal to the sum of the signal from the remote conferee plus the decompressed signals from all of the wireless handset conferees, except for the one to whom the combined signal will be sent. This combined signal must be compressed for each wireless handset conferee separately since each combined signal is different, and sent to the proper part
  • An analog-to-digital stage which converts the incoming signal from the remote conferee to a digital signal prior to summing it with the decompressed signals from the wireless handset users may also be required. These steps provide the handset users ' input signals for the conference call.
  • FIG. 1 shows a schematic diagram for a standard implementation of the processing stages needed for a conference call between four wireless handset users and one remote conferee.
  • the diagram of Fig. 1 represents the functional features of a conference call system of the type described in literature discussing conferencing in PCM based wireless or wired systems.
  • each of the four wireless handset users are identified by a slot or signal channel having a number from one to four.
  • Each wireless handset includes means for converting the analog signal representing the voice of the user to a digital signal, compressing the digital signal, and transmitting the compressed signal to the base station.
  • the digital signal coming into the station in compressed form from each of the handsets is decompressed or expanded by data decompression units 10.
  • the expanded signals are summed by adder 12 and then put through a digital-to-analog converter (not shown) and sent out on a telephone line 14 to the remote conferee. This provides the incoming conference call signal for the remote conferee.
  • the expanded signals from the wireless handsets are also provided as inputs to adders 20. 22, 24. and 26.
  • the expanded signals provided to each adder do not include the one corresponding to the slot or user for which that summed signal is intended.
  • adder 20 does not receive as an input the expanded signal corresponding to slot one.
  • the expanded signals may be attenuated prior to summing by adder 12 or adders 20. 22. 24. and 26
  • the incoming signal on telephone line 14 from the remote conferee is put through an analog-to- digital converter (not shown) and then routed to each of adders 20. 22. 24. and 26. where that signal is summed with the partial sums from the expanded signals transmitted by the wireless handsets
  • Each of the resulting sums is put through a data compression unit 30 and then transmitted to the appropriate user
  • the digital data Upon receipt by the wireless handset users, the digital data is decompressed and converted to an analog signal.
  • the conference call system shown in Fig. 1 can be expanded to serve any number of conference call participants.
  • the base station requires M data decompressors and M compressors. This imposes lower limits on the amount of processing capability, memory, and power required for a communication system which is designed to handle conference calls with multiple users.
  • M data decompressors and M compressors This imposes lower limits on the amount of processing capability, memory, and power required for a communication system which is designed to handle conference calls with multiple users.
  • European Patent Application EP 0 135 383, published March 27, 1985, and entitled "Conference Bridge Circuit Arrangements2 teaches a circuit for allowing a multi-user conference call to be conducted over a PCM telephone system.
  • the system uses wires or data buses to carry signals from a plurality of telephone set users to a central phone station. At the station, signals from one or more of the buses are selected, the selected signals are serially added, the output obtained by serially adding the signals is multiplexed, and the multiplexed signals are retransmitted to the conference call participants.
  • the circuitry described in the EP application permits multiple parties using the telephone system to participate in a conference call, its is believed that the circuit design disclosed introduces a serious disadvantage during the conduct of such a call.
  • the signals which are serially added are not subject to attenuation prior to being added.
  • the lack of such attenuation can create two possible problems. Firstly, saturation of the adder can occur due to data overflow.
  • the circuit does incorporate a means of checking for overflow, the system ' s response to an overflow condition results in a corruption of the signal data.
  • the second disadvantage is that each conferee will hear its own signal at full strength with a given system delay after its transmission. This can produce a confusing and distracting echo signal which degrades the quality of the conference call.
  • the echo may be removed by using a delay echo canceler in the conferees' handsets. This increases the cost and complexity of the system, however, it may be worthwhile in some situations. If the system delay is sufficiently small, the echo will instead be heard as a sidetone. a feature which is required in many communication systems. However, the sidetone produced by the system described in the EP patent application is at a fixed level which may be a disadvantage in using it within some communication systems, since different systems have different sidetone level specifications.
  • EP application conference call circuit is designed to be implemented in a dedicated piece of hardware which operates within a wired telephone system This places limits on its expandibility, which can become a problem as the number of users of the svstem increases. What is desired is a system and method for conducting conference calls between multiple users of a wired or wireless personal communication system and a remote conferee which reduces the number of signal compression and decompression stages required in present systems
  • the present invention is directed to a communication system and method for cost-effectivel conducting a conference call between multiple wired or wireless handset users and a remote conferee communicating over a telephone line.
  • Each of the incoming compressed signals from the handset users are decompressed and attenuated, prior to being added together.
  • the summed signals are then put through a digital-to-analog converter and sent to the remote conferee on the telephone line This provides the incoming signal for the remote conferee.
  • the summed signals are also added to the output signal resulting from the operation of an analog- to-digital converter on the incoming signal from the remote conferee, and the entire summed signal is compressed and sent out to each of the handset users.
  • Fig 1 shows a schematic diagram for a standard implementation of the processing stages needed for 5 a conference call between four wireless handset users and one remote conferee
  • Fig 2 shows a schematic diagram for an implementation of the processing stages needed for a conference call between four wireless handset users and one remote conferee according to the present invention
  • the inventor of the present invention has recognized that the amount of processing capabihtv
  • FIG 2 shows a schematic diagram for an implementation of the processing stages needed for a conference call between four wireless handset users and one remote conferee according to the present invention As shown m Fig 2, each of the four wireless handset users are identified bv a slot or signal
  • the digital signal commg to the station in compressed form from each of the handsets is decompressed or expanded bv decompression units 100
  • the expanded signals are then attenuated bv attenuators 102 which attenuate the signals from the wireless handset users in order to prevent data overflow and reduce the signal strength hen the summed signals are later provided to each of the users
  • the signal strength reduction caused bv the ) attenuation stage can be compensated for bv circuitrv in the handsets This insures that the signal heard bv the handset users is at an appropnate level
  • the attenuation factor is normallv chosen to be the reciprocal of the number of handset users Thus for the case of four such users shown in Fig 2 the attenuation factor is one-fourth l e the v oltage corresponding to the incoming signal is reduced to one-fourth its v alue
  • N is the number of handset users
  • the attenuation factor can also be adiusted so that the signals are attenuated sufficientlv to reduce the signal bv anv desired amount
  • the attenuated signals are then summed bv adder 104 put through a digital-to-analog co erter (not shown), and sent out on a telephone lme 105 to the remote conferee (not shown) This prov ides the incoming conference call signal for the remote conferee
  • the output of adder 104 is also prov ided as an mput to adder 106
  • the incoming signal on telephone lme 105 from the remote conferee is put through an analog-to-digital converter (not shown) and then serves as the other input for adder 106
  • the output of adder 106 i e the sum of the inputs is put through a smgle data compression unit 110 and then provided to each of the wireless handset users as the incoming conference call signal
  • An important aspect of the present invention is that the use of attenuators 102 provides two pnmarv benefits, firstly, it permits the incoming signals to be summed m adder 104 without creating data overflow problems, and secondly, under appropriate conditions it provides a sidetone so that each handset user receives a signal having as one component a reduced amplitude version of their own transmission As the existence of an appropnate level sidetone is a requirement of manv commumcation svstems the svstem shown m
  • a 1/N divider as an attenuation unit provides a sidetone havmg a level ithin the required boundanes for a range of users
  • m die DECT Digital European Cordless Telecommunications
  • the sidetone level attenuation is required to be 13 ⁇ 5 dB, or between 8 and
  • a 1 N divider provides an attenuation in signal equal to 20 log 1Q (1 N dB for N users Therefore for 3 users the attenuation is 9 6 dB, while for 7 users the attenuation is 16 9 dB
  • the appropnate level sidetone can be provided for between 3 and 7 users
  • the present invention can be implemented bv means of am standard programmable digital signal processor This makes the svstem more flexible (easilv reconfigurable) and cost efficient than a hardware based svstem which unnecessary and costlv equipment mav be mcluded
  • AGC automatic gam control
  • Fig 2 depicts onlv four wireless handset users engaged in a conference call the number mav be increased bv simplv adding a data decompression unit and attenuator for each user
  • the attenuation factor is altered as mentioned so that it equals the reciprocal of the number of wireless handset users
  • the svstem requires M data decompression units one (1) data compression unit and M attenuators hav g an attenuauon factor of 1/M
  • M attenuauon factors mav also be used to maintain the signals at a desired level in order to satisfv the commumcation svstem specifications
  • the AGC circuitrv in the handsets this also prov ides a means for producmg a desired signal lev el for the handset users
  • the method of the present inv ention reduces the number of data compression stages/units needed for multiple conferees and provides a savings in cost and complexity of the svstem With the data compression and decompression steps being implemented in the form of software the cost sa ings of M-

