Frequency agile broadband communications system

• US 5,594,726 A
• Filed: 03/30/1994
• Issued: 01/14/1997
• Est. Priority Date: 09/17/1993
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Ritchie, John A. Jr., Dubberly, Gregory T., Thompson, Leo J.
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Patel, Ajit
• Application Number:
  US08/219,848
• Time in Patent Office: 1,021 Days
• Field of Search: 348/12, 348/11, 348/14, 348/15, 370/69.1, 370/71, 370/73, 370/110.1, 370/112, 375/219, 375/222, 375/202, 455/5.1, 455/6.10, 455/4.1, 455/6.3, 455/6.2, 455/3.1
• US Class Current: 370/485
• CPC Class Codes: H04H 20/79 using downlink of the CATV systems, e.g. audio broadcast via CATV network
• CPC Class Codes: H04H 20/81 combined with telephone network over which the broadcast is continuously available
• CPC Class Codes: H04H 60/96 CATV systems for accessing the Internet H04H60/86
• CPC Class Codes: H04H 60/97 using uplink of the CATV systems
• CPC Class Codes: H04J 1/12 Arrangements for reducing cross-talk between channels in line transmission systems H04B3/32; in cables or lines H04B3/26 - H04B3/30
• CPC Class Codes: H04J 2203/0041 Star, e.g. cross-connect, concentrator, subscriber group equipment, remote electronics
• CPC Class Codes: H04J 2203/0089 Multiplexing, e.g. coding, scrambling, SONET
• CPC Class Codes: H04J 3/1623 Plesiochronous digital hierarchy [PDH]
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04M 7/006 Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP) , including next generation networks with a packet-switched transport layer H04L65/00 takes precedence; aspects not specific to the type of network H04M3/00; special services in those networks H04M3/42
• CPC Class Codes: H04N 2007/1739 the upstream communication being transmitted via a separate link, e.g. telephone line
• CPC Class Codes: H04N 7/10 Adaptations for transmission by electrical cable H04N7/12 takes precedence
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections
• CPC Class Codes: H04Q 2213/13332 Broadband, CATV, dynamic bandwidth allocation

Abstract

A broadband communications system for coupling telephony or other digital networks to a CATV network. The system transmits a multiplex of telephony signals in the forward band of the CATV network. Each forward channel is QPR modulated on a carrier and contains multiple subscriber telephony signals. The forward telephony channels are demodulated and demultiplexed by a plurality of subscriber terminals into the individual telephony signals directed to an addressed subscriber. Audio and control signals returning from the subscriber are digitized into standard telephony signals and QPSK modulated on a carrier onto the reverse band of the CATV network. The multiplicity of reverse band telephony channels are demodulated and multiplexed into a standard telephony signal which is directly interfaced to the telephony network. The reverse band modulators are frequency agile and modulate telephony signals from a subscriber in a selected one or more frequency subbands in the reverse band of the subscription network, so as to provide selectably changeable frequencies and selectably variable bandwidth in the reverse band commensurate with a selected subscriber communication feature. e.g. a single voice line, multiple voice lines, ISDN service, data communications services, security monitoring services, etc.

Claims

1. A bidirectional signal communications system for receiving a multiplexed input signal comprising a plurality of input data channels and for providing a multiplexed output signal comprising a plurality of output data channels, wherein each input data channel in the multiplexed input data signal corresponds to a particular one of a plurality of destinations connected via a broadband communications medium and wherein each output data channel corresponds to a particular one of a plurality of origins connected via said broadband communications medium, said system comprising:

a first converter for converting data in said input data channels into modulated downstream carriers in downstream channels associated with particular destinations;

a first transmitter for transmitting said modulated downstream carriers to said plurality of said destinations;

at least one demodulator for demodulating an assigned carrier of said modulated downstream carriers at a destination and recovering incoming data in a particular data channel associated with said particular one of said destinations;

at least one modulator for modulating outgoing data from said particular one of stud plurality of origins on an assigned carrier for one of a plurality of upstream channels;

at least one second transmitter for transmitting said modulated assigned carrier from said particular one of said origins;

a second converter for converting said assigned carriers in said upstream channels into said output data channels for said multiplexed output signal,

a noise monitor for monitoring the noise level in a particular upstream channel, and

equipment for reassigning outgoing data to a carrier at a different frequency in a different upstream channel in response to noise level exceeding a predetermined level in said particular upstream channel.

