Scheduling of Isochronous Traffic in Time and Frequency To Reduce Contention

• US 20110205998A1
• Filed: 02/23/2010
• Published: 08/25/2011
• Est. Priority Date: 02/23/2010
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Hart, Brian D., Qian, Lu, Diener, Neil R.
• Granted Patent: US 8,331,312 B2
• Time in Patent Office: Days
• US Class Current: 370/330
• CPC Class Codes: H04W 72/20 Control channels or signalling for resource management
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 72/566 of the information or information source or recipient

Abstract

Techniques are provided to reduce contention (interference) between bursts associated with multiple isochronous traffic flows. Generally, the techniques involve, at a plurality of wireless access point devices and/or a plurality of wireless client devices in a wireless network, initiating bursts of wireless transmissions carrying isochronous traffic from wireless access point devices to their associated client devices and/or from wireless client devices to their respective wireless access point devices at start times that are scheduled so as to reduce a likelihood of interference between multiple bursts of wireless transmissions for different isochronous traffic flows.

Claims

1. A method comprising:

at a plurality of wireless access point devices and/or a plurality of wireless client devices in a wireless network, initiating bursts of wireless transmissions carrying isochronous traffic from wireless access point devices to their associated client devices and/or from wireless client devices to their respective wireless access point devices at start times that are scheduled so as to reduce a likelihood of interference between multiple bursts of wireless transmissions for different isochronous traffic flows.

2. The method of claim 1, and further comprising, at a controller apparatus that communicates with the plurality of wireless access point devices and/or wireless client devices:

receiving from the wireless access point devices and/or wireless client devices messages indicating relatively long-lived isochronous traffic flows to be wirelessly transmitted from wireless access point devices to their associated client devices and/or from wireless client devices to their respective wireless access point devices;

determining which of the plurality of wireless access point devices and/or wireless client devices are in sufficient radio frequency proximity so as to interfere with each other;

based on the messages received from the wireless access point devices and/or wireless client devices concerning the isochronous traffic flows and the radio frequency proximity of wireless access point devices, generating schedule data representing the start times for wireless transmission bursts within each isochronous traffic flow from respective ones of the plurality of wireless access point devices and/or respective ones of the plurality of wireless client devices; and

transmitting messages containing the schedule data to the plurality of wireless access point devices and/or wireless client devices.

3. The method of claim 2, wherein generating the schedule data comprises generating staggered start times for wireless transmission bursts within each isochronous traffic flow from one or more wireless access point devices and/or one or more wireless client devices to minimize overlap of the wireless transmission bursts from different isochronous flows.

4. The method of claim 2, wherein generating the schedule data comprises generating staggered start times for wireless transmission bursts of within each isochronous traffic flow from one or more wireless access point devices and/or one or more wireless client devices across multiple frequency channels to minimize overlap in time and frequency of the wireless transmission bursts from different isochronous flows.

5. The method of claim 4, wherein generating the schedule data comprises assigning isochronous flows with different periodicity to different frequency subchannels.

6. The method of claim 2, wherein generating schedule data comprises generating start times for beacon frames broadcasted by wireless access point devices to wireless client devices that are configured with a power-save mode, which beacon frames indicate that a packet that is part of a multicast isochronous traffic flow is waiting to be transmitted, and wherein the start times for the beacon frames from multiple wireless access point devices are staggered to avoid overlap of bursts of wireless transmissions for multicast isochronous traffic from multiple wireless access point devices to wireless client devices.

7. The method of claim 2, wherein generating schedule data further comprises generating data for quiet elements to be transmitted by one or more of the wireless access point devices to their associated wireless client devices to cause their associated wireless client devices to end their transmissions before the start times for wireless transmission bursts from the wireless access point devices that are determined to be in sufficient radio frequency proximity so as to interfere with each other.

8. The method of claim 2, wherein generating schedule data comprises generating data defining a superframe interval comprising a plurality of subframe intervals such that the wireless transmission of isochronous traffic is constrained to align on a burst interval that is a multiple of the superframe interval, wherein each subframe interval has a duration that is a percentage of a maximum wireless transmission burst duration, and further comprising assigning a relative priority for each of the plurality of wireless access point devices or wireless client devices to a subframe such that preference for a subframe is given to the isochronous traffic flow from a wireless access point device or wireless client device with a highest priority for that subframe.

9. The method of claim 8, wherein generating schedule data further comprises generating configuration data to cause a highest priority wireless access point device to request a transmit opportunity interval for a wireless transmission burst to complete prior to the end of the subframe to allow for an overhang interval for use for transmission of a wireless transmission burst for a next highest priority wireless access point or wireless client device on a collision-free basis and to cause other wireless access point devices or wireless client devices to, in response to reception of a message received from the wireless access point device or wireless client device associated with the highest priority isochronous traffic flow, to wait a number of time slots within the subframe prior to requesting a transmit opportunity interval in the subframe.

10. The method of claim 8, wherein generating comprises generating data that causes the wireless access point device or wireless client device with the highest priority isochronous traffic flow to transmit a null message when it does not have any isochronous traffic to be transmitted so that lower priority wireless access point devices or wireless client devices can determine their turn to obtain a transmit opportunity during the subframe.

11. The method of claim 8, wherein generating schedule data comprises generating data that causes the wireless access point devices and/or wireless client devices to raise and lower its distributed channel access parameters according to its relative priority within a subframe.

12. The method of claim 2, wherein receiving, determining and generating schedule data are performed in a controller apparatus that resides in one of the plurality of wireless access point devices.

