(12) United States Patent
`Oestreich
`
`USOO6349197B1
`US 6,349,197 B1
`(10) Patent No.:
`Feb. 19, 2002
`(45) Date of Patent:
`
`(54) METHOD AND RADIO COMMUNICATION
`SYSTEM FORTRANSMITTING SPEECH
`INFORMATION USING A BROADBAND OR
`A NARROWBAND SPEECH CODING
`METHOD DEPENDING ON TRANSMISSION
`POSSIBILITIES
`
`(75) Inventor: Stefan Oestreich, Holzkirchen (DE)
`(73) Assignee: Siemens Aktiengesellschaft, Munich
`(DE)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`Notice:
`
`(*)
`
`(21) Appl. No.: 09/245,619
`(22) Filed:
`Feb. 5, 1999
`(30)
`Foreign Application Priority Data
`Feb. 5, 1998
`(DE) ......................................... 198 04 581
`(51) Int. Cl." ............................... H04B 1/10; H04J 3/22
`(52) U.S. Cl. ......................... 455/63; 455/517; 455/423;
`370/468
`(58) Field of Search .......................... 455/63, 424, 425,
`455/423,517, 501, 403, 560, 561; 370/468,
`235,332, 333
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`..
`563 A : 13.R.
`felt et al. ........
`5768.314 A
`6/1998 Kapadia et al... 375/242
`5.940.439 A 3 s/1999 Kleider et al... 455/67.1
`5,953,666 A * 9/1999 Lehtimaki .....
`... 455/439
`5.991,716 A * 11/1999 Lehtimaki ................... 704/212
`
`8/2000 Navaro et al. .............. 455/561
`6,108,560 A
`9/2000 Lehtimaki ................... 370/435
`6,125,120 A
`6,134,220 A * 10/2000 Le Strat et al. ............. 370/468
`6,138,020 A * 10/2000 Galyas et al. ............... 455/561
`FOREIGN PATENT DOCUMENTS
`
`DE
`DE
`EP
`GB
`GB
`WO
`
`44 16 407
`19647 630
`O 472511
`2287 381
`2 29O 201
`98/48580
`
`............ HO4O/7/20
`11/1995
`5/1998 ..... ... HO4O/7/20
`2/1992 ..... ... HO4O/7/04
`9/1995 ..... ... HO4O/7/38
`12/1995
`.....
`... HO4L/25/OO
`10/1998 ............ HO4O/7/20
`
`OTHER PUBLICATIONS
`J. Biala, “Mobilfunk and intelligente Netze,” Vieweg Verlag,
`1995, 96-102.
`Abe, M. et al., “More Natural Sounding Voice Quality Over
`the Telephone!", NTT Review, (1995), pp. 104–109.
`* cited by examiner
`Primary Examiner William Trost
`ASSistant Examiner Rafael Perez-Gutierrez
`(74) Attorney, Agent, or Firm-Schiff Hardin & Waite
`(57)
`ABSTRACT
`A Speech coder/decoder can Select a broadband and a
`narrowband Speech coding method. For a connection to a
`mobile Station, a monitoring of transmission possibilities is
`performed, and, given limited transmission possibilities,
`there is a changeover from broadband to narrowband speech
`coding methods. The received narrowband Speech informa
`tion is expanded to a greater bandwidth at the receive side.
`The Subjective speech impression is improved by the bridg
`ing of this changeover effect. This guarantees an improved
`Speech quality to the listener, particularly with the introduc
`tion of adaptive multirate coding.
`17 Claims, 5 Drawing Sheets
`
`DIGITALIANALOG
`CONVERTER
`
`BANDWDTH
`EXPANSION DEVICE
`RECEIVER
`
`
`
`MOBILE
`STATION
`
`CONTROLLER
`
`CONVERTER
`
`MODULE
`SPEECH
`CODER/DECODER
`
`
`
`DUPLEXER
`MODULE
`TRANSMITTER
`
`- 1 -
`
`Sony v. Jawbone
`
`U.S. Patent No. 8,019,091
`
`Sony Ex. 1012
`
`

