March 2009

Graham Smith, DSP Group

Slide 1

doc.: IEEE 802.11-09/0347-00-00aa

Submission

OBSS “OSQAP” QoS Issues

Date: 2009-16-03

Name Affiliations Address Phone email Graham Smith DSP Group 2491 Sunrise Blvd,

#100, Rancho Cordova, CA 95742

916 851 9191 X209

Graham.smith@dspg.com

Authors:

March 2009

Graham Smith, DSP Group

Slide 2

doc.: IEEE 802.11-09/0347-00-00aa

Submission

Abstract

The main objective of this presentation is to examine and discuss the QoS issues related to OBSS and the proposal “OSQAP”

When presenting 09/0230r0, the concept of peak traffic arose. An objective of this presentation is to clarify how traffic allocation is handled

March 2009

Graham Smith, DSP Group

Slide 3

doc.: IEEE 802.11-09/0347-00-00aa

Submission

QLoad Element

• OSQAP introduced QLoad Element, including:

– QLoad Self

– QLoad Total

– Overlap

2

Overlap and Priority

1

Q LoadSelf

2

b0 b6 b7

Channel Priority

Overlap and Priority Octet

Q LOAD Element

CHP = 1 HigherCHP = 0 Lower

Q LoadTotal

Reserved

2

Overlap (4 bits)

QLoad SelfPotential QoS traffic for this QAP (as per Medium Time)QLoad TotalPotential QoS traffic for sharing QAPs, NOTE: If QLoad Total>Q Load Self, indicates sharingOverlapNumber of APs that are sharing this channel and are overlapping

March 2009

Graham Smith, DSP Group

Slide 4

doc.: IEEE 802.11-09/0347-00-00aa

Submission

Qload Self

Proposal is that QAP builds up the QLoad self by:

1. QSTAs sends a TSPEC with Inactivity Interval set to 0 (or 1) for instant timeout

2. QAP remembers TSPECs associated with QSTAs

Idea is that the QAP is advertising its potential load to other QAPs who may be considering sharing

If QSTA disassociates, the QLoad Self adjusts accordingly

March 2009

Graham Smith, DSP Group

Slide 5

doc.: IEEE 802.11-09/0347-00-00aa

Submission

QLoad total

• QLoad total indicates the total potential (peak) Qload of ALL QAPs that are overlapping, both directly and indirectly

• If QLoad total <100%, then each sharing QAP can allocate its Qload self traffic

• If Qload total >100%, then this indicates that an over allocation situation exists

Note: “100%” is meant to indicate the total bandwidth capacity, not necessarily 100% of the bandwidth.

March 2009

Graham Smith, DSP Group

Slide 6

doc.: IEEE 802.11-09/0347-00-00aa

Submission

Example #1 Extended

Adding new QAPs is straightforward using defined Rules Adding to QLoad Self is straightforward using defined Rules

Also note that each QAP is aware of the hidden QAPsOverlaps are: A = 2:2:1; B = 2:2:1; C = 1:2; D = 1:2

QAP D joins BInitially QAP D has no Qload SelfD Overlap 1 QLoad Self = 0% QLoad Total = 90% (Rule #1)A Overlap 2 QLoad Self = 30% QLoad Total = 90% B Overlap 2 QLoad Self = 25% QLoad Total = 90%C Overlap 1 QLoad Self = 35% QLoad Total = 90%

QAP D adds to its QLoad SelfD Overlap 1 QLoad Self = 20% QLoad Total = 110% (Rule #2)QAP B must adjust QLoad TotalB Overlap 2 QLoad Self = 25% QLoad Total = 110% (Rule #1)QAP A must then adjust Qload TotalA Overlap 2 QLoad Self = 30% QLoad Total = 110% (Rule #1)QAP C must then adjust Qload TotalC Overlap 1 QLoad Self = 35% QLoad Total = 110% (Rule #1)

A

B

C

D

March 2009

Graham Smith, DSP Group

Slide 7

doc.: IEEE 802.11-09/0347-00-00aa

Submission

QLoad Total value

• The QLoad Element provides all the information required to allow the OBSS networks to carry out a “policy” for sharing and allocation

• If QLoad Total <100% then there is no policy required, each QAP can allocate its QLoad Self traffic knowing that there is sufficient bandwidth

• If QLoad Total >100% then a sharing policy is required and ONLY if >100%

Note: QAPs should use the QLoad total, advertised in the QLoad Element to avoid joining QAPs with high QLoad Total

March 2009

Graham Smith, DSP Group

Slide 8

doc.: IEEE 802.11-09/0347-00-00aa

Submission

Probability of Zero or One overlap100% Assignment

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

24 22 19 17 11 9

Channels

Pro

bab

lili

ty

Detached Houses, 12 overlaps

Terrace Houses, 16 overlaps

Town Houses, 24 overlaps

Single Apartments, 28 overlaps

Double Apartments, 53 overlaps

Results from “08/1470r4“

Zero or One overlap is almost guaranteed for 20MHz channelsSuggestions made for dropping from 40 to 20MHzi.e. Typical condition is not to have multiple overlaps

March 2009

Graham Smith, DSP Group

Slide 9

doc.: IEEE 802.11-09/0347-00-00aa

Submission

Sharing Options

• First Come First Served– Each QAP allocates its traffic as it arises.

– As QLoad Total is a PEAK traffic indicator, there exists a probability that ALL traffic being allocated together – hopefully not 100%

– Possibility exists that quality does get hit

– Dependent upon actual QLoad Total value (what if 200%?)

• Proportional Sharing– Each QAP reduces its QLoad Self in proportion

e.g. If QLoad Total = 120%, QLoad Self = 60% Allowable allocation = 60 x 100/120 = 50%

– Playing safe – too safe?

March 2009

Graham Smith, DSP Group

Slide 10

doc.: IEEE 802.11-09/0347-00-00aa

Submission

Proposal

• For QLoad Total up to X%– Allocation shall be “First Come First Served”

• For QLoad Total above X%, – Each QAP shall reduce its allocation capacity by 100/Y, where Y

% is the QLoad Total and Y>X

March 2009

Graham Smith, DSP Group

Slide 11

doc.: IEEE 802.11-09/0347-00-00aa

Submission

X%

• What value for X? Points:– If QLoad Total was high one would hope that QAPs would not

willingly share anyway – X could be seen as “limit” for joining

– Video traffic tends to be long term, hence, unlike voice, say, peak to mean traffic may be closer than ‘normally assumed’

– Could use Poisson distribution, but what durations should be used?Hours?

– Pick a number? Not too big as possibility does exist that over-allocation will occur

– Suggest X = 120%

March 2009

Graham Smith, DSP Group

Slide 12

doc.: IEEE 802.11-09/0347-00-00aa

Submission

SUMMARY• Concept of advertising Peak Traffic loads is useful

– QAPs considering sharing can use this– As long as QLoad Total is <100%, there is no conflict

• If QLoad Total > 100% and <120%:– First Come First Served

Each QAP may allocate traffic up to its Qload Self

• If QLoad Total > 120%:– Each QAP shall reduce its allocation capacity by 120/Y, where Y

% is the QLoad Total– Note that the QLoad Self value does not change.

ALTERNATIVES• Declare “Out of Scope”• Suggest/define with ‘informative text’