(19) 0
`
`)
`
`E“'°"""°’°“°“""°"'“""
`
`European Patent Office
`Office européen des brevets
`
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`
`(11)
`
`0
`
`(12)
`
`EUROPEAN PATENT APPLICATION
`
`(43) Date of publication:
`09.12.1998 Bulletin 1998/50
`
`(51) Int. ci.6: Ho4L 27/26
`
`(21) Application number: 97401210.6
`
`(22) Date of filing: 02.06.1997
`
`(84) Designated Contracting States:
`AT BE CH DE DK ES FI FR GB GR IE IT LI LU MC
`NL PT SE
`Designated Extension States:
`AL LT LV RO SI
`
`(71) Applicant:
`ALCATEL ALSTHOM COMPAGNIE GENERALE
`
`D'ELECTRICITE
`75008 Paris (FR)
`
`(72) Inventors:
`- Vanzieleghem, Etienne
`1360 Perwez (BE)
`- Defoort, Frank Cyriel Michel
`2630 Aartselaar (BE)
`- Reusens, Peter Paul Frans
`9270 Laarne (BE)
`
`(74) Representative: Narmon, Gisele
`Industrial Property Department,
`Alcatel Bell N.\/.,
`Francis Wellesplein 1
`2018 Antwerpen (BE)
`
`(54) Multi-carrier telecommunication system with power reduction means
`
`for a
`(TU)
`A telecommunication transmitter
`(57)
`multi-carrier transmission system of the Digital Sub-
`scriber Line [DSL] type and which includes a coding cir-
`cuit (MMC) able to generate "symbols" derived from
`carriers (C1-Cn) modulated by incoming data, and a line
`driver circuit (LDC) to amplify these symbols. When idle
`data are received, the power dissipated in the transmit-
`ter is reduced because the symbols are then merely
`derived from a few or even a single carrier (the "pilot
`tone") instead as from all the available carriers. The
`power dissipated is even more reduced because the
`line driver circuit comprises the parallel connection of a
`high voltage but low efficiency (LL) and a lower voltage
`but higher performant (LH)
`line amplifier. The higher
`performant, and thus less power consuming, amplifier
`(LH) is used when idle data are received at the input
`(IN). In a variant, there is only one line amplifier of which
`the quiescent current is controlled in function of the data
`traffic. In another variant, the number of carriers used by
`the coding circuit (MMC) is a function of the mean traffic
`of effective data received.
`
`EP0883269A1
`
`Primed by Xe rox (UK) Business Services
`2.16.6/3.4
`
`Dish
`Exhibit 1005, Page 1
`
`

`
`EP 0 883 269 A1
`
`Description
`
`The present invention relates to a telecommunica-
`tion transmitter for a multi-carrier transmission system,
`said transmitter
`including coding means coupled
`between a transmitter input and a transmitter output and
`able to modulate a plurality of carriers with data
`received at said transmitter input and to derive there-
`from symbols which are transmitted towards said trans-
`mitter output.
`A multi-carrier transmission system including such
`a telecommunication transmitter is already known in the
`art and is for instance a Digital Subscriber Line [DSL]
`Transceiver Unit [TU] as defined in international stand-
`ards such as,
`for instance,
`the Asymmetrical Digital
`Subscriber Line [ADSL] standard. This standard is the
`"ANSI TI.413 - American National Standard for Tele-
`communicafions - Network and Customer installation
`
`interfaces - Asymmetric Digital Subscriber Line (ADSL)
`Meta//ic Interface" of the American National Standards
`
`Institute [ANSI], New York - 1995. The digital data
`received at the input of such a known transmitter is
`grouped into frames comprising a predetermined
`number of bits and wherefore the coding means gener-
`ates corresponding symbols which are transmitted to a
`telecommunication line connected to the transmitter
`
`output. Since the voltage of each symbol may have dif-
`ferent peak values, the signal voltage transmitted on the
`telecommunication line may vary within a relatively
`large range. As a consequence, the power dissipated in
`the telecommunication transmitter
`is
`relatively high
`because it has to support a large value of signal voltage
`to avoid, or at least minimize, occasional clipping.
`An object of the present invention is to provide a tel-
`ecommunication transmitter of the above known type
`but whereof
`the power dissipation is dramatically
`reduced.