13. The method of claim 1, and further comprising generating schedule data representing the start times for the wireless transmission bursts according to computations made at a designated wireless access point device or at multiple wireless access point devices and sharing information pertaining to the schedule data using messages sent between the wireless access point devices.

14. An apparatus comprising:

a network interface device configured to enable communications over a network to communicate with a plurality of wireless devices configured for wireless communication in a wireless network;

a processor configured to be coupled to the network interface, wherein the processor is configured to;

generate schedule data configured to control a plurality of wireless network access point devices and/or a plurality of wireless client devices to initiate bursts of wireless transmissions carrying isochronous traffic from wireless access point devices to their associated client devices and/or from wireless client devices to their respective wireless access point devices at start times so as to reduce a likelihood of interference between bursts of wireless transmissions for different isochronous traffic flows.

15. The apparatus of claim 14, wherein the processor is further configured to:

receive from the wireless access point devices and/or wireless client devices messages indicating relatively long-lived isochronous traffic flows to be wirelessly transmitted from wireless access point devices to their associated client devices and/or from wireless client devices to their respective wireless access point devices;

determine which of the plurality of wireless access point devices and/or wireless client devices are in sufficient radio frequency proximity so as to interfere with each other;

based on the messages received from the wireless access point devices and/or wireless client devices concerning the isochronous traffic flows and the radio frequency proximity of wireless access point devices, generate schedule data representing the start times for wireless transmission bursts within each isochronous traffic flow from respective ones of the plurality of wireless access point devices and/or respective ones of the plurality of wireless client devices; and

generate messages for transmission to the plurality of wireless network access point devices and/or wireless client devices, the messages containing the schedule data.

16. The apparatus of claim 15, wherein the processor is configured to generate the schedule data comprising staggered start times for wireless transmission bursts within each isochronous traffic flow from one or more wireless access point devices and/or one or more wireless client devices to minimize overlap of the wireless transmission bursts from different isochronous flows.

17. The apparatus of claim 15, wherein the processor is configured to generate the schedule data comprising staggered start times for wireless transmission bursts of within each isochronous traffic flow from one or more wireless access point devices and/or one or more wireless client devices across multiple frequency channels to minimize overlap in time and frequency of the wireless transmission bursts from different isochronous flows.

18. The apparatus of claim 15, wherein the processor is configured to generate schedule data comprising start times for beacon frames broadcasted by wireless access point devices to wireless client devices that are configured with a power-save mode, which beacon frames indicate that a packet that is part of a multicast isochronous traffic flow is waiting to be transmitted, and wherein the start times for the beacon frames from multiple wireless access point devices are staggered to avoid overlap of bursts of wireless transmission for multicast isochronous traffic from multiple wireless access point devices to wireless client devices.

19. The apparatus of claim 15, wherein the processor is configured to generate schedule data comprising data defining a superframe interval comprising a plurality of subframe intervals such that the wireless transmission of isochronous traffic is constrained to align on a burst interval that is a multiple of the superframe interval, wherein each subframe interval has a duration that is a percentage of a maximum wireless transmission burst duration, and to assign a relative priority for each of the plurality of wireless access point devices or wireless client devices to a subframe such that preference for a subframe is given to the isochronous traffic flow from a wireless access point device or wireless client device with a highest priority for that subframe.

20. A processor readable medium storing instructions that, when executed by a processor, cause the processor to:

receive from a plurality of wireless access point devices and/or wireless client devices operating in a wireless network, messages indicating relatively long-lived isochronous traffic flows to be wirelessly transmitted from wireless access point devices to their associated client devices and/or from wireless client devices to their respective wireless access point devices;

determine which of the plurality of wireless access point devices and/or wireless client devices are in sufficient radio frequency proximity so as to interfere with each other;

based on the messages received from the wireless access point devices and/or wireless client devices concerning the isochronous traffic flows and the radio frequency proximity of wireless access point devices, generate schedule data representing the start times for wireless transmission bursts within each isochronous traffic flow from respective ones of the plurality of wireless access point devices and/or respective ones of the plurality of wireless client devices so as to reduce a likelihood of interference between multiple bursts of wireless transmissions for different isochronous traffic flows; and

generate messages for transmission to the plurality of wireless network access point devices and/or wireless client devices, the messages containing the schedule data.

21. The processor readable medium of claim 20, wherein the instructions that cause the processor to generate the schedule data comprises instructions to cause the processor to generate staggered start times for wireless transmission bursts within each isochronous traffic flow from one or more wireless access point devices and/or one or more wireless client devices to minimize overlap of the wireless transmission bursts from different isochronous flows.

22. The processor readable medium of claim 20, wherein the instructions that cause the processor to generate the schedule data comprise instructions that cause the processor to generate data for quiet elements to be transmitted by one or more of the wireless access point devices to their associated wireless client devices to cause their associated wireless client devices to end their transmissions before the start times for wireless transmission bursts from the wireless access point devices that are determined to be in sufficient radio frequency proximity so as to interfere with each other.

23. The processor readable medium of claim 20, wherein the instructions that cause the processor to generate the schedule data comprise instructions that cause the processor to generate data defining a superframe interval comprising a plurality of subframe intervals such that the wireless transmission of isochronous traffic is constrained to align on a burst interval that is a multiple of the superframe interval, wherein each subframe interval has a duration that is a percentage of a maximum wireless transmission burst duration, and further comprising instructions that cause the processor to assign a relative priority for each of the plurality of wireless access point devices or wireless client devices to a subframe such that preference for a subframe is given to the isochronous traffic flow from a wireless access point device or wireless client device with a highest priority for that subframe.