(12) United States Patent
`(12) United States Patent
`Spruyt et al.
`Spruyt et ai.
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US006370156B2
`US006370156B2
`(10) Patent No.:
`US 6,370,156 B2
`US 6,370,156 B2
`(10) Patent No.:
`* Apr. 9, 2002
`(45) Date of Patent:
`*Apr. 9, 2002
`(45) Date of Patent:
`
`(54) MODULATION/DEMODULATION OFA
`(54) MODULATION/DEMODULATION OF A
`PILOT CARRIER, MEANS AND METHOD
`PILOT CARRIER, MEANS AND METHOD
`TO PERFORM THE MODULATION/
`TO PERFORM THE MODULATION/
`DEMODULATION
`DEMODULATION
`(75) Inventors: Paul Marie Pierre Spruyt, Prinses
`Inventors: Paul Marie Pierre Spruyt, Prinses
`(75)
`-
`-
`Lydialaan; Frank Octaaf Van der
`Lydialaan; Frank octaaf Van der
`Putten, Vinkstraat; Peter Paul Frans
`Putten, Vinkstraat; Peter Paul Frans
`Reusens, Warande, all of (BE)
`Reusens, Warande, all of (BE)
`(73) Assignee: Alcatel, Paris (FR)
`(73) Assignee: AIcatel, Paris (FR)
`(*) Notice:
`This patent issued on a continued pros
`( *) Notice:
`This patent issued on a continued pros(cid:173)
`ecution application filed under 37 CFR
`ecution application filed under 37 CFR
`1.53(d), and is subject to the twenty year
`1.53( d), and is subject to the twenty year
`patent term provisions of 35 U.S.C.
`patent term provisions of 35 U.S.c.
`154(a)(2).
`154(a)(2).
`Subject to any disclaimer, the term of this
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`U.S.c. 154(b) by 0 days.
`
`(21) Appl. No.: 08/844,383
`(21) Appl. No.: 08/844,383
`(22) Filed:
`Apr. 18, 1997
`(22) Filed:
`Apr. 18, 1997
`(30)
`Foreign Application Priority Data
`(30)
`Foreign Application Priority Data
`Jan. 31, 1997 (EP) ............................................ 97.400.221
`Jan. 31, 1997
`(EP) ............................................ 97400221
`
`(51) Int. Cl." .............................. H04B 3/10; H04J 3/06;
`(51)
`Int. CI? .............................. H04B 3/10; H04J 3/06;
`H04L 7/00
`H04L 7/00
`(52) U.S. Cl. ....................... 370/480; 370/206; 370/491;
`(52) U.S. CI. ....................... 370/480; 370/206; 370/491;
`370/515; 375/222; 375/357; 375/367
`370/515; 375/222; 375/357; 375/367
`(58) Field of Search ................................. 370/203, 204,
`(58) Field of Search ................................. 370/203, 204,
`370/206, 207, 208, 480, 484, 491, 515,
`370/206, 207, 208, 480, 484, 491, 515,
`468,210, 332, 474; 375/222, 357, 367,
`468,210,332,474; 375/222, 357, 367,
`377, 200, 285, 131; 455/10
`377, 200, 285, 131; 455/10
`
`(56)
`(56)
`
`References Cited
`References Cited
`U.S. PATENT DOCUMENTS
`U.S. PATENT DOCUMENTS
`5,103,459 A * 4/1992 Gilhousen et al. .......... 370/206
`5,103,459 A *
`4/1992 Gilhousen et al. .......... 370/206
`5,241,544 A * 8/1993 Jasper et al. ................ 370/206
`5,241,544. A * 8/1993 Jasper et al. .........
`... 370/206
`5,311,541 A * 5/1994 Sanderford, Jr ............. 375/131
`5,311,541 A * 5/1994 Sanderford, Jr. .....
`... 375/131
`5,400,322 A * 3/1995 Hubt et al.
