DYNAMICALLY AND FAIRLY ALLOCATING RF CHANNEL BANDWIDTH IN A WIDEBAND CABLE SYSTEM

• US 20100226390A1
• Filed: 03/06/2009
• Published: 09/09/2010
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Yan, Anlu, Sheng, Jin, Mikkelson, Chad, Achilleoudis, Nicos
• Granted Patent: US 8,861,546 B2
• Time in Patent Office: Days
• US Class Current: 370/468
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/2865 Logical combinations
• CPC Class Codes: H04L 12/2878 Access multiplexer, e.g. DSLAM generic distributed time multiplexers, e.g. TDM/TDMA H04J3/1694
• CPC Class Codes: H04L 47/70 Admission control; Resource allocation
• CPC Class Codes: H04L 47/762 triggered by the network
• CPC Class Codes: H04L 47/805 QOS or priority aware

Abstract

In one example, a Cable Modem Termination System (CMTS) determines target Radio Frequency (RF) bandwidth amounts for Data Over Cable System Interface Specification (DOCSIS) bonding groups according to the DOCSIS priority of active flows within the bonding groups. The CMTS then tunes bandwidth allocation amongst the DOCSIS bonding groups according to the target bandwidth amounts. The target bandwidth amounts can be recalculated at intervals, and the bandwidth allocation re-tuned at the intervals, to account for changes in flow activity or DOCSIS priority assignment.

Claims

1. A computer readable medium encoded with instructions that, if executed, result in:

selecting a plurality of Data Over Cable System Interface Specification (DOCSIS) bonding groups and associated Radio Frequency (RF) channels;

determining an aggregate demand value for each DOCSIS bonding group and a target bandwidth amount for each of the DOCSIS bonding groups, wherein the target bandwidth amount for a particular one of the DOCSIS bonding groups is the product of that DOCSIS bonding group'"'"'s aggregate demand value and a ratio of the total bandwidth of all the RF channels over the sum of all of the determined demand values; and

scheduling transmission of downstream DOCSIS bonding group traffic from a Cable Modem Termination System (CMTS) over a cable network according to the target bandwidth amounts.

2. The computer readable medium of claim 1, wherein the instructions, if executed, result in determining the aggregate demand value for each DOCSIS bonding group by summing values corresponding to the assigned DOCSIS priority of active service flows within that DOCSIS bonding group.

3. The computer readable medium of claim 1, wherein the instructions, if executed, result in:

if a first potential distribution of RF channel bandwidth amongst the DOCSIS bonding groups will result in bandwidth assignments having a threshold difference from the target bandwidth amounts, generating a second potential distribution of RF channel bandwidth amongst the DOCSIS bonding groups by adjusting the first potential distribution.

4. The computer readable medium of claim 3, wherein the instructions, if executed, result in:

comparing a first difference between the bandwidth assignments under the first potential distribution and the target bandwidth amounts to a second difference between bandwidth assignments under the second potential distribution and the target bandwidth amounts; and

if the comparison indicates a threshold improvement in the second potential distribution over the first potential distribution, generating a third potential distribution of RF channel bandwidth amongst the DOCSIS bonding groups by adjusting the second potential distribution.

5. The computer readable medium of claim 4, wherein the instructions, if executed, result in:

if the comparison does not indicate the threshold improvement in the second potential distribution over the first potential distribution, utilizing the second potential distribution when scheduling the transmission of downstream DOCSIS bonding group traffic.

6. The computer readable medium of claim 4, wherein the instructions, if executed, result in:

repeating the comparison between a newest difference and a previous difference until reaching an earlier of N comparisons or one of the comparisons indicating no significant improvement.

7. The computer readable medium of claim 1, wherein the CMTS is an Integrated CMTS (I-CMTS) or a Modular CMTS (M-CMTS).

8. The computer readable medium of claim 3, wherein generating second potential distribution includes:

selecting a first one of the DOCSIS bonding groups having a greatest bandwidth surplus;

filtering the DOCSIS bonding groups to identify only those bonding groups sharing at least one of the selected DOCSIS bonding group'"'"'s RF channels;

selecting, from the filtered DOCSIS bonding groups, a second one of the DOCSIS bonding groups having a greatest bandwidth deficit; and

shifting surplus bandwidth from the first DOCSIS bonding group to the second DOCSIS bonding group.

