Forward compatible and expandable high speed communications system & method of operation

Abstract

A high speed communications system is provided which uses a selectable, desirable portion of the total available bandwidth of a transmission channel. In a preferred embodiment, the invention is an ADSL compatible modem which selects a sub-set of the available downstream DMT sub-channels based on an evaluation of such sub-channels by appropriate signal processing circuitry. An analog front end (AFE) contains sub-band filtering causes an upstream transceiver to use only this selected number of available sub-channels for downstream data transmission. This reduces hardware costs and complexity while still preserving compatibility with applicable ADSL standards and providing a high speed data link. The target data rate of the modem can be further enhanced to the point of achieving fill protocol capability by increasing or upgrading the AFEs, and/or the signal processing circuitry in order to increase the number of processable transmitted downstream sub-channels.

What is claimed is:  
     
         1 . A high speed communications system capable of supporting a downstream data transmission from an upstream transceiver using an analog signal consisting of M data carrying signals contained within a bandwidth F, said system comprising: 
 a channel interface circuit for coupling to and receiving said analog signal; and    a front end receiving circuit for processing the analog signal and converting it to a digital signal;    a processing circuit for extracting N data carrying signals (N<M) from the digital signal using a first frequency portion f 1  of the digital signal (f 1 <F).    
     
     
         2 . The system of    claim 1   , wherein the N data carrying signals are selected by the processing circuit based so as to minimize the amount of processing required to extract the selected data from the digital signal.  
     
     
         3 . The system of    claim 2   , wherein the N data carrying signals can be selected during an initialization process setting up a data link to the upstream transceiver.  
     
     
         4 . The system of    claim 3   , wherein M data carrying signals can be sent by the upstream transmitter during an initialization process, and thereafter, only N data carrying signals are sent.  
     
     
         5 . The system of    claim 1   , wherein the front end circuit includes: (i) a sub-band filter for passing the first frequency bandwidth portion f 1  of said bandwidth F; (ii) and an analog to digital converter.  
     
     
         6 . The system of    claim 1   , wherein the selected data further includes data obtained from an additional second frequency bandwidth portion f 2  of said bandwidth F, so that an additional number of data carrying signals P from the M data carrying signals (N+P<M) can be processed.  
     
     
         7 . The system of    claim 6   , further including one or more sub-band filters for passing the first frequency bandwidth portion f 1  and second frequency bandwidth portion f 2  of said bandwidth F and an analog to digital converter.  
     
     
         8 . The system of    claim 7   , wherein a target data rate of the system can be increased by processing an additional number of data carrying signals P from the M data carrying signals, where N+P<M.  
     
     
         9 . The system of    claim 1   , wherein the selected data to be extracted from the bandpassed data can be controlled by a user of such system.  
     
     
         10 . The system of    claim 9   , wherein a user of such system can increase a target data rate of the system by modularly augmenting the front end circuit to include additional bandwidth and analog to digital conversion capacity such that an additional number of data carrying signals P from the M data carrying signals (N+P<M) can be processed.  
     
     
         11 . The system of    claim 1   , further including a front end transmitting circuit for transmitting control information to cause said upstream transceiver to transmit downstream data only using the N data carrying signals.  
     
     
         12 . The system of    claim 11   , wherein the control information transmitted to the upstream transceiver includes feedback information indicating that only N of the M data carrying signals are desirable for downstream data transmission, even during times when said channel is capable of supporting more than N data carrying signals.  
     
     
         13 . The system of    claim 12   , wherein the control information transmitted to the upstream transceiver further includes feedback information indicating that: (i) the system can support any data protocols used by said upstream transceiver; and (ii) that they are connected through a channel with substantial signal attenuation characteristics for data signals other than the N data carrying signals.  
     
     
         14 . The system of    claim 1   , further including a front end transmitting circuit for transmitting an upstream data signal using a second frequency bandwidth F 2  different from F, and L data carrying signals, and where L<M.  
     
     
         15 . A high speed communications system capable of supporting an upstream transceiver which can transmit M modulated sub-channels using an analog signal through a channel to said system, said system comprising: 
 a channel interface circuit for coupling to and receiving said analog signal from the channel;    an analog front end circuit for processing the analog signal and converting it to a digital signal, the front end circuit including a sub-band filter and an analog to digital converter;    a processing circuit for extracting data from the digital signal, the digital signal including data from a first number N of said sub-channels, where N≦M.    
     
     
         16 . The system of    claim 15   , wherein the selected data is derived from the N sub-channels which minimize the amount of processing required to extract the selected data from the digital signal.  
     
     
         17 . The system of    claim 16   , wherein the N sub-channels can be selected by an initialization process to set up a data link to the upstream transceiver.  
     
     
         18 . The system of    claim 17   , wherein the M sub-channels can be received from the upstream transmitter during an initialization process, and thereafter, only N sub-channels are received.  
     