`5,400,322 A * 3/1995 Hubt et al. ................. 370/468
`................. 370/468
`
`
`
`5,406,551 A * 4/1995 Saito et al.
`5,406,551 A * 4/1995 Saito et al. ................. 370/203
`................. 370/203
`5,414,734 A * 5/1995 Marchetto et al. .......... 375/267
`5,414,734. A * 5/1995 Marchetto et al. .......... 375/267
`5,477,199 A * 12/1995 Montreuil ................... 332/103
`5,477,199 A * 12/1995 Montreuil ................... 332/103
`5,506,865 A * 4/1996 Weaver, Jr .................. 370/206
`5,506,865 A * 4/1996 Weaver, Jr. ................. 370/206
`5,546,190 A 8/1996 Hill et al.
`5,546,190 A
`8/1996 Hill et al.
`5,548,344 A
`8/1996 Park
`º: º :: º1996 Park
`5,623,485 A * 4/1997 Bi .............................. 370/209
`2- -->
`/1997 Bi .............................. 370/209
`5,627,863 A * 5/1997 Aslamis et al. .............. 375/357
`5,627,863 A * 5/1997 Aslanis et al. .............. 375/357
`5,703,873 A * 12/1997 Ojanpera et al. ........... 370/332
`5,703,873 A * 12/1997 Ojanpera et al.
`........... 370/332
`
`(List continued on next page.)
`(List continued on next page.)
`
`OTHER PUBLICATIONS
`OTHER PUBLICATIONS
`
`“A Multicarrier–E1–HDSL Transceiver Systgem with
`"A Multicarrier-E1-HDSL Transceiver Systgem with
`Coded Modulation” by Chow et al in vol. 4, No. 3, May–Jun.
`Coded Modulation" by Chow et al in vol. 4, No.3, May-Jun.
`1993 issue of Journal of European Transactions pp.
`issue of Journal of European Transactions pp.
`1993
`257–266.
`257-266.
`“Network and Customer Installation Interfaces, Asymmetric
`"Network and Customer Installation Interfaces, Asymmetric
`Digital Subscriber Line (ADSL) Metallic Interface” from
`Digital Subscriber Line (ADSL) Metallic Interface" from
`ANSI T1B1.413–1995, top page only.
`ANSI TlE1.413-1995, top page only.
`
`Primary Examiner—Hassan Kizou
`Primary Examiner---Hassan Kizou
`Assistant Examiner-John Pezzlo
`Assistant Examiner—John Pezzlo
`(74) Attorney, Agent, or Firm—Ware, Fressola, Van Der
`(74) Attorney, Agent, or Firm-Ware, Fressola, Van Der
`Sluys & Adolphson LLP
`Sluys & Adolphson LLP
`(57)
`ABSTRACT
`ABSTRACT
`(57)
`For synchronisation purposes, a transmitter (TX) multi
`For synchronisation purposes, a transmitter (TX) multi(cid:173)
`plexes a pilot carrier with carriers whereon data elements
`plexes a pilot carrier with carriers whereon data elements
`(DATA) are modulated, and transmits the pilot carrier
`(DATA) are modulated, and transmits the pilot carrier
`together with the modulated carriers to a receiver (RX). The
`together with the modulated carriers to a receiver (RX). The
`immunity of the pilot carrier from interference, such as radio
`immunity of the pilot carrier from interference, such as radio
`amateur signals, is improved by modulating the pilot carrier
`amateur signals, is improved by modulating the pilot carrier
`with a non-constant signal, for instance a random signal, an
`with a non-constant signal, for instance a random signal, an
`alternating signal or even scrambled data elements (DATA),
`alternating signal or even scrambled data elements (DATA),
`before transmission thereof. Since demodulation of the pilot
`before transmission thereof. Since demodulation of the pilot
`carrier in the receiver (RX) and averaging successive
`carrier in the receiver (RX) and averaging successive
`demodulated pilot carriers reduces the effect of the interfer
`demodulated pilot carriers reduces the effect of the interfer(cid:173)
`ence induced on the non-constantly modulated pilot carrier,
`ence induced on the non-constantly modulated pilot carrier,
`the degradation of the synchronisation between transmitter
`the degradation of the synchronisation between transmitter
`(TX) and receiver (RX) is reduced significantly.
