Signal compression for fiber node

Abstract

A method, device and network ( 100, 200 ) for compressing cable modem data signals and conserving bandwidth within the network. Cable modems ( 110, 210 ) transmit upstream data signals to a fiber node ( 130, 230 ) which compresses the data signals and transmits the compressed signals upstream to a headend ( 112, 212 ) which decompresses the data signals. The fiber node ( 130, 230 ) compression may be by a shaping filter ( 142, 144 ) or a fast Fourier transform (FFT) function 270. The headend decompression may be by an inverse shaping filter ( 162 ) or an inverse FFT function ( 272 ).

What is claimed is:  
     
         1 . In a cable network including a headend providing data transmission to a cable modem via a fiber node, the fiber node providing service to a plurality of cable modem users and set-top box users, a method of data transmission, comprising: 
 receiving an upstream data signal from a cable modem;    compressing the upstream signal to a narrow bandwidth for upstream data signal bands required; and    sending the compressed upstream data signal to the headend.    
     
     
         2 . The method according to  claim 1  wherein the compressing comprises: 
 programming a signal frequency; and  
 identifying bands with silence within the upstream data signal for set-top boxes, wherein silent bands are not included in the compressed upstream data signal sent to the headend.  
 
     
     
         3 . The method according to  claim 2  wherein the compressing comprises: 
 demodulating the upstream signal.  
 
     
     
         4 . The method according to  claim 3  wherein the compressing comprises: 
 correcting forward errors.  
 
     
     
         5 . The method according to  claim 1  wherein the method is performed within a fiber node of a cable network.  
     
     
         6 . The method according to  claim 5 , further comprising: 
 decompressing the upstream signal.    
     
     
         7 . The method according to  claim 6  wherein the decompressing is performed within a headend.  
     
     
         8 . A fiber node comprising: 
 an analog-to-digital converter (ADC) coupled to a cable modem, the ADC adapted to convert an analog data signal received from the cable modem to a digital data signal, the digital data signal having a central frequency;    a down converter coupled to the ADC for moving the central frequency of the digital data signal down;    a decimater coupled to the down converter for decimating the digital data signal;    an automatic gain control (AGC) amplifier coupled to the decimater adapted to amplify the decimated digital data signal;    a quantizer coupled to the AGC amplifier adapted to quantize the digital data signal;    a switch having an input and an output, the input being coupled to the quantizer, the switch being adapted to produce a digital signal at the output; and    an analysis and control circuit coupled to and adapted to control the AGC, quantizer and switch, wherein an upstream data signal received from a cable modem is compressed.    
     
     
         9 . The fiber node according to  claim 8  further comprising a low pass filter (LPF) coupled between the decimater and the down converter for filtering the digital data signal.  
     
     
         10 . The fiber node according to  claim 9  further comprising a shaping filter coupled between the decimater and the AGC, the shaping filter adapted to filter the decimated digital data signal.  
     
     
         11 . The fiber node according to  claim 9  further comprising a fast Fourier transform (FFT) function coupled between the decimater and the AGC, the FFT adapted to perform a FFT on the decimated digital data signal.  
     
     
         12 . The fiber node according to  claim 11  wherein the FFT function comprises a microprocessor.  
     
     
         13 . The fiber node according to  claim 8  wherein the analysis and control circuit, AGC amplifier, and quantizer comprise a digital signal processor (DSP).  
     
     
         14 . The fiber node according to  claim 8  wherein the analysis and control circuit turns off the switch when no data signal is present.  
     
     
         15 . In a cable network including a headend providing data transmission to a cable modem and a set-top box via a fiber node, the fiber node providing service to a plurality of cable modem users, the fiber node comprising an analog-to-digital converter (ADC) adapted to convert an analog data signal received from the cable modem to a digital data signal, the digital data signal having a central frequency, the fiber node comprising a down converter coupled to the ADC for moving the central frequency of the digital data signal down, the fiber node comprising a decimater coupled to the down converter for decimating the digital data signal, the fiber node comprising an automatic gain control (AGC) amplifier coupled to the decimater adapted to amplify the decimated digital data signal, the fiber node comprising a quantizer coupled to the AGC amplifier adapted to quantize the digital data signal, the fiber node comprising a switch having an input and an output, the input being coupled to the quantizer, the switch being adapted to produce a digital signal at the output, the fiber node comprising an analysis and control circuit adapted to control the AGC, quantizer and switch, wherein an upstream data signal received from a cable modem is compressed: 
 a headend for a cable network adapted to decompress the compressed data signal received from the fiber node.  
 
     
     
         16 . The headend according to  claim 15 , comprising: 
 a zero padding function coupled to the fiber node switch, the zero padding function adapted to add silence to the digital data signal in time periods where the fiber node switch is turned off;    an inverse AGC amplifier coupled to the zero padding function adapted to divide the signal by the amplification added by the fiber node AGC;    an interpolation module for interpolating the digital data signal; and    a up converter adapted to move the central frequency of the digital data signal.    
     
     
         17 . The headend according to  claim 16 , wherein the zero padding function, inverse AGC, interpolation module and up converter comprise a digital signal processor (DSP).  
     
     
         18 . The headend according to  claim 16 , further comprising a digital-to-analog converter coupled to the up converter adapted to convert the decompressed digital data signal to an analog data signal.  
     
     
         19 . The headend according to  claim 16 , further comprising: 
 an inverse shaping filter coupled between the inverse AGC amplifier, wherein the fiber node further comprises a shaping filter coupled between the decimater and the AGC amplifier, the fiber node shaping filter adapted to filter the decimated digital data signal, wherein the headend inverse shaping filter reverses the effect of the fiber node shaping filter.    
     
     
         20 . The headend according to  claim 16 , further comprising: 
 an inverse fast Fourier transform (FFT) function coupled between the zero padding function and the inverse AGC amplifier, wherein the fiber node further comprises a fast Fourier transform (FFT) function coupled between the decimater and the AGC, the FFT function adapted to perform a FFT function on the decimated digital data signal, wherein the headend inverse FFT function reverses the effect of the fiber node FFT function.    
     
     
         21 . The headend according to  claim 20  further comprising a quantizer coupled between the inverse FFT function and the inverse AGC amplifier, the quantizer adapted to quantize the data signal.  
     
     
         22 . In a cable network including a headend providing data transmission to a cable modem via a fiber node, the fiber node providing service to a plurality of cable modem users and set-top box users, a data transmission means within the fiber node, comprising: 
 means for receiving an upstream data signal from a cable modem;    means for compressing the upstream signal to a narrow bandwidth for required upstream data signal bands; and    means for sending the compressed upstream data signal to the headend.    
     
     
         23 . The data transmission means according to  claim 22 , further comprising: 
 a means for identifying bands with silence for set-top boxes within the upstream data signal, wherein silent bands are not included in the compressed upstream data signal sent to the headend.    
     
     
         24 . A cable network, comprising: 
 a plurality of cable modems;    a fiber node coupled to the cable modems facilitating cable network service to the plurality of cable modems and set-top boxes; and    a headend coupled to the fiber node providing cable modem service to the cable modems through the fiber node, wherein the fiber node is adapted to receive an upstream data signal from a cable modem, compress the upstream signal to a narrow bandwidth for required upstream data signal bands, and send the compressed upstream data signals to the headend.    
     
     
         25 . The cable network according to  claim 24  wherein the fiber node is adapted to program a signal frequency and identify bands of silence within the upstream data signal for set-top boxes, wherein silent bands are not included in the compressed upstream data signal sent to the headend.  
     
     
         26 . The cable network method according to  claim 25  wherein the headend is adapted to decompress the upstream signal.