`
`According to the invention, this object is achieved
`due to the fact that said telecommunication transmitter
`
`further includes carrier selection means adapted to
`apply said carriers to said coding means, and data traf-
`fic detection means adapted to detect if idle data are
`received at said transmitter input and,
`if idle data are
`detected,
`to control said carrier selection means to
`apply a predetermined reduced set of said carriers to
`said coding means.
`In this way, when idle data are received at the trans-
`mitter
`input,
`the symbols generated by the coding
`means are merely derived from a few carriers instead of
`from all the carriers as it is the case when effective data
`
`are applied to the transmitter input. The power on the
`line is thereby dramatically reduced, as well as the rela-
`tively high power dissipated in the coding means and
`thus in the telecommunication transmitter.
`
`Since the symbols, which are generated when idle
`data are received at the transmitter input, contain only a
`few carriers, the power dissipated in the transmitter is
`reduced. In other words, if the number of carriers drops,
`
`the dissipated power is reduced accordingly.
`Another characteristic feature of the present inven-
`tion is that said predetermined reduced set of carriers
`comprises only one carrier that is applied to said coding
`means.
`
`For frequency synchronization purposes, the only
`one remaining symbol transmitted on the line can be
`chosen to be derived from a so—called ”pilot tone”. The
`transmission system remains thus efficient
`in that it
`allows a fast restart owing to the fact that the synchroni-
`zation on the telecommunication line is maintained,
`while the power dissipated is dramatically reduced with
`respect to that of the known system.
`In a preferred embodiment, the present invention is
`further characterized in that said telecommunication
`transmitter
`further
`includes data selection means
`
`adapted to apply said data to said coding means. and in
`that said data traffic detection means is further adapted,
`if idle data are detected, to control said data selection
`means to discard the idle data received at said transmit-
`
`ter input.
`in some circumstances, be
`As idle data may,
`dummy data, the latter could be used by the coding
`means to modulate the few or single carrier(s) from
`which symbols could then be derived and transmitted
`on the telecommunication line. However, owing to the
`present invention such dummy data would be discarded
`and the single carrier will remain un-modulated. As a
`result, the power dissipation is then minimal.
`It should be noted that the switching between sym-
`bols derived from effective data and symbols derived
`from idle data, and vice—versa, can be fast whereby the
`power savings can be improved.
`Preferably,
`said telecommunication transmitter
`operates according to a predetermined mapping and
`modulating protocol defined by a digital subscriber line
`[DSL] standard such as the Asymmetrical Digital Sub-
`scriber Line [ADSL] standard, and said symbols derived
`from said data are Discrete Multi-Tone [DMT] symbols.
`It is obvious for a person skilled in the art that the
`above multi-carrier transmission technique is not limited
`to ADSL applications using DMT symbols, but can for
`instance also be used in High speed Digital Subscriber
`Line [HDSL] applications,
`in Very high speed Digital
`Subscriber Line [VDSL] applications,
`in Symmetrical
`Digital Subscriber Line [SDSL] applications as well as in
`relation with Orthogonal Frequency Division Multiplex-
`ing [OFDM] and/or Discrete Wavelet Multi Tone [DWM1]
`applications. The latter are also multi-carrier transmis-
`sion techniques differing from ADSL in that, for instance
`for DWM1', the Fourier and inverse-Fourier transformers
`used therein are replaced byfilterbanks, wavelets trans-
`formers and/or Discrete Cosine Transformers [DC'l].
`Also another characteristic feature of the present
`invention is that said coding means is adapted to count
`the number of symbols transmitted towards said trans-
`mitter output and to transmit at least one synchroniza-
`tion symbol after each group of N symbols, said
`
`Dish
`Exhibit 1005, Page 2
`
`

`
`3
`
`EP 0 883 269 A1
`
`synchronization symbol being derived from a frame of
`synchronization signals received at said data selection
`means, and that said N symbols and said one synchro-
`nization symbol form together a super-frame.
`In case of idle data, and as already mentioned, the
`frequency synchronization between the transmitter and
`a receiver at the other end of the telecommunication line
`
`is maintained owing to the presence of the pilot tone. By
`sending one synchronization symbol for every N sym-
`bols,
`the framing synchronization is also maintained
`between the transmitter and the receiver.
`The invention is further also characterized in that
`
`said coding means is adapted to transmit at least one
`line monitoring super—frame alter each group of M
`super-frames, said line monitoring super—frame includ-
`ing N symbols and at least one synchronization symbol,
`in that said M super—frames and said line monitoring
`super—frame form together a hyper—frame, and in that
`said data traffic detection means is adapted to control
`said carrier selection means to apply all the carriers of
`said plurality to said coding means during the transmis-
`sion of said line monitoring super-frame.