`(TX) and receiver (RX) is reduced significantly.
`
`12 Claims, 1 Drawing Sheet
`12 Claims, 1 Drawing Sheet
`
`DATA
`
`, -
`
`f-+ TI
`-
`
`MOD
`
`i
`TPT
`TPT
`
`S
`
`TM
`TM
`
`S'
`
`r - -
`RI ~ DMOD
`
`DATA
`
`-
`
`RX
`
`i
`RPT
`RPT
`
`TX
`
`TQ Delta Exhibit 2004
`Cisco Systems, Inc. v. TQ Delta LLC
`IPR2016-01020
`
`1
`
`

`

`US 6,370,156 B2
`US 6,370,156 B2
`Page 2
`Page 2
`
`U.S. PATENT DOCUMENTS
`U.S. PATENT DOCUMENTS
`-
`5,745,839 A * 4/1998 Lieberman ................... 455/10
`5,745,839 A * 4/1998 Lieberman ................... 455/10
`5,748,677 A * 5/1998 Kumar ....................... 375/285
`5,748,677 A * 5/1998 Kumar .........
`... 375/285
`5,751,761 A * 5/1998 Gilhousen ................... 375/200
`5,751,761 A * 5/1998 Gilhousen .....
`... 375/200
`5,790,514 A * 8/1998 Marchok et al. ............ 370/208
`5,790,514 A * 8/1998 Marchok et al. .
`... 370/208
`5,850,415 A * 12/1998 Hunsinger et al. .......... 375/216
`5,850,415 A * 12/1998 Hunsinger et al. .......... 375/216
`
`5,867,528 A * 2/1999 Veruceken .................. 375/222
`5,867,528 A * 2/1999 Veruceken .................. 375/222
`5,910,970 A * 6/1999 Lu ............................. 375/377
`5,910,970 A * 6/1999 Lu ............................. 375/377
`5,943,361 A * 8/1999 Gilhousen et al. .......... 375/200
`5,943,361 A * 8/1999 Gilhousen et al. .......... 375/200
`5,991,308 A * 11/1999 Fuhrmann et al. .......... 370/474
`5,991,308 A * 11/1999 Fuhrmann et al. .......... 370/474
`6,118,758 A * 9/2000 Marchok et al. ............ 370/210
`6,118,758 A * 9/2000 Marchok et al. ..... ... 370/210
`* cited by examiner
`* cited by examiner
`
`
`
`2
`
`

`

`u.s. Patent
`U.S. Patent
`
`Apr. 9, 2002
`Apr. 9,2002
`
`US 6,370,156 B2
`US 6,370,156 B2
`
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`

`US 6,370,156 B2
`US 6,370,156 B2
`
`1
`1
`MODULATION/DEMODULATION OF A
`MODULATION/DEMODULATION OF A
`PILOT CARRIER, MEANS AND METHOD
`PILOT CARRIER, MEANS AND METHOD
`TO PERFORM THE MODULATION/
`TO PERFORM THE MODULATION/
`DEMODULATION
`DEMODULATION
`
`TECHNICAL FIELD
`TECHNI CAL FIELD
`The present invention relates to a method for transmitting
`The present invention relates to a method for transmitting
`data elements from a transmitter to a receiver, wherein the
`data elements from a transmitter to a receiver, wherein the
`data elements are modulated on at least one carrier; wherein
`data elements are modulated on at least one carrier; wherein
`a pilot carrier is used for synchronisation between the
`a pilot carrier is used for synchronisation between the
`transmitter and the receiver which is multiplexed with the at
`transmitter and the receiver which is multiplexed with the at
`least one carrier; and wherein the at least one carrier and the
`least one carrier; and wherein the at least one carrier and the
`pilot carrier are transmitted over a transmission medium
`pilot carrier are transmitted over a transmission medium
`interconnecting the transmitter and the receiver.