`

`U.S. Patent
`
`Feb. 19, 2002
`
`Sheet 1 of 5
`
`US 6,349,197 B1
`
`Fig. 1
`
`Z, Abis
`
`ASub
`
`A
`
`CELLY
`BASE1
`STATION
`
`Y
`
`SWITCHING
`DEVICE
`
`
`
`STATION
`CONTROL
`
`MOBILE as
`STATION
`
`1
`
`
`
`EXCHANGE
`
`
`
`
`
`BSS
`(PRIOR ART)
`
`Fig. 2
`
`MOBILE
`STATION
`
`PUBLIC
`TELEPHONE
`NETWORK
`
`MOBILE
`STATION
`
`PEECH
`copiechoer
`
`CONTROLLER
`
`
`
`SPEECH
`CODER/DECODER
`
`- 2 -
`
`

`

`U.S. Patent
`
`Feb. 19, 2002
`
`Sheet 2 of 5
`
`US 6,349,197 B1
`
`Fig. 3
`TFO
`
`sfin
`
`
`
`BASE
`STATION
`
`MOBILE
`STATION
`
`BTS -o-
`
`SPEECH
`DECODING
`
`CHANNEL
`DECODNG
`
`MS -o- BTS -o-
`SE
`NETWORK
`
`
`
`MOBILE
`STATION
`
`CHANNEL
`CODING
`
`
`
`CHANNEL
`DECODING
`
`CHANNEL
`CODING
`
`
`
`
`
`ISDN
`TERMINAL DEs
`EQUIPMENT
`
`NETWORK
`
`Fig. 4
`NOTFO
`
`BASE
`STATION
`
`TRANSCODER
`PCM
`MS - O BTS - O TRAU -o
`
`SPEECH
`CODING
`
`MOBILE
`STATION
`
`SPEECH
`DECODING
`
`CHANNEL
`DECODING
`BASE
`STATION
`
`CHANNEL
`CODING
`
`TRANSCODER
`
`MS-C-
`
`-H TRAU
`
`PCM
`
`SPEECH
`CODING
`CHANNEL
`DECODING
`
`MOBILE
`STATION
`CHANNEL
`CODING
`
`ES
`
`- 3 -
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`

`

`U.S. Patent
`
`Feb. 19, 2002
`
`Sheet 3 of 5
`
`US 6,349,197 B1
`
`TRANSCODER
`Fig 5 al
`d
`BSCV
`-o-
`ga, Ms. -o- TRAU
`STATION
`TRANSCODER
`BSCV
`BSCV
`1- TRAU2 --
`
`BSCV
`
`MOBILE
`STATION
`
`TRANSCODER
`Fig. 5 b
`9.
`BSCV
`SSCV
`-O TRAU1 -O-
`
`TRANSCODER
`BSCV
`SSCV
`-- TRAU2 --
`
`MOBILE
`STATION
`
`MOBILE
`STATION
`
`F e
`TRANSCODER
`9. C
`BSCV
`SSCV
`ME,Ms. -o- TRAU
`- D
`STATION
`TRANSCODER
`SSCV
`SSCV
`-- TRAU2 --
`
`MOBILE
`STATION
`
`TRANSCODER
`Fig. d
`i 5
`9.
`SSCV
`BSCV
`-o- RAU1 -O-
`
`TRAU
`
`TRANSCODER
`BSCV
`-- T
`RAU2
`
`c S C V
`
`MOBILE
`STATION
`
`MOBILE
`STATION
`
`NETWORK
`
`NETWORK
`
`NETWORK
`
`NETWORK
`
`- 4 -
`
`

`

`U.S. Patent
`
`Feb. 19, 2002
`
`Sheet 4 of 5
`
`US 6,349,197 B1
`
`Fig. 6
`MOBILE
`STATION
`
`
`
`
`
`DIGITALIANALOG
`CONVERTER
`BANDWDTH
`EXPANSION DEVICE
`RECEIVER
`
`CONTROLLER
`
`DUPLEXER
`MODULE MODULE
`SPEECH
`CODER/DECODER
`TRANSMITTER
`Fig. 7
`BANDWDTH EXPANSION DEVICE
`
`
`
`
`
`
`
`FILTER
`
`
`
`CONTROLLER
`
`SPEECH
`CODER/DECODER
`
`BSCV
`fl-f3
`
`SSCV
`f2
`
`MODULE
`
`MODULE
`
`f = 50.300 HZ
`f2 = 300.3.4 kHz
`f3 = 3.4.7 kHz
`fl-f3 = 50 HZ 7 kHZ
`
`- 5 -
`
`

