Presentation on theme: "Doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 1 Update on 11n Greenfield Transmissions Causing False DFS Detects and."— Presentation transcript:
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 1 Update on 11n Greenfield Transmissions Causing False DFS Detects and Resolution of Related LB124 Comments Date: 2008-05-14 Authors:
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 2 An update on latest tests providing realistic evidence of GF- DFS problem – Yet rejecting related CIDs for now… TGn has been presented with evidence that GF transmissions can cause false radar detects on legacy 802.11a devices, creating unnecessary interruptions and lowering their throughputs −It’s revealed that there’re at least 2 different vendors with these problems In LB 124, there are 10 CIDs from individuals of different companies that asks TGn to consider this issue and adapt the solution proposed in 08/0302r5 at the Mar 2008 Orlando meeting08/0302r5 Based on feedback received, we’ve improved this solution so that opposing viewpoints are included, i.e., it’s a better compromise. (See later slide 4.) −As TGn has originally planned to complete LB124 in July 2008, we had planned to bring forth this new compromise then Kudos to members of TGn, comment resolution has moved forward rapidly and we are on schedule to motion for a new LB before end of this week! −However, we don’t believe we’ve obtained enough data or have enough time to explain this new compromise yet But in the interest of moving forward so that TGn can go to LB, at this time we: −Provide an update on the new results that we have collected supporting the GF-DFS issue −Explain the new improved solution −Propose to reject these CIDs −(We will submit comments on this issue in the next TGn LB and we encourage those who submitted the same to do so again.)
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 3 Latest tests show GF interferer can cause false triggers to multi-tenant environments 1.Same GF interferers as in 08/351r2 was placed at location “A” on the same floor 11a APs at pink and red locations indicated DFS radar detects 2.Same GF interferer as in 08/351r2 was placed at location “A” on the floor above 11a AP at red location indicated DFS radar detects These 11a APs are at least several tens of feet and a solid wall or a solid floor away from the GF interferers! This implies 11a users sharing a floor or on a nearby floor with GF users can be affected A This side of office being tested. Solid wall between two sides of floor. ~30 ft
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 4 Proposing improved prevention mechanism that narrows scope of scenarios that requires protection The proposed prevention mechanism is the same as that presented in 08/0302r5 but now:08/0302r5 −Only applies to regulatory classes that are subject to DFS with 50-100 microsecond radar pulses −Only forbids GF frames of durations between 50 and 100 us Effectively this applies only to the 5 GHz DFS bands in USA, Canada and Japan Overview of prevention mechanism: −When HT GF AP detects a beacon from an 11a AP, if they are in a long-pulse DFS regulatory class, the HT GF network switches to disabling 50-100 us GF transmissions −No monitoring or scanning on clients at all −Monitoring of non-HT OBSS only on the AP −No client requirements other than changing their behavior according to AP’s beacon −No new fields but re-uses existing 11n bits and signaling schemes −Minor changes from D2.0 behavior −Preserves 11n GF evolution path −Achieves true definition of having a “greenfield”. HT Greenfield AP Non-HT AP Beacon Anything but 50-100 us GF Proposed text for this mechanism is in 08/0302r6.
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 5 Proposing to reject GF-DFS CIDs for now so 11n can move forward but continue discussion of this issue in the next LB Reject CIDs 6181, 6326, 6073, 6196, 6137, 6074, 6304, 6231, 6179, 6067 with resolution text: “Reject: The problem of false detections in legacy devices is not limited to GF receptions. TGn does not feel this is an issue to act upon until further evidence is provided.”
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 6 Backup slides
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 7 Latest tests with WiFi draft 11n testbed devices show GF-DFS problem is beyond theoretical and commonly occurs Vendor Z (HT Greenfield AP) Test Setup: Vendor Y (HT Greenfield Client on laptop) Vendor Y (HT Greenfield Client on laptop) Vendor X (802.11a device) Bi-directional VoIP streams Radar Detects!!! Vendor X (802.11a device) Vendor X (802.11a device) On a DFS Channel 11a clients generating real over the air network traffic WAN Neighboring APs in range but on different channels
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 8 More details on the test and setup: VoIP streams were generated by latest version of IxChariot, industry designated network traffic generation and testing tool for WiFi certifications We used the G.711U codec used with default settings. −This is the most prevalent VoIP codec used in the industry False radar triggers began shortly after VoIP traffic began, eg. within 5 minutes Vendor X Legacy APs did not have any record of falsing for a long time before tests commenced or between tests Same intensity of false detects with different VoIP codecs and open real WLAN environment
doc.: IEEE 802.11-08/0666r0 Submission May 2008 Chan et al. (Cisco Systems) Slide 9 References “Compliance Measurement Procedures for Unlicensed-national Information Infrastructure Devices Operating In The 5250-5350 Mhz and 5470-5725 Mhz Bands Incorporating Dynamic Frequency Selection”, Appendix to Revision of Parts 2 and 15 of the Commission’s Rules to Permit Unlicensed National Information Infrastructure (U-NII) devices in the 5 GHz band, FCC 06-96, June 30, 2006. Submission 07/0329r2 Submission 07/2849r0 Submission 08/0111r2 Submission 08/0301r0 Submission 08/0302r5 Submission 08/0351r2
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