9. The computer readable medium of claim 8, wherein generating second potential distribution includes:

after adjusting the first potential distribution by shifting the surplus bandwidth, selecting a third one of the DOCSIS bonding groups having a greatest bandwidth deficit;

re-filtering the DOCSIS bonding groups to identify only those bonding groups sharing at least one of the selected third DOCSIS bonding group'"'"'s RF channels;

selecting, from the re-filtered DOCSIS bonding groups, a fourth one of the DOCSIS bonding groups having a greatest bandwidth surplus; and

shifting surplus bandwidth from the fourth DOCSIS bonding group to the third DOCSIS bonding group.

10. The computer readable medium of claim 1, wherein the instructions, if executed, result in repeating the determining and the scheduling at regular intervals.

11. A Cable Modem Termination System (CMTS), comprising:

a network interface to receive, from an access network, data to be transmitted on a cable network; and

a fairness computation device in communication with the network interface and configured to;

determine an aggregate demand value for a plurality of DOCSIS bonding groups;

determine a target bandwidth amount for the DOCSIS bonding groups, wherein the target bandwidth amount for a particular one of the DOCSIS bonding groups is based on that DOCSIS bonding group'"'"'s aggregate demand value, the total bandwidth of all the Radio Frequency (RF) channels associated with the DOCSIS bonding groups, and the determined aggregate demand values of the remaining DOCSIS bonding groups; and

schedule transmission of downstream DOCSIS bonding group traffic from the Cable Modem Termination System (CMTS) over a cable network according to the target bandwidth amounts.

12. The CMTS of claim 11, wherein the fairness computation device is configured to:

monitor transmission buffers associated with service flows of the DOCSIS bonding groups;

identify an assigned Quality of Service (QoS) metric for at least some of the service flows; and

determine the aggregate demand values according to the monitoring and the identified QoS metrics.

13. The CMTS of claim 12, wherein the fairness computation device is configured to:

determine whether or not the transmission buffers associated with the flows of the DOCSIS bonding groups contain a threshold amount of data during a monitoring window; and

identify the assigned QoS metric for only those service flows that correspond to those buffers containing the threshold amount of data during the monitoring window.

14. The CMTS of claim 12, wherein the assigned QoS metric is an assigned DOCSIS priority value ranging from zero to seven.

15. The CMTS of claim 11, wherein the fairness computation device is configured to repeat the determinations and the scheduling at regular intervals.

16. A method, comprising:

determining an aggregate demand value for a plurality of DOCSIS bonding groups;

determining a target bandwidth amount for the DOCSIS bonding groups, wherein the target bandwidth amount for a particular one of the DOCSIS bonding groups is based on that DOCSIS bonding group'"'"'s aggregate demand value, the total bandwidth of all the Radio Frequency (RF) channels associated with the DOCSIS bonding groups, and the determined aggregate demand values for the remaining DOCSIS bonding groups;

scheduling transmission of downstream DOCSIS bonding group traffic from a Cable Modem Termination System (CMTS) over a cable network according to the target bandwidth amounts; and

transmitting received data downstream from the CMTS over the cable network according to the scheduling.

17. The method of claim 16, further comprising:

monitoring activity of service flows associated with the DOCSIS bonding groups;

identifying an assigned Quality of Service (QoS) metric for at least some of the service flows; and

determining the aggregate demand values according to the flow activity monitoring and the identified QoS metrics.

18. The method of claim 16, further comprising:

comparing each DOCSIS bonding group'"'"'s target bandwidth amount to actual bandwidth that the respective DOCSIS bonding group would receive under a potential bandwidth allocation.

19. The method of claim 18, further comprising:

if the comparison indicates more than a threshold difference, determine whether the potential bandwidth allocation has been adjusted a predetermined number of times or whether the comparison indicates no threshold improvement over a previous comparison; and

if the potential bandwidth allocation has not been adjusted a predetermined number of times and if the comparison indicates at least the threshold improvement over the previous comparison, adjusting the potential bandwidth allocation to improve fairness.

20. The method of claim 19, further comprising:

if the potential bandwidth allocation has been adjusted a predetermined number of times or if the comparison indicates no threshold improvement over the previous comparison, then dynamically allocate RF channel bandwidth amongst the DOCSIS bonding groups according to the potential bandwidth allocation.