     
         19 . The system of    claim 15   , wherein the front end circuit includes: (i) a sub-band filter for passing only the N sub-channels; (ii) and an analog to digital converter.  
     
     
         20 . The system of    claim 15   , wherein the selected data further includes data obtained from an additional second number of sub-channels P, so that an additional number of sub-channels (N+P<M) can be processed.  
     
     
         21 . The system of    claim 20   , further including one or more sub-band filters for passing the first number N and second number P of said sub-channels and an analog to digital converter.  
     
     
         22 . The system of    claim 21   , wherein a target data rate of the system can be increased by processing an additional number of sub-channels P from the M sub-channels, and where N+P<M.  
     
     
         23 . The system of    claim 15   , wherein the selected data to be extracted from the bandpassed data can be controlled by a user of such system.  
     
     
         24 . The system of    claim 23   , wherein a user of such system can increase a target data rate of the system by modularly augmenting the front end circuit to include additional bandwidth and analog to digital conversion capacity such that an additional second number of sub-channels P from the M sub-channels (N+P<M) can be processed.  
     
     
         25 . The system of    claim 24   , further including a front end transmitting circuit for transmitting control information to cause said upstream transceiver to transmit downstream data only using the N sub-channels.  
     
     
         26 . The system of    claim 25   , wherein the control information transmitted to the upstream transceiver includes feedback information indicating that only N of the M sub-channels are usable for downstream data transmission, even during times when said channel is capable of supporting more than N sub-channels.  
     
     
         27 . The system of    claim 26   , wherein the control information transmitted to the upstream transceiver further includes feedback information indicating that: (i) the system can support any data protocols used by said upstream transceiver; and (ii) that the system and upstream transceiver are connected through a channel with substantial signal attenuation characteristics for sub-channels other than the N sub-channels.  
     
     
         28 . The system of    claim 15   , wherein the upstream transceiver uses discrete multi-tone (DMT) modulation for generating the M modulated sub-channels, and the channel supports asymmetric digital subscriber loop (ADSL) transmission standards.  
     
     
         29 . The system of    claim 15   , further including a front end transmitting circuit for transmitting an upstream data signal using a second set of sub-channels L separate from M, where L<M.  
     
     
         30 . A high speed communications data receiver for communicating through a channel at a data rate X with an upstream transmitter capable of transmitting a data stream at a rate Y (X<Y), the receiver comprising: 
 a channel interface circuit for coupling to and receiving said data stream; and    an analog front end circuit for data sampling the analog signal and converting it to a digital signal; and    a processing circuit for extracting selected data from the digital signal, and for generating a transmission control signal for causing said upstream transmitter to transmit at a data rate substantially equal to said data rate X during a data stream transmission; and    wherein data sampling requirements of the analog front end circuit and extracting of the processing circuit are reduced because data sampling and extracting is only performed for a fractional portion of the data stream.    
     
     
         31 . The system of    claim 30   , wherein the analog front end circuit further includes one or more sub-band filters for filtering the analog data signal to generate the fractional portion of the data stream that requires data sampling and extracting.  
     
     
         32 . The system of    claim 30   , further including a front end transmitting circuit for transmitting the transmission control signal from the processing circuit to cause said upstream transceiver to transmit downstream data only at said data rate X.  
     
     
         33 . The system of    claim 32   , wherein the control information transmitted to the upstream transceiver includes feedback information indicating that the maximum downstream data transmission data rate is x, even during times when said channel is capable of supporting more than said data rate X.  
     
     
         34 . The system of    claim 30   , further including a front end transmitting circuit for transmitting an upstream data transmission using a data rate Z, where Z<Y.  
     
     
         35 . The system of    claim 30   , wherein the ratio of X to Y is approximately 0.5 or less, and this ratio can be increased through modular additions to the analog front end circuit.  
     
     
         36 . A high speed communications system for processing an analog data signal from a channel capable of supporting a downstream data transmission from an upstream transciever using a bandwidth F, said system comprising: 
 a channel interface circuit for coupling to and receiving said analog data signal from the channel; and    a front end receiving circuit for processing the analog data signal and converting it to a digital signal;    a processing circuit for extracting selected data from the digital signal, the digital signal including data from a first frequency bandwidth portion f 1  of said bandwidth and for generating feedback information indicating to the upstream transceiver that the bandwidth other than f 1  is unsuitable for data transmission even when said channel can support said bandwidth F.    
     
     
         37 . The system of    claim 36   , wherein the feedback information contains intentionally altered channel characteristic information.  
     
     
         38 . The system of    claim 37   , wherein the feedback information, including the size and center of first frequency bandwidth portion f 1 , can be controlled by a user of such system.  
     
     
         39 . The system of    claim 38   , wherein the ratio of f 1  to F is approximately 0.5 or less, and this ratio can be increased through modular additions to the front end receiving circuit.  
     
