Method of CATV cable same-frequency time division duplex data transmission

• US 8,365,237 B2
• Filed: 02/27/2011
• Issued: 01/29/2013
• Est. Priority Date: 01/22/2010
• Status: Active Grant

• Current Assignee: Vecima Networks Incorporated
• Original Assignee: Gainspeed Incorporated (Nokia Corporation)
• Inventors: Rakib, Selim Shlomo
• Primary Examiner(s): SHANG, ANNAN Q
• Application Number:
  US13/035,993
• Publication Number:
  US 20110185394A1
• Time in Patent Office: 702 Days
• Field of Search: 725106-126, 709217-232
• US Class Current: 725/111
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 5/1469 using time-sharing
• 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

Abstract

Method of bidirectional Time Division Duplex (TDD) data transmission over the same RF frequency ranges of a CATV cable system. The system'"'"'s slave modem clocks are time synchronized to the master clock of a master modem. The master-to-slave signal propagation times are determined and used to precisely schedule transmissions with de-minimize guard times. The frequency range may be chosen to be in the high frequency CATV range around 1 GHz to maximize backward compatibility with legacy systems, and this frequency may in turn be subdivided into multiple frequencies. In some embodiments, the CATV cable tree may be further partitioned into multiple TDD domains, and multiple local master modems, connected by a special-use optical fiber, may communicate with multiple local slave modems. The system may use MAP allocation schemes that may frequently reallocate TDD time slots and frequencies according to current or projected slave modem data needs.

Claims

1. A method of bidirectional Time Division Duplex data transmission over the same frequency ranges of a CATV cable system:

said CATV cable system comprising;

a CATV cable tree with a root master modem configured with a master clock, and a plurality of slave modems connected to various locations of said CATV cable tree, each said slave modem configured with a slave clock, said plurality of slave modems being disposed at various distances along said CATV cable tree from said root master modem;

said plurality of slave modems comprising at least a nearest slave modem disposed along the shortest CATV cable tree path from said master modem, and a furthest slave modem disposed along the longest CATV cable tree path from said master modem;

said method comprising;

time synchronizing the slave clocks of said plurality of slave modems to the master clock of said master modem;

determining the signal propagation times between said master modem and each of said plurality of slave modems;

determining the current or projected upstream and downstream data needs for each of said plurality of slave modems;

using said signal propagation times and said current or projected upstream and downstream data needs for each of said plurality of slave modems to construct a MAP Time Division Duplex allocation scheme, and transmitting said MAP Time Division Duplex allocation scheme to each of said plurality of slave modems;

and using said MAP Time Division Duplex allocation scheme to control the bi-directional data transmission between said master modem and said plurality of slave modems.

2. The method of claim 1, in which each slave modem is allocated upstream time slots by said MAP Time Division Duplex allocation scheme, and the guard time between different upstream time slots is a de-minimis guard time.

3. The method of claim 1, in which the difference in the signal propagation times between said master modem and said nearest slave modem, and said master modem and said furthest slave modem, is a spread time;

said MAP Time Division Duplex allocation scheme dynamically allocates upstream time slots to said plurality of slave modems on a block of upstream time slots basis;

and the upstream-to-downstream guard time between the end of said block of upstream time slots and the beginning of the MAP Time Division Duplex time allocated to downstream data from the master modem to the slave modems is at least twice the spread time.

4. The method of claim 3, in which the propagation time between the master modem and said nearest slave modem is a span time;

and

the time allocated to said block of upstream time slots varies according to said span time.

5. The method of claim 1, in which said MAP Time Division Duplex allocation scheme dynamically allocates slots for upstream transmission by the plurality of slave modems on a time and frequency basis;

and

each of those slave modems assigned time to transmit by said allocation scheme are assigned a unique combination of time and frequency.

6. The method of claim 5, in which said frequency is a plurality of frequencies, and said frequencies are modulated with data in a manner so that the spectral spread induced in said frequencies due to data modulation is such as to avoid overlap between said frequencies.

7. The method of claim 5, in which said frequencies is a plurality of orthogonally modulated frequencies, and said frequencies are modulated with data in a manner so that the spectral spread induced in said frequencies due to data modulation results in some overlap between said frequencies, but said overlap may be compensated for due to the orthogonal nature of the frequency modulation.

8. The method of claim 1, in which said MAP Time Division Duplex scheme dynamically allocates slots for upstream transmission on the basis of upstream data requests by each of said plurality of slave modems.

9. The method of claim 1, in which any of said master mode or said slave modems determines either path distortions or signal strength loss on its respective CATV cable tree path between said master modem and said slave modems, and in which said master modem and said slave modems exchange information pertaining to said path distortions or signal strength loss.

10. The method of claim 9, in which any of said slave modems communicate either said path distortions or signal strength loss on its respective CATV cable path to said master modem, and said master modem uses said path distortions or signal strength loss to construct its MAP Time Division Duplex allocation scheme.

11. The method of claim 9, in which any of said master or slave modems modulate the power of its transmitted signal according to the signal strength path loss or path distortion on its CATV cable tree path between said master modem and said slave modems.