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Telephonic Communication Services (AREA)
  • Telephone Function (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un système et un procédé de communications permettant de mener à moindres coûts une téléconférence entre une pluralité d'utilisateurs de combinés avec ou sans fil et un intervenant, qui est éloigné, et communiquant par une ligne téléphonique (105). Chacun des signaux entrants comprimés provenant des utilisateurs de combinés est décomprimé et atténué, puis ces signaux sont ajoutés ensemble. Les signaux ajoutés passent ensuite dans un convertisseur analogique - numérique et sont envoyés - l'intervenant de la conférence, qui est éloigné, sur la ligne téléphonique. Les signaux additionnés sont également ajoutés au produit de la conversion faite par le convertisseur analogique - numérique sur le signal arrivant provenant de l'intervenant, qui est éloigné, et l'ensemble des signaux additionnés est comprimé et envoyé à chacun des utilisateurs des combinés.
PCT/US1995/009935 1994-08-04 1995-08-04 Systeme et procede pour mener une teleconference dans un systeme de communications a compression des signaux vocaux WO1996004744A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1019960701711A KR960705440A (ko) 1994-08-04 1995-08-04 음성 압축을 사용하는 통신 시스템에서의 회의 통화를 수행하는 시스템 및 방법(system and method for conducting conference calls in a communication system utilizing voice compression)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US28585994A 1994-08-04 1994-08-04
US08/285,859 1994-08-04