     
         40 . A high speed communications system for transmitting digital information in a channel capable of supporting a transmission bandwidth F, said system comprising: 
 an upstream data transceiver capable of modulating the digital information to generate an analog data signal data transmission using said transmission bandwidth F; and    a downstream data transceiver channel interface circuit for coupling to and receiving said analog data signal from the upstream data transciever through said channel, the downstream data transceiver including: 
 (i) a front end receiving circuit for processing the analog data signal and converting it to a digital signal; and  
 (ii) a processing circuit for demodulating the digital signal, the digital signal including data from a first frequency bandwidth portion f 1  of said bandwidth and for generating feedback information indicating to the upstream transceiver that the bandwidth other than f 1  is unsuitable for data transmission; and  
 (iii) a front end transmitting circuit for transmitting the feedback information using a second frequency bandwidth portion f 2  to cause said upstream transceiver to transmit downstream data only using the first frequency portion f 1 .  
   
     
     
         41 . The system of    claim 40   , wherein the ratio of f 1  to F is approximately 0.5 or less, and this ratio can be increased through modular additions to the front end receiving circuit.  
     
     
         42 . The system of    claim 40   , wherein the feedback information contains intentionally altered channel characteristic information.  
     
     
         43 . The system of    claim 41   , wherein the feedback information, including the size and location of first frequency portion f 1 , can be controlled by a user of such system.  
     
     
         44 . A method of operating a high speed communications system that is coupled to an upstream transceiver through a channel capable of supporting an analog data transmission having a bandwidth F, said method comprising: 
 (a) receiving said analog data signal from the upstream transceiver through the channel; and    (b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion f 1 ; and    (c) processing the digital signal to extract data from the digital signal; and    (d) generating feedback information indicating to the upstream transceiver that the bandwidth other than f 1  should not be used for data transmission, even if an analog data signal with bandwidth f 1  is supportable in the channel.    
     
     
         45 . The method of    claim 44   , further including a step prior to step (a): receiving a control signal from a user of such system for determining size and location of first frequency bandwidth portion f 1 .  
     
     
         46 . The method of    claim 44   , further including a step: determining an optimal size and location of first frequency bandpass portion f 1  so as to minimize the amount of processing required to extract the data from the digital signal.  
     
     
         47 . The method of    claim 44   , wherein: 
 step (a) occurs during an initialization period, and said received analog transmission signal has a bandwidth F; and    after step (d) the upstream transceiver only transmits an analog data signal within first frequency bandwidth portion f 1 .    
     
     
         48 . The method of    claim 40   , wherein the system transmits feedback information containing intentionally altered channel characteristic information.  
     
     
         49 . A method of operating a high speed communications system that is coupled to an upstream transceiver through a channel capable of supporting an analog data transmission signal including M modulated sub-channels, said method comprising: 
 (a) receiving said analog data transmission signal from the upstream transceiver through the channel; and    (b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion f 1 ; and    (c) processing the digital signal to extract data from N of the sub-channels, where N≦M; and    (d) generating feedback information indicating to the upstream transceiver that the sub-channels other than the N sub-channels should not be used for data transmission, even if said channel is capable of supporting more than N sub-channels.    
     
     
         50 . The method of    claim 49   , further including a step prior to step (a): receiving a control signal from a user of such system for determining the identity of the N sub-channels.  
     
     
         51 . The method of    claim 49   , further including a step: determining an optimal set of N sub-channels so as to minimize the amount of processing required to extract the data from the digital signal.  
     
     
         52 . The method of    claim 49   , wherein: 
 step (a) occurs during an initialization period, and said received analog transmission signal includes data for M sub-channels; and    after step (d) the upstream transceiver only transmits an analog data signal using the N sub-channels.    
     
     
         53 . The method of    claim 49   , wherein the system transmits feedback information containing intentionally altered channel characteristic information.  
     
     
         54 . A method of operating a high speed communications system that is coupled through a channel to an upstream transceiver operating at a maximum data rate Y using a bandwidth F, said method comprising: 
 (a) receiving an analog initialization signal having a bandwidth F from the upstream transceiver through the channel; and    (b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion f 1 , where f 1 <F; and    (c) processing the digital signal to extract data from the digital signal such that an effective receiving rate X (where X<Y) is achieved by the system;    (d) generating feedback information pertaining to the channel transmission characteristics indicating to the upstream transceiver that data rates higher than X should not be used;    (e) thereafter receiving an analog data signal transmitted by the upstream transceiver to have a bandwidth f 1 ;    (f) repeating steps (b) and (c).    
     
     
         55 . The method of    claim 54   , further including a step prior to step (a): receiving a control signal from a user of such system for determining the effective receiving rate X.  
     
     
         56 . The method of    claim 54   , further including a step: determining an optimal bandwidth portion f 1  so as to minimize the amount of processing required to extract the data from the digital signal at the receiving rate X.