Wideband cable modem with narrowband circuitry

• US 7,720,101 B2
• Filed: 05/20/2005
• Issued: 05/18/2010
• Est. Priority Date: 05/25/2004
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Slane, Albert A., Chapman, John T., Fox, David B.
• Primary Examiner(s): Yao; Kwang B.
• Assistant Examiner(s): Elpenord; Candal
• Application Number:
  US11/134,659
• Publication Number:
  US 20050265394A1
• Time in Patent Office: 1,824 Days
• Field of Search: 370/480, 370/489, 370/536, 370/395.65, 370/395.61, 370437-439, 370/465, 725/111, 725/117, 725/126
• US Class Current: 370/480
• CPC Class Codes: H04L 12/2801 Broadband local area networks

Abstract

A hybrid cable modem includes wideband circuitry configured to receive data over multiple different downstream channels at the same time. The wideband circuitry demodulates signals on the different downstream channels and then formats the demodulated signals back into packets or frames for sending out over an Internet Protocol (IP) home network. Narrowband cable modem circuitry is coupled to the wideband circuitry and selectively extracts Data Over Cable Service Interface Specifications (DOCSIS) data from one of the multiple downstream channels being processed by the wideband circuitry.

Claims

1. A cable modem, comprising:

wideband circuitry configured to receive radio frequency (RF) band data arriving downstream from a cable modem termination system (CMTS) external to the cable modem over multiple different downstream channels at the same time, the wideband circuitry demodulating signals in the different downstream channels and then formatting the demodulated signals into individual packets or frames for sending out over an Internet Protocol (IP) network interface;

a narrowband circuit configured to operate in a narrowband mode; and

a control bus coupling the narrowband circuit and the wideband circuitry and configured to allow the narrowband circuit to control the wideband circuitry via the control bus in order to selectively extract Data Over Cable Service Interface Specification (DOCSIS) data in a preconverted, modulated format from one of the multiple downstream channels such that the narrowband circuit receives the data after the data has been preprocessed by a conversion operation in the wideband circuitry and while the data is in a modulated format suitable for demodulation by the narrowband circuit;

wherein the wideband circuitry includes a first Quadrature Amplitude Modulation (QAM) demodulator and the narrowband circuit comprises a second different QAM demodulator; and

wherein the control bus passes the selectively extracted DOCSIS data from the wideband circuitry prior to such data being processed by the first QAM demodulator such that the selectively extracted DOCSIS data bypasses the first QAM demodulator of the wideband circuitry and is directed to the second different QAM demodulator of the narrowband circuit for demodulation.

2. The cable modem according to claim 1 including a central processing unit (CPU) in the narrowband circuit controlling through the control bus a wideband tuner in the wideband circuitry to connect a modulated one of the downstream channels to the narrowband circuit.

3. The cable modem according to claim 1 including a digital to analog (D/A) converter coupling a selected one of multiple digital outputs from an analog to digital (A/D) converter in the wideband circuitry to an A/D converter in the narrowband circuit.

4. The cable modem according to claim 1 including switching circuitry coupling a wideband downstream framer and a wideband upstream framer in the wideband circuitry with the narrowband circuit.

5. The cable modem according to claim 4 wherein the switching circuitry includes Ethernet switching logic that switches Ethernet frames between the wideband downstream framer, the wideband upstream framer, the narrowband circuit, and the IP network interface.

6. The cable modem according to claim 5 wherein the switching circuitry switches the Ethernet frames according to tags located in Ethernet packet headers.

7. The cable modem according to claim 1 including a snooping circuit in the wideband circuitry that monitors packets or frames received from all of the multiple downstream channels and forwards identified packets or frames to the narrowband circuit.

8. The cable modem according to claim 1 wherein the narrowband circuit and the wideband circuitry use a same upstream channel for sending data on an upstream path of a cable plant.

9. The cable modem according to claim 1 wherein same data flows are transported over the multiple different downstream channels at the same time.

10. A method for operating a cable modem, comprising:

receiving radio frequency (RF) band data signals arriving downstream from a cable modem termination system (CMTS) external to the cable modem over multiple different wideband downstream RF channels;

operating wideband circuitry that processes the RF band data signals on the multiple wideband channels and converts the wideband channel signals into Internet Protocol (IP) packets for sending over an IP network interface; and

operating a narrowband cable modem circuit to control the wideband circuitry via a control bus to selectively extract Data Over Cable Service Interface Specification (DOCSIS) data in a preconverted, modulated format from one of the multiple wideband channels processed in the wideband circuitry and to send the selectively extracted DOCSIS data over the IP network interface;

wherein the wideband circuitry includes a first QAM demodulator and the narrowband cable modem circuit comprises a second different QAM demodulator, and wherein the method further comprises;

passing the selectively extracted DOCSIS data from the wideband circuitry prior to such data being processed by the first QAM demodulator such that the selectively extracted DOCSIS data bypasses the first QAM demodulator of the wideband circuitry and is directed to the second different QAM demodulator of the narrowband cable modem circuit for demodulation.

