doc: ieee 802.11-07/0467r1may 2007 submission joe kwak( interdigital), jokela, durand 1 interference...

Submission Joe Kwak( InterDigital), Jokela, Durand1

doc: IEEE 802.11-07/0467r1May 2007

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 <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, 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 < [email protected]> 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 <[email protected]>.

Authors:

Name Company Address Phone email

Joe Kwak InterDigital Bolingbrook, IL 630-739-4159 [email protected]

Jari Jokela Nokia Visiokatu 1, 33720 Tampere, Finland

+358 50 486 0445

[email protected]

Roger Durand RIM [email protected]


doc: IEEE 802.11-07/0467r1May 2007

OUTLINE Introduction Interference definitions New Interference Measurands Measurement details Normative text framework Usefulness of Diagnostic Alert Conclusions


doc: IEEE 802.11-07/0467r1May 2007

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.


doc: IEEE 802.11-07/0467r1May 2007

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.


doc: IEEE 802.11-07/0467r1May 2007

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)


doc: IEEE 802.11-07/0467r1May 2007

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.


doc: IEEE 802.11-07/0467r1May 2007

RFI Relation to ANPI and RSNI Received Channel Power Level dBm (S + N + I)

Operating Margin Required Min

RSPL Level

Des

ire

d S

ign

al

Po

wer

dB

m

Interference Power at Input

Boltzman’s C (-198dBm/Hz/K)

Antenna Connector: InputPower Level (S+ N + I)

Input RFSNIR Ratio

(RSNI atantenna conn)

Thermal Input Noise Level (-100 dBm)

Theoretical SNRfor 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 ModemImplementationLosses (TML)

FEC Decoder Loss, if any

Demodulator Loss

Rx Amp Noise Figure + IM Distortion

dBm

Observed Digital

SNIR Ratio

Input RF SNR RatioTotal

ChannelConditionLosses

Observed Analog

SNIR Ratio

o

(ANPI at antenna

connector)

(RFI)


doc: IEEE 802.11-07/0467r1May 2007

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

802.11frame

EDT/CCA thresh level

BT

fr

ame

Low level RFIdetected in ANPI

Hi level RFIdetected in ChanLoad

Chan Busy


doc: IEEE 802.11-07/0467r1May 2007

Simple(r) RFI MeasurandsID Measurand Use Description Pros/Cons

1 ANPI AP & 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 ChanLoad AP & 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 FER AP & 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?? .


doc: IEEE 802.11-07/0467r1May 2007

Derived RFI MeasurementsID Measurement Use Description

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.


3 ANPI . AP_ANPI

STA Detects local interference at a STA compared to AP baseline.


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.


doc: IEEE 802.11-07/0467r1May 2007

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 (FCSErrorCountn- FCSErrorCountn-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.


doc: IEEE 802.11-07/0467r1May 2007

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


doc: IEEE 802.11-07/0467r1May 2007

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


doc: IEEE 802.11-07/0467r1May 2007

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.


doc: IEEE 802.11-07/0467r1May 2007

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


doc: IEEE 802.11-07/0467r1May 2007

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


doc: IEEE 802.11-07/0467r1May 2007

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.


doc: IEEE 802.11-07/0467r1May 2007

STRAW POLL

Do you support use of this simplified Triggered Interference Request/Report?

YES _______ NO _______ ABSTAIN _______


doc: IEEE 802.11-07/0467r1May 2007

doc: ieee 802.11-07/0467r1may 2007 submission joe kwak( interdigital), jokela, durand 1 interference...

Documents