SCHEDULING FOR RF OVER FIBER OPTIC CABLE [RFoG]

• US 20100083330A1
• Filed: 09/29/2008
• Published: 04/01/2010
• Est. Priority Date: 09/29/2008
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Skrobko, John, Chapman, John Torrence, Bernstein, Alon
• Granted Patent: US 8,797,854 B2
• Time in Patent Office: Days
• US Class Current: 725/111
• CPC Class Codes: H04L 47/15 in relation to multipoint traffic arrangements for broadcast or multicast in data networks H04L12/18
• 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 7/17309 Transmission or handling of upstream communications
• CPC Class Codes: H04N 7/22 Adaptations for optical transmission

Abstract

A method for use in an RFoG cable network calls for allocating upstream bandwidth to CM devices, wherein allocating bandwidth includes selecting a start time and allocating respective time slots relative to the selected start time to at least one of the requesting CM devices; and further, allocating the same timeslots over multiple selected upstream channels, thereby aligning upstream transmissions from the requesting CMs across the selected upstream channels. Several embodiments are disclosed to enable DOCSIS 3.0 type scheduling over an RFoG network.

Claims

1. A Cable Modem Termination System (CMTS) for use in an RFoG network comprising:

a scheduler for scheduling upstream bandwidth for CMs via an optical network;

wherein the scheduler is arranged to replicate upstream bandwidth allocation grants over multiple upstream channels.

2. A CMTS according to claim 1 wherein the scheduler replicates the upstream bandwidth allocation grants by generating multiple MAP messages, each MAP message assigning the allocation grants on a respective one of the upstream channels.

3. A CMTS according to claim 1 wherein the MAP messages assign the upstream bandwidth allocation grants to four upstream channels.

4. A CMTS according to claim 3 wherein the four upstream channels are selected for compatibility with a DOCSIS 3.0 compliant CM having at least four transceivers, thereby increasing the CM bandwidth by up to a factor of four.

5. A CMTS according to claim 1 wherein the CMTS schedules the upstream bandwidth based on polling the CMs, an unsolicited grant service, or a request/grant procedure.

6. Scheduler software code stored in machine-readable media for execution on a processor in an RFoG network, the code comprising:

first code for receiving upstream bandwidth requests from a plurality of CM devices in the RFoG network;

second code for allocating upstream bandwidth responsive to the requests, the allocations including selecting a start time and allocating respective time slots relative to the selected start time to at least one of the requesting CM devices; and

third code for replicating the time slot allocations over multiple upstream channels.

7. The scheduler software code of claim 6 wherein the third code replicates the time slot allocations by generating a plurality of MAP messages, each MAP message granting the same time slot allocations on a different one of the multiple upstream channels.

8. The scheduler software code of claim 7 including code for selecting the upstream channels consistent with DOCSIS 3.0 specifications.

9. The scheduler software code of claim 7 wherein the third code divides a virtual allocation of minislots by the number of the multiple upstream channels.

10. The scheduler software code of claim 7 wherein the third code replicates the time slot allocations over four upstream channels, for compatibility with CMs having four transceivers.

11. The scheduler software code of claim 7 wherein the code is arranged for execution in conjunction with a cable modem termination system (CMTS).

12. The scheduler software code of claim 7 wherein the second code includes code for scheduling logical channels;

and wherein the third code replaces NULL grants of the logical channels with grants of minislots to the same SID on all channels.

13. A method for use in an RFoG cable network comprising:

determining upstream bandwidth requirements for a plurality of CM devices in the RFoG network, each CM device having a corresponding identifier SID; and

allocating bandwidth to the CMs, wherein allocating bandwidth includes;

selecting a start time and allocating respective time slots relative to the selected start time to at least one of the CM devices; and

allocating the same timeslots relative to the selected start time over multiple selected upstream channels, thereby aligning upstream transmissions from the CMs across the selected upstream channels.

14. The method of claim 13 wherein the bandwidth allocations are transmitted downstream in the network in a group of MAP messages, each MAP message of the group allocating bandwidth relative to the selected start time on a corresponding one of the selected upstream channels.

15. The method of claim 14 and further comprising scheduling a NULL grant over all of the selected upstream channels, and then detecting transmitted power, if any, on one of the upstream channels during the NULL grant, to identify a malfunctioning ONU.

16. The method of claim 15 wherein scheduling the NULL grant includes replacing an Initial Maintenance slot with a NULL grant whereby the NULL grants are aligned over the upstream channels.

17. The method of claim 14 wherein an integer N upstream channels are selected, thereby providing up to N times increase in total upstream bandwidth allocated to the requesting CMs.

18. The method of claim 14 wherein the selected upstream channels are configured consistent with DOCSIS 3.0 specifications.

19. The method of claim 14 wherein at least one of the requesting CMs has at least two transceivers, each transceiver compatible with a corresponding one of the selected upstream channels, whereby the CM can transmit at a rate up to at least two times its single-channel rate.

20. The method of claim 14 wherein allocating bandwidth to the CMs includes conducting non-real time polling of the CMs to avoid upstream request collisions.

21. The method of claim 14 wherein the method is implemented in a scheduler of the RFoG cable network, and further including:

scheduling an Initial Maintenance (IM) slot on at least one of the selected upstream channels;

receiving Initial Maintenance messages from the CMs; and

in the event of a collision among the US IM messages, employing a re-try algorithm.