`

`U.S. Patent
`
`Feb. 19, 2002
`
`Sheet 5 of 5
`
`US 6,349,197 B1
`
`Fig. 8
`
`kBit/s
`22.8
`
`11.4
`
`CHANNEL CODING
`
`SPEECH CODING
`
`SPEECH
`CODINGS
`
`WB
`WIDE
`BAND
`
`FR3/ HR2 HR3
`HR1
`HALF
`RATE
`
`FULL
`RATE
`
`BSCV --
`BROAD BAND
`
`-o- SSCV
`NARROW BAND
`
`- 6 -
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`

`

`US 6,349,197 B1
`
`1
`METHOD AND RADIO COMMUNICATION
`SYSTEM FORTRANSMITTING SPEECH
`INFORMATION USING A BROADBAND OR
`A NARROWBAND SPEECH CODING
`METHOD DEPENDING ON TRANSMISSION
`POSSIBILITIES
`
`BACKGROUND OF THE INVENTION
`The invention relates to a method and a radio communi
`cation System for transmitting speech information.
`The cellular mobile radio system GSM (Global System
`for Mobile Communication) is an example of a radio com
`munication System. In this System, the multiple acceSS
`method TDMA (Time Division Multiple Access) is used,
`whereby mobile stations are distinguished by different time
`Slots of a time division multiplex System.
`FIG. 1 depicts a block diagram of such a mobile radio
`network whose Service area is divided into a plurality of
`cells Z. In a cell Z, the telecommunication Service from and
`to a mobile station MS is made available by a base station
`BTS. One or more base stations BTS are connected to a base
`station control BSC. The base station control BSC executes
`the local functions of the call Switching, monitoring, and
`maintenance. The adaptation of the data of the mobile radio
`network to a telephone network is performed by a transcoder
`unit TRAU.
`The totality of the base stations BTS, the base station
`control BSC, and the transcoder unit TRAU is referenced as
`a base station system BSS. A plurality of base station
`controls BSC are connected to an exchange MSC, which is
`a constituent of a Switching means SSS which is connected
`to a public telephone network PSTN. The telephone network
`PSTN can be constructed as an ISDN network, as another
`mobile radio network, or as another kind of telephone or
`data network. The interface between base station BTS and
`base station control BSC is referenced as an Abis interface,
`and the interface between base station control BSC and
`transcoder unit TRAU is referenced as an ASub interface.
`The transmission occurs in wire-bound fashion via a PCM24
`or a PCM30 link.
`In a transmission of Speech to or from a mobile Station, it
`is generally known to Sample analog Speech information on
`the transmit Side and to convert this into digitally coded
`Speech information in a speech coder, and to transmit this
`error-protected, as warranted. On the receive Side, the digi
`tally coded Speech information is converted back into analog
`Speech information.
`In the above-mentioned mobile radio network GSM,
`which serves below only to illustrate the technical back
`ground of the present invention without restricting the
`generality of its use, the transcoder unit TRAU executes the
`adjustment of the data rate which is communicated by the
`telephone network PSTN to the data rate specified in the
`mobile radio network, (see German reference DE 19647
`630). A speech coding is executed not only in the mobile
`station MS, but also in the transcoder unit TRAU. A channel
`coding is typically executed for a radio transmission
`between mobile station MS and base station BTS.
`With the introduction of radio communication systems of
`the third generation (UMTS), it is provided that speech
`information should be transmittable broadband beyond the
`bandwidths from 300 Hz to 3.4 kHz, which are typical in
`telephone technology. The previously employed narrowband
`transmission should thus be replaced, and the Speech quality
`improved. In previous narrowband transmission methods, it