`the
`In the digital subscriber
`line transmission,
`receiver measures the quality of the transmission on the
`line and informs the transmitter about this quality. The
`measurement is performed by means of the line monitor
`symbols transmitted in the line monitoring super—frame.
`If the quality of the transmission becomes to low, the
`receiver may request the transmitter to go back to the
`power-up status even if idle data are received at the
`transmitter input.
`Still another characteristic feature of the present
`invention is that said data traffic detection means is
`
`adapted to control said data selection means to discard
`idle data received at said transmitter input after idle data
`has been detected tor a predetermined period of time.
`In a preferred application, said data received at said
`transmitter
`input are Asynchronous Transfer Mode
`[ATM] cells.
`Also according to the present invention, the power
`dissipated in the telecommunication transmitter can be
`even more reduced owing to the characteristic feature
`that said telecommunication transmitter further includes
`
`line driver means coupled between said coding means
`and said transmitter output and adapted to amplify the
`symbols generated by said coding means prior to trans-
`mit them to said transmitter output, said line driver
`means comprising the parallel connection of a relatively
`low efficiency line amplifier and a relatively high effi-
`ciency line amplifier, that said amplifiers operate in a
`complementary way so that only one of said amplifiers
`is operational at a predetermined time moment, and
`that said data traffic detection means is further adapted
`to control the operation of said relatively high efficiency
`line amplifier if idle data are detected, and to control the
`operation of said relatively low efficiency line amplifier
`else.
`
`When sending only the pilot tone, the line drive
`
`means do not need to comprise a class—A or class—AB
`amplifier that is a high voltage and high performant line
`amplifier. It may then advantageously be replaced by a
`lower voltage and thus also less power consuming line
`amplifier, i.e. an amplifier with a smaller idle power dis-
`sipation or a smaller supply voltage.
`It is to be noted that this last characteristic feature
`
`of the present invention is preferably, but not necessary,
`combined with the features mentioned above. It is thus
`
`instance possible to have a telecommunication
`for
`transmitter with line driver means comprising the paral-
`lel connection of a low efficiency line amplifier and a
`high efficiency line amplifier operating in a complemen-
`tary way, but without carrier selection means and possi-
`bly data selection means as mentioned above.
`In a preferred embodiment,
`if
`idle data are
`detected. said one carrier applied to said relatively high
`efficiency line amplifier is a sinusoidal wave.
`In a variant embodiment, said data traffic detection
`means is further adapted, if idle data are detected, to
`control the quiescent current of said line driver means in
`order to reduce the power consumption thereof.
`Thereby, instead of changing from line amplifier as
`above, the power consumption may also be reduced by
`making the amplifier less linear but more efficient only
`for a few number of carriers.
`
`It is to be noted that, in the two last cases, the qual-
`ity of the symbols derived, e.g., from the pilot tone and
`transmitted on the telecommunication line by the high
`efficiency line drive means remains sufficient to main-
`tain the frequency synchronization between the trans-
`mitter and the receiver.
`
`The present invention is also characterized in that
`said data traffic detection means is further adapted to
`compute the mean traffic of effective data received at
`said transmitter input over a predetermined period of
`time, and, accordingly, to control said carrier selection
`means to apply a predetermined reduced set of said
`carriers to said coding means in function of the com-
`puted mean traffic.
`The amount of carriers used by the coding means
`and their power is then a function of the data traffic. By
`using only the number of carriers that are necessary to
`transmit the effective data, and each with less power,
`i.e. modulated with less bits of the data,
`instead of
`always using all the carriers when the actual data are
`reduced, the power consumption of the transmitter is
`reduced in function of the data traffic. This switching
`between high and low capacity could be done in a simi-
`lar fashion as switching between high capacity and idle.
`The above and other objects and features of the
`invention will become more apparent and the invention
`itself will be best understood by referring to the following
`description of an embodiment taken in conjunction with
`the accompanying drawings wherein:
`
`1 represents a telecommunication transmitter
`FIG.