11. The method according to claim 10 including:

using a wideband tuner in the wideband circuitry to convert analog signals received over the multiple wideband channels into associated digital data streams;

converting a selected one of the digital data streams back into an analog signal; and

inputting the analog signal into the narrowband cable modem circuit for processing as a narrowband downstream channel.

12. The method according to claim 11 including using a central processing unit (CPU) in the narrowband cable modem circuit to select via the control bus a modulated one of the digital data streams in the wideband circuitry for connecting to the narrowband cable modem circuit.

13. The method according to claim 12 including communicating between the CPU and the wideband circuitry using a control bus, wherein the control bus is an I²C bus interface or a Serial Peripheral Interconnect (SPI) bus interface.

14. The method according to claim 10 including switching packets or frames between a wideband downstream framer in the wideband circuitry, the narrowband cable modem circuit, and an external IP network interface according to tags or IP addresses in the packets or frames.

15. The method according to claim 10 including identifying packets or frames in any of the multiple wideband channels that contain particular types of data and forwarding the identified packets or frames to the narrowband cable modem circuit.

16. The method according to claim 10 including outputting data from the narrowband cable modem circuit and the wideband circuitry over a same upstream channel on a cable plant.

17. The method according to claim 10 including:

storing the IP packets into an external memory;

reading the IP packets in resequenced order from the external memory;

conducting sequential packet processing operations on the IP packets read in resequenced order from the external memory in hardware without further accessing the external memory; and

sending the IP packets to the IP network interface after the sequential packet processing operations.

24. The method of claim 10, further comprising:

demodulating any portion of the received RF band data signals that does not correspond to the selectively extracted DOCSIS data using the first QAM; and

demodulating a remaining portion of the received RF band data signals that does correspond to the selectively extracted DOCSIS data using the second QAM;

wherein the wideband circuitry and the narrowband cable modem circuit are operating in a same wideband cable modem.

18. A cable modem, comprising:

wideband circuitry configured to receive radio frequency (RF) band data arriving downstream from a cable modem termination system (CMTS) external to the cable modem over multiple different downstream channels at the same time, the wideband circuitry including a block converter for down converting the RF band data as a block over the multiple different downstream channels, a first Quadrature Amplitude Modulation (QAM) demodulator for demodulating signals in the different downstream channels, and a framer for formatting the demodulated signals into individual packets or frames for sending out over an Internet Protocol (IP) network interface; and

a narrowband circuit coupled to the wideband circuitry configured to operate in a narrowband mode and including a processor configured to control the wideband circuitry via a control bus to selectively extract Data Over Cable Service Interface Specification (DOCSIS) data from one of the multiple downstream channels after the DOCSIS data is processed by the block converter and before the DOCSIS data is processed by the first QAM demodulator;

wherein the narrowband circuit comprises a second different QAM demodulator; and

wherein the control bus passes the selectively extracted DOCSIS data from the wideband circuitry prior to such data being processed by the first QAM demodulator such that the selectively extracted DOGS IS data bypasses the first QAM demodulator of the wideband circuitry and is directed to the second different QAM demodulator of the narrowband circuit for demodulation.

19. The cable modem according to claim 18 wherein the wideband circuitry includes an analog-to-digital (A/D) converter to convert analog signals received over the multiple downstream channels into associated digital data streams and the cable modem further includes a digital-to-analog (D/A) converter for converting a selected one of the digital data streams back into an analog signal for inputting into the narrowband circuit.

20. The cable modem of claim 19 wherein the narrowband circuit includes an A/D converter and the selected one of the digital data streams is coupled by the D/A converter from the A/D converter in the wideband circuitry to the A/D converter in the narrowband circuit.

21. The cable modem of claim 20 wherein the processor is a Central Processing Unit (CPU) in the narrowband circuit configured to select via the control bus a modulated one of the digital data streams in the wideband circuitry.

22. The cable modem of claim 21 wherein the control bus uses an I²C bus interface or a Serial Peripheral Interconnect (SPI) bus interface.

23. The cable modem of claim 22 further including a first packet processing stage converting the RF band data into downstream transport packets and storing the packets in a serial buffering operation in an external memory.

25. An apparatus, comprising:

a narrowband cable modem having a first Quadrature Amplitude Modulation (QAM) demodulator;

wideband circuitry coupled to the narrowband cable modem and configured to receive radio frequency (RF) band data arriving downstream from a cable modem termination system (CMTS) over multiple different downstream channels at the same time, the wideband circuitry including a second QAM configured to demodulate signals in the different downstream channels;

wherein the narrowband cable modem and the wideband circuitry are located in a same wideband cable modem; and

means for selectively extracting Data Over Cable Service Interface Specification (DOCSIS) data from one of the multiple downstream channels and passing said selectively extracted DOCSIS data from the wideband circuitry prior to such data being processed by the first QAM demodulator such that the selectively extracted DOCSIS data bypasses the first QAM demodulator of the wideband circuitry and is directed to the second different QAM demodulator of the narrowband cable modem for demodulation.

26. The apparatus of claim 25, further comprising a processing device configured to transmit upstream transmissions to an Edge QAM (EQAM) of a distributed CMTS.