Publications (1)

Publication Number Publication Date
WO1996004744A1 true WO1996004744A1 (fr) 1996-02-15

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PCT/US1995/009935 WO1996004744A1 (fr) 1994-08-04 1995-08-04 Systeme et procede pour mener une teleconference dans un systeme de communications a compression des signaux vocaux

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WO (1) WO1996004744A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2774250A1 (fr) * 1998-01-23 1999-07-30 Sagem Reseau local de telephonie sans fil permettant l'etablissement de conferences avec un reseau telephonique et terminal d'un tel reseau
WO2001008394A1 (fr) * 1999-07-26 2001-02-01 Thomson Licensing S.A. Procede et appareil de connexion de telephones filaires et telephones sans fil pour des conferences telephoniques et des communications par interphone
EP1059009A4 (fr) * 1998-02-27 2003-09-03 Motorola Inc Procede et appareil pour etablir une communication multi-abonnes dans un systeme de communication
WO2006005566A1 (fr) * 2004-07-13 2006-01-19 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Terminal de conference a reduction d'echo pour un systeme de conference
JP2013165378A (ja) * 2012-02-10 2013-08-22 Jvc Kenwood Corp インターカムシステム及びインターカムシステムの制御方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0081799A1 (fr) * 1981-12-10 1983-06-22 Alcatel N.V. Procédé et circuit pour l'établissement d'une communication de conférence
JPS6018052A (ja) * 1983-07-11 1985-01-30 Matsushita Electric Ind Co Ltd デイジタル式会議通話装置
EP0135383A2 (fr) * 1983-09-08 1985-03-27 Plessey Overseas Limited Montages de pont de conférence
US4730306A (en) * 1984-10-11 1988-03-08 Iwatsu Electric Co., Ltd. Conference system
US4797876A (en) * 1987-07-10 1989-01-10 Solid State Systems, Inc. Conferencing bridge
JPH04367148A (ja) * 1991-06-14 1992-12-18 Fujitsu Ltd 会議通話方式

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0081799A1 (fr) * 1981-12-10 1983-06-22 Alcatel N.V. Procédé et circuit pour l'établissement d'une communication de conférence
JPS6018052A (ja) * 1983-07-11 1985-01-30 Matsushita Electric Ind Co Ltd デイジタル式会議通話装置
EP0135383A2 (fr) * 1983-09-08 1985-03-27 Plessey Overseas Limited Montages de pont de conférence
US4730306A (en) * 1984-10-11 1988-03-08 Iwatsu Electric Co., Ltd. Conference system
US4797876A (en) * 1987-07-10 1989-01-10 Solid State Systems, Inc. Conferencing bridge
JPH04367148A (ja) * 1991-06-14 1992-12-18 Fujitsu Ltd 会議通話方式

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 17, no. 241 (E - 1364) 14 May 1993 (1993-05-14) *
PATENT ABSTRACTS OF JAPAN vol. 9, no. 136 (E - 320) 12 June 1985 (1985-06-12) *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2774250A1 (fr) * 1998-01-23 1999-07-30 Sagem Reseau local de telephonie sans fil permettant l'etablissement de conferences avec un reseau telephonique et terminal d'un tel reseau
EP0933915A1 (fr) * 1998-01-23 1999-08-04 Sagem Sa Réseau local de téléphonie sans fil permettant l'établissement de conférences avec un réseau téléphonique et terminal d'un tel réseau local
EP1059009A4 (fr) * 1998-02-27 2003-09-03 Motorola Inc Procede et appareil pour etablir une communication multi-abonnes dans un systeme de communication
WO2001008394A1 (fr) * 1999-07-26 2001-02-01 Thomson Licensing S.A. Procede et appareil de connexion de telephones filaires et telephones sans fil pour des conferences telephoniques et des communications par interphone
WO2006005566A1 (fr) * 2004-07-13 2006-01-19 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Terminal de conference a reduction d'echo pour un systeme de conference
DE102004033866B4 (de) * 2004-07-13 2006-11-16 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Konferenz-Endgerät mit Echoreduktion für ein Sprachkonferenzsystem
US7853007B2 (en) 2004-07-13 2010-12-14 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Conference terminal with echo reduction for a voice conference system
JP2013165378A (ja) * 2012-02-10 2013-08-22 Jvc Kenwood Corp インターカムシステム及びインターカムシステムの制御方法

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