2. A bidirectional communications system as set forth in claim 1 wherein:

said multiplexed input signal is a standard digital telephony signal.

3. A bidirectional communications system as set forth in claim 2 wherein:

said standard digital telephony signal includes at least one of the group of a DS-0 format signal, a DS-1 format signal, a DS-2 format signal, and a DS-3 format signal.

4. A bidirectional communications system as set forth in claim 1, wherein:

said multiplexed output signal is a standard digital telephony signal.

5. A bidirectional communications system as set forth in claim 4, wherein:

said standard digital telephony signal includes at least one of the group of a DS-0 format signal, a DS-1 format signal, a DS-2 format signal, and a DS-3 format signal.

6. A bidirectional communications system as set forth in claim 1 wherein:

said central point is the headend of a CATV network; and

said origins and destinations of data are subscribers of said CATV network.

7. A bidirectional communications system as set forth in claim 1, wherein:

said origins and destinations of data are subscribers in a tree-type network extending from said central point.

8. A bidirectional communications system as set forth in claim 7, further comprising:

equipment operative for associating at least one upstream channel with a particular subscriber'"'"'s telephony equipment; and

equipment for associating at least one downstream channel with said telephony equipment.

9. A bidirectional communications system as set forth in claim 7, further comprising a customer interface unit (CIU) defining a destination for incoming data and an origin for outgoing data, said CIU including said at least one demodulator, said at least one modulator, and said at least one second transmitter.

10. A bidirectional communications system as set forth in claim 1, further comprising:

equipment for associating a plurality of upstream channels and a plurality of downstream channels to a single subscriber to provide for selectably variable bandwidth service.

11. A bidirectional communications system as set forth in claim 10, wherein said selectably variable bandwidth service comprises telephony service selected from single line service, multiple line service, ISDN service, and T1 service.

12. An apparatus for the communication of telephony signals to and from a telephony network and to and from a plurality of subscribers of a subscription system including a subscription network having a first band of frequencies for communicating signals to subscribers in the subscription network and a second band of frequencies for communicating signals from the subscribers, comprising:

a telephony network modulator for modulating the telephony signals from the telephony network on said first band of said subscription network utilizing a first modulation scheme;

a subscriber terminal including a subscriber terminal demodulator for demodulating the telephony signals in said first band from the subscription network and coupling them to a subscriber;

at least one frequency agile second modulator for modulating telephony signals from said subscriber in a selected one of a plurality of frequency subbands in said second band of the subscription network utilizing a second modulation scheme; and

a telephony network demodulator for demodulating the telephony signals from said second band of the subscription network and coupling them to the telephony network.

13. The apparatus of claim 12, wherein a plurality of said frequency agile second modulators is operative for modulating telephony signals from the subscriber in a plurality of frequency subbands in said second band of the subscription network so as to provide selectably variable bandwidth in said second band commensurate with a selected subscriber communication feature.

14. The apparatus of claim 13, wherein said selected subscriber communication feature comprises voice grade telephone service.

15. The apparatus of claim 13, wherein said selected subscriber communication feature comprises ISDN telephone service.

16. The apparatus of claim 13, wherein said selected subscriber communication feature comprises plural voice grade telephone service.

17. The apparatus of claim 13, wherein said selectably variable bandwidth comprises at least one subband provided in said second band of said subscription network.

18. The apparatus of claim 17, wherein said subband is 128 kHz.

19. The apparatus of claim 17, wherein said selectably variable bandwidth comprises a plurality of non contiguous 128 kHz subbands.

20. The apparatus of claim 17, further comprising:

a noise monitor for monitoring the noise level in a selected subband in said second band associated with a selected subscriber, and

wherein said frequency agile second modulator is operative to reassign signals in said selected subband to another subband at another frequency in response to a determination by said noise monitor that the noise level in said selected subband exceeds a predetermined level.