`TU according to the invention;
`
`Dish
`Exhibit 1005, Page 3
`
`

`
`5
`
`EP 0 883 269 A1
`
`6
`
`FIG. 2 shows, at different time scales, a super-
`frame SF and a hyper-frame HF of signals used in
`the transmitter of the FIG. 1; and
`
`FIG. 3 represents a possible implementation of the
`line driver circuit LDC included in the telecommuni-
`cation transmitter TU of FIG. 1.
`
`The telecommunication transmitter TU shown in
`
`is of the type "ADSL Transceiver Unit - Central
`FIG. 1
`office side" [ATU-C] used in multi-carrier transmission
`system as for instance defined in the above mentioned
`Asymmetrical Digital Subscriber Line [ADSL] standard.
`Several of such transmitters are mounted in a rack
`
`which is subjected to maximum power dissipation
`requirements. The transmitter TU has an input
`IN
`whereat digital data, e.g. Asynchronous Transfer Mode
`[ATM] cells, are applied, and an output OUT where so-
`called "symbols" are provided. These symbols are the
`result of, amongst other, mapping and modulating oper-
`ations performed by a data handling circuit, generally
`referred to as DHC, on the data received at the input IN.
`The transmitter TU further also includes a line driver cir-
`
`cuit LDC coupling the data handling circuit DHC to the
`output OUT via a terminal LI and amplifying the symbols
`prior to transmit them on a telecommunication line con-
`nected to the output OUT The telecommunication line is
`a copper twisted pair of wires whereof the other end is
`connected to a remote ADSL transceiver (not shown).
`It is to be noted that in FIG. 1, the schematic repre-
`sentation of the ADSL transmitter TU has been largely
`simplified in order to show only the elements which are
`essential to understand the scope of the invention.
`The data received at the input IN is applied to an
`input DATA of a data selector DS forming part of the
`data handling circuit DHC. The data selector DS has a
`second input SYNC at which synchronization signals
`are supplied, as will be explained later. An output of DS
`is connected to an input of a mapping and modulating
`circuit, hereafter merely called coding circuit MMC, of
`which another input is connected to an output of a car-
`rier selector CS. An output of the coding circuit MMC is
`connected to a terminal Ll further connected to an input
`of the line driver circuit LDC whereof an output is con-
`nected to the transmitter output OUT.
`Both MMC and CS form part of the data handling
`circuit DHC. Several carriers C1,
`Cp,
`Cn, of which
`the frequencies are spread over the frequency spec-
`trum of the Digital Subscriber Line [DSL] system and
`that may be pre-selected amongst a full set of carriers
`for their good transmission qualities for the particular
`line connected to the transmitter TU, are applied to like-
`named input terminals of the carrier selector CS. These
`carriers are sinusoidal waves and one of them, referred
`to as Cp, is the so-called “pilot tone" that insures the fre-
`quency synchronization between the present transmit-
`ter and a receiver included in the ADSL transceiver at
`the other end of the telecommunication line.
`The data selector DS and the carrier selector CS
`
`are controlled by a data traffic detection circuit DDC via
`a terminal LX connected to control terminals DX and CX
`
`of DS and CS respectively. The incoming data of the
`transmitter TU is received in DDC via an input thereof
`that is connected to the transmitter input IN. The data
`traffic detection circuit DDC is adapted to detect the
`type of digital data: idle or effective, as well as the mean
`traffic of this data, received at the input IN. According to
`the result of this detection, DDC controls the selectors
`DS and CS as will be explained below.
`If effective data are received at the transmitter input
`IN, and thus also at the data input DATA of the data
`selector DS, the latter circuit groups the bits of the data
`into "frames". These frames are then transferred to the
`
`coding circuit MMC that maps them to the carriers C1-
`Cn received via the carrier selector CS. MMC further
`modulates these carriers C1—Cn in function of
`the
`
`the mapping thereby generating Discrete
`results of
`Multi-Tone [DMT] symbols that are transferred to the
`line driver circuit LDC. It is to be noted that the pilot tone
`Cp is preferably not modulated to ensure the above
`mentioned frequency synchronization; The purpose of
`the line driver circuit LDC is to amplify the symbols prior
`to transmit them on the telecommunication line, its oper-
`ation will be described in more detail later.
`
`For every N=68 DMT symbols transmitted on the
`line, at least one synchronization symbol is sent. To this
`end, at the occurrence of the 69”‘ symbol, the data
`selector DS selects its second input SYNC to get the
`synchronization signals instead of the data from its first
`input DATA. As for the data, the synchronization signals
`are also grouped into frames by the data selector DS.