`interconnecting the transmitter and the receiver.
`It is also directed to a transmitter adapted to transmit data
`It is also directed to a transmitter adapted to transmit data
`elements to a receiver via a transmission medium, the
`elements to a receiver via a transmission medium, the
`transmitter comprising modulation means to a first input of
`transmitter comprising modulation means to a first input of
`which the data elements are applied, the modulation means
`which the data elements are applied, the modulation means
`being adapted to modulate the data elements on at least one
`being adapted to modulate the data elements on at least one
`carrier, and to multiplex the at least one carrier with a pilot
`carrier, and to multiplex the at least one carrier with a pilot
`carrier used for synchronisation between the transmitter and
`carrier used for synchronisation between the transmitter and
`the receiver; pilot information means, adapted to generate
`the receiver; pilot information means, adapted to generate
`information to identify the pilot carrier, and to apply the
`information to identify the pilot carrier, and to apply the
`information to a second input of the modulation means; and
`information to a second input of the modulation means; and
`line interface means, coupled between an output of the
`line interface means, coupled between an output of the
`modulation means and an input of the transmission medium
`modulation means and an input of the transmission medium
`and adapted to condition the at least one carrier and the pilot
`and adapted to condition the at least one carrier and the pilot
`carrier to be transmitted over the transmission medium.
`carrier to be transmitted over the transmission medium.
`It is additionally directed to a receiver adapted to receive
`It is additionally directed to a receiver adapted to receive
`a signal transmitted thereto by a transmitter via a transmis
`a signal transmitted thereto by a transmitter via a transmis(cid:173)
`sion medium, the receiver comprising: line interface means,
`sion medium, the receiver comprising: line interface means,
`coupled to an output of the transmission medium and
`coupled to an output of the transmission medium and
`adapted to condition the signal to be applied to components
`adapted to condition the signal to be applied to components
`of the receiver; demodulating means, an input of which is
`of the receiver; demodulating means, an input of which is
`coupled to an output of the line interface means, the
`coupled to an output of the line interface means, the
`demodulating means being adapted to demultiplex in the
`demodulating means being adapted to demultiplex in the
`signal a pilot carrier from at least one carrier whereon data
`signal a pilot carrier from at least one carrier whereon data
`elements are modulated, and to demodulate the data ele
`elements are modulated, and to demodulate the data ele(cid:173)
`ments from the at least one carrier; and pilot information
`ments from the at least one carrier; and pilot information 40
`40
`means, adapted to generate information to identify the pilot
`means, adapted to generate information to identify the pilot
`carrier, and to apply the information to a second input of the
`carrier, and to apply the information to a second input of the
`demodulation means.
`demodulation means.
`It is still further directed to a transmission system com
`It is still further directed to a transmission system com(cid:173)
`prising a transmitter, a receiver and a transmission medium,
`prising a transmitter, a receiver and a transmission medium, 45
`45
`coupled between an output of the transmitter and an input of
`coupled between an output of the transmitter and an input of
`the receiver, wherein the transmitter and receiver are of the
`the receiver, wherein the transmitter and receiver are of the
`above described type.
`above described type.
