US 7,257,328 B2 · System and method for transmitting data on return path of a cable television system

Abstract

An optical signal return path system includes a transmitter having a sample clock generator for generating a sample clock and an RF signal receiver for receiving and converting an analog RF data signal into a first data stream of digitized RF data samples at a rate determined by the sample clock. Supplemental channel circuitry provides a second data stream. A multiplexor receives and combines the first data stream and second data stream, and an optical transmitter converting the combined data stream into a serialized optical data signal for transmission over an optical fiber. The second data stream may contain maintenance data reflecting an operational state of the transmitter. A receiver receives the optical data signal and recovers therefrom a digital data stream and an associated first clock having an associated first clock rate. The data stream is stored in a memory device at the first clock rate. A clock generator generates a second clock having an associated second clock rate that is adjusted in accordance with a clock control signal. A control circuit reads data from the memory device at a rate corresponding to the second clock rate and generates a fullness signal that indicates whether the memory device is more full than a predefined threshold fullness level. A clock speed adjusting circuit generates the clock control signal in accordance with the fullness signal.

Claims27

Dependent claims

A return path transmitter for use in conjunction with a local system that generates an analog RF data signal to be conveyed to a head end system, the return path transmitter comprising:

a sample clock generator having a first clock oscillator for generating a sample clock;
an RF signal receiver, coupled to the sample clock generator, for receiving and converting the analog RF data signal into a first data stream of digitized RF data samples at a rate determined by the sample clock;
supplemental channel circuitry for providing a second data stream;
a multiplexor coupled to the RF signal receiver and the supplemental channel circuitry to receive the first data stream and second data stream and to output a combined data stream;
an output clock generator having a second clock oscillator for generating an output clock;
an optical transmitter for converting the combined data stream into a serialized optical data signal for transmission over an optical fiber at a rate determined by the output clock;
a first memory device configured to buffer the first data stream;
and
a second memory device configured to buffer the second data stream;
wherein:
the sample clock has an associated sample rate;
the second data stream is generated by the supplemental channel circuitry at a rate that is less than the sample rate;
the multiplexor is configured to monitor a fullness level of the first memory device, output data stored in the first memory device in a first mode when the fullness level of the first memory device is more than a predefined threshold level, and to output data stored in the first memory device and data stored in the second memory device in a second interleaved mode when the fullness level of the first memory device is less than the predefined threshold level.

10 more elements

A return path transmitter for use in conjunction with a local system that generates an analog RF data signal to be conveyed to a head end system, the return path transmitter comprising:

a sample clock generator having a first clock oscillator for generating a sample clock;
an RF signal receiver, coupled to the sample clock generator, for receiving and converting the analog RF data signal into a first data stream of digitized RF data samples at a rate determined by the sample clock;
supplemental channel circuitry for providing a second data stream;
a multiplexor coupled to the RF signal receiver and the supplemental channel circuitry to receive the first data stream and second data stream and to output a combined data stream;
an output clock generator having a second clock oscillator for generating an output clock;
an optical transmitter for converting the combined data stream into a serialized optical data signal for transmission over an optical fiber at a rate determined by the output clock;
a port for receiving a third data stream from a source external to the return path transmitter, the third data stream having a data rate of at least 5 Mb/s;
and
merge circuitry for merging the first and third data streams into a merged data stream;
wherein the multiplexor is coupled to the merge circuitry and the supplemental channel circuitry to receive the merged data stream and second data stream and to output the combined data stream.

7 more elements

A return path transmitter for use in conjunction with a local system that generates an analog RF data signal to be conveyed to a head end system, the return path transmitter comprising:

a sample clock generator having a first clock oscillator for generating a sample clock;
an RF signal receiver, coupled to the sample clock generator, for receiving and converting the analog RF data signal into a first data stream of digitized RF data samples at a rate determined by the sample clock;
supplemental channel circuitry for providing a second data stream, the supplemental channel circuitry configured to generate maintenance data indicative of an operational state of the return path transmitter and including the maintenance data in the second data stream, the supplemental channel circuitry including at least one sensor for measuring an operational parameter selected from a group consisting of temperature and supply voltage;
a multiplexor coupled to the RF signal receiver and the supplemental channel circuitry to receive the first data stream and second data stream and to output a combined data stream;
and
an output clock generator having a second clock oscillator for generating an output clock;
an optical transmitter for converting the combined data stream into a serialized optical data signal for transmission over an optical fiber at a rate determined by the output clock.

4 more elements

A return path transmitter for use in conjunction with a local system that generates an analog RF data signal to be conveyed to a head end system, the return path transmitter comprising:

a sample clock generator having a first clock oscillator for generating a sample clock;
an RF signal receiver, coupled to the sample clock generator, for receiving and converting the analog RF data signal into a first data stream of digitized RF data samples at a rate determined by the sample clock;
supplemental channel circuitry for providing a second data stream, the supplemental channel circuitry configured to generate maintenance data indicative of an operational state of the return path transmitter and including the maintenance data in the second data stream, the supplemental channel circuitry including an internal memory device configured to store data including at least one of a serial number, model number, date of manufacture, software revision number and hardware revision number of the transmitter, the supplemental channel circuitry being configured to include at least a portion of the data stored in the internal memory device in the maintenance data;
a multiplexor coupled to the RF signal receiver and the supplemental channel circuitry to receive the first data stream and second data stream and to output a combined data stream;
an output clock generator having a second clock oscillator for generating an output clock;
and
an optical transmitter for converting the combined data stream into a serialized optical data signal for transmission over an optical fiber at a rate determined by the output clock.

4 more elements

A return path transmitter for use in conjunction with first and second local systems that generate first and second respective analog RF data signals to be conveyed to a head end system, the return path transmitter comprising:

a sample clock generator for generating a sample clock;
first and second RF signal receivers, coupled to the sample clock generator, for receiving and converting the first and second respective analog RF data signals into first and second data streams of digitized RF data samples at a rate determined by the sample clock;
supplemental channel circuitry for providing a third data stream;
a multiplexor coupled to the RF signal receivers and the supplemental channel circuitry to receive the first, second and third data streams and to output a combined data stream;
an optical transmitter for converting the combined data stream into a serialized optical data signal for transmission over an optical fiber;
a first memory device configured to buffer the first data stream;
a second memory device configured to buffer the second data stream;
a third memory device configured to buffer the third data stream;
and
an output clock generator for generating an output clock;
wherein:
the sample clock has an associated sample rate;
the third data stream is generated by the supplemental channel circuitry at a rate that is less than the sample rate;
the multiplexor is configured to monitor a fullness level of the first memory device, output data stored in the first and second memory devices in a first mode when the fullness level of the first memory device is more than a predefined threshold level, and to output data stored in the first and second memory devices and data stored in the third memory device in a second interleaved mode when the fullness level of the first memory device is less than the predefined threshold level.

11 more elements

Dependencies are inferred from the claim text.

System and method for transmitting data on return path of a cable television system

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System and method for transmitting data on return path of a cable television system

Life of this patent

Abstract

Claims27