Daryl Kaiser, Cisco Systems

Submission Page 1Page 1

November 2002 doc.: IEEE 802.11-02/677r0

Radio Measurement Actions

Daryl Kaiser (Cisco Systems)

12 November 2002

Daryl Kaiser, Cisco Systems

Submission Page 2Page 2

November 2002 doc.: IEEE 802.11-02/677r0

Where do radio measurement actions fit intothe proposed RRM framework?

First, Define and Add Passively Observable Parameters to 802.11 MIB

• Standard Impact Minimal

While the above is being balloted

• Transfer of Parameters between STA to AP

• Actively Measured Parameters: extend TGh?

– May Need some architectural thinking

While the above is being balloted

• Work on Control Issues: Maybe a next TG

– Definitely Need some architectural thinking

Daryl Kaiser, Cisco Systems

Submission Page 3Page 3

November 2002 doc.: IEEE 802.11-02/677r0

Defining the focus of this presentation

What it addresses: Measurements that require specific action

• Measurements that are not part of normal processing, or

• Measurements that make sense to perform in “snapshots”

• Suggests measurement contents for further discussion

Not addressed: Status and statistics requiring no specific action

• E.g., authentication/association status, link counter statistics

• Can populate MIB objects for these without measurement action

Daryl Kaiser, Cisco Systems

Submission Page 4Page 4

November 2002 doc.: IEEE 802.11-02/677r0

Specific RRM goals that require radio measurement action

Detect possible rogue APs to help the WLAN administrator plug security holes

Quantify WLAN radio topology to facilitate automatic frequency selection and AP/client power limits

Measure BSS overlap to help balance coverage, capacity and QoS (current topic in TGe)

Quantify each station’s local performance for better network visualization and to facilitate roaming and load balancing

Detect non-802.11 interference and quantify noise to facilitate adjustments in WLAN configuration

Daryl Kaiser, Cisco Systems

Submission Page 5Page 5

November 2002 doc.: IEEE 802.11-02/677r0

Requests

• Set through measurement action table in MIB

• Include any required measurement parameters

• May pertain to AP radio and/or client radios

Measurements

• Serving channel is measured without disrupting traffic

• Off-channel measurements temporarily disrupt traffic

• Station’s traffic is buffered if it measures off-channel

• Station may decline if measurement poses undue burden

Reports

• Reports communicated through new MIB tables

Define a request/report mechanism

Daryl Kaiser, Cisco Systems

Submission Page 6Page 6

November 2002 doc.: IEEE 802.11-02/677r0

Action #1 = Beacon Report (and probe responses, too)

Purpose:

• Detects possible rogue APs

• Quantifies WLAN radio topology

• Measures BSS overlap

How it works:

• Each request specifies channels or asks for current beacon table

• Measure at AP radio and/or client radios

• Measure on serving channel or off-channel

• For each detected beacon and probe response,– Always report channel, BSSID, RSSI and time of detection

– Optionally report other fixed fields and information elements

Daryl Kaiser, Cisco Systems

Submission Page 7Page 7

November 2002 doc.: IEEE 802.11-02/677r0

Diagram of Beacon Request/Report

Access Point

Client Station

Write beacon reports to MIB• Detected BSSID, SSID, channel• Other detected beacon parameters• TSFTIMER offset versus serving AP• Detected signal strength per STA

One request

Periodic poll/trap

Periodic requests

One report per request

Retrieve reports• Poll or trap (TBD)

External Network Manager

Schedule radio measurements• AP follows scan parameters• Trigger measurements on schedule• Measure locally and request of clients

Request via MIB• Scan interval and channels• Active and/or passive scan• AP and/or client stations

Send one report per request• Passive co-channel scan• Active off-channel scan• Accumulated beacon table

MIB MIB

Local measurement access• Client saves in MIB• Available via MLME-SAP• Need SME vendor support

Issues• How should this work in IBSS?• When is STA allowed to decline?• How to enforce minimal disruption?

Daryl Kaiser, Cisco Systems

Submission Page 8Page 8

November 2002 doc.: IEEE 802.11-02/677r0

Action #2 = Extended CCA Report

Purpose:

• Quantifies each station’s current local performance

How it works:

• Measure at AP radio and/or client radios

• Measure on serving channel only

• Measured parameters– CCA busy fraction indicates degree of local contention at STA

– Histogram of recent backoff translates to radio-related jitter at STA

Daryl Kaiser, Cisco Systems

Submission Page 9Page 9

November 2002 doc.: IEEE 802.11-02/677r0

Action #3 = Non-802.11 RPI Histogram Report

Purpose:

• Detects non-802.11 interference and quantifies noise

How it works:

• Measure at AP radio and/or client radios

• Measure on serving channel only

• Measured parameters– Received power indicator (RPI) is a quantized measure of received power

– TGh defines eight RPI levels with 5-dB ranges for inner levels

– RPI Histogram measures occurrences of each RPI level

– RPI Histogram in TGh does not distinguish non-802.11 energy

Daryl Kaiser, Cisco Systems

Submission Page 10Page 10

November 2002 doc.: IEEE 802.11-02/677r0

What could external management entity do if AP detects acceptable CCA, but station detects unacceptably high CCA ?

• With just CCA information…not much could be done

• Need to know which stations are causing the contention

• Define one more radio measurement action for this case:

Action #4 = Frame Report

Daryl Kaiser, Cisco Systems

Submission Page 11Page 11

November 2002 doc.: IEEE 802.11-02/677r0

Action #4 = Frame Report

Purpose:

• Identifies a station’s local contending stations

How it works:

• Measure at AP radio or client radios, but typically client

• Measure on serving channel only

• Report one sub-element for each detected contending station– Transmitter MAC address

– BSSID to which contending STA belongs

– Number of frames decoded from STA

– Average signal strength of frames from STA

Daryl Kaiser, Cisco Systems

Submission Page 12Page 12

November 2002 doc.: IEEE 802.11-02/677r0

Store the reported measurement table in MIB under SMT

dot11reportedStatsTable

Measurements taken at STA itself

Measurements taken by other STAs and reported back

Daryl Kaiser, Cisco Systems

Submission Page 13Page 13

November 2002 doc.: IEEE 802.11-02/677r0

Summary of proposed radio measurement actions

• Beacon report detects possible rogue APs, quantifies WLAN radio topology and measures BSS overlap

• Extended CCA report quantifies each station’s current local performance in terms of CCA busy fraction and backoff experience

• Non-802.11 RPI histogram report detects non-802.11 interference and quantifies noise

• Frame report identifies a station’s local contending stations