`BACKGROUND OF THE INVENTION
`BACKGROUND OF THE INVENTION
`Such a method for transmitting data elements, such a
`Such a method for transmitting data elements, such a
`transmitter and receiver, and such a transmission system are
`transmitter and receiver, and such a transmission system are
`already known in the art, e.g. from the specifications of the
`already known in the art, e.g. from the specifications of the
`ANSI (American National Standards Institute, Inc.) Stan
`ANSI (American National Standards Institute, Inc.) Stan(cid:173)
`dard on ADSL, the approved version of which has the
`dard on ADSL, the approved version of which has the
`reference T1E1.413-1995 and title "Network and Customer
`reference T1E1.413-1995 and title “Network and Customer
`Installation Interfaces, Asymmetric Digital Subscriber Line
`Installation Interfaces, Asymmetric Digital Subscriber Line
`(ADSL) Metallic Interface”. Therein, data elements are
`(ADSL) Metallic Interface". Therein, data elements are
`modulated on a set of carriers. In case of discrete multi tone
`modulated on a set of carriers. In case of discrete multi tone
`(DMT) modulation, these carriers have equidistant frequen
`(DMT) modulation, these carriers have equidistant frequen- 60
`60
`cies. As is indicated in paragraphs 6.9.1.2 and 7.9.1.2 on
`cies. As is indicated in paragraphs 6.9.1.2 and 7.9.1.2 on
`pages 46 and 58 of the above cited standard, published in
`pages 46 and 58 of the above cited standard, published in
`1995, one of the carriers is reserved as a pilot carrier. This
`1995, one of the carriers is reserved as a pilot carrier. This
`pilot carrier is used for synchronisation between transmitter
`pilot carrier is used for synchronisation between transmitter
`and receiver and is modulated by a constant signal. In a
`and receiver and is modulated by a constant signal. In a 65
`65
`vector plane, wherein the modulation constellation is rep
`vector plane, wherein the modulation constellation is rep(cid:173)
`resented by a collection of points, the pilot carrier is thus
`resented by a collection of points, the pilot carrier is thus
`
`35
`35
`
`2
`2
`represented by a single point. On the transmission medium,
`represented by a single point. On the transmission medium,
`e.g. on a telephone line interconnecting the ADSL transmit
`e.g. on a telephone line interconnecting the ADSL transmit(cid:173)
`ter and ADSL receiver in the known system, the pilot carrier
`ter and ADSL receiver in the known system, the pilot carrier
`thus represents a sine or cosine which does not change in
`thus represents a sine or cosine which does not change in
`phase, amplitude or frequency in time (in case a guard bond
`5 phase, amplitude or frequency in time (in case a guard bond
`or cyclic prefix is added whose length does not contain an
`or cyclic prefix is added whose length does not contain an
`integer number of periods of the pilot tone, the pilot tone
`integer number of periods of the pilot tone, the pilot tone
`might be discontinuous at the edges of the DMT symbol).
`might be discontinuous at the edges of the DMT symbol).
`A well-known source of narrowbanded or single fre
`A well-known source of narrowbanded or single fre-
`quency disturbances is a radio amateur or an AM radio
`10
`10 quency disturbances is a radio amateur or an AM radio
`station, which broadcasts radio signals at frequencies close
`station, which broadcasts radio signals at frequencies close
`to carrier frequencies. Forward error correction techniques,
`to carrier frequencies. Forward error correction techniques,
`well-known in the art, can reduce the effect of such distur
`well-known in the art, can reduce the effect of such distur(cid:173)
`bances on data carried by the affected carriers. An alternative
`bances on data carried by the affected carriers. An alternative
`way to protect data against such interferers, proposed by
`15
`15 way to protect data against such interferers, proposed by
`Peter S. Chow et al. in the article “A multicarrier E1-HDSL
`Peter S. Chow et al. in the article "A multicarrier E1-HDSL
`Transceiver System with Coded Modulation” from the
`Transceiver System with Coded Modulation" from the
`authors Peter S. Chow, Noafal Al-Dhahir, John M. Cioffi and
`authors Peter S. Chow, NoafaIAl-Dhahir, John M. Cioffi and
`John A. C. Bingham published in issue No. 3 May/June 1993
`JohnA. C. Bingham published in issue No.3 May/June 1993
`of the Journal of European Transactions on Telecommuni
`20
`20 of the Journal of European Transactions on Telecommuni(cid:173)
`cations and Related Technologies (ETT), pages 257–266, is
`cations and Related Technologies (ETT), pages 257-266, is
`bitswapping: bit and energy allocations are updated so that
`bitswapping: bit and energy allocations are updated so that
`the affected carriers carry less data bits then before. This
`the affected carriers carry less data bits then before. This
`technique requires an additional communication between
`technique requires an additional communication between
`25
`transmitter and receiver.
