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Dynamic Frequency Selection (DFS) for 5 GHz RLANs

Dynamic Frequency Selection (DFS) for 5 GHz RLANs. Johnny Dixon. Overview. Available channels in the 5 GHz band Who is currently using the 5 GHz band? Why do we need DFS? What does DFS do? How will DFS operate? Why is it all so important? Can the UK ignore all this?

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Dynamic Frequency Selection (DFS) for 5 GHz RLANs

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  1. Dynamic Frequency Selection (DFS) for 5 GHz RLANs Johnny Dixon

  2. Overview • Available channels in the 5 GHz band • Who is currently using the 5 GHz band? • Why do we need DFS? • What does DFS do? • How will DFS operate? • Why is it all so important? • Can the UK ignore all this? • What about the Interim Arrangements? • What happens if we don’t implement DFS? • What about the 5725 - 5875 MHz band? • Conclusion © British Telecommunications plc, 2002

  3. Available channels in 5 GHz band • 5150 - 5350 MHz; 8 channels available • 5470 - 5725 MHz; 11 channels available • What is the problem? • According to the ITU Radio Regulations, these bands are (currently) primarily for other users, not for RLANs © British Telecommunications plc, 2002

  4. Who is currently using the 5 GHz band? • 5150 - 5250 MHz used for MSS feeder links • Need to ensure even distribution of RLAN channel occupancy • 5300 - 5900 MHz used for radars • Meteorological radars • Instrumentation radars (mostly military) • Maritime surveillance • (Aeronautical Radionavigation) © British Telecommunications plc, 2002

  5. Why do we need DFS? • To enable usage of the 5 GHz band for RLANs, we need to: • Ensure that the RLANs operate evenly across the channels • Ensure that an RLAN does not interfere with an existing radar system • Therefore 5 GHz RLANs need a Dynamic Frequency Selection (DFS) mechanism © British Telecommunications plc, 2002

  6. What does DFS do? Before operation • Chooses an operating channel at random • Checks whether it is currently being used During operation • Continues to “listen” for other users © British Telecommunications plc, 2002

  7. How will DFS operate ? • Choose an operating channel at random • “Listen” to that channel for Channel Availability Check Time, for any signals greater than Detection threshold • If the channel is clear, then it can be used by the RLAN, however… • … the RLAN must continue to listen to the channel for any signals which are greater than Detection threshold (“In Service monitoring”) © British Telecommunications plc, 2002

  8. How will DFS operate ? (continued) • If the In Service Monitoring detects a radar, the RLAN must leave the channel within Channel Move Time • The RLAN then needs to identify a new operating channel (i.e. perform a Channel Availability Check) • Studies are currently underway to identify agreed values for the various parameters © British Telecommunications plc, 2002

  9. Why is it all so important? • The ITU Radio Regulations are an International Treaty on the global use of the radio spectrum • Currently no allocation for RLANs in the (body of the) Radio Regulations • For global adoption of RLANs • We need a (Primary) Mobile Service allocation • We need ability to share with existing users • We need DFS © British Telecommunications plc, 2002

  10. Why is it all so important? (continued) • A European Decision (ERC DEC(99)23) identified 5 GHz band for RLANs, providing • Indoor operation only in 5150 - 5350 MHz • Power limits (EIRP) • Transmitter Power Control (TPC) • Dynamic Frequency Selection (DFS) • That has the basis for all work over the last 3 years © British Telecommunications plc, 2002

  11. Can the UK ignore all this? • The UK does have obligations to protect MSS & radars • The UK has signed up to the ERC Decision, as the best solution for the 5 GHz band • The UK is always keen to promote a responsible and equitable attitude towards frequency sharing matters • We want a consistent policy for all countries, to enable a global market for products © British Telecommunications plc, 2002

  12. What about the “Interim arrangements”? • There is already demand to allow RLAN devices in the 5 GHz band • There is not (yet) an agreed DFS mechanism which can be implemented • The IR allows the deployment of 5 GHz RLAN devices in the short term, without DFS • “Interim Arrangements” are only for the Interim • DFS will be essential in the long term © British Telecommunications plc, 2002

  13. What happens if we don’t implement DFS? • The World Radio Conference 2003 is reviewing spectrum allocations at 5 GHz • A lot of work has been done to demonstrate sharing between RLANs & other services • A pre-requisite is that an effective DFS mechanism will be available • If we don’t accept DFS, then the 5 GHz band will NOT be identified for RLANs © British Telecommunications plc, 2002

  14. What about the 5725 - 5875 MHz band? • Some of the radars operate in the 5725 - 5875 MHz band • An agreed DFS mechanism would enable frequency sharing in the band (for FWA) • DFS “modules” designed for the 5150 - 5350 & 5470 - 5725 MHz band could be easily implemented in 5725 - 5875 MHz band © British Telecommunications plc, 2002

  15. Conclusion • We need a Primary allocation for RLANs in the ITU Radio Regulations • We need to demonstrate that RLANs can share the 5 GHz band • DFS is an a pre-requisite for those sharing studies • Devices without DFS are permitted on a limited basis for an interim period, but not in the long term © British Telecommunications plc, 2002

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