21. The apparatus of claim 12, wherein said first modulation scheme is QPR, and said second modulation scheme is QPSK.

22. The apparatus of claim 12, further comprising an address and control unit (ACU) for associating frequency subbands in said second band of the subscription network with subscribers.

23. The apparatus of claim 22, wherein said ACU maintains an allocation table in memory storing information in association selected from the group comprising:

subscriber identification, frequency subband, noise level, service level, security status, and line status.

24. The apparatus of claim 12, further comprising:

a broadcast message information source for generating a telephony message for broadcast to a selected group of subscribers on the subscription network; and

a device for coupling said broadcast message to a carrier in the forward band of the subscription network for communication to said selected group of subscribers,

whereby a telephony message is generated at a single source and delivered to plural subscribers.

25. The apparatus of claim 12, wherein said first modulation scheme is QPR, and said second modulation scheme is QPSK.

26. The apparatus of claim 12, further comprising an address and control unit (ACU) for associating frequency subbands in said second band of the subscription network with subscribers.

27. A method of operating a communication system to couple telephony signals to and from a telephony network and to and from a plurality of subscribers of a subscription system including a tree-and-branch type broadband subscription network extending from a headend to the subscribers, comprising the steps of:

providing a telephony network interface for telephony signals from the telephony network to the headend;

providing an interface for telephony signals from a subscriber to a subscriber terminal connected to the subscription network;

providing a first band of frequencies for communicating signals to subscribers from the headend;

modulating the telephony signals from the telephony network on the first band of the subscription network utilizing a first modulation scheme;

providing a second band of frequencies for communicating signals to the headend from subscribers;

subdividing the second band of frequencies into a plurality of selectable subbands;

in response to a request for telephony service with a subscriber, selectably allocating a particular one of the selectable subbands in the second band of frequencies to the subscriber; and

modulating telephony signals from the subscriber in the particular subband utilizing a second modulation scheme to transmit said telephony signals from the subscriber to said telephony network interface.

28. The method of claim 27, wherein the second modulation scheme comprises a modulation scheme that is relatively noise-resistant in the upstream direction in the tree-and-branch network structure.

29. The method of claim 28, wherein the second modulation scheme is quadrature phase shift keying (QPSK).

30. The method of claim 27, further comprising the step of allocating one or more selected frequency subbands in the second band of the subscription network so as to provide selectably variable bandwidth commensurate with a selected subscriber communication feature.

31. The method of claim 27, wherein the request for telephony service originates at a subscriber having a default level of telephony service.

32. The method of claim 31, wherein the default level of telephone service is DS0 (64 kbps).

33. The method of claim 27, wherein the request for telephony service originates at a subscriber having selected one of a plurality of selectable levels of communications service available to the subscriber.

34. The method of claim 33, wherein each of the plurality of selectable levels of communications services requires a predetermined data communications bandwidth, and further comprising the step of selecting a plurality of frequency subbands in the second band of the subscription network.

35. The method of claim 34, wherein the request for telephone service originating at a subscriber comprises a request selected from:

single line telephony service, multiple line telephony service, ISDN telephony service, data communications service, videoconferencing service, interactive television service, video game service, security monitoring service.

36. The method of claim 33, further comprising the steps of:

communicating a request for a selected service level to the headend;

determining identity of the subscriber requesting the selected service level;

verifying that the subscriber is authorized to receive the requested service level;

in response to verification that the subscriber is authorized to receive the requested service level, allocating one or more selected frequency subbands in the second band of the subscription network so as to provide selectably variable bandwidth commensurate with selected service level;

communicating the identify of the one or more selected frequency subbands to the subscriber; and

receiving signals from the subscriber in the one or more selected frequency subband from the subscriber at the headend.