`25 transmitter and receiver.
`Although data transmitted over the telephone line from
`Although data transmitted over the telephone line from
`the transmitter to the receiver may be protected by one of the
`the transmitter to the receiver may be protected by one of the
`above mentioned techniques, the presence of noise or an
`above mentioned techniques, the presence of noise or an
`interferer, for instance a radio amateur signals with a fre
`interferer, for instance a radio amateur signals with a fre-
`30
`quency in the vicinity of the frequency of the pilot carrier,
`30 quency in the vicinity of the frequency of the pilot carrier,
`may still cause an offset between the received point repre
`may still cause an offset between the received point repre(cid:173)
`senting the pilot carrier in the above defined vector plane and
`senting the pilot carrier in the above defined vector plane and
`the expected point. If this offset in the vector plane is not
`the expected point. If this offset in the vector plane is not
`sufficiently random, it biases the synchronisation
`sufficiently random, it biases the synchronisation
`mechanism, resulting in a performance degradation. This is
`mechanism, resulting in a performance degradation. This is
`e.g. the case if the instantaneous phase of the interferer is
`e.g. the case if the instantaneous phase of the interferer is
`very slowly varying in time with respect to the duration of
`very slowly varying in time with respect to the duration of
`the DMT symbol or if this interferer is constant.
`the DMT symbol or if this interferer is constant.
`SUMMARY OF THE INVENTION
`SUMMARY OF THE INVENTION
`It is an object of the present invention to provide a method
`It is an object of the present invention to provide a method
`for transmitting data elements and related equipment of the
`for transmitting data elements and related equipment of the
`known type, but wherein the immunity of the pilot carrier
`known type, but wherein the immunity of the pilot carrier
`from interference is increased significantly, and conse
`from interference is increased significantly, and conse(cid:173)
`quently wherein the degradation of the synchronisation
`quently wherein the degradation of the synchronisation
`mechanism between transmitter and receiver is reduced.
`mechanism between transmitter and receiver is reduced.
`According to the present invention, this object is achieved
`According to the present invention, this object is achieved
`by a method for transmitting data elements from a trans
`by a method for transmitting data elements from a trans-
`mitter to a receiver, wherein the data elements are modulated
`50 mitter to a receiver, wherein the data elements are modulated
`50
`on at least one carrier; a pilot carrier used for synchronisa
`on at least one carrier; a pilot carrier used for synchronisa(cid:173)
`tion between the transmitter and the receiver is multiplexed
`tion between the transmitter and the receiver is multiplexed
`with the at least one carrier; the at least one carrier and the
`with the at least one carrier; the at least one carrier and the
`pilot carrier are transmitted over a transmission medium
`pilot carrier are transmitted over a transmission medium
`interconnecting the transmitter and the receiver, character
`55 interconnecting the transmitter and the receiver, character(cid:173)
`55
`ized in that the pilot carrier is modulated with a non-constant
`ized in that the pilot carrier is modulated with a non-constant
`signal before it is transmitted.
`signal before it is transmitted.