`is taught in the reference “More Natural Sounding Voice
`
`2
`Quality Over the Telephone” (M. Abe and Y. Yoshide, NTT
`Review, Vol. 7, Nr. 3, May 1995:104-109) to execute an
`artificial bandwidth expansion on the receive Side, in order
`to imitate a natural speech sound. This described bandwidth
`expansion is applied continuously and should be indepen
`dent of the conditions of the terminal equipment (see p. 105,
`bottom, to p. 106, top).
`SUMMARY OF THE INVENTION
`It is an object of the present invention to provide a method
`and radio communication System for transmitting Speech
`information which can correspond to the variable transmis
`Sion conditions with respect to the Speech coding/decoding.
`The inventive method for transmitting Speech information
`in a radio communication System presupposes Speech coder/
`decoders, which are arranged in a mobile Station, or
`respectively, in a transcoder unit. By means of the coder/
`decoders at least one broadband and one narrowband Speech
`coding method can be Selected. Furthermore, for a connec
`tion to the mobile Station, a monitoring of transmission
`possibilities is executed, and given limited transmission
`possibilities, a Switchover is executed from the broadband to
`the narrowband Speech coding method. That is, the Speech
`information is transmitted narrowband via at least parts of a
`transmission channel between the Speech coder/decoderS.
`The broadband Speech coding method requires a high net
`data rate, which no longer exists with Sufficient error pro
`tection under these transmission conditions.
`A narrowband Speech coding method leads to a different
`Speech perception at the receive Side, however, whereby the
`changeover, in particular, leads to undesirable and disruptive
`Sound alterations. The received narrowband Speech infor
`mation is inventively expanded to a greater bandwidth at the
`receive Side. The Subjective Speech impression improves by
`means of the bridging of this changeover effect. This applies
`particularly to short changeover phases from broadband to
`narrowband Speech coding methods.
`According to an advantageous development of the present
`invention, the Selected narrowband Speech coding method
`provides a higher coding protection than the broadband
`Speech coding method. Thus, in the case of temporary Signal
`interruptions, which are frequent in radio communication
`Systems, the transmission is guaranteed, and the previously
`perceived Subjective Speech impression is maintained at the
`listener.
`According to other advantageous embodiments of the
`present invention, there are reactions to limitations of the
`transmission possibilities, which limitations are brought
`about, via the radio interface, by an at least partial failure of
`a previously used tandem free operation (TFO) mode or by
`poor transmission conditions. The limited transmission pos
`Sibilities can also arise due to a changeover to another data
`rate (for example, half-rate), which is necessary due to the
`capacity utilization of System resources. In all these cases,
`the inventive method creates an improved Subjective speech
`impression.
`The Speech coding for the connection is advantageously
`executed in a TFO mode, and the changeover is thus
`executed for both devices taking part in the connection,
`whether it be a mobile Station, another terminal equipment,
`or a transcoder unit. The TFO mode replaces a speech
`coding/decoding at the network Side, in the transcoder unit
`TRAU, for example, by a transparent transmission of the
`Speech-encoded speech information from terminal equip
`ment to terminal equipment. Due to the transparency of the
`TFO mode, given transmission disturbances, an adaptation
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`

