1. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 1 Interference Diagnostics Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// ieee802.org/guides/bylaws/sb-bylaws.pdfstuart.kerry@philips.compatcom@ieee.org Authors : NameCompanyAddressPhoneemail Joe KwakInterDigitalBolingbrook, IL630-739-4159joekwak@sbcglobal.net Jari JokelaNokiaVisiokatu 1, 33720 Tampere, Finland +358 50 486 0445 Jari.jokela@nokia.com Roger Durand RIM rdurand@rim.com

2. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 2 OUTLINE Introduction Interference definitions New Interference Measurands Measurement details Normative text framework Usefulness of Diagnostic Alert Conclusions

3. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 3 Introduction The detection and measurement of RF Interference (RFI) is important for managing radio and network resources. Hi RFI levels degrade link performance, causing errors and retransmissions, reduced data rates and decreased radio range. TGv has incorporated features to detect and report on internal interference: Co-located Interference Request/Report. This proposal considers a new Management Diagnostic for external interference reporting.

4. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 4 Progress since March 07/0467r0 presented at last meeting. SP indicated good support 58%, with discussion questions and concern over: Complexity of described measurement Need for simulations Have addressed both concerns here by simplifying the measurands with more detailed explanation of measurements.

5. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 5 What is RF Interference Not thermal noise Not the intended receive signal But everything else: Local RFI from nearby electronics (electric motors, microwaves), remote in-band users of other technologies (bluetooth, radars), remote in-band users of 802.11 in nearby BSSs, space radiation, etc. Characterized as: Transient or steady state (SS) Wide area (affecting all STAs iin BSS) Local (affecting some STAs in BSS)

6. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 6 Interference Measurement No easy direct measurement for RFI Lab/field installation measurements usually conducted by “controlling” RFI sources and measuring received power with/without interference. Not practical for operating networks. RFI presence may be indirectly inferred from other directly measurable parameters: ANPI, ChannelLoad, FER RFl increases ANPI (only when RFI < EDT/CCA). RFI increases ChannelLoad (only when RFI < EDT/CCA). RFI decreases RSNI and may increase FER and retransmissions. This proposal uses existing measurements to detect RFI. Continuous measurement and reporting triggers used for RFI monitoring and diagnostic alerts to AP.

7. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 7 RFI Relation to ANPI and RSNI Received Channel Power Level dBm (S + N + I) Operating Margin Required Min RSPL Level Desired Signal Power dBm Interference Power at Input Boltzman’s C (-198dBm/Hz/K) Antenna Connector: Input Power Level (S+ N + I) Input RF SNIR Ratio (RSNI at antenna conn) Thermal Input Noise Level (-100 dBm) Theoretical SNR for required BER (RCPI at antenna connector) NBW = 22MHz = 73.4dB Temp = 290K = 24.6dB Channel Impairments (CI) ) (fading + multipath + etc, = 0 in AWGN) dBm Total Modem Implementation Losses (TML) FEC Decoder Loss, if any Demodulator Loss Rx Amp Noise Figure + IM Distortion dBm Observed Digital SNIR Ratio Input RF SNR Ratio Total Channel Condition Losses Observed Analog SNIR Ratio o (ANPI at antenna connector) (RFI)

8. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 8 Channel Load vs ANPI Channel Load is % of time channel is busy as determined by CCA. ANPI is measured on idle channel (not busy). If RFI > EDT/CCA, RFI affects Chan Load but not ANPI If RFI < EDT/CCA, RFI affects ANPI but not Chan Load Simulations not needed to demonstrate the obvious. CCA RF @ ANT 802.11 frame EDT/CCA thresh level BT frame Low level RFI detected in ANPI Hi level RFI detected in ChanLoad Chan Busy

9. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 9 Simple(r) RFI Measurands IDMeasurandUseDescriptionPros/Cons 1 ANPIAP & STA Same measurand defined in TGk Detects RFI < EDT/CCA. Doesn’t detect RFI > EDT/CCA. 2 d/dt[ANPI]AP & STA Rate of change for RFI onset. 3 ChanLoadAP & STA Same measurand defined in TGk Detects RFI > EDT/CCA. Doesn’t detect RFI < EDT/CCA. 4 d/dt[ChanLoad]AP & STA Rate of change for RFI onset. 5 FERAP & STA Simple FER based on MAC counters. Requires updates of AP baseline at STA. Fails for RFI > EDT. 6 d/dt[FER]AP & STA Detects local interference at a STA compared to AP baseline. Requires updates of AP baseline at STA. Fails for RFI < EDT. 7 ????] Others??.

10. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 10 Derived RFI Measurements IDMeasurementUseDescription 1 ANPI Null_Ant_ANPI AP & STA Null_Ant_ANPI= Dummy load or config Detects SS RFI as background level. Derived by setting appropriate trigger threshold on ANPI. 2 ANPI. Quiet_ANPI AP & STA Quiet_ANPI= No activity ANPI (3AM?) Detects changes from background level, both SS and transient interference. Derived by setting appropriate trigger threshold on ANPI. 3 ANPI. AP_ANPI STA Detects local interference at a STA compared to AP baseline. Derived by setting appropriate trigger threshold on ANPI. 4 STA_ChanLoad AP_ChanLoad STA Detects local interference at a STA compared to AP baseline. Derived by setting appropriate trigger threshold on ChanLoad. 6 Others??STA Detects local interference at a STA compared to AP baseline. 7 d [AP ChanLoad] dt [ BSS_Thruput] AP Detects SS and transient RFI.

11. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 11 Simplified d/dt Processing Rate of change measurand computed as ratio of A/B where: A is most recent measurand value B is moving average value of same measurand with specified decay constant FER is computed using existing MAC counters, FER is ratio of A/B where: A is (FCSErrorCount n - FCSErrorCount n-1 ) or (QosRetriesReceivedCount n - QosRetriesReceivedCount n-1 ) B is (ReceivedFragmentCount n - ReceivedFragmentCount n-1 ) or (QosReceivedFragmentCount n - QosReceivedFragmentCount n-1 ) BSSThruput needs new definition using received MPDU size and received data rate.

12. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 12 Why is d/dt (differential) needed? ANPI varies slowly as distant neighbor BSS/cell interferers come and go. ANPI varies suddenly with onset of local RFE d/dt detection indicates local effects. ANPI d/dt[ANPI] d/dt thresh level Aggregate, distant RFI Local RFI

13. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 13 Create new Diagnostic Management Alert for RFI detection, similar to Multicast Diagnostic Request/Report. Triggered Interference Request/Report would permit requestor to: Select RFI Measurand Select measurement duration and interval Select trigger thresholds Select reporting period Once requested, RFI detection runs continuously until cancelled. One Request for each measurand may run concurrently. Framework for RFI Reporting

14. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 14 Element Format Outline Triggered Interference Request element contains: Measurand ID Trigger threshold UP (optional, for QOS APs) Aging Window (optional, for d/dt measurands) Reporting period (minimum time between reports) Triggered Interference Report element contains only the Measurand value. Dialog tokens match report to request. Measurement is continuous, reset by special value. Multiple measurements allowed, only 1 per Measurand ID.

15. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 15 What we have vs What we need TGk already provides ability to measure ChanLoad and ANPI. No continuous measurements, no triggers for diagnostic alerts. FER not defined at MAC level, can derive FER from existing MAC counters. Measurand expandability for new PHYs and expanded MACs

16. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 16 What Happens Upon RFI Alert? Like other Measurement and Management tools, out of scope for specification. Possible AP actions upon receipt: Determine scope of interference (more measurements) Decrease data rates Increase Tx powers Limit BSS rate sets Limit new admissions Consider channel switch Consider load shedding

17. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 17 Conclusions Interference detection using multiple simple measurands is practical and easy to implement. External interference measurement complements the TGv internal interference diagnostic. Table of measurands designed to allow growth as new detection techniques emerge. As WIFI uptake continues, and as unlicensed applications proliferate, RFI detection becomes increasingly important for WLAN performance. If supported, draft normative text will be presented at next meeting. Triggered Interference Request/Report satisfies a a real need and complements existing TGv/TGk measurements.

18. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 18 STRAW POLL Do you support use of this simplified Triggered Interference Request/Report? YES _______ NO _______ ABSTAIN _______

19. doc: IEEE 802.11-07/0467r1May 2007 Submission Joe Kwak( InterDigital), Jokela, Durand 19