37. The method of claim 27, wherein the request for telephony service originates at the headend in response to an incoming communication directed to a subscriber, and further comprising the steps:

determining identity of the particular subscriber to receive the incoming communication;

determining an appropriate service level to provide the communication to the particular subscriber;

allocating one or more selected frequency subbands in the second band of the subscription network so as to provide selectably variable bandwidth commensurate with determined appropriate service level;

communicating the identity of the one or more selected frequency subbands to the particular subscriber;

communicating the incoming communication to the particular subscriber in the first band of frequencies;

at the subscriber terminal associated with the particular subscriber, receiving the identity of the one or more selected frequency subbands for communications back to the headend; and

communicating subscriber signals to the headend in the one or more selected frequency subbands.

38. The method of claim 37, further comprising the steps:

receiving signals at the headend from the particular subscriber in the one or more selected frequency subbands;

demodulating the signals to obtain standard telephony signals;

routing the standard telephony signals from the particular subscriber to a communications port associated with the incoming communication directed to the particular subscriber.

39. The method of claim 38, further comprising the steps:

multiplexing a plurality of standard telephony signals obtained from a plurality of subscribers into a standard multiplexer telephony signal.

40. The method of claim 39, wherein the standard telephony signal is a DS0 format, and wherein the standard multiplexed telephony signals are selected from formats DS1, DS2, DS3, E1, T1, and SONET.

41. A method of operating a bidirectional communication system to couple telephony signals to and from a telephony network and to and from a plurality of subscribers of a subscription system including a broadband subscription network extending from a headend to the subscribers, each subscriber having a subscriber terminal, comprising the steps of:

receiving a multiplexed telephony signal containing a plurality of predetermined telephony signals in a plurality of telephony channels;

demultiplexing the multiplexed telephony signal to obtain a particular telephony signal from a particular telephony channel;

communicating the particular telephony signal from the headend to a particular subscriber at a subscriber destination associated with the particular subscriber in a first frequency band in the subscription system;

selecting a particular subband in a second frequency band in the subscription system to receive subscriber telephony signals from the particular subscriber;

communicating the identity of the selected particular subband in the second frequency band to the particular subscriber from the headend so as to cause a subscriber terminal to transmit the subscriber'"'"'s telephony signals in the selected subband;

communicating subscriber telephony signals from the particular subscriber at the subscriber destination to the headend in the selected particular subband; and

coupling the subscriber telephony signals to the particular telephony channel.

42. The method of claim 41, wherein the multiplexed telephony signal comprises a SONET signal.

43. The method of claim 41, wherein the multiplexed telephony signal is communicated via an optical fiber link from a telephony central office to the headend.

44. The method of claim 41, wherein the multiplexed telephony signal is communicated from a telephony central office to the headend, and thence via an optical fiber link from the headend to a fiber node.

45. The method of claim 41, wherein the step of communicating the identity of the selected particular subband in the second frequency band to the particular subscriber comprises the step of providing a signaling channel for communication of status signals between a subscriber and the headend.

46. The method of claim 41, further comprising the step of changing the frequency from the selected subband in the second frequency band to another frequency subband during a communication session involving the particular subscriber.

47. The method of claim 46, further comprising the step of monitoring the noise level in the selected subband, and wherein the step of changing the frequency of the selected subband is carried out in response to a determination in the monitoring step that the noise level in the selected subband exceeds a predetermined threshold.

48. The method of claim 47, wherein the subscriber telephony signals are digital signals transmitted in a plurality of packets of digital data, and wherein the step of monitoring the noise level in the selected subband comprises the steps:

determining a cyclic redundancy check (CRC) value for each packet of digital data comprising the subscriber telephony signal prior to transmission of the signal;

receiving the CRC value at the headend;

in response to a determination that the CRC value is incorrect, incrementing an error count register;

comparing the error count register to a predetermined value;

when the error count register exceeds a predetermined threshold value, setting a noisy channel status flag; and

changing the frequency in response to setting the noisy channel status flag.

49. The method of claim 48, wherein the step of comparing the error count register to the predetermined threshold value is carried out on a periodic basis so as to determine the number of transmission errors associated with a predetermined number of packets transmitted in a predetermined time.