`

`US 6,349,197 B1
`
`15
`
`3
`must also occur for both transmissions. However, it is just as
`possible that a failure of the TFO module represents the
`disturbance and that there must be a changeover to a PCM
`transmission at the network side. The inventive method
`leads to an improved speech impression in the changeover
`phase in this case also.
`Another frequently occurring disturbing influence is a
`handover process during the TFO mode. The TFO mode is
`then potentially temporarily interrupted, and there is a
`changeover to a narrowband Speech coding until the TFO
`mode is reestablished.
`If the interference lasts longer, for example, longer than 5
`S, then it is advantageous to gradually reduce the bandwidth
`expansion of the received narrowband Speech information.
`The transition is thus Smoothed for a Subsequent narrowband
`transmission. The bandwidth expansion can be gradually
`reduced or can be Suppressed by digital filtering. These
`adjustments can be executed according to the individual
`receiver.
`According to an advantageous embodiment of the present
`invention, the Speech coder/decoder is Subdivided into mod
`ules for at least two frequency ranges, So that the broadband,
`or respectively, narrowband Speech coding method can be
`Specified by the Selection of one or more modules. These
`modules are easy to add, or respectively, remove, So that the
`Speech coder/decoder can be adapted to the transmission
`conditions by Simple parametrization.
`It also is within the framework of the present invention
`that the speech coder/decoder provides two broadband
`speech coding methods (i.e., the bandwidth is greater than
`300 Hz to 3.4 kHz), the more narrowband of the two speech
`coding methods being more sharply limited in the higher
`frequency range. But an addition of the lower frequencies
`already improves the Sound perception. This also has the
`advantage that e.g. 50 Hz to 3.4 kHz can be transmitted
`PCM-encoded. The higher frequencies are additionally arti
`ficially generated in a bandwidth expansion.
`
`4
`DCS-1800 and a PCS-1900 system), for example, via which
`the Speech information and data can be transmitted from and
`to mobile radio Subscribers (mobile stations MS). The
`present invention can also be utilized in radio communica
`tion Systems of the third generation.
`The functioning of the Speech coding and decoding as
`well as of the Speech transmission can be derived from the
`German Patent P 44 16 407. TRAU frames transport the
`Speech-encoded speech information with a speech period of
`20 mSec.
`FIG. 2 Schematically depicts the Speech transmission, via
`a mobile radio network, between two mobile stations MS
`with speech coder/decoders SC1, SC2. The speech coder/
`decoders SC1, SC2 contain modules, which are depicted
`below, for broadband and narrowband Speech transmission,
`between which it is possible to Switch. It is assumed that the
`broadband speech coding method BSCV is selected for a
`connection to a mobile station MS.
`The broadband transmission of Speech information occurs
`with a TFO mode. That is, a speech coding does not occur
`for the transmission in the network. Since the broadband
`Speech coding method BSCV requires a higher Sampling
`rate than a narrowband speech coding method SSCV, the
`broadband Speech information can not be transmitted over
`the network PCM-encoded (G.711 Aulaw, 8 kHz, sampling
`rate). The TFO mode defines a separate transmission method
`in the network.
`Control means SE which monitor the transmission pos
`sibilities are provided at the network side. These control
`means SE are integrated in the base station controls BSC, for
`example. The control means SE Specifies parameters with
`respect to the transmission possibilities for a connection to
`a mobile Station MS. By the comparison of these parameters,
`e.g., the comparison of the bit error rate with a threshold
`value, a degraded transmission quality for the radio interface
`between mobile station MS and base station BTS is detected.
`An additional, or respectively, alternative functionality of
`the control means SE consists in the detection of interrup
`tions in the TFO transmission, or of bottlenecks in the
`allocation of radio resources, or in the transmission, which
`are conditioned by handover processes. The transmission
`possibilities are also limited by these influences. If a
`changeover is necessary in a half-rate mode, then a narrow
`band speech coding method SSCV should likewise be
`Selected.
`FIG. 3 depicts a transmission direction of the speech
`transmission for the TFO mode, which is typically instanced
`as a duplex connection, in which a speech coding and a
`channel coding are executed in a mobile Station MS prior to
`the transmission of the Speech information to the base
`station BTS. In the base station BTS, a channel decoding
`takes place, whereupon the Still Speech-encoded speech
`information is Switched over the network to a base Station
`BTS for the other Subscriber. There is a second mobile
`station MS located in the radio range of this base station
`BTS. The base station BTS executes the channel coding for
`the Subsequent radio transmission, whereupon a channel
`decoding and a speech decoding is executed in the Second
`mobile station MS. If the other Subscriber is not a mobile
`station, but an ISDN terminal equipment KEG, for example,
`then a repeated channel coding/decoding is eliminated.
`For a transmission without TFO mode (FIG. 4), a speech
`decoding is executed prior to a Switching at the network Side
`in the transcoder unit TRAU, and the speech information is
`transmitted PCM-coded. In the case of a mobile second
`Subscriber, a corresponding Speech coding is, in turn,
`executed in a transcoder unit TRAU Subsequent to the
`Switching.
`
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`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The features of the present invention which are believed
`to be novel, are set forth with particularity in the appended
`claims. The invention, together with further objects and
`advantages, may best be understood by reference to the
`following description taken in conjunction with the accom
`panying drawings, in the Several Figures of which like
`reference numerals identify like elements, and in which:
`FIG. 1 depicts a mobile radio network;
`FIG. 2 depicts Speech transmission via a mobile radio
`network;
`FIG. 3 depicts speech transmission in the TFO mode;
`FIG. 4 depicts speech transmission without the TFO
`mode,
`FIGS. 5a-5d depict different possibilities for a utilization
`of the inventive method;
`FIG. 6 depicts a mobile station;
`FIG. 7 depicts speech coder/decoder with a plurality of
`coding methods, and
`FIG. 8 depicts various transmission methods for speech
`information.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`The mobile radio network that is depicted in FIG. 1 and
`described above is a GSM mobile radio system (or a
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`

