Time division multiplexing over broadband modulation method and apparatus

• US 20020126685A1
• Filed: 03/12/2001
• Published: 09/12/2002
• Est. Priority Date: 03/12/2001
• Status: Active Grant

• Current Assignee: Inceptia LLC
• Original Assignee: Advent Networks, Inc.
• Inventors: Leatherbury, Ryan M., Johnson, Robert Edward Lee
• Granted Patent: US 6,763,025 B2
• Time in Patent Office: Days
• US Class Current: 370/432
• CPC Class Codes: H04L 2012/5605 Fibre
• CPC Class Codes: H04L 2012/5606 Metallic
• CPC Class Codes: H04L 2012/561 Star, e.g. cross-connect, concentrator, subscriber group equipment, remote electronics
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A packet switch router that processes downstream digital information to provide dedicated bandwidth to each subscriber destination in a hybrid fiber coax (HFC) network. The router includes a network module that terminates a network connection, a switch that forwards data from the network module, and a channel module. The channel module includes a switch interface, a cell processing engine, one or more modulators, and a radio frequency (RF) transmitter network. The switch interface forwards packetized data from the switch to the cell processing engine. The cell processing engine organizes the packetized data into multiple data streams, encapsulates data in each data stream into data cells, and multiplexes the data cells into a multiplexed cell stream. Each modulator is configured to modulate a multiplexed cell stream into an analog signal. The RF transmitter network up converts and combines a plurality of analog signals into a combined electrical signal for transmission.

Claims

1. A method of processing digital information by a point of distribution to provide dedicated bandwidth to a plurality of subscriber destinations via an HFC network, comprising:

forwarding data packets into a plurality of data streams, each data stream corresponding to one of the plurality of subscriber destinations;

framing each data packet in each data stream;

segmenting encapsulated data packets into data segments;

encapsulating data segments of each of the plurality of data streams into data cells to form a corresponding one of a plurality of cell streams;

multiplexing the plurality of cell streams into a multiplexed cell stream; and

modulating the multiplexed cell stream into a modulated signal within a frequency channel.

2. The method of claim 1, prior to said forwarding, further comprising:

receiving digital information; and

processing the digital information into data packet information.

3. The method of claim 1, wherein said framing each data packet comprises appending a packet header including a length value indicative of the size of the data packet.

4. The method of claim 3, wherein said segmenting includes incorporating the packet header in a first segment for each segmented data packet.

5. The method of claim 4, wherein said encapsulating data segments comprises appending a cell header to each data segment, the cell header including an offset value indicating a beginning of a next segmented data packet in the multiplexed cell stream.

6. The method of claim 5, further comprising:

verifying that each offset value is compatible with a length value for a corresponding segmented data packet.

7. The method of claim 5, wherein said cell header includes a synchronization value.

8. The method of claim 5, wherein said encapsulating data segments further comprises:

padding incomplete data cells with null values to achieve equal-sized data cells in the multiplexed cell stream.

9. The method of claim 1, wherein said multiplexing the plurality of cell streams comprises:

inserting data cells from each of the plurality of cell streams into the multiplexed cell stream in a round-robin manner.

10. The method of claim 1, wherein said multiplexing the plurality of cell streams comprises:

channelizing the multiplexed cell stream into cell groups, each cell group having an equal number of time slots; and

inserting data cells from each of the plurality of cell streams into the time slots of each cell group.

11. The method of claim 10, further comprising:

assigning at least one transport channel to each data stream, each transport channel comprising a series of corresponding time slots; and

said inserting comprising inserting data cells from each of the plurality of cell streams into corresponding time slots of assigned transport channels.

12. The method of claim 1, further comprising:

sending the multiplexed cell stream as a synchronous cell stream to a modulator.

13. The method of claim 12, further comprising:

inserting null cells to maintain a continuous synchronized cell stream.

14. The method of claim 12, further comprising:

inserting a delay between each data cell of the multiplexed cell stream.

15. The method of claim 1, wherein said encapsulating data segments includes appending a cell header to each data cell, the cell header including a synchronization value.