`It is also achieved by a transmitter, adapted to transmit
`It is also achieved by a transmitter, adapted to transmit
`data elements to a receiver via a transmission medium, the
`data elements to a receiver via a transmission medium, the
`transmitter comprising: modulation means to a first input of
`transmitter comprising: modulation means to a first input of
`which the data elements are applied, the modulation means
`which the data elements are applied, the modulation means
`being adapted to modulate the data elements on at least one
`being adapted to modulate the data elements on at least one
`carrier, and to multiplex the at least one carrier with a pilot
`carrier, and to multiplex the at least one carrier with a pilot
`carrier used for synchronisation between the transmitter and
`carrier used for synchronisation between the transmitter and
`the receiver; pilot information means, adapted to generate
`the receiver; pilot information means, adapted to generate
`information to identify the pilot carrier, and to apply the
`information to identify the pilot carrier, and to apply the
`information to a second input of the modulation means; and
`information to a second input of the modulation means; and
`
`4
`
`

`

`US 6,370,156 B2
`US 6,370,156 B2
`
`3
`3
`line interface means, coupled between an output of the
`line interface means, coupled between an output of the
`modulation means and an input of the transmission medium,
`modulation means and an input of the transmission medium,
`and adapted to condition the at least one carrier and the pilot
`and adapted to condition the at least one carrier and the pilot
`carrier to be transmitted over the transmission medium,
`carrier to be transmitted over the transmission medium,
`characterised in that the modulation means is further adapted
`characterised in that the modulation means is further adapted
`to modulate the pilot carrier with a non-constant signal.
`to modulate the pilot carrier with a non-constant signal.
`It is still further achieved by a receiver, adapted to receive
`It is still further achieved by a receiver, adapted to receive
`a signal transmitted thereto by a transmitter via a transmis
`a signal transmitted thereto by a transmitter via a transmis(cid:173)
`sion medium, the receiver comprising line interface means,
`sion medium, the receiver comprising line interface means,
`coupled to an output of the transmission medium and
`coupled to an output of the transmission medium and 10
`10
`adapted to condition the signal to be applied to components
`adapted to condition the signal to be applied to components
`of the receiver; demodulating means, an input of which is
`of the receiver; demodulating means, an input of which is
`coupled to an output of the line interface means, the
`coupled to an output of the line interface means, the
`demodulating means being adapted to demultiplex in the
`demodulating means being adapted to demultiplex in the
`signal a pilot carrier from at least one carrier whereon data
`signal a pilot carrier from at least one carrier whereon data 15
`15
`elements are modulated, and to demodulate the data ele
`elements are modulated, and to demodulate the data ele(cid:173)
`ments from the at least one carrier; and pilot information
`ments from the at least one carrier; and pilot information
`means, adapted to generate information to identify the pilot
`means, adapted to generate information to identify the pilot
`carrier, and to apply the information to a second input of the
`carrier, and to apply the information to a second input of the
`demodulation means, characterised in that the demodulating
`demodulation means, characterised in that the demodulating 20
`20
`means further is adapted to demodulate a non-constant
`means further is adapted to demodulate a non-constant
`signal from the pilot carrier and to use the demodulated pilot
`signal from the pilot carrier and to use the demodulated pilot
`carrier for synchronisation.
`carrier for synchronisation.
`It is still further achieved by a transmission system
`It is still further achieved by a transmission system
`comprising a transmitter, a receiver and a transmission
`comprising a transmitter, a receiver and a transmission 25
`25
`medium, coupled between an output of the transmitter and
`medium, coupled between an output of the transmitter and
`an input of the receiver, the transmitter comprising: modu
`an input of the receiver, the transmitter comprising: modu(cid:173)
`lation means to a first input of which data elements are
`lation means to a first input of which data elements are
`applied, the modulation means being adapted to modulate
`applied, the modulation means being adapted to modulate
`the data elements on at least one carrier, and to multiplex the
`the data elements on at least one carrier, and to multiplex the 30
`30
`at least one carrier with a pilot carrier used for synchroni
`at least one carrier with a pilot carrier used for synchroni(cid:173)
`sation between the transmitter and the receiver; pilot infor
`sation between the transmitter and the receiver; pilot infor(cid:173)
`mation means, adapted to generate information to identify