`S
`FIG. 5a depicts the case of the TFO transmission with
`broadband speech coding BSCV from mobile station MS1 to
`mobile Station MS2, whereby a repeated Speech coding is
`not executed in the transcoder units TRAU1 and TRAU2.
`If the TFO mode in the network fails, the scheme accord
`ing to FIG. 5b results. Between the transcoder units TRAU1
`and TRAU2, the Speech transmission occurs narrowband.
`For the transmission direction depicted in FIG. 5b, the
`broadband speech information is reduced in bandwidth in
`the transcoder unit TRAU1, and Subsequent to the narrow
`band transmission, the bandwidth expansion occurs in the
`transcoder unit TRAU2, the mobile station MS2 thus receiv
`ing broadband speech information already. The bandwidth
`reduction, or respectively, expansion can also be initiated
`gradually, however.
`Given a longer lasting failure of the TFO mode, the
`bandwidth expansion can be gradually reduced in the
`transcoder unit TRAU2, and there can ultimately be a
`changeover, onto another broadband Speech coding method
`BSCV with a narrower band, between mobile station MS1
`and transcoder unit TRAU1 and/or between mobile station
`MS2 and transcoder unit TRAU2. This second broadband
`speech coding method BSCV, which has a narrower band,
`advantageously has an expanded frequency range into the
`low frequencies. That is, with this Specific broadband Speech
`coding method BSCV, speech information can be transmit
`ted over existing networks PCM-coded according to G.711.
`A reduction of the changeover interference already arises if
`a repeated bandwidth expansion is not executed in the
`transcoder unit TRAU2.
`If the transmission conditions for the radio interface
`deteriorate, then the transmission occurs between mobile
`station MS1 and transcoder unit TRAU1 (according to FIG.
`5d), or respectively, between transcoder unit TRAU2 and
`mobile station MS2 (according to FIG. 5c), according to a
`narrowband speech coding method SSCV. The bandwidth
`expansion respectively occurs at the receiving end of the
`part of the transmission channel with limited transmission
`possibilities. Assuming the situation in FIG. 5c, the narrow
`band transmission can additionally include the transmission
`between the transcoder units TRAU1 and TRAU2 and
`ultimately also from the transcoder unit TRAU2 to the
`mobile station MS2. The changeover according to FIG. 5d
`is usually immediately connected to a changeover between
`the transcoder units TRAU1 and TRAU2 to a narrowband
`transcoding method SSCV. The bandwidth expansion would
`thus occur either in the transcoding unit TRAU2 or even in
`the mobile station MS2.
`FIG. 6 depicts an inventive mobile station MS. It contains
`a loudspeaker L, a digital/analog converter DAC, a micro
`phone M, and an analog/digital converter ADC. By means of
`these subassemblies L., M, ADC, DAC, the speech input/
`output is connected to a digital part TRXD, which, in
`addition to executing a baseband processing (not depicted),
`executes a Speech coding/decoding. To this end, the digital
`part TRXD contains a speech coder/decoder SCI, which
`readies modules BSCV, SSCV for broadband, or
`respectively, narrowband Speech coding/decoding, between
`which it is possible to Switch. A subassembly of the
`transcoder unit TRAU, TRAU1, TRAU2 corresponds to the
`digital part TRXD and executes a speech coding/decoding.
`The following considers only the reception, that is, the
`decoding, for the mobile station MS. Three modules are
`provided for the broadband speech decoding BSCV, these
`covering the frequency ranges fl=50 Hz to 300 Hz, f2=300
`HZ to 3.4 kHz, and f3=3.4 kHz to 7 kHz. For the narrowband
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`6
