HFC cable system with shadow fiber and coax fiber terminals

• US 9,326,039 B1
• Filed: 08/25/2014
• Issued: 04/26/2016
• Est. Priority Date: 01/22/2010
• Status: Active Grant

• Current Assignee: Vecima Networks Incorporated
• Original Assignee: Gainspeed Incorporated (Nokia Corporation)
• Inventors: Rakib, Shlomo Selim
• Primary Examiner(s): Goodarzi, Nasser
• Assistant Examiner(s): Ocak, Adil
• Application Number:
  US14/467,738
• Time in Patent Office: 610 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H04B 10/25751 Optical arrangements for CATV or video distribution adaptations of television systems for optical transmission H04N7/22
• CPC Class Codes: H04H 20/78 CATV [Community Antenna Television] systems
• CPC Class Codes: H04N 21/238 Interfacing the downstream path of the transmission network, e.g. adapting the transmission rate of a video stream to network bandwidth; Processing of multiplex streams hybrid fiber coaxial [HFC] networks for downstream channel allocation for video distribution H04L12/2801; flow control in packet networks H04L47/10; real-time communication protocols in data switching networks H04L65/00; scheduling or organising the servicing of application requests H04L67/60
• CPC Class Codes: H04N 21/239 Interfacing the upstream path of the transmission network, e.g. prioritizing client content requests hybrid fiber coaxial [HFC] networks for upstream channel allocation for video distribution H04L12/2801; flow control in data networks H04L47/10; real-time communication protocols in data switching networks H04L65/00; scheduling or organising the servicing of application requests H04L67/60
• 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: H04N 7/10 Adaptations for transmission by electrical cable H04N7/12 takes precedence
• CPC Class Codes: H04N 7/22 Adaptations for optical transmission

Abstract

System and method to extend the upstream data capacity of an HFC CATV system by extending a “shadow” optical fiber network deeper into the various CATV cable neighborhoods, with coax fiber terminals (CFT) spaced roughly according to the distribution of CATV active devices such as RF amplifiers. The CFT can intercept local upstream data from various neighborhood sub-regions and transform this upstream data into upstream optical data, thus relieving upstream data congestion in the 5-42 MHz CATV frequency region. The system can produce an order of magnitude improvement in upstream capability, while maintaining high compatibility with legacy HFC equipment. The CFT may exist in multiple embodiments ranging from low-cost “dumb” CFT to sophisticated CFT that can additionally provide GigE to the home (GTTH) service. Methods to maintain good compatibility with legacy CMTS devices, and methods to utilize DOCSIS MAP data for more efficient data transmission are also discussed.

Claims

1. A method for enhancing the upstream data carrying capacity of a hybrid fiber cable (HFC) network with a cable head, at least one trunk optical fiber, at least one trunk optical fiber node terminating on at least one CATV trunk cable, said CATV trunk cable connected to a plurality of CATV active devices, with at least one branch CATV cables connected to said plurality of CATV active devices, thus forming a CATV Tree and Branch Network, and a plurality of cable modems or Ethernet terminals connected to said CATV Tree and Branch Network, said method comprising:

operating at least one shadow optical fiber from said trunk optical fiber to Coax Fiber Terminals associated with at least some of said plurality of CATV active devices,

wherein said Coax Fiber Terminals are connected to said CATV cable and intercept local upstream CATV RF signals being transmitted by said plurality of cable modems or Ethernet terminals connected to said trunk or branch CATV cables;

using said Coax Fiber Terminals to remove at least some of said intercepted upstream CATV RF signals from said trunk or branch CATV cables connected to said CATV active devices; and

using said at least one shadow optical fiber to backhaul at least the information carried by the removed upstream CATV RF signals.

2. The method of claim 1, wherein said upstream CATV RF signals comprise DOCSIS signals, and wherein at least some of said DOCSIS signals are removed by said Coax Fiber Terminals and backhauled using said at least one shadow optical fiber.

3. The method of claim 1, wherein all of said upstream CATV RF signals are removed by said coax fiber terminals and backhauled using said shadow optical fibers.

4. The method of claim 1, wherein said at least one shadow optical fiber comprises a passive optical network.

5. The method of claim 1, wherein said Coax Fiber Terminals:

digitize at least some of said upstream CATV RF signals; and

transduce at least some of the digitized upstream CATV RF signals to optical signals to produce upstream optical signals.

6. The method of claim 5, wherein the Coax Fiber Terminals digitize said upstream CATV RF signals by:

obtaining Mini-slot Allocation Packet (MAP) data for at least some of said upstream CATV RF signals;

using said Mini-slot Allocation Packet (MAP) data to demodulate and extract at least some of the upstream digital information carried by at least some of said upstream CATV RF signals;

repackaging said upstream digital information in an alternative format for optical transmission; and

transmitting said upstream digital information in said alternative format along said shadow optical fiber.

7. The method of claim 6, wherein said alternative format is an optical Ethernet format.

8. The method of claim 6, wherein the Coax Fiber Terminals further digitize said upstream CATV RF signals by:

using said Mini-slot Allocation Packet (MAP) data to subsequently remodulate said upstream digital information into reconstituted upstream CATV RF signals at said cable head to produce reconstituted upstream CATV RF signals; and

supplying said reconstituted upstream CATV RF signals to a Cable Modem Termination System.

