January 2003

Simon BlackSimon Black, Qosine

Slide 1

doc.: IEEE 802.11-03/071r0

Submission

A Brief Introduction to the IEEE802.11h Draft

TGk Radio Resource MeasurementJanuary 2003

Simon Blacksimon.black@qosine.co.uk

January 2003

Simon BlackSimon Black, Qosine

Slide 2

doc.: IEEE 802.11-03/071r0

Submission

What is IEEE802.11h?

• A draft supplement to the IEEE802.11 WLAN Standard– ‘Spectrum management in the 5GHz band in Europe’

• ‘Defines mechanisms for dynamic frequency selection (DFS) and transmit power control (TPC) that may be used to satisfy regulatory requirements for operation in the 5GHz band in Europe.’

• A protocol tool-kit for Transmit Power Control (TPC) and Dynamic Frequency Selection (DFS)

January 2003

Simon BlackSimon Black, Qosine

Slide 3

doc.: IEEE 802.11-03/071r0

Submission

Why is IEEE802.11h interesting for Radio Resource Measurement?

• TPC and DFS involve radio resource measurement!

• The management model is relevant– Where are the decisions made?

– What supporting protocol is required?

• Some of the management frames & elements may be usable

• A complete and stable draft exists and is currently undergoing the sponsor ballot process

January 2003

Simon BlackSimon Black, Qosine

Slide 4

doc.: IEEE 802.11-03/071r0

Submission

TPC Service

• The TPC service provides for the:– Association of STAs with an AP in a BSS based on the

STAs power capability– Specification of regulatory and local maximum

transmit power levels for the current channel– Selection of a transmit power for each transmission in a

channel within constraints imposed by regulatory requirements

– Adaptation of transmit power based on a range of information, including path loss and link margin estimates

January 2003

Simon BlackSimon Black, Qosine

Slide 5

doc.: IEEE 802.11-03/071r0

Submission

DFS Service

• The DFS service provides for:– Association of STAs with an AP in a BSS based on the STAs’

supported channels– Quieting the current channel so it can be tested for the presence of

radar with less interference from other STAs– Testing channels for radar before using a channel and while

operating in a channel– Discontinuing operations after detecting radar in the current

channel to avoid interference with radar– Detecting radar in the current and other channels based on

regulatory requirements– Requesting and reporting of measurements in the current and other

channels– Selecting and advertising a new channel to assist the migration of

a BSS or IBSS after radar is detected

January 2003

Simon BlackSimon Black, Qosine

Slide 6

doc.: IEEE 802.11-03/071r0

Submission

IEEE802.11h Layer Model

MAC Timing

MeasurementProtocol

MeasurementPolicy

Channel Switch Decision

MeasurementFrames

SME

MLME

Channel Switch Timing

PLME

ME

AS

UR

E

CH

AN

NE

L S

WIT

CH

MR

EQ

UE

ST

&

MR

EP

OR

T

Policy

Protocol

ML

ME

Fra

me

s

January 2003

Simon BlackSimon Black, Qosine

Slide 7

doc.: IEEE 802.11-03/071r0

Submission

IEEE802.11h Management FramesExtensions to existing frames

• Element based, building on existing IEEE802.11 management protocol

• Beacon/Probe Response extensions– Country– Power Constraint– Channel Switch Announcement– Quiet– IBSS DFS– TPC Report

• Association/Reassociation Request extensions– Supported Channels– Power Capability

January 2003

Simon BlackSimon Black, Qosine

Slide 8

doc.: IEEE 802.11-03/071r0

Submission

IEEE802.11h Management FramesAction frames

• Action management frame defined to minimise the number of management frame subtypes used– The IEEE802.11e draft shares this mechanism

• Defined spectrum management action frames– Measurement Request– Measurement Report– TPC Request– TPC Report– Channel Switch Announcement

January 2003

Simon BlackSimon Black, Qosine

Slide 9

doc.: IEEE 802.11-03/071r0

Submission

Requesting Measurements

• Requested using Measurement Request Action frame– Dialog Token identifies measurement– Timing can overlap, or be separate from other measurements– Duration of measurement defined in the request– Three measurement types defined

• Basic• CCA (Clear Channel Assessment)• RPI (Receive Power Indication) Histogram

– Only Basic measurement is mandatory– STA can refuse to perform a measurement even though it may be

capable• Measurement results returned in a Measurement Report

Action frame

January 2003

Simon BlackSimon Black, Qosine

Slide 10

doc.: IEEE 802.11-03/071r0

Submission

Category = 0(Spectrum Management)

Action = 0(Measurement Request)

DialogToken

Activation Delay(Beacon intervals)

MeasurementRequest Element

MeasurementRequest Element

Measurement Request Element

MeasurementOffset (TU)

Example of Measurement Request Frame Body Format – Basic Request

Element ID = 38(Measurement Request)

MeasurementDuration (TU)

Length = 6Measurement

TokenMeasurementRequest Mode

Measurement Type = 0(Basic Request)

ChannelNumber

January 2003

Simon BlackSimon Black, Qosine

Slide 11

doc.: IEEE 802.11-03/071r0

Submission

Example of Measurement Report FrameBody Format – Basic Report

Category = 0(Spectrum Management)

Action = 1(Measurement Report)

DialogToken

MeasurementReport Element

MeasurementRequest Element

Element ID = 39(Measurement Request)

MeasurementDuration (TU)

Length = 7Measurement

TokenMeasurementReport Mode

Measurement Type = 0(Basic Report)