50. A telephony system for communicating telephony signals between a telephony network and a broadband communication network including a headend communicating to a plurality of subscribers, comprising:

a modulator, coupled between the telephony network and the headend, for modulating the telephony signals from the telephony network on a carrier in a first band of the broadband communication network;

equipment for determining a selected service level for a particular subscriber and for communicating information for effecting the selected service level indicating one or more selected frequency subbands in a second band of the broadband communication network to the particular selected subscriber; and

a demodulator, coupled between the telephony network and the headend, for demodulating the telephony signals from the particular subscriber in the one or more selected frequency subbands and coupling them to the telephony network.

51. The system of claim 50, wherein the broadband communication network includes a subscriber terminal for demodulating the telephony signals in the first band of broadband network and coupling them to the subscriber, and for modulating the telephony signals from the subscriber in the one or more selected frequency subbands in the second band of the broadband network for communication to the headend.

52. The system of claim 51, wherein the subscriber terminal includes a frequency agile modulator for modulating the telephony signals in the one or more selected frequency subband in the second band, and further comprising:

a noise monitor for monitoring the noise level in a selected frequency subband associated with a particular subscriber, and

equipment responsive to the noise monitor for communicating a frequency change signal to a particular subscriber when the noise level in the selected frequency subband exceeds a predetermined threshold,

whereby the subscriber terminal changes the frequency for communicating at least some of the telephony signals to a different selected frequency subband when a given channel becomes too noisy.

53. The system of claim 50, wherein the broadband communication network is a cable television (CATV) network, and further comprising equipment for providing television program signals in said first band of frequencies to subscribers.

54. The system of claim 50, wherein the equipment for determining the selected service level comprises:

equipment for communicating in the first band a directory message in a directory channel containing subscriber identification information and the identity of one or more selected frequency subbands in the second band associated with the subscriber identification information.

55. The system of claim 50, wherein the information for effecting the selected service level comprises a message including address information corresponding to a selected subscriber and frequency subband information corresponding to the one or more selected frequency subbands.

56. The system of claim 55, wherein said channel assignment message is transmitted in a directory channel.

57. The system of claim 50, further comprising:

a frequency agile modulator located at the subscriber operative to change the frequency at which telephony signals are being communicated to the headend from a first frequency subband to a second frequency subband in response to a command received from the headend.

58. The system of claim 57, wherein the frequency agile modulator comprises a quadrature phase shift keying (QPSK) modulator operative at selectable carrier frequencies varying in discrete increments of 128 kHz channels, beginning at a nominal initial carrier frequency of 5.12 MHz, with a nominal data rate of 144 kbps per channel.

59. The system of claim 58, wherein each said 144 kbps channel comprises two 64 kbps DS0 telephony () channels and one 16 kbps overhead channel including data headers, address information, and CRC data.

60. The system of claim 58, wherein each 128 kHz channel comprises a 108 kHz bandwidth data channel and 20 kHz in guard bands.

61. The system of claim 50, wherein telephony signals from the headend communicated to the subscriber are transmitted in said first frequency band as downstream signals, and further comprising:

a customer interface unit including a demodulator for demodulating said downstream signals in the first frequency band to obtain an incoming telephony signal and coupling said incoming telephony signal to a telephony port.

62. The system of claim 61, wherein said downstream signals are communicated to the customer interface unit via QPR modulation.

63. The system of claim 61, wherein said downstream signals communicated in the first frequency band comprise:

a plurality of incoming telephony signals arranged in a plurality of channels;

at least one directory channel containing said second signals; and

at least one signaling channel containing status information.

64. The system of claim 63, wherein the downstream signals comprise a 3.168 MHz QPR modulated signaling containing 96 DS0 digital incoming telephony signals, said directory channel, said signaling channel, and CRC data associated with a frame of digital signals.

65. A customer interface unit for connection to a broadband communication network, the customer interface unit operative for receiving first signals in a first frequency band from a headend associated with the broadband communication network, for receiving second signals from the headend, and for communicating telephony signals between a subscriber and the headend, said customer interface unit comprising:

a first demodulator for demodulating first signals in the first frequency band and for coupling them to an output port of the customer interface unit;

a second demodulator for receiving second signals and for identifying, from said second signals, one of a plurality of frequency subbands in a second band of frequencies in the broadband communication network for communicating telephony signals to the headend; and

a frequency agile modulator responsive to the identified one of said plurality of frequency subbands in the second band of frequencies for modulating the telephony signals from the customer interface unit in the identified frequency subband.