9. The method of claim 5, wherein the Coax Fiber Terminals digitize said upstream CATV RF signals by:

sampling the CATV RF signals at a sample rate that is at least twice the frequency of the highest upstream CATV RF signal frequency;

performing an analog to digital conversion on said sampled CATV RF signals to produce digitized upstream CATV signals.

10. The method of claim 9, wherein the Coax Fiber Terminals remodulate said digitized upstream CATV RF signals into reconstituted upstream CATV RF signals at said cable head to produce reconstituted upstream CATV RF signals and supply said reconstituted upstream CATV RF signals to a Cable Modem Termination System.

11. The method of claim 1, wherein at least some remaining upstream CATV RF signals continue to be transmitted along said CATV Tree and Branch Network after at least some CATV RF signals have been intercepted and removed by said Coax Fiber Terminals.

12. The method of claim 11, wherein said Coax Fiber Terminals actively regenerate said at least some remaining upstream CATV RF signals and pass said remaining upstream CATV RF signals back onto the CATV trunk cable after first removing and digitizing all of said upstream CATV RF signals.

13. The method of claim 1, wherein said at least one CATV trunk cable or at least some of said plurality of branch CATV cables, and a plurality of Coax Fiber Terminals are addressed as a plurality of domains, so that one set of cable devices attached to said at least one CATV trunk cable or at least some of said plurality of branch CATV cables that is local to and served by a first Coax Fiber Terminal may be addressed on a first domain basis, and other sets of cable devices attached to said at least one CATV trunk cable or at least some of said plurality of branch CATV cables that is serviced by a second Coax Fiber Terminal may be addressed on a second domain basis.

14. The method of claim 1, wherein Mini-slot Allocation Packet (MAP) data is used to mask upstream RF signals according to time windows designated for upstream transmission, thereby reducing the amount of noise in the upstream data that is carried by said shadow optical fiber.

15. The method of claim 1 further comprising:

using said at least one shadow optical fiber and said Coax Fiber Terminals to transmit downstream Gigabit Ethernet data; and

modulating said downstream Gigabit Ethernet data into downstream CATV RF signals at said Coax Fiber Terminals.

16. The method of claim 1 further comprising using said at least one shadow optical fiber and said Coax Fiber Terminals to transmit upstream and downstream data according to a Time Division Duplex scheme.

17. The method of claim 1, wherein said Coax Fiber Terminals backhaul said information by performing a direct electrical to optical conversion of said intercepted upstream CATV RF signals.

18. A method for enhancing the upstream data carrying capacity of a hybrid fiber cable (HFC) network with a cable head, at least one trunk optical fiber, at least one trunk optical fiber node terminating on at least one CATV trunk cable, said CATV trunk cable connected to a plurality of CATV active devices, with a plurality of branch CATV cables connected to said plurality of CATV active devices, thus forming a CATV Tree and Branch Network, and a plurality of cable modems or Ethernet terminals connected to said CATV Tree and Branch Network, said method comprising:

operating at least one shadow optical fiber from said trunk optical fiber to Coax Fiber Terminals associated with at least some of said plurality of CATV active devices,

wherein said at least one shadow optical fiber comprises a passive optical network,

wherein said Coax Fiber Terminals are connected to said CATV cable and intercept upstream CATV RF signals being transmitted by said plurality of branch CATV cables connected to said CATV active devices;

using said Coax Fiber Terminals to remove at least some of said intercepted upstream CATV RF signals from said branch CATV cables connected to said CATV active devices; and

using said at least one shadow optical fiber to backhaul at least the information carried by the removed upstream CATV RF signals,

wherein said Coax Fiber Terminals digitize at least some of said upstream CATV RF signals and transduce at least some of the digitized upstream CATV RF signals to optical signals to produce upstream optical signals,

wherein the Coax Fiber Terminal digitize said upstream CATV RF signals by;

obtaining Mini-slot Allocation Packet (MAP) data for at least some of said upstream CATV RF signals;

using said Mini-slot Allocation Packet (MAP) data to demodulate and extract at least some of the upstream digital information carried by at least some of said upstream CATV RF signals;

repackaging said upstream digital information in an alternative format for optical transmission; and

transmitting said upstream digital information in said alternative format along said shadow optical fiber,

wherein said alternative format is an optical Ethernet format.

19. The method of claim 18, wherein said at least one CATV trunk cable or at least some of said plurality of branch CATV cables, and a plurality of Coax Fiber Terminals are addressed as a plurality of domains, so that one set of cable devices attached to said at least one CATV trunk cable or at least some of said plurality of branch CATV cables that is served by a first Coax Fiber Terminal may be addressed on a first domain basis, and other sets of cable devices attached to said at least one CATV trunk cable or at least some of said plurality of branch CATV cables that is serviced by a second Coax Fiber Terminal may be addressed on a second domain basis.

20. The method of claim 18 further comprising:

using said at least one shadow optical fiber and said Coax Fiber Terminals to transmit downstream Gigabit Ethernet data; and

modulating said downstream Gigabit Ethernet data into downstream CATV RF signals at said Coax Fiber Terminals.