ChannelNumber

Map

January 2003

Simon BlackSimon Black, Qosine

Slide 12

doc.: IEEE 802.11-03/071r0

Submission

Measurement Types

• Basic– Simple flags for BSS, radar, OFDM preamble,

unidentified

• CCA– Fraction of measurement duration CCA was busy

• RPI Histogram– Distribution of received power density over

measurement duration quantised into eight bins

January 2003

Simon BlackSimon Black, Qosine

Slide 13

doc.: IEEE 802.11-03/071r0

Submission

Decision to request measurement from peer STA

SME MLME MLME SME

IEEE802.11h STA IEEE802.11h STA

MLME-MREQUEST.req

MLME-MREQUEST.ind

Decision to accept measurement request from

peer STA

MLME-MEASURE.req

MeasurementProcess

MLME-MEASURE.cfm

Compile Measurement Report

MLME-MREPORT.req

MEASUREMENT REQUEST FRAME

MEASUREMENT REPORT FRAME

MLME-MREQUEST.cfm

MLME-MREPORT.ind

MLME-MREPORT.cfm

Measurement Request Completed

Measurement MSC – STA Accepts

January 2003

Simon BlackSimon Black, Qosine

Slide 14

doc.: IEEE 802.11-03/071r0

Submission

Decision to request measurement from peer STA

SME MLME MLME SME

IEEE802.11h STA IEEE802.11h STA

MLME-MREQUEST.req

MLME-MREQUEST.ind

Decision to refuse measurement request

from peer STA or unsupported request

MLME-MREPORT.req

MEASUREMENT REQUEST FRAME

MEASUREMENT REPORT FRAME

MLME-MREQUEST.cfm

MLME-MREPORT.ind

MLME-MREPORT.cfm

Measurement Request Completed

Measurement MSC – STA Refuses

January 2003

Simon BlackSimon Black, Qosine

Slide 15

doc.: IEEE 802.11-03/071r0

Submission

IEEE802.11h Quiet Interval

• Facility to quieten BSS– May be used to assist in making measurements without

interference from transmissions by members of the BSS

• May be included in Beacon and Probe Response Frames

• Quiet interval scheduling– Single, or periodic

– Starts at a defined offset from the TBTT

– Duration in units of TU (1024us)

January 2003

Simon BlackSimon Black, Qosine

Slide 16

doc.: IEEE 802.11-03/071r0

Submission

IEEE802.11h TPC• STAs signal maximum and minimum transmit power

capability in Association Request frames

• AP determines local transmit power constraint (with regard to regulatory requirements) and communicates this in Beacon frames

• Adaption of transmit power (optional)– TPC request Action frame may be sent to any STA

– STA responds with the transmit power used to transmit the TPC response and the link margin for the received TPC request

January 2003

Simon BlackSimon Black, Qosine

Slide 17

doc.: IEEE 802.11-03/071r0

Submission

Decision to adapt transmit power

SME MLME MLME SME

IEEE802.11h STA IEEE802.11h STA

MLME-TPCADAPT.req

TPC Protocol

TPC REQUEST FRAME

TPC REPORT FRAME

MLME-TPCADAPT.cfm

TPC Protocol

TPC Adjust MSC

January 2003

Simon BlackSimon Black, Qosine

Slide 18

doc.: IEEE 802.11-03/071r0

Submission

Channel Switching

• May be used to try and move a BSS to a new operating channel if a radar signal is detected

• Announced by Channel Switch Announcement Action frame– Broadcast (unacknowledged)– May be transmitted more than once and the information

included in Beacon & Probe Response Frames to increase probability of reception

• Actual channel switch is synchronised to TBTT• Facility to quieten BSS until switch occurs

January 2003

Simon BlackSimon Black, Qosine

Slide 19

doc.: IEEE 802.11-03/071r0

Submission

Decision to switch channel

SME MLME MLME SME

IEEE802.11h STA IEEE802.11h STA

MLME-CHANNELSWITCH.req MLME-CHANNEL

SWITCH.ind

Decision to follow channel switch

CHANNEL SWITCH ANNOUNCEMENT

MLME-CHANNELSWITCH.cfm

Channel switch complete

MLME-CHANNELSWITCH.resp

PLME PLME

MLME-CHANNELSWITCH.cfm

PLME-SETPLME-SET

Channel switch complete

T T

CHANNEL SWITCHANNOUNCEMENT

CHANNEL SWITCHANNOUNCEMENT

Channel Switching MSC

Announcements Repeated in Beacon

Frames

January 2003

Simon BlackSimon Black, Qosine

Slide 20

doc.: IEEE 802.11-03/071r0

Submission

IBSS DFS

• There is no AP function for collating measurements, or coordinating a channel switch

• The lack of an association protocol means– No exchange of supported channel information– No way to determine membership of the IBSS at a given instant for

requesting measurements

• The IBSS DFS protocol attempts to provide a solution– A DFS Owner service provides a central point of coordination for a

channel switch.– Each STA includes a Channel Map field within the IBSS DFS elements

that it transmits. This communicates the STA supported channel set and basic measurement reports for that STA.

– Best effort due to hidden node issue!

January 2003

Simon BlackSimon Black, Qosine

Slide 21

doc.: IEEE 802.11-03/071r0

Submission

Basis for Radio Resource Measurement?

• Use the management model• Use/adapt/extend some of the MAC Management

messages– Measurement request/report mechanism

• Use the simple TPC principles

January 2003

Simon BlackSimon Black, Qosine

Slide 22

doc.: IEEE 802.11-03/071r0

Submission

A Brief Introduction to the IEEE802.11h Draft

TGk Radio Resource MeasurementJanuary 2003

Simon Blacksimon.black@qosine.co.uk