Methods and apparatus for dynamically controlling subcarrier spacing on a communications link with a modem

1. A method of operating a base station connected to a modem by a cable, the method comprising:

determining information relating to buffering of downlink data supplied by said cable, said information including one or both of: i) a data accumulation rate (DAR) of a downlink buffer used to store downlink data supplied by said cable and ii) an average data arrival time (ADAT) of the downlink buffer;

determining, at the base station, a subcarrier spacing (SCS) to be used by the base station to transmit data to one or more wireless devices based on the determined information relating to buffering of downlink data supplied by said cable; and

using the determined SCS to transmit data stored in the downlink buffer to one or more wireless devices.

2. The method of claim 1 further comprising:

wherein determining, at the base station, the SCS to be used by the base station to transmit data to one or more wireless devices includes making a decision whether to i) increase a current SCS, ii) decrease the current SCS or iii) leave the current SCS unchanged.

3. The method of claim 2 , further comprising:

using an initial SCS as the current SCS the first time said step of determining, at the base station, a SCS to be used by the base station to transmit data to one or more wireless device based on the determined information relating to buffering of downlink data supplied by said cable, said initial SCS being a default SCS or an SCS based on a measured transmission latency.

4. The method of claim 2 , further comprising:

measuring data transmission latency between the modem and base station; and

selecting the initial SCS based on the measured data transmission latency between the modem and base station.

5. The method of claim 2 , wherein determining, at the base station, SCS to be used by the base station to transmit data to one or more wireless devices includes:

determining, based on one or both of the DAR and ADAT whether to i) increase the current SCS used to communicate data to one or more wireless terminals, ii) decrease the current SCS used to communicate data to one or more wireless terminals or iii) leave the current SCS being used to communicate data to one or more wireless terminals unchanged.

6. The method of claim 5 , wherein determining, at the base station, SCS to be used by the base station to transmit data to one or more wireless devices includes:

determining to i) increase the current SCS used to communicate data to one or more wireless terminals in response to determining that the DAR is less than the first threshold (T 1 ) and that the ADAT is below the second threshold (T 2 ).

7. The method of claim 5 , wherein determining, at the base station, SCS to be used by the base station to transmit data to one or more wireless devices includes:

determining to ii) decrease the current SCS used to communicate data to one or more wireless terminals in response to determining that both the DAR is greater than a first threshold (T 1 ) and the ADAT is greater than a second threshold (T 2 ).

8. The method of claim 5 , wherein determining, at the base station, SCS to be used by the base station to transmit data to one or more wireless devices includes:

determining to iii) leave the current SCS being used to communicate data to one or more wireless terminals unchanged in response to determining that i) at least one of: the DAR is not greater than T 1 and the ADAT is not greater than T 2 and also that ii) at least one of: the DAR is not less than T 1 and the ADAT is not less than T 2 .

9. The method of claim 2 , further comprising:

sending, from the base station, a message to the modem to trigger measurement of a latency between a modem termination system and the modem; and

receiving, at the base station, from the modem, information indicating the measured latency modem termination system to modem latency.

10. The method of claim 9 , further comprising:

determining based on the cable modem termination system (CMTS) to cable modem (CM) latency a period for which the determined SCS is to be used.

11. The method of claim 10 , wherein said period is determined to be a first period having a first duration when the CMTS to CM latency is below a latency threshold (LTN) and said period is determined to be a second period having a second duration when the CMTS to CM latency is not below the latency threshold (LTN).

12. The method of claim 10 , further comprising:

determining at the base station if a time has been reached to determine a new SCS; and

in response to determining at the base station that the time has been reached to determine a new SCS, repeating said steps of:

i) determining information relating to buffering of downlink data supplied by said cable, said information including one or both of: i) a data accumulation rate (DAR) of a downlink buffer used to store downlink data supplied by said cable and ii) an average data arrival time (ADAT) of the downlink buffer; and

ii) determining, at the base station, a SCS to be used by the base station to transmit data to one or more wireless device based on the determined information relating to buffering of downlink data supplied by said cable.

13. The method of claim 12 , wherein determining at the base station if a time has been reached to determine a new SCS includes determining if a predetermined point in time before the determined SCS use time period expires has been reached.

14. A base station connected to a modem by a cable, the base station comprising:

a processor configured to:

determine information relating to buffering of downlink data supplied by said cable, said information including one or both of: i) a data accumulation rate (DAR) of a downlink buffer used to store downlink data supplied by said cable and ii) an average data arrival time (ADAT) of the downlink buffer;

determine, at the base station, a subcarrier spacing (SCS) to be used by the base station to transmit data to one or more wireless devices based on the determined information relating to buffering of downlink data supplied by said cable; and

operate the base station to use the determined SCS to transmit data stored in the downlink buffer to one or more wireless devices.

15. The base station of claim 14 , wherein said processor is configured to:

make a decision whether to: i) increase a current SCS, ii) decrease the current SCS or iii) leave the current SCS unchanged, as part of being configured to determine the SCS to be used by the base station to transmit data to one or more wireless devices.

16. The base station of claim 15 , wherein said processor is further configured to:

use an initial SCS as the current SCS the first time said step of determining, at the base station, a SCS to be used by the base station to transmit data to one or more wireless device based on the determined information relating to buffering of downlink data supplied by said cable, said initial SCS being a default SCS or an SCS based on a measured transmission latency.

17. The base station of claim 15 , wherein said processor is further configured to:

measure data transmission latency between the modem and base station; and

select the initial SCS based on the measured data transmission latency between the modem and base station.

18. The base station of claim 15 , wherein said processor is configured to:

determine, based on one or both of the DAR and ADAT whether to i) increase the current SCS used to communicate data to one or more wireless terminals, ii) decrease the current SCS used to communicate data to one or more wireless terminals or iii) leave the current SCS being used to communicate data to one or more wireless terminals unchanged, as part of being configured to determine, at the base station, SCS to be used by the base station to transmit data to one or more wireless devices.

19. The base station of claim 18 , wherein said processor is configured to:

determine to i) increase the current SCS used to communicate data to one or more wireless terminals in response to determining that the DAR is less than the first threshold (T 1 ) and that the ADAT is below the second threshold (T 2 ), as part of being configured to determine, at the base station, SCS to be used by the base station to transmit data to one or more wireless devices.

20. A non-transitory computer readable medium including computer executable instructions which when executed by a processor of a base station connected to a modem by a cable cause the base station to perform the steps of:

determining information relating to buffering of downlink data supplied by said cable, said information including one or both of: i) a data accumulation rate (DAR) of a downlink buffer used to store downlink data supplied by said cable and ii) an average data arrival time (ADAT) of the downlink buffer;

determining, at the base station, a subcarrier spacing (SCS) to be used by the base station to transmit data to one or more wireless devices based on the determined information relating to buffering of downlink data supplied by said cable; and

using the determined SCS to transmit data stored in the downlink buffer to one or more wireless devices.