`The synchronization symbol derived from such a frame
`is used for performing framing synchronization between
`the transmitter TU and the receiver at the other end of
`
`the line. A set of N=68 DMT symbols (numbered from 0
`to 67) and one synchronization symbol SS (numbered
`68)
`form together a so-called "super-frame" SF as
`shown in FIG. 2.
`
`e.g.
`after having generated M,
`Furthermore,
`M=256, of the above super-frames, the coding circuit
`MMC generates at least one so—called "line-monitoring
`super—frame" MSF This special super-frame MSF con-
`tains line monitoring information used by the receiver to
`measure the quality of the transmission on the line. A
`set of M super-frames and one or more line monitoring
`super—frame(s) MSF form together a so—called "hyper-
`frame". An example of such a hyper frame HF with
`M=256 super-frames SF (numbered from 0 to 255) and
`one line monitoring super-frame MSF (numbered 0) is
`shown in FIG. 2 at a time period t‘ that is larger than the
`time period t showing the super-frame SF in the same
`figure. A line monitoring super-frame MSF includes
`N=68 line monitoring symbols and the synchronization
`symbol SS. Each line monitoring symbol being gener-
`ated by applying all the carriers C1 to Cn to the coding
`circuit MMC.
`
`The operation of the data handling circuit DHC and
`
`Dish
`Exhibit 1005, Page 4
`
`

`
`7
`
`EP 0 883 269 A1
`
`8
`
`more particularly that of the coding circuit MMC will not
`be described in more detail here since all the details of
`
`the functioning of these circuits may be found in the
`above mentioned Asymmetrical Digital Subscriber Line
`[ADSL] standard.
`The power dissipated in the transmitter TU if effec-
`tive data are transmitted is of about 3 Watt for 100 milli-
`
`Watl effectively transmitted on the telecommunication
`line. This low efficiency is due to several ADSL require-
`ments such as the signal quality requirement. Hereafter
`will be explained how this power dissipation will be
`reduced in function of the traffic on the line.
`
`If idle data are received at the transmitter input IN,
`it is detected by the data traffic detection circuit DDC
`which then controls, via the terminal CX, the carrier
`selector CS to allow only a few of the carriers C1 -Cn to
`be transferred to the coding circuit MMC. By generating
`symbols that are derived from a reduced number of car-
`riers, the power dissipated in the transmitter TU is dra-
`matically reduced.
`If the set of selected carriers is
`reduced to one, the pilot tone Cp is preferably chosen,
`with respect to the other carriers C1—Cn, as the single
`remaining carrier because it allows to maintain the fre-
`quency synchronization between the transmitter and
`the receiver.
`In some cases, such as for instance for the trans-
`mission of ATM cells, the idle data are in fact dummy
`data that could be grouped in frames by the data selec-
`tor DS and then be transferred to the coding circuit
`MMC. To avoid the generation of symbols derived from
`such dummy data, the data traffic detection circuit DDC
`also controls, via the terminal DX, the data selector DS
`to discard any idle data received at the input DATA. As a
`result, no data are then applied to the coding circuit
`MMC.
`In other words, if idle data are received in the trans-
`mitter TU and detected by the data traffic detection cir-
`cuit DDC, the latter controls the carrier selector CS and
`the data selector DS in such a way that the coding cir-
`cuit MMC generates for instance un-modulated sym-
`bols, generally called "pilot symbols",
`instead of the
`above discrete multi—tone DMT symbols. The frequency
`synchronization is ensured by the choice of the pilot
`tone Cp forming always part of the selected carriers,
`whilst the frame synchronization is ensured by the syn-
`chronization symbols SS that are generated as usual.
`i.e. as with effective data. The line monitoring super-
`frame MSF is composed of idle or effective symbols but
`in any case with all the carriers C1 to Cn selected and
`applied to the coding circuit MMC.
`Another parameter that influences the power dissi-
`pation is the so—called "crest factor“. The crest factor is
`the ratio of the peak voltage over the Root Mean Square
`[RMS] voltage on the telecommunication line and is
`thus a function of the voltage of the symbol transmitted
`on the line. The crest factor of the line signal in a multi-
`carrier transmission system is rather unfavorable.