16. The method of claim 15, wherein said synchronization value is in accordance with MPEG-2 format.

17. The method of claim 15, after said multiplexing and prior to said modulating, further comprising:

modifying periodic synchronization values within cell headers that are appended to each data cell;

scrambling a payload of each data cell within the multiplexed cell stream; and

encoding data cells in the multiplexed cell stream.

18. The method of claim 17, wherein said encoding is according to the Reed-Solomon encoding scheme.

19. The method of claim 1, wherein said modulating is according to quadrature amplitude modulation (QAM).

20. The method of claim 19, wherein said modulating is according to QAM-256 modulation.

21. The method of claim 1, further comprising:

said multiplexing comprising multiplexing the plurality of cell streams into a plurality of multiplexed cell streams;

modulating each multiplexed cell stream into a corresponding modulated signal within a corresponding one of a plurality of frequency channels; and

combining the plurality of frequency channels into a single electrical signal.

22. The method of claim 21, further comprising:

converting the electrical signal into an optical signal for transmission to an optical node.

24. The method of claim 23, prior to said forwarding digital information, further comprising:

receiving data packets at a distribution hub;

decapsulating the data packets to obtain packet data in an original packet format; and

re-assembling the packet data into packets of the original packet format.

25. The method of claim 24, wherein the original packet format is an IP packet format.

26. The method of claim 24, prior to said receiving data packets, comprising:

receiving an optical signal from a headend; and

converting the optical signal into the data packets.

27. The method of claim 23, further comprising:

said forwarding digital information including determining digital addresses associated with the plurality of subscriber destinations.

28. The method of claim 23, prior to said forwarding, further comprising:

converting the digital information into data packets.

29. The method of claim 28, wherein said encapsulating further comprises:

segmenting the data packets in each data stream into packet segments;

framing the packet segments with frame headers; and

encapsulating framed packet segments into the data cells, each data cell including a cell header.

30. The method of claim 29, further comprising:

said framing including appending a frame header with a length value indicative of the length of a data packet; and

said encapsulating including appending a cell header with a pointer value indicative of the start of an encapsulated data packet.

31. The method of claim 30, further comprising:

verifying a pointer value with a length value to ensure data integrity.

32. The method of claim 30, wherein said encapsulating includes inserting a synchronization value according to MPEG-2 format in the cell header.

33. The method of claim 23, wherein said multiplexing further comprises:

inserting data cells from each of the plurality of data streams in a round-robin manner to form the multiplexed cell stream.

34. The method of claim 23, wherein said multiplexing further comprises:

assigning each of the plurality of data streams to at least one of a predetermined number of transport channels of the multiplexed cell stream; and

inserting data cells from the plurality of data streams into assigned transport channels of the multiplexed cell stream.

35. The method of claim 23, prior to said modulating the multiplexed cell stream, further comprising:

encoding each data cell of the multiplexed cell stream.

36. The method of claim 35, wherein said encoding comprises encoding each data cell according to a Reed-Solomon encoding scheme.

37. The method of claim 35, prior to said encoding each data cell of the multiplexed cell stream, further comprising:

scrambling each data cell of the multiplexed cell stream.

38. The method of claim 23, wherein said modulating comprises modulating the multiplexed cell stream according to quadrature amplitude modulation (QAM).

39. The method of claim 23, further comprising:

said multiplexing comprising multiplexing the data cells of the multiple data streams into a plurality of multiplexed cell streams;

said modulating comprising modulating each of the plurality of multiplexed cell streams into a corresponding plurality of analog signals;

up converting each of the plurality of analog signals into a corresponding one of a plurality of frequency channels; and

combining the plurality of frequency channels into an electrical signal.

40. The method of claim 39, further comprising:

converting the electrical signal to an optical signal.

41. The method of claim 23, wherein said transmitting further comprises:

transmitting the optical signal to an optical node;

converting, by the optical node, the optical signal to an electrical signal; and

transmitting, by the optical node, the electrical signal to the plurality of subscriber destinations via a coaxial cable.

