1. doc.: IEEE 802.11-10/0528r0 Submission March 2010 Slide 1 Slot Time Synchronization for Coexistence of 5 MHz, 10 MHz and 20 MHz Systems Date: 2010-05-11 Authors:

2. doc.: IEEE 802.11-10/0528r0 Submission Outline Problem Description Proposed Solutions Conclusions References 9/11/2015 2

3. doc.: IEEE 802.11-10/0528r0 Submission Problem Description Three channel bandwidths, 5 MHz, 10 MHz and 20 MHz, are considered to use in TVWS for 1, 2 and 4 contiguous available channels. Networks with different bandwidth may overlap in space and frequency, e.g., a 10 MHz network operates in Ch 20, 21 and a 5 MHz network operates in Ch 20. According to Table 17-15 in [1], the parameters of aSlotTime and aSIFSTime are different for different channel bandwidth. The network with longer slot time will get much less medium access opportunity. 9/11/2015 3 Characteristics20 MHz10 MHz5 MHz aSlotTime9 μs13 μs21 μs aSIFSTime16 μs32 μs64 μs

4. doc.: IEEE 802.11-10/0528r0 Submission Proposed Solutions All 802.11af devices use longest slot times –aSlotTime = 21 μs, aSIFSTime = 64 μs –Simple implementation –Worse throughput performance Dynamic slot time adaptation –Explore the slot times used by other networks and modify to a larger one –Require Radio Measurement –Better throughput performance 9/11/2015 4

5. doc.: IEEE 802.11-10/0528r0 Submission Dynamic Slot Time Adaption STAs shall change slot times based on one passive and one active mechanisms: Passive mechanism – Set slot times according to slot time information contained in Beacon, Probe Response, Association Response, and Reassociation Response from other networks. Active mechanism – Set slot times according to radio measurement results. 9/11/2015 5

6. doc.: IEEE 802.11-10/0528r0 Submission Passive Mechanism – (1) B10 – Short Slot Time is not required in TVWS. Use B10 and B12 to indicate slot times: (B10 B12) –(0 0): aSlotTime= 21 μs, aSIFSTime=64 μs –(0 1): aSlotTime= 13 μs, aSIFSTime=32 μs –(1 0): aSlotTime= 9 μs, aSIFSTime=16 μs –(1 1): Reserved 9/11/2015 6

7. doc.: IEEE 802.11-10/0528r0 Submission Passive Mechanism – (2) MIB attributes should also include the slot time information –Current 802.11 dot11ShortSlotTimeOptionImplemented (1 bit) dot11ShortSlotTimeOptionEnabled (1 bit) – 802.11af dot11SlotTimeOptionSelection (2 bit) –00: aSlotTime= 21 μs, aSIFSTime=64 μs –01: aSlotTime= 13 μs, aSIFSTime=32 μs –10: aSlotTime= 9 μs, aSIFSTime=16 μs –11: Reserved 9/11/2015 7

8. doc.: IEEE 802.11-10/0528r0 Submission Passive Mechanism – (3) STAs shall set the MAC variable aSlotTime and aSIFSTime to the corresponding values indicated in Capability Information field (B10 and B12) upon reception of Beacon, Probe Response, Association Response, and Reassociation Response from other 802.11 networks. 9/11/2015 8

9. doc.: IEEE 802.11-10/0528r0 Submission Radio Measurement – (1) Utilize dot11 radio measurement service to identify if there are other networks of different bandwidth. –Include detection of dot11 networks with different bandwidth in the Basic request. 9/11/2015 9 NameMeasurement Type Basic request0 Clear channel assessment (CCA) request1 Receive power indication (RPI) histogram request2 Reserved3 – 255 Table 7-30—Measurement Type definitions for measurement reports [1]

10. doc.: IEEE 802.11-10/0528r0 Submission Radio Measurement – (2) The 5 MHz network does not need to perform measurement since it cannot change its slot times. The 10 MHz network should measure if there is a 5 MHz network and adjust its slot times. The 20 MHz network should measure if there is a 10 MHz network or a 5 MHz network and adjust its slot times to the one used by a network with smallest bandwidth. Utilize 2 of the 3 reserved bits in the Map field of the basic measurement report to indicate existence of dot11 networks of different channel bandwidth. 9/11/2015 10

11. doc.: IEEE 802.11-10/0528r0 Submission 9/11/2015 11 Radio Measurement – (3) Map field format of the basic measurement report b5b6b5b6 00No other dot11 networks 01A 5 MHz network exists 10A 10 MHz network exists 11Reserved

12. doc.: IEEE 802.11-10/0528r0 Submission Conclusions Two parallel mechanisms are proposed to synchronize slot times for dot11 networks which are overlapped in frequency and space. Slot time information is included in Capability information field and MIB to support dynamic slot time selection. The measurement of other dot11 networks with different bandwidth is proposed to be included in the basic request of the dot11 radio measurement service. The reserved bits of the Map field of the basic measurement report are used to indicate the existence of other dot11 networks with different bandwidth. All overlapping dot11 networks will use the same slot times and fairly access the wireless medium. 9/11/2015 12

13. doc.: IEEE 802.11-10/0528r0 Submission References 1.IEEE Standard, "IEEE Standard for Information Technology- Telecommunications and Information Exchange Between Systems-Local and Metropolitan Area Networks-Specific Requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications," IEEE, New York, NY, June 2007. 9/11/2015 13