doc.: ieee 802. 15-10-0322-00-0007 submission to ieee 802.15.7 19th may 2010 j. w. walewski and m....

19th May 2010

J. W. Walewski and M. BahrSlide 1

doc.: IEEE 802. 15-10-0322-00-0007

Submission to IEEE 802.15 .7

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: Colour stabilization of CSK links by use of visibility frames – motivation and outline Date Submitted: 19th May 2010Source: Joachim W. Walewski and Michael Bahr Company Siemens AG, Corporate Technology, Communication Technologies Address Munich, GermanyVoice: +49-89-636-45850, FAX: +49-89-636-51115, E-Mail: [email protected]

Re: N/A

Abstract: We present a new strategy to colour stabilization of CSK constellation diagrams and touch on the changes to IEEE 802.15.7 that are advocated in our contribution 15-10-0262-00-0007. We also suggest next steps for integration of 15-10-0262-00-0007 into D2 when this change to IEEE 802.15.7 is accepted by the committee.

Purpose: Helping TG 802.15.7 to assess contribution 15-10-0262-00-0007 towards inclusion into IEEE 802.15.7 D2

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.

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Colour stabilization of CSK links by use of visibility frames – motivation and outline

Joachim W. Walewski and Michael Bahr

Siemens AGCorporate Technology

Communication TechnologiesMunich, Germany

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Historical recap

• Proposed colour-stabilisation scheme for links with at least one CSK Tx/Rx pair in 15-10-0089-02-0007

• Relied on H matrix already proposed in the standard• Originally only addressed high-frequency response of

LEDs (see doc 15-10-0146-01-0007)• Also covering low-frequency response, i.e. colour

fidelity of LED output, required major extension of current “H scheme” in D0

• Proposal by Samsung: use visibility patterns instead and rely on existing association scheme for negotiating colour-stabilisation capability minimise changes needed

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Executive summary of contribution 15-10-0262-01-0007

• Developed compensation scheme not based on H matrix

• Propose revised visibility patterns for CSK colour stabilisation

• Propose “minimum-intrusion” extension of MLME and MAC commands for initialisation of colour stabilisation and exchange of compensation messages.

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Reminder: Issue at heart

• Quantum-efficiency of individual emitters in tri-colour LEDs change differently due to aging and temperature changes

• Currently only accounted for on Rx side

• Could, in principle, be compensated for on Tx side

• Two options: measure at Tx or at Rx

• Here: Rx option (piggy back on VLC duplex link)

driving current

Rad

iant

pow

er

i i’

P0

P’0

initial quantum efficiency

new quantum efficiency

LED E-O characteristic function

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Impact on CSK

• Large arrow: wander of centre of gravity due to drift of slow response of LED (“DC quantum efficiency”)

• Small arrows: wander of off-centre constellation points due to drift of “AC quantum efficiency”

01

10

00

11 R

B

G

01

10

00

11 R

B

G(xj,yj)

(xi,yi)

(xk,yk)

(xp,yp)

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Proposed control loop

Tri-Band Tx Tri-Band Rx

Visibility Pattern

CSK Link

Signal Values (optional)

TxRx

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Algorithm

• Simply relay received signals back to Tx

• Provide algorithms for how to compensate (colour-stabilisation module)

ColorCoding

xyto

i, j, k

Optical source PDs

D/A

D/A

D/A

i, j, kto xy

ColourDecoding

Band i

Band j

Band k

Band i

Band j

Band k

ReceivedSignals

D/A

D/A

D/A

(b)ic

(b)jc

(b)kc

Back Channel (optional)

VisibilityPattern

Color-StabilizationModule

• Also covers LED non-linearity (!)

• Control loop only to be invoked infrequently (second-hour scale)

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Visibility patterns for CSK colour stability

• Ideally send symbol = centre of constellation map• Not feasible for 8 CSK• Compromise: Cycle through corner of triangle or any other

suitable set of symbols• Caveat: Only works under the assumption of quasi-linear

characteristic curves (around working point)

-0.2 0 0.2 0.4 0.6 0.8-0.2

0

0.2

0.4

0.6

0.8

x

y

Genarated Signal Simbol for CMC

R positionG positionB positionSimbol position

4 CSK(2bits/Symbol)

R

G

B

-0.2 0 0.2 0.4 0.6 0.8-0.2

0

0.2

0.4

0.6

0.8

x

y

Genarated Signal Simbol for CCM


-0.2 0 0.2 0.4 0.6 0.8-0.2

0

0.2

0.4

0.6

0.8

x

y

Genarated Signal Simbol for CMC


8 CSK(3bits/Symbol)

16 CSK(4bits/Symbol)

R

G

B

R

G

B

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


DC stabilisation

• Each CSK typically symbol shorter than 1 µs• Need longer symbols for stabilisation of

centre of gravity (see 15-10-0146-01-0007)• Trick: Seamlessly repeat each symbol (e.g.

“corners”, typically 100 – 1000 times)

i i i j j j k i… …

k k i i… …

measure!

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Establishing colour stabilisationrevised capability

information revised MAC field

revised capabilityinformation

revised MAC field

new

par

amet

er:

Cap

abili

tyN

egot

iatio

nRes

pons

e

new parameter:CapabilityNegotiationResponse

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Change to MLME-ASSOCIATE.response and .confirm

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


New capability information field

new capability function

space for future extensions

space for future extensions

bits for colour-stabilisation capability: 00 none, 01 exists

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


CapabilityNegotiationResponse

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


New MAC command frames

modified

New: setting time between

stabilization updates

CSK-Rx signals

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


New association-response command and colour-stabilisation time

Amendment of association-response command (MAC) for inclusion of capability-negotiation response (message from coordinator):

New MAC command frame for change of colour-stabilisation timer:

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Colour-stabilisation command and new MAC PIBs

Top: New MAC command for communication of measured signals between CSK Rx and CSK Tx.

Bottom: New MAC attributes used for colour-stabilisation and timer setting

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Maybe AC stabilisation too?

• Same scheme also suitable for AC compensation, i.e. keeping distance between constellation points fixed

• Would need its own set of functions etc. (VERY similar to what is already in 15-10-0262-01-0007)

01

10

00

11 R

B

G

01

10

00

11 R

B

G(xj,yj)

(xi,yi)

(xk,yk)

(xp,yp)

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Suggested next steps …

• Attend existing typos and potential glitches; need cooperation of CSK expert plus any volunteers – 8B10B interference, etc.)– Figure out what –if any- compensation algorithm to advocate

in IEEE 802.15.7– …

• Rewrite 15-10-0262-00-0007 so that it readily can be ported to into IEEE 802.15.7 draft

• Integrate into D2• Wait for comments from recirculation • …

19th May 2010


doc.: IEEE 802. 15-10-0322-00-0007


Summary

• Upon suggestion from Samsung reworked colour stabilisation scheme

• Tried to minimise changes to existing PHY and MAC sub-layer

• Perks– Covers multiple types (“any”) of LED E-O

characteristic functions– Can be extended to compensating constellation-

point spacing• Needed: committee decision on adoption of

proposal

doc.: ieee 802. 15-10-0322-00-0007 submission to ieee 802.15.7 19th may 2010 j. w. walewski and m....

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