66. The customer interface unit of claim 65, wherein the broadband communication network is a cable television (CATV) network.

67. The customer interface unit of claim 66, wherein said first signals comprise television program signals, and wherein said output port comprises a video signal port for connection to a CATV set top converter.

68. The customer interface unit of claim 65, wherein said output port comprises a telephony port for receiving the telephony signals into the customer interface unit.

69. The customer interface unit claim 65, wherein said output port comprises:

a video signal output port for coupling to a cable television set top terminal; and

at least one telephony signal port for coupling to a subscriber'"'"'s home telephony network.

70. The customer interface unit of claim 69, further comprising:

a subscriber input port for receiving subscriber signals associated with an interactive consumer device selected from;

pay per view television, interactive television, video games, and shopping channel television selection.

71. The customer interface unit of claim 65, wherein the second signals are communicated in the first frequency band.

72. The customer interface unit of claim 65, wherein the second signals comprise a message including address information corresponding to a selected subscriber and frequency subband information corresponding to the one or more selected frequency subbands.

73. The customer interface unit of claim 65, wherein said second signals are transmitted in a directory channel.

74. The customer interface unit of claim 65, wherein said frequency agile modulator is operative to change the frequency at which telephony signals are being communicated to the headend from a first frequency subband to a second frequency subband in response to a command received as the second signal.

75. The customer interface unit of claim 65, wherein said frequency agile modulator comprises a quadrature phase shift keying (QPSK) modulator operative at selectable carrier frequencies varying in discrete increments of 128 kHz channels, beginning at a nominal initial carrier frequency of 5.12 MHz, with a nominal data rate of 144 kbps per channel.

76. The customer interface unit of claim 75, wherein each said 144 kbps channel comprises two 64 kbps DS0 telephony channels and one 16 kbps overhead channel including data headers, address information, and CRC data.

77. The customer interface unit of claim 75, wherein each 128 kHz channel comprises a 108 kHz bandwidth data channel and 20 kHz in guard bands.

78. The customer interface unit of claim 65, wherein telephony signals from the headend communicated to the subscriber are also transmitted in said first frequency band as downstream signals, wherein said customer interface unit further comprises:

a third demodulator for demodulating said downstream signals in the first frequency band to obtain an incoming telephony signal and coupling said incoming telephony signal to a telephony port.

79. The customer interface unit of claim 78, wherein said downstream signals are communicated to the customer interface unit via QPR modulation.

80. The customer interface unit of claim 78, wherein said downstream signals communicated in the first frequency band comprise:

a plurality of incoming telephony signals arranged in a plurality of channels;

at least one directory channel containing said second signals; and

at least one signaling channel containing status information.

81. The customer interface unit of claim 80, wherein the downstream signals comprise a 3.168 MHz QPR modulated signaling containing 96 DS0 digital incoming telephony signals, said directory channel, said signaling channel, and CRC data associated with a frame of digital signals.

82. A method of operating a broadband communication network, including a telephony network interface for connection to a telephony network, for communicating signals between subscribers and the telephony network, comprising the steps of:

receiving a multiplexed incoming telephony signal from the telephony network comprising a plurality of telephony signals provided in a standard multiplexed telephony format;

demultiplexing the incoming multiplexed telephony signal to obtain at least one selected incoming telephony signal intended for a particular subscriber on the broadband communication network;

transmitting the selected incoming telephony signal to the particular subscriber in a first frequency band on the broadband communication network utilizing a first modulation scheme;

receiving the selected incoming telephony signal at a customer interface unit connected to the broadband communication network associated with the particular subscriber;

coupling the selected incoming telephony signal transmitted via the first modulation scheme to a telephony port associated with the customer interface unit;

receiving outgoing telephony signals from a subscriber at the telephony port;

transmitting the outgoing telephony signals on at least one assigned carrier in a selected subband in a second frequency band on the broadband communication network utilizing a second modulation scheme;

demodulating the outgoing telephony signals transmitted via the second modulation scheme in the selected subband to obtain an outgoing telephony signal associated with the particular subscriber;

multiplexing the outgoing telephony signal from the particular subscriber with other telephony signals associated with other subscribers to obtain a multiplexed outgoing telephony signal comprising a plurality of telephony signals in a standard multiplexed telephony format to telephony network; and

coupling the multiplexed outgoing telephony signal to the telephony network.