`speech decoding SSCV, only one module f2=300 Hz to 3.4
`kHz is required. A more narrowband broadband transmis
`sion is likewise possible if only the modules f1 and f2 are
`used. The Speech coder/decoder SC1 also contains a means
`BE for bandwidth expansion and a control S. Their functions
`are detailed with reference to FIG. 7.
`The digital part TRXD is connected to analog receiving
`means RXA and transmitting means TXA, which are in turn
`connected to an antenna Via a duplexer K. In the receiving
`means RXA and the transmitting means TXA, an
`amplification, filtering and mixing of the receive and trans
`mit Signals are executed.
`In the speech decoder SC1 according to FIG. 7, a broad
`band expansion is executed in the means BE in the course of
`(that is, before, during, or after) a speech decoding of
`narrowband Speech information, whereby an algorithm is
`used from the reference “More Natural Sounding Voice
`Quality Over the Telephone” (M. Abe and Y. Yoshide, NTT
`Review; Vol. 7; No. 3, May 1995: 104-109), for example.
`The same applies to the opposite transmission direction.
`Subsequent to the bandwidth expansion, a filtering in a
`digital filter F is performed, which gradually returns the
`bandwidth expansion to the bandwidth of the narrowband
`transmission. This is an option which is used given longer
`limitations of the transmission possibilities, and can also be
`replaced by an adaptation within the bandwidth expansion
`algorithm.
`The changeover between broadband and narrowband
`transmission is triggered by the control S, which evaluates
`the transmission possibilities and parameters of the trans
`mission conditions, or respectively, which is prompted to do
`this by a signalling at the network Side. The control S also
`effects the adjustment of the band expansion algorithm, or
`respectively, the parametrization of the digital filter F. A
`selection of the modules f1, f2, f3 for the broadband BSCV
`and narrowband SSCV Speech coding/decoding is also
`prompted by the control S.
`Broadband and narrowband are relative terms which,
`according to FIG. 8, can be related to a multitude of different
`speech codings (see J. Biala, “Mobilfunk and intelligente
`Netze,” Vieweg Verlag, 1995: 96–102), whereby, for the
`broadband transmission within the data rate of the radio
`interface of, for example, 22.8 or 11.4 kBit/s, a greater Share
`should preferably be provided for the speech coding. From
`the combination of Speech coding and channel coding,
`different ratios of protective bits to useful bits, that is,
`different coding protections, arise for the data rates of 22.8
`or 11.4. Given the same groSS data rate, a narrowband
`method is more resistant to interference and is chosen given
`poor transmission conditions.
`For short-term interferences, for example, given radio
`shadow effects or temporary failure of the TFO mode by
`handover, and in order to maintain the Sound impression of
`the broadband transmission at the listener the bandwidth
`expansion of the Speech information that is received, nar
`rowband only, Subsequent to the changeover is executed.
`Given longer disturbances, the bandwidth expansion is
`gradually reduced to the bandwidth of the narrowband
`transmission. Particularly with the introduction of adaptive
`multirate coders (AMR), this guarantees an improved
`Speech quality to the listener, which is also effective in
`mobile radio, with its rapidly changing channel conditions.
`The invention is not limited to the particular details of the
`method and apparatus depicted and other modifications and
`applications are contemplated. Certain other changes may be
`made in the above described method and apparatus without
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`

