Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

August 18, 2004

Bill Shvodian, Freescale SemiconductorSlide 1

doc.: IEEE 802.15-<04-0436r1>

Submission

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: [Polling vs. Token Passing for bi-directional CTAs]Date Submitted: [16 August 2004]Source: [Bill Shvodian] Company [Freescale Semiconductor]Address [8133 Leesburg Pike, Suite 700, Vienna, VA 22182, USA]Voice:[703-269-3047], FAX: [], E-Mail:[bill.shvodian @ freescale.com]

Re: [TG3b call for contributions]

Abstract: [This proposal describes token passing vs. Polling for bi-directional CTAs. An accompanying Excel spreadsheet compares performance.]

Purpose: [The author would like the IEEE to consider adoption of polling for TG3b.]

Notice: This document has been prepared to assist the IEEE P802.15. 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 acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Scenarios for comparison of polling and token passing for bi-directional CTAs

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Background

• Token Passing has been proposed for bi-directional traffic in TG3b

• A comparison between polling and token passing throughput was created to compare the performance of the two

• The accompanying spreadsheet (doc 15-04-0437-01) shows the relative performance of the two approaches

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Token Passing

• Owner of a CTA (srcID) always initiates transmission in a CTA. • Because it is the only DEV that all of the DEVs using the CTA

must hear, the token always comes back to the owner of the CTA before being sent to another DEV

• A new Token frame type is required • Token frames are not ACKed (per discussions in Portland)• Options for comparison purposes:

– Token single - token holder is only allowed to send one data frame when it receives the token (this scenario is not recommended but was included for comparison purposes)

– Token Multi – Token holder can send up to TBD frames or TBD duration

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Polling

• The owner of a CTA sends a frame to a particular destination DEV. The header contains the srcID, destID and polleeID

• Polling options for comparison:– Polling single - Poller/pollee holder can only send

one frame per poll– Polling Multi – Poller/Pollee can send up to TBD

frames or TBD duration. (this scenario is not recommended but was included for comparison purposes.)

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Implied ACK

• Thrown in to the throughput comparison for old times sake

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doc.: IEEE 802.15-<04-0436r1>

Submission

Scenario overview

• 6 scenarios were used to represent different traffic scenarios in a piconet

• For each of these scenarios, the throughput was calculated for polling and token passing and delayed ACK

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Scenarios

• Scenario 1: only CTA Owner has traffic• Scenario 2: only 1 CTA non-Owner has traffic• Scenario 3: all DEVs have traffic• Scenario 4: 2 DEVs have traffic (Owner has traffic to

all)• Scenario 5: only CTA Owner has traffic to one DEV• Scenario 6: only CTA Owner & 1 DEV have traffic

and only to each other

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Scenario 1: only CTA Owner has traffic

Data/poll ACK Data/pollPACK ACK PACK Data/poll ACK PACKPolling single

Data ACKToken single Data ACKTKN TKN TKN

Data Data Data/poll PACKPolling

DataToken multi Data Data ACK TKN

ACK

Del ACK

Imm ACK

Data/poll Data/pollPACK PACK Data/poll PACKPolling single

DataToken multi Data Data TKN

No ACK

Data1->n ACKImplied ACK Data1->n ACK Data1-n ACK

Implied ACK

TKN

DataToken single DataTKN TKN TKN TKN TKN TKN

TKN

Data ACKToken multi Data ACK Data ACK TKN TKN TKN

TKN

Polling multi?

Polling multi? Data Data Data/poll PACK

Data ACK Data ACK Data/poll ACK PACK

TKN TKN

TKN TKN TKN

Data/poll PACK

1->2 2->1 1->3 3->1 1->4 4->1

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Scenario 2: only 1 CTA non-Owner has traffic

Poll Data ACKPolling multi?

Token single DataTKN

Polling

DataToken Data Data ACK TKN

Del ACK

Imm ACK

No ACK

Implied ACK

Implied ACK

Poll PACK

TKN TKN ACK

Data2->1

Poll Data PACKACK Poll

Poll PACK

TKN TKN TKN

Data Data

DataToken single TKN TKN TKNTKN TKN TKN

Polling single Poll Data Poll PACK Poll PACK

Data ACK

TKN TKN TKN

PACKPoll

TKN TKN

ACKNull NullACK ACKNull

Poll Data ACKPolling single Poll PACK Poll PACK

Token multi Data Data ACK TKN TKN TKN ACK TKN TKN TKN

Polling multi? Poll Data PACKPoll PACK Poll Data Data

DataToken multi Data Data TKNTKN TKN TKNTKN TKN

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Scenario 3: all DEVs have traffic

Data ACKPolling multi

Token single Data

Polling


Del ACK

Imm ACK

Polling multi?


No ACK

Implied ACK

Implied ACK

ACK

Data

Data2->x

ACK Data Data

Data Data/poll

DataACK

TKN TKN

ACK

Data/poll ACK

Data ACK

Data/poll Data/poll

Data

Data Data/poll

Data TKN

Data1->2 Data3->x ACK Data1->3

Data ACKPolling single Data/poll ACK

Token multi Data Data ACK ACK TKN

Polling single Data Data/poll Data Data/poll

DataToken single TKN Data TKN Data TKN

Data

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Scenario 4: 2 DEVs have traffic

Polling multi

Polling


Del ACK

Imm ACK

Polling multi?

DataToken multi Data TKN

No ACK

Implied ACK

Implied ACK

Data

ACK Data Data

Data Data/poll

Token multi Data Data ACK ACK TKN

Data/poll Data/poll

Data

Data/poll

Data

Data1->2 Data2->x ACK

PACK

Data ACKPolling single Data/poll ACK Data/poll ACK Data/poll

Token single Data ACK TKN TKN Data ACK

Polling single Data Data/poll Data/poll PACK

DataToken single TKN Data TKN TKN TKNTKN TKN

ACKNull ACKNull

Data ACK Data ACK Data/poll ACK Data

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Scenario 5: only CTA Owner has traffic to one DEV

Data/poll ACK PACKPolling single




ACK

Del ACK

Imm ACK

Data/poll PACKPolling single


No ACK


Implied ACK

TKN


TKN


TKN

Polling multi?


Data ACK Data ACK Data/poll ACK PACK

TKN TKN

TKN TKN TKN

Poll PACK

Data/poll ACK PACK Data/poll ACK PACK

Data/poll PACK Data/poll PACK

Data

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Scenario 6: only CTA Owner & 1 DEV have traffic to each other

Data/poll ACKPolling single




ACK

Del ACK

Imm ACK

Data/poll PACKPolling single


No ACK


Implied ACK

TKN


TKN


TKN

Polling multi?


Data ACK Data ACK Data/poll

TKN TKN

TKN TKN TKN

Poll PACK

Data/poll ACK PACK

Data/poll PACK Data/poll PACK

Data

Data

1->2 2->1 1->3 3->1 1->4 4->1

1->2 2->1

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Conclusion

• The spreadsheets in document 15-04-0437-01compare the throughput for these scenarios

• Polling provides throughput as good as or better than token passing in every scenario

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Recommended Action

• Adopt polling to provide bidirectional traffic in a CTA to support protocols like TCP

• Add an 8 bit pollee field and a new polling enable bit to the header

August 18, 2004


doc.: IEEE 802.15-<04-0436r1>

Submission

Fallback Action

• Redefine the ACK policy to include Delayed ACK

Documents

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)