1. DFS Regulatory Update Date: 2005-05-14 Authors: May 2005 May 2005
doc.: IEEE yy/xxxxr0
May 2005
DFS Regulatory Update
Date:
Authors:
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Greg Chesson, Atheros
Greg Chesson, Atheros

2. May 2005
doc.: IEEE yy/xxxxr0
May 2005
Abstract
Dynamic Frequency Selection (DFS) is required in certain radar bands. Regulations and tests are being developed and will be adopted. As a result, some a bands may become less useful. A mesh should be better able to reliably detect radar than separate APs would.
Greg Chesson, Atheros
Greg Chesson, Atheros

3. May 2005
DFS Regulation
Dynamic Frequency Selection (DFS) required in certain radar bands:
Ghz
Ghz
But not Ghz
Wireless devices must detect radar and vacate the band for at least 30 minutes before returning
Greg Chesson, Atheros

4. May 2005
Regulatory Scope
Includes all 5 Ghz devices sharing bands where radar is the primary user.
Includes non systems, but test procedures are unclear for non
Will affect mesh networks, but tests focus on APs and do not anticipate mesh networks.
This may become a problem for TGs unless every TGs device can detect radar and pass the AP certification test.
Greg Chesson, Atheros

5. Industry/Regulatory Cooperation
May 2005
Industry/Regulatory Cooperation
FCC/NTIA/DoD providing new test signal and test procedure.
Vendors working with USG for consensus agreement on new regulations.
Validation lab tests scheduled for August.
Validation field test (real radar).
Final drafts and rulemaking
Will be mandatory certification for APs.
Greg Chesson, Atheros

6. May 2005
Test Overview
New draft test generates random us linear FM-chirped pulse bursts for 12 seconds.
Pulses resemble collisions between voip frames but with different modulation (FM not OFDM).
AP must detect the 12 second radar event while transmitting a 50% capacity video stream.
The AP cannot receive every radar pulse and will experience some level of false positive detects.
Greg Chesson, Atheros

7. May 2005
Possible Outcomes
New hardware designs may be needed to reduce false detection in future systems.
Some 11a channels may become less useful.
A mesh may better be better at detecting radar reliably than an AP (more receivers).
Greg Chesson, Atheros

8. May 2005
References
Greg Chesson, Atheros