`mation means, adapted to generate information to identify
`the pilot carrier, and to apply the information to a second
`the pilot carrier, and to apply the information to a second
`input of the modulation means; and line interface means,
`input of the modulation means; and line interface means, 35
`35
`coupled between an output of the modulation means and an
`coupled between an output of the modulation means and an
`input of the transmission medium, and adapted to condition
`input of the transmission medium, and adapted to condition
`the at least one carrier and the pilot carrier to be transmitted
`the at least one carrier and the pilot carrier to be transmitted
`over the transmission medium, and the receiver comprising:
`over the transmission medium, and the receiver comprising:
`line interface means, coupled to an output of the transmis
`line interface means, coupled to an output of the transmis- 40
`40
`sion medium and adapted to condition a signal received
`sion medium and adapted to condition a signal received
`therefrom to be applied to components of the receiver;
`therefrom to be applied to components of the receiver;
`demodulating means, an input of which is coupled to an
`demodulating means, an input of which is coupled to an
`output of the line interface means, the demodulating mean
`output of the line interface means, the demodulating mean
`being adapted to demultiplex in the signal the pilot carrier
`being adapted to demultiplex in the signal the pilot carrier 45
`45
`from the at least one carrier, and to demodulate data ele
`from the at least one carrier, and to demodulate data ele(cid:173)
`ments from the at least one carrier; and pilot information
`ments from the at least one carrier; and pilot information
`means, adapted to generate information to identify the pilot
`means, adapted to generate information to identify the pilot
`carrier, and to apply the information to a second input of the
`carrier, and to apply the information to a second input of the
`demodulation means, characterised in that the modulation
`demodulation means, characterised in that the modulation 50
`50
`means is further adapted to modulate the pilot carrier with a
`means is further adapted to modulate the pilot carrier with a
`non-constant signal; and the demodulating means is adapted
`non-constant signal; and the demodulating means is adapted
`to demodulate the non-constant signal from the pilot carrier
`to demodulate the non-constant signal from the pilot carrier
`and to use the demodulated pilot carrier for synchronisation.
`and to use the demodulated pilot carrier for synchronisation.
`In this way, by modulating the pilot carrier with a non
`In this way, by modulating the pilot carrier with a non- 55
`55
`constant signal, the pilot carrier appears on the transmission
`constant signal, the pilot carrier appears on the transmission
`medium as a sine or cosine with non-constant phase and/or
`medium as a sine or cosine with non-constant phase and/or
`amplitude. Demodulation of such a pilot carrier at the
`amplitude. Demodulation of such a pilot carrier at the
`receiver’s side, re-generates the unmodulated pilot carrier,
`receiver's side, re-generates the unmodulated pilot carrier,
`i.e. a sine or cosine with non varying phase and/or amplitude
`i.e. a sine or cosine with non varying phase and/or amplitude 60
`60
`from the transmitted modulated pilot carrier. For interfer
`from the transmitted modulated pilot carrier. For interfer(cid:173)
`ence induced on the modulated pilot carrier, this demodu
`ence induced on the modulated pilot carrier, this demodu(cid:173)
`lation has an averaging effect as will be explained in more
`lation has an averaging effect as will be explained in more
`detail later on in the description. The effect of an interferer
`detail later on in the description. The effect of an interferer
`on different states of the modulation constellation is thus
`on different states of the modulation constellation is thus 65
`65
`averaged by demodulation. The final effect of an interferer
`averaged by demodulation. The final effect of an interferer
`after demodulation is far less than the effect of the interferer
`after demodulation is far less than the effect of the interferer
`
`4
`4
`on one single state in the modulation constellation scheme as
`on one single state in the modulation constellation scheme as
`a result of which the transmission system according to the
`a result of which the transmission system according to the
`present invention has a significantly increased immunity for
`present invention has a significantly increased immunity for
`narrowband interferers, compared to the above described
`narrowband interferers, compared to the above described
`known system.
`5 known system.
`It is noted that the implementation of the synchronisation
`It is noted that the implementation of the synchronisation
`means can be simplified if the constellation points of the
`means can be simplified if the constellation points of the
`pilot carrier are well chosen, e.g. if all points have the same
`pilot carrier are well chosen, e.g. if all points have the same