`US 6,349,197 B1
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`7
`departing from the true Spirit and Scope of the invention
`herein involved. It is intended, therefore, that the subject
`matter in the above depiction shall be interpreted as illus
`trative and not in a limiting Sense.
`What is claimed is:
`1. A radio communication System for transmitting speech
`information, comprising:
`mobile Stations, each having a first speech coder/decoder;
`at least one transcoder unit having a Second speech
`coder/decoder;
`at least one broadband Speech coding method and one
`narrowband Speech coding method that are Selectable,
`at least by one of the first and Second Speech coder/
`decoders,
`a control device for monitoring transmission possibilities
`for a transmission channel between the first and Second
`Speech coder/decoders,
`given limited transmission possibilities for at least parts of
`the transmission channel, a changeover being effected
`from broadband to narrowband Speech coding meth
`ods, and
`a device for bandwidth expansion which expands trans
`mitted narrowband Speech information to a larger
`bandwidth, wherein the selected narrowband speech
`coding method provides a higher level of coding pro
`tection than a level of coding protection of the broad
`band Speech coding method.
`2. The radio communication System according to claim 1,
`wherein the device for bandwidth expansion is arranged in
`at least one of the mobile Station and the transcoder unit.
`3. The radio communication System according to claim 1,
`wherein a filter is allocated to the device for bandwidth
`expansion.
`4. A method for transmitting Speech information in a radio
`communication System having at least two speech coder/
`decoders which are arranged in mobile Stations, or
`respectively, at a network Side and Separated by a transmis
`Sion channel, comprising the Steps of:
`Selecting at least one broadband Speech coding method
`and one narrowband Speech coding method by a speech
`coder/decoder;
`monitoring transmission possibilities for a connection to
`a mobile Station;
`changing over, given limited transmission possibilities for
`at least parts of the transmission channel, from the
`broadband Speech coding method to the narrowband
`Speech coding method;
`transmitting speech information with the narrowband
`Speech coding method; and
`expanding the transmitted narrowband Speech informa
`tion to a larger bandwidth, wherein the Selected nar
`rowband Speech coding method provides a higher level
`of coding protection than a level of coding protection of
`the broadband Speech coding method.
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`15
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`5. The method according to claim 4, wherein parts of the
`transmission channel with limited transmission possibilities
`relate to radio interface, and wherein the transmission poS
`sibilities are limited by one of deteriorated transmission
`conditions or a changeover onto another data rate by System
`CSOUCCS.
`6. The method according to claim 4, wherein at least one
`Speech coder/decoder is Subdivided into modules for at least
`two frequency ranges, and wherein the broadband, or
`respectively, narrowband Speech coding method is Specified
`by Selection of at least one of Said modules.
`7. The method according to claim 4, wherein the speech
`coder/decoder provides two broadband Speech coding
`methods, a more narrowband Speech coding method of the
`two broadband Speech coding methods being more sharply
`limited in a higher frequency range.
`8. The method according to claim 7, wherein the more
`narrowband of the two broadband Speech coding methods is
`limited with respect to frequency Such that Speech informa
`tion is transmitted PCM-coded.
`9. The method according to claim 4, wherein a tandem
`free operation (TFO) mode is used for at least parts of the
`transmission channel, and wherein the limited transmission
`possibilities arise due to an at least partial failure of the TFO
`mode.
`10. The method according to claim 4, wherein the selec
`tion of the Speech coding method and the bandwidth expan
`Sion of the received narrowband Speech information are
`initiated in response to rapidly changing transmission pos
`Sibilities.
`11. The method according to claim 4, wherein the
`changeover is executed for both mobile stations and ISDN
`terminal equipment affected by the limited transmission
`possibilities of the transmission channel of the connection.
`12. The method according to claim 4, wherein the Selec
`tion of the Speech coding method and the bandwidth expan
`Sion of the received narrowband Speech information are
`initiated in response to a handover process.
`13. The method according to claim 4, wherein the band
`width expansion of the received narrowband Speech infor
`mation is gradually reduced.
`14. The method according to claim 13, wherein the
`bandwidth expansion is reduced to a bandwidth of the
`narrowband Speech information.
`15. The method according to claim 4, wherein the band
`width expansion occurs in one of a mobile Station or a
`transcoder unit.
`16. The method according to claim 4, wherein the band
`width is reduced at a receive side by digital filtering.
`17. The method according to claim 16, wherein the
`bandwidth expansion is reduced to a bandwidth of the
`narrowband Speech information.
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`k
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`k
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`k
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`k
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`k
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