83. The method of claim 82, wherein the second modulation scheme is quadrature phase shift keying (QPSK).

84. The method of claim 82, further comprising the step of:

allocating one or more selected frequency subbands in the second frequency band on the broadband communication network so as to provide selectably variable bandwidth service.

85. The method of claim 84, wherein said selectably variable bandwidth service comprises telephony service selected from a single line service, multiple line service, ISDN service and T1 service.

86. The method of claim 82, wherein the multiplexed incoming telephony signal comprises a SONET signal.

87. The method of claim 82, wherein the multiplexed incoming telephony signal is communicated via an optical fiber link from a telephony central office to a headend of the broadband communication network.

88. The method of claim 82, wherein the multiplexed incoming signal is communicated from a telephony central office to a headend of the broadband communication network, and thereafter is communicated via an optical fiber link from the headend to a fiber node.

89. The method of claim 82, wherein the multiplexed outgoing telephony signal is communicated via an optical fiber link from a headend of the broadband communications network to a telephony central office.

90. The method of claim 82, wherein the multiplexed outgoing signal is communicated via an optical fiber link from a fiber node to a headend of the broadband communication network, and thereafter is communicated from the headend to a telephony central office.

91. The method of claim 82, further comprising the step of:

changing the frequency from the selected subband in the second frequency band on the broadband communication network to another frequency subband during a communication session.

92. The method of claim 91, further comprising the step of:

monitoring the noise level in the selected subband, and wherein said step of changing the frequency of the selected subband is carried out in response to a determination in said monitoring step that the noise level in the selected subband exceeds a predetermined threshold.

93. The method of claim 92, wherein said step of monitoring the noise level in the selected subband comprises the steps of:

determining a cyclic redundancy check (CRC) value for each packet of digital data comprising the telephony signal prior to transmission of the signal;

receiving the CRC value at the headend;

in response to a determination that the CRC value is incorrect, incrementing an error count register;

comparing the error count register to a predetermined value;

when the error count register exceeds a predetermined threshold value, setting a noisy channel status flag; and

changing the frequency in response to setting the noisy channel status flag.

94. The method of claim 93, wherein the step of comparing the error count register to the predetermined threshold value is carried out on a periodic basis so as to determine the number of transmission errors associated with a predetermined number of packets transmitted in a predetermined time.

95. A method of operating a bidirectional communication system to couple telephony signals to and from a telephony network and to and from a plurality of subscribers of a subscription system including a broadband subscription network extending from a headend to the subscribers, comprising the steps of:

receiving a multiplexed telephony signal containing a plurality of predetermined telephony signals in a plurality of telephony channels;

demultiplexing the multiplexed telephony signal to obtain a particular telephony signal from a particular telephony channel;

communicating the particular telephony signal from the headend to a particular subscriber at a subscriber destination associated with the particular subscriber in a first frequency band in the subscription system;

selecting a particular subband in a second frequency band in the subscription system to receive subscriber telephony signals from the particular subscriber;

communicating subscriber telephony signals from the particular subscriber at the subscriber destination to the headend in the selected particular subband; and

coupling the subscriber telephony signals to the particular telephony channel; and

changing the frequency from the selected subband in the second frequency band to another frequency subband during a communication session involving the particular subscriber.

96. The method of claim 95, further comprising the step of communicating the identity of the selected subband in the second frequency band to the particular subscriber from the headend so as to cause the subscriber terminal to transmit the subscriber'"'"'s telephony signals in the selected subband.

97. The method of claim 96, wherein the step of communicating the identity of the selected subband in the second frequency band to the particular subscriber comprises the step of providing a signaling channel for communication of status signals between a subscriber and the headend.