23. A method of providing dedicated bandwidth to each of a plurality of subscriber destinations for delivering source information over an HFC network, comprising:

forwarding digital information into a plurality of data streams, each data stream corresponding to one of the plurality of subscriber destinations;

encapsulating the digital information in each data stream into data cells;

multiplexing the data cells of each of the plurality of data streams into a multiplexed cell stream;

modulating the multiplexed cell stream into an analog signal in a frequency channel;

converting the analog signal to an optical signal; and

transmitting the optical signal to the plurality of subscriber destinations over an HFC network.

42. A channel module that processes downstream digital information at a point of distribution to provide dedicated bandwidth for each of a plurality of subscriber destinations in an HFC network, comprising:

an interface that receives packetized data;

a cell processing engine, coupled to the interface, comprising;

a switch that forwards the packetized data into a plurality of data streams;

an encapsulator that encapsulates the packetized data in each data stream into data cells; and

a channelizer that multiplexes the data cells of the plurality of data streams into a multiplexed stream of data cells;

a modulator, coupled to the cell processing engine, that modulates the multiplexed stream of data cells into an analog signal; and

a radio frequency (RF) transmitter network that up converts the analog signal into a frequency channel.

43. The channel module of claim 42, wherein the cell processing engine further comprises:

a frame processor, coupled to the interface and the switch, that decapsulates the packetized data and re-assembles IP packets.

44. The channel module of claim 43, wherein the encapsulator further comprises:

a packet adaptation procedure (PAP) processor, coupled to the switch, that frames IP packets in each data stream with a frame header which includes a length value indicative of the size of each IP packet.

45. The channel module of claim 44, wherein the encapsulator further comprises:

a cell convergence procedure (CCP) processor, coupled to the PAP processor and the channelizer, that generates the data cells by segmenting framed IP packets and encapsulating each segment with a CCP header that includes a pointer value indicative of the location of a next frame header in a stream of data cells.

46. The channel module of claim 45, wherein the CCP processor pads partial segments with at least one null value to create equal-sized data cells.

47. The channel module of claim 46, wherein the CCP processor further generates null data cells if input packetized data is not available.

48. The channel module of claim 45, wherein the CCP processor adds a synchronization value in accordance with MPEG-2 to the CCP header.

49. The channel module of claim 42, wherein the channelizer organizes the multiplexed stream of data cells into cell groups, each cell group including a plurality of time slots.

50. The channel module of claim 49, wherein the channelizer inserts data cells from each of the plurality of data streams according to assigned time slots.

51. The channel module of claim 50, further comprising:

a memory, coupled to the channelizer, that stores a lookup table that maps each time slot to an address of a corresponding subscriber destination.

52. The channel module of claim 42, wherein the cell processing engine inserts a delay between each data cell of the multiplexed stream of data cells while transmitting to the modulator.

53. The channel module of claim 42, wherein the modulator further comprises:

a randomizer;

an encoder; and

a quadrature amplitude modulator (QAM).

54. The channel module of claim 53, wherein the encoder comprises a Reed-Solomon encoder.

55. The channel module of claim 53, wherein the QAM performs QAM-256 modulation.

56. The channel module of claim 42, further comprising:

the cell processing engine providing a plurality of multiplexed data cell streams;

a plurality of modulators, each receiving a corresponding one of the plurality of multiplexed data cell streams; and

the RF transmitter network including a combiner that combines a plurality of frequency channels into a single electrical signal.

57. A packet switch router channel module that processes downstream digital information at a point of distribution to provide dedicated bandwidth for each of a plurality of subscriber destinations in an HFC network, comprising:

a network interface module that terminates a network connection;

a switch, that forwards packetized data from the network interface module; and

at least one channel module, coupled to the switch, comprising;

a switch interface that receives packetized data from the switch;

a cell processing engine, coupled to the switch interface, that forwards the packetized data into a plurality of data streams, that encapsulates the packetized data in each data stream into data cells, and that multiplexes the data cells of the plurality of data streams into at least one multiplexed stream of data cells;

a plurality of modulators, each coupled to the cell processing engine and each configured to modulate a corresponding multiplexed stream of data cells into an analog signal; and

a radio frequency (RF) transmitter network, coupled to plurality of modulators, that up converts and combines a plurality of analog signals into a combined electrical signal for transmission.