12. The method of claim 9, in which any of said master or slave modems precode its transmissions to compensate for path distortions on its respective CATV cable tree path between said master modem and said slave modems.

13. The method of claim 1, in which said master modem is a Cable Fiber Terminal device that transmits and receives at least some data using shadow optical fiber;

or in which said master modem sends its signals to said slave modems through shadow optical fiber and Cable Fiber Terminal devices.

14. The method of claim 1, in which said frequency range is a frequency range above 860 MHz, and the frequency range less than 860 MHz is reserved for other modes of communication.

15. The method of claim 1, in which time synchronizing the slave clocks of said plurality of slave modems to the master clock of said master modem is done by having said master modem transmit a tone or periodic sequence to said plurality of slave modems.

16. A method of bidirectional Time Division Duplex data transmission over the same frequency ranges of a CATV cable system:

said CATV cable system comprising;

a CATV cable tree with a root master modem configured with a master clock, and a plurality of slave modems connected to various locations of said CATV cable tree, each said slave modem configured with a slave clock, said plurality of slave modems being disposed at various distances along said CATV cable tree from said root master modem;

said plurality of slave modems comprising at least a nearest slave modem disposed along the shortest CATV cable tree path from said master modem, and a furthest slave modem disposed along the longest CATV cable tree path from said master modem;

said method comprising;

time synchronizing the slave clocks of said plurality of slave modems to the master clock of said master modem;

determining the signal propagation times between said master modem and each of said plurality of slave modems;

determining the current or projected upstream and downstream data needs for each of said plurality of slave modems;

using said signal propagation times and said current or projected upstream and downstream data needs for each of said plurality of slave modems to construct a MAP Time Division Duplex allocation scheme;

wherein said MAP Time Division Duplex allocation scheme dynamically allocates slots for upstream transmission by said plurality of slave modems on a time and frequency basis;

each of those slave modems assigned time to transmit by said allocation scheme are assigned a unique combination of time and frequency;

transmitting said MAP Time Division Duplex allocation scheme to each of said plurality of slave modems;

using said MAP Time Division Duplex allocation scheme to control the bi-directional data transmission between said master modem and said plurality of slave modems;

wherein bi-directional data transmission between said master modem and said plurality of slave modems contains data is encoded using one or more error correction algorithms; and

which said frequency range is a frequency range above 860 MHz, and the frequency range below 860 MHz is reserved for other modes of communication.

17. The method of claim 16, in which each slave modem is allocated upstream time slots by said MAP Time Division Duplex allocation scheme, and the guard time between different upstream time slots is a de-minimis guard time.

18. The method of claim 16, in which the difference in the signal propagation times between said master modem and said nearest slave modem, and said master modem and said furthest slave modem, is a spread time;

said MAP Time Division Duplex allocation scheme dynamically allocates upstream time slots to said plurality of slave modems on a block of upstream time slots basis;

and the upstream-to-downstream guard time between the end of said block of upstream time slots and the beginning of the MAP Time Division Duplex time allocated to downstream data from the master modem to the slave modems is at least twice the spread time.

19. The method of claim 18, in which the propagation time between the master modem and said nearest slave modem is a span time;

and

the time allocated to said block of upstream time slots varies according to said span time.

20. The method of claim 16, in which said frequency is a plurality of frequencies, and said frequencies are modulated with data in a manner so that the spectral spread induced in said frequencies due to data modulation is such as to avoid overlap between said frequencies.

21. The method of claim 16, in which said frequencies is a plurality of orthogonally modulated frequencies, and said frequencies are modulated with data in a manner so that the spectral spread induced in said frequencies due to data modulation results in some overlap between said frequencies, but said overlap may be compensated for due to the orthogonal nature of the frequency modulation.

22. The method of claim 16, in which said MAP Time Division Duplex scheme dynamically allocates slots for upstream transmission on the basis of upstream data requests by each of said plurality of slave modems.

23. The method of claim 16, in which any of said master modem or said slave modems determines either path distortions or signal strength loss on its respective CATV cable tree path between said master modem and said slave modems;

and in which said master modem and said slave modems exchange information pertaining to said path distortions or signal strength loss.

24. The method of claim 23, in which any of said slave modems communicate either said path distortions or signal strength loss on its respective CATV cable path to said master modem, and said master modem uses said path distortions or signal strength loss to construct its MAP Time Division Duplex allocation scheme.

25. The method of claim 23, in which any of said master modems or said slave modems modulate the power of its transmitted signal according to the signal strength path loss or path distortion on its CATV cable tree path between said master modem and said slave modems.

26. The method of claim 23, in which any of said master modem or said slave modems precode its transmissions to compensate for path distortions on its respective CATV cable tree path between said master modem and said slave modems.

27. The method of claim 16, in which time synchronizing the slave clocks of said plurality of slave modems to the master clock of said master modem is done by having said master modem transmit a tone or periodic sequence to said plurality of slave modems.

28. The method of claim 16, in which said master modem is a Cable Fiber Terminal device that transmits and receives at least some data using shadow optical fiber;

or in which said master modem sends its signals to said slave modems through a shadow optical fiber and a Cable Fiber Terminal device.