`In
`practice, the power dissipated in the transmitter is much
`
`higher than the power actually transmitted on the line. It
`is known that the lowest crest factor is obtained by a
`sinusoidal wave wherefore it is then equal to the root of
`2. Since all the carriers, including the pilot tone, are pure
`sinusoidal waves, the pilot symbols generated if
`idle
`data are detected have the lowest crest factor and the
`
`power dissipated is then minimal.
`The power dissipated in the transmitter TU when
`only pilot symbols are transmitted reduces from the
`above 3 Watt to about 1 Watt.
`
`the transmitter TU
`In a preferred embodiment,
`informs the receiver that pilot symbols will be sent in
`order to avoid unnecessary decoding operations at the
`receiver side. On the other hand,
`in order to avoid
`excessive swaps between the transmission of DMT
`symbols and pilot symbols, i.e. swaps between a power-
`up and a power-down status respectively, the data traffic
`detection circuit DDC measures the time during which
`idle data are received at the transmitter input IN. DDC
`then controls the carrier selector CS and the data selec-
`
`tor DS of the data selection handling DHC so that pilot
`symbols are only generated after a predetermined time
`of idle data being received.
`In a variant of this imple-
`mentation, the data traffic detection circuit DDC may
`oount a predetermined number of frames of idle data
`received. The behavior of DDC is then the same as
`when it measures time.
`
`the data handling circuit
`As already mentioned,
`DHC has an output terminal Ll coupled to a line driver
`circuit LDC that is itself connected to the transmitter out-
`
`put OUT LDC amplifies the symbols generated by DHC
`prior to transmit them on the telecommunication line. To
`this end, the line driver circuit LDC generally includes a
`high voltage line amplifier that is generally a class-AB or
`a class-A amplifier. A drawback of this amplifier is that it
`has a low efficiency and consumes a lot of power. How-
`ever,
`in case of transmission of idle data,
`i.e. of pilot
`symbols, such a high voltage amplifier is not necessary.
`The low efficiency line amplifier may then advanta-
`geously be replaced by a lower voltage, higher perform-
`ant and thereby loss power consuming line amplifier.
`Such an implementation is shown in FIG. 3, where a low
`efficiency line amplifier LL is coupled in parallel with a
`higher efficiency line amplifier LH between the terminals
`LI and OUT. The operation of the line driver circuit LDC
`is such that only one of the amplifiers LL or LH operates
`at a predetermined time moment. They are therefore
`controlled by the data traffic detection circuit DDC via its
`output terminal LX.
`In more detail, if effective data are
`transmitted, DDC controls the low performant but high
`voltage line amplifier LL to operate, while it prevents the
`symbols to be transmitted through the amplifier LH. On
`the contrary, if idle data, i.e. pilot symbols, are transmit-
`ted, DDC prevents the amplifier LL to operate, while it
`controls the higher performant and lower voltage line
`amplifier LH to operate.
`In a variant (not shown) of this embodiment, the line
`driver circuit LDC only comprises one,
`low efficiency,
`
`Dish
`Exhibit 1005, Page 5
`
`

`
`9
`
`EP 0 883 269 A1
`
`10
`
`line amplifier and, if idle data are transmitted, the data
`traffic detection circuit DDC controls the quiescent cur-
`rent [Iq] thereof. Although the line amplifier is thereby
`mode less linear, its power consumption is dramatically
`reduced and becomes thus more efficient when only a
`few number of carriers are used.
`
`In the two last cases, a gain of about 1 Watt may be
`obtained on the power consumption. However, the qual-
`ity of the signals transmitted on the telecommunication
`line via the high efficiency line amplifier has to remain
`sufiicient to maintain the synchronization between the
`transmitter and the receiver. To control this quality, each
`transmitted hyper—frame HF includes, as already men-
`tioned, a line monitor super-frame MSF that is used by
`the receiver to measure the quality of the transmission.
`The receiver informs the transmitter about the results of
`
`the measurements and, when the quality is too low, the
`receiver requests the transmitter to go back to the
`power-up status, even if only idle data are received at
`the transmitter input.
`Because the power dissipated in the transmitter TU
`is a function of the number of carriers used and of the
`
`kind of symbols transmitted on the telecommunication
`line, the data traffic detection circuit DDC is further
`designed to measure the mean traffic of
`the data
`received at the input IN. According to the result of this
`measurement performed for a predetermined time
`period, the data traffic detection circuit DDC controls,
`via the terminal CX, the carrier selector CS to allow a
`reduced set of carriers C1-Cp to be transferred to the
`coding circuit MMC. The number of carriers selected by
`CS is a function of the mean traffic detected. By using
`only the number of carriers that are necessary to trans-
`mit the data instead of using all the available carriers, as
`when effective data are received, the power consump-
`tion of the transmitter is reduced.
