Transmission modulator for cable television upstream data transmission
First Claim
1. A method of subscriber terminal upstream data transmission for use in a cable television system in which a plurality of subscriber terminals are coupled to a headend by a network and in which a common network reference signal is regenerated at each subscriber terminal, said method comprising the steps of:
- generating an upstream carrier signal having a carrier frequency;
receiving said network reference signal having a reference signal frequency;
first frequency dividing said upstream carrier by a divisor M to provide a frequency divided upstream carrier signal;
second frequency dividing said network reference signal by a divisor N to provide a frequency divided network reference signal;
phase and frequency comparing said frequency divided upstream carrier and network reference signals to produce an error signal;
controlling the frequency and phase of said upstream carrier signal in response to said error signal;
modulating upstream transmission data upon said upstream carrier signal to produce a modulated upstream carrier signal;
applying said modulated upstream carrier signal to said network.
1 Assignment
0 Petitions
Accused Products
Abstract
A cable television upstream data transmission system provides a plurality of uniquely assignable time slots for use by subscriber terminals in upstream data transmission. The unique assignment of time slots provides guaranteed access for each subscriber terminal during its time slot. The width and number of time slots are controlled by a pair of programmable values which may be downloaded from the cable system headend to accommodate dynamic changes of the cable system. A transmission modulator used within the subscriber terminal produces an upstream transmission carrier having a frequency locked to a common network reference signal such as the system symbol clock. The frequency of the carrier signal produced by the transmission modulator is programmably controlled by a plurality of program values which are selected to provide frequency and phase lock of the modulator'"'"'s carrier to the symbol clock network reference signal.
-
Citations
15 Claims
-
1. A method of subscriber terminal upstream data transmission for use in a cable television system in which a plurality of subscriber terminals are coupled to a headend by a network and in which a common network reference signal is regenerated at each subscriber terminal, said method comprising the steps of:
-
generating an upstream carrier signal having a carrier frequency; receiving said network reference signal having a reference signal frequency; first frequency dividing said upstream carrier by a divisor M to provide a frequency divided upstream carrier signal; second frequency dividing said network reference signal by a divisor N to provide a frequency divided network reference signal; phase and frequency comparing said frequency divided upstream carrier and network reference signals to produce an error signal; controlling the frequency and phase of said upstream carrier signal in response to said error signal; modulating upstream transmission data upon said upstream carrier signal to produce a modulated upstream carrier signal; applying said modulated upstream carrier signal to said network. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. Subscriber terminal upstream data transmission means for use in a cable television system in which a plurality of subscriber terminals are coupled to a headend by a network and in which a common network reference signal is regenerated at each subscriber terminal, said subscriber terminal upstream data transmission means comprising:
-
means for generating an upstream carrier signal having a carrier frequency; means for receiving said network reference signal having a reference signal frequency; first means for frequency dividing said upstream carrier by a divisor M to provide a frequency divided upstream carrier signal; second means frequency dividing said network reference signal by a divisor N to provide a frequency divided network reference signal; means for phase and frequency comparing said frequency divided upstream carrier and network reference signals to produce an error signal; means for controlling the frequency and phase of said upstream carrier signal in response to said error signal; means for modulating upstream transmission data upon said upstream carrier signal to produce a modulated upstream carrier signal; means for applying said modulated upstream carrier signal to said network. - View Dependent Claims (8, 9, 10, 11, 12)
-
-
13. A method of subscriber terminal upstream data transmission for use in a cable television system in which a plurality of subscriber terminals are coupled to a headend by a network and in which data is transferred to said subscriber terminals using N-level symbols at a symbol clock rate and a symbol clock signal is generated at each subscriber terminal, said method comprising the steps of:
-
generating an upstream carrier signal having a carrier frequency; receiving said symbol clock signal having a symbol clock frequency; first frequency dividing said upstream carrier by a divisor M to provide a frequency divided upstream carrier signal; second frequency dividing said symbol clock signal by a divisor N to provide a frequency divided symbol clock signal; phase and frequency comparing said frequency divided upstream carrier and symbol clock signals to produce an error signal; controlling the frequency and phase of said upstream carrier signal in response to said error signal; modulating upstream transmission data upon said upstream carrier signal to produce a modulated upstream carrier signal; and applying said modulated upstream carrier signal to said network. - View Dependent Claims (14)
-
-
15. Subscriber terminal upstream data transmission means for use in a cable television system in which a plurality of subscriber terminals are coupled to a headend by a network and in which data is transferred to said subscriber terminals using N-level symbols at a symbol clock rate and a symbol clock signal is generated at each subscriber terminal, said subscriber terminal upstream data transmission means comprising:
-
means for generating an upstream carrier signal having a carrier frequency; means for receiving said symbol clock signal having a symbol clock frequency; first means for frequency dividing said upstream carrier by a divisor M to provide a frequency divided upstream carrier signal; second means frequency dividing said symbol clock signal by a divisor N to provide a frequency divided symbol clock signal; means for phase and frequency comparing said frequency divided upstream carrier and symbol clock signals to produce an error signal; means for controlling the frequency and phase of said upstream carrier signal in response to said error signal; means for modulating upstream transmission data upon said upstream carrier signal to produce a modulated upstream carrier signal; and means for applying said modulated upstream carrier signal to said network.
-
Specification