98. The method of claim 95, further comprising the step of monitoring the noise level in the selected subband, and wherein the step of changing the frequency of the selected subband is carried out in response to a determination in the monitoring step that the noise level in the selected subband exceeds a predetermined threshold.

99. An apparatus for the communication of telephony signals to and from a telephony network and to and from a plurality of subscribers of a subscription system including a subscription network having a first band of frequencies for communicating signals to subscribers in the subscription network and a second band of frequencies for communicating signals from the subscribers, comprising:

a telephony network modulator for modulating the telephony signals from the telephony network on said first band of said subscription network utilizing a first modulation scheme;

a subscriber terminal including a subscriber terminal demodulator for demodulating the telephony signals in said first band from the subscription network and coupling them to a subscriber;

a plurality of frequency agile second modulators for modulating telephony signals from said subscriber in a plurality of frequency subbands in said second band of the subscription network utilizing a second modulation scheme so as to provide selectably variable bandwidth in said second band commensurate with a selected subscriber communication feature; and

a telephony network demodulator for demodulating the telephony signals from said second band of the subscription network and coupling them to the telephony network.

100. The apparatus of claim 99, wherein said selected subscriber communication feature comprises voice grade telephone service.

101. The apparatus of claim 99, wherein said selected subscriber communication feature comprises ISDN telephone service.

102. The apparatus of claim 99, wherein said selected subscriber communication feature comprises plural voice grade telephone service.

103. The apparatus of claim 99, wherein said selectably variable bandwidth comprises at least one subband provided in said second band of said subscription network.

104. The apparatus of claim 103, wherein said selectably variable bandwidth comprises a plurality of non contiguous subbands.

105. The apparatus of claim 103, further comprising:

a noise monitor for monitoring the noise level in a selected subband in said second band associated with a selected subscriber, and

wherein said frequency agile second modulators are operative to reassign signals in said selected subband to another subband at another frequency in response to a determination by said noise monitor that the noise level in said selected subband exceeds a predetermined level.

106. An apparatus for the communication of telephony signals to and from a telephony network and to and from a plurality of subscribers of a subscription system including a subscription network having a first band of frequencies for communicating signals to subscribers in the subscription network and a second band of frequencies for communicating signals from the subscribers, comprising:

a telephony network modulator for modulating the telephony signals from the telephony network on said first band of said subscription network utilizing a first modulation scheme;

a subscriber terminal including a subscriber terminal demodulator for demodulating the telephony signals in said first band from the subscription network and coupling them to a subscriber;

at least one frequency agile second modulator for modulating telephony signals from said subscriber in a selected one of a plurality of frequency subbands in said second band of the subscription network utilizing a second modulation scheme;

a telephony network demodulator for demodulating the telephony signals from said second band of the subscription network and coupling them to the telephony network; and

an address and control unit (ACU) for associating frequency subbands in said second band of the subscription network with subscribers, said ACU maintaining an allocation table in a memory storing information in association selected from the group comprising;

subscriber identification, frequency subband, noise level, service level, security status, and line status.

107. The apparatus of claim 106, wherein a plurality of said frequency agile second modulators is operative for modulating telephony signals from the subscriber in a plurality of frequency subbands in said second band of the subscription network so as to provide selectably variable bandwidth in said second band commensurate with a selected subscriber communication feature.

108. The apparatus of claim 107, wherein said selected subscriber communication feature comprises voice grade telephone service.

109. The apparatus of claim 107, wherein said selected subscriber communication feature comprises ISDN telephone service.

110. The apparatus of claim 107, wherein said selected subscriber communication feature comprises plural voice grade telephone service.

111. The apparatus of claim 107, wherein said selectably variable bandwidth comprises at least one subband provided in said second band of said subscription network.

112. The apparatus of claim 111, wherein said selectably variable bandwidth comprises a plurality of non contiguous subbands.

113. The apparatus of claim 111, further comprising:

a noise monitor for monitoring the noise level in a selected subband in said second band associated with a selected subscriber, and

wherein said frequency agile second modulator is operative to reassign signals in said selected subband to another subband at another frequency in response to a determination by said noise monitor that the noise level in said selected subband exceeds a predetermined level.