`It is to be noted that the different embodiments and
`
`variants of the present transmitter as described above
`may be used separately or in combination. For instance,
`it is possible to have a telecommunication transmitter
`whereof the power consumption is reduced owing to the
`use of a line driver circuit LDC comprising the parallel
`connection of a low efficiency line amplifier LL and a
`high efficiency line amplifier LH operating in a comple-
`mentary way, but without a carrier selector CS and pos-
`sibly a data selector DS.
`While the principles of the invention have been
`described above in connection with specific apparatus,
`it
`is to be clearly understood that this description is
`made only by way of example and not as a limitation on
`the scope of the invention, as defined in the appended
`claims.
`
`Claims
`
`ter input (IN) and a transmitter output (OUT) and
`able to modulate a plurality of carriers (C1-Cn) with
`data received at said transmitter input and to derive
`therefrom symbols which are transmitted towards
`said transmitter output, characterized in that said
`telecommunication
`transmitter
`(TU)
`further
`includes carrier selection means (CS) adapted to
`apply said carriers (C1-Cn) to said coding means
`(MMC), and data traffic detection means (DDC)
`adapted to detect if idle data are received at said
`transmitter input (IN) and, if idle data are detected,
`to control
`(CX) said carrier selection means to
`apply a predetermined reduced set (Cp) of said car-
`riers to said coding means.
`
`Telecommunication transmitter according to claim
`1,
`characterized in
`that
`said predetermined
`reduced set of carriers comprises only one carrier
`(Cp) that is applied to said coding means (MMC).
`
`Telecommunication transmitter according to claim
`2, characterized in that said one carrier (Cp) is a
`pilot symbol.
`
`Telecommunication transmitter according to claim
`1, characterized in that said telecommunication
`transmitter
`(TU)
`further
`includes data selection
`means (DS) adapted to apply said data to said cod-
`ing means (MMC), and in that said data traffic
`detection means (DDC) is further adapted,
`if idle
`data are detected, to control (DX) said data selec-
`tion means to discard the idle data received at said
`
`transmitter input (IN).
`
`Telecommunication transmitter according to claim
`1, characterized in that said transmitter operates
`according to a predetermined mapping and modu-
`lating protocol defined by a digital subscriber line
`[DSL] standard such as the Asymmetrical Digital
`Subscriber Line [ADSL] standard, and in that said
`symbols derived from said data are Discrete Multi-
`Tone [DM'l1 symbols.
`
`Telecommunication transmitter according to claim
`4, characterized in that said ooding means (MMC)
`is adapted to count the number of symbols trans-
`mitted towards said transmitter output (OUT) and to
`transmit at least one synchronization symbol (SS)
`after each group of N (68) symbols, said synchroni-
`zation symbol being derived from a frame of syn-
`chronization signals (SYNC) received at said data
`selection means (DS), and in that said N symbols
`and said one synchronization symbol form together
`a super-frame (SF).
`
`1. Telecommunication transmitter (TU) for a multi-car-
`rier transmission system, said transmitter including
`coding means (MMC) coupled between a transmit-
`
`Telecommunication transmitter according to claim
`6, characterized in that said coding means (MMC)
`is adapted to transmit at least one line monitoring
`
`Dish
`Exhibit 1005, Page 6
`
`

`
`11
`
`EP0883269A1
`
`12
`
`(LDC) in order to reduce the power consumption
`thereof.
`
`. Telecommunication transmitter according to claim
`1, characterized in that said data traffic detection
`means (DDC) is further adapted to compute the
`mean traffic of effective data received at said trans-
`
`mitter input (IN) over a predetermined period of
`time, and, accordingly, to control (CX) said carrier
`selection means (OS) to apply a predetermined
`reduced set of said carriers (C1-Cn) to said coding
`means (MMC) in function of the computed mean
`traffic.
`
`super—frame (MSF) after each group of M (256)
`super-frames (SF), said line monitoring super-
`frame including N (68) symbols and at least one
`synchronization symbol (SS), in that said M super-
`frames and said line monitoring super—frame form
`together a hyper—frame (HF), and in that said data
`traffic detection means (DDC) is ad