doc.: ieee 802.15-09-0840-02-0007 submission to ieee 802.15.7 17th december 2009 randel et al.slide...
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17th December 2009
Randel et al.Slide 1
doc.: IEEE 802.15-09-0840-02-0007
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: Toward higher data ratesDate Submitted: 17th December 2009Source: Sebastian Randel,1 Klaus-Dieter Langer,2 Harald Rohde,3 Oscar Cristobal Gaete Jamett,4 and Joachim W. Walewski1 Company 1) Siemens AG, Corporate Technology, Communication Technologies; 2) Fraunhofer Institute for Telecommunications, Heinrich-Hertz Institut; 3) Nokia Siemens Networks, COO; 4) Technical University of Munich, Institute for Communications Engineering; Address 1,3,4) Munich, Germany; 2) Berlin, Germany;Voice: +49-89-636-45850, FAX: +49-89-636-51115, E-Mail: [email protected]
Re: N/A
Abstract: Overview of avenues for achieving higher data rates. The ideas presented are complementary to the strategies chosen in the VLC base-line draft.
Purpose: Helping TG 802.15.7 to shape the use-case scope of a VLC standard
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.
17th December 2009
Randel et al.Slide 2
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Toward higher data rates
Joachim W. Walewski and Johannes Riedl
Siemens AGCorporate Technology
Communication TechnologiesMunich, Germany
Klaus-Dieter LangerFraunhofer Institute for
Telecommunications, Heinrich-Hertz-Institut
Berlin, Germany
Harald RohdeNokia Siemens Networks, COO
Munich, Germany
Oscar Cristobal Gaete JamettTechnical University of Munich,
Institute for Communications Engineering
Munich, Germany
17th December 2009
Randel et al.Slide 3
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Motivation for this contribution
• 3+ years track record in high-speed VLC• Provide our thoughts on achieving higher
data rates (with an emphasis on lighting scenarios)
• Ideas presented complement avenues in base-line draft (15-09-0786-01-0007)
• Smorgasbord: You pick and chose (or don’t pick at all)
• Upon request we happily provide more details on chosen topics
17th December 2009
Randel et al.Slide 4
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Outline
• Now or later?• Higher data rates through exploitation of
– Spatial diversity– Colour diversity– High SNR
• Summary and Conclusions• References• Acknowledgment
17th December 2009
Randel et al.Slide 5
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Now or later?
• Relevant for current base-line draft or follow up?
• Reality: Up to draft sponsors
• However: If interest to integrate (some of) ideas presented in extension of IEEE 802.15.7 ensure that current standard does not bar future extensions
17th December 2009
Randel et al.Slide 6
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting spatial diversity
Principle:• Array of LEDs that can be individually
modulated• Zero-dimensional detector• Total radiant LED power equals symbol
value; need 2n emitters for n bits per symbol
• Random selection of configuration for intermediary symbol levels ensures illumination uniformity
• Choose “max value” brighter and “0” dimmer (or vice versa). Other binary modulation formats work too, e.g. VPM
• Power-averaged idle sequence, e.g. “30”• One-dimensional or two-dimensional
receiver n emitters for n bits per symbol
“3” “2”
“2”
“2”
“1”
“1”
“1”
“0”
17th December 2009
Randel et al.Slide 7
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting spatial diversity, contd.
Advantages:• Very simple driving
circuit (on and off)• Can be combined with
Manchester coding (low data rate), VPM (earlier – later), and CCM (each tile an RGB diode)
• Higher data rates for same bandwidth with single-colour LEDs
“1” “1”“1” “1” “0”“1”
“0” “1”“1”
“1” “1”“0”
“0” “0”“1”
“0” “1”“0”
“1” “0”“0”
“0” “0”“0”
17th December 2009
Randel et al.Slide 8
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting colour diversity
Principle:• CCM: Intensity of each
elementary colour contributes to symbol
• Additional freedom: phase relationship between colours (at least two more bits per sent CCM symbol)
Implementation example• BPSK on sub-carrier for
white constellation point Aggregate data stream: 0110
Ra
dian
t Pow
erR
adi
ant
Pow
er
0 1
Rad
iant
Po
we
r
Time
1 0
17th December 2009
Randel et al.Slide 9
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting colour diversity, contd.
Benefits etc.• PSK on all carriers possible
(at least three extra bits per cycle), but with our approach clock recovery very simple (here: red)
• Phase-shift symbols “orthogonal” to CCM symbols support of two independent data streams (e.g., “payload” and control data)
• Con: need linear driving circuit. Pro: already at hand (CCM!) Aggregate data stream:
0110
Ra
dian
t Pow
erR
adi
ant
Pow
er
0 1
Rad
iant
Po
we
r
Time
1 0
17th December 2009
Randel et al.Slide 10
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting prevalent high SNRs
• SNRs in lighting scenarios very high, e.g. ~ 58 dB for [Grubor, 2008]– 400 lx– phoshporescent LEDs– blue-filtered detection– 20 MHz modulation bandwidth
• What about PWM dimming?– Only duty-cycle variation, not peak amplitude– Thus: same high SNR during “on” state
• What about single-colour or phosphorescent white LEDs when it comes to high data rates?
• Suggested strategy: several bits per symbol. How?– Adaptive multi-level pulse-amplitude modulation (PAM)– Symbol-length coding
17th December 2009
Randel et al.Slide 11
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting prevalent high SNRs: multi-level PAM
• Investigated two major approaches within OMEGA: Discrete multi-tone (OFDM, used in DSL) and multi-level PAM
• PAM supports higher data rates and simpler to implement [Randel, 2009]
• However: how to accommodate dimming?
...Opt
ical
Pow
er
P0
111 000 101 010 110 100
Tc
Ts
17th December 2009
Randel et al.Slide 12
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting prevalent high SNRs: multi-level PAM, contd.
Accommodating dimming:• Granularity of PAM
symbols depends on length of “chip”– Low dimming high
granularity– High dimming low
granularity• Seamless integration
with VPM possible• Flicker? Probably
negligible. Simulations on request.
...
a)
Opt
ical
Pow
er
P0
...
b)
Opt
ical
Pow
er
P0
111 000 101 010 110 100 001
TcTs
Ts
11 10 01 00 11 01 10
...
c)O
ptic
al P
ower
P0
Tc
Ts
0111 1000 0100 0010 1110 1011 1000
17th December 2009
Randel et al.Slide 13
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting prevalent high SNRs: symbol-length coding
• Already in the base-line draft: alternating length of VPM symbols in order to achieve low-granularity dimming
• Proposal: map symbols onto alternation symbol-length coding
• Can be combined with VPM• Caution: no inherent flicker
suppression. Simulation of expected flicker on request.
• Decrease granularity by flexibly choosing length of shortest chip and # of bits / symbol
a) b)
PWMIcc
η
ILED
PWMIcc
η
ILED
VLC
data
ηi
LED LED
...
a)
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ptic
al P
ower
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Tt
...
b)O
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ower i = 1, S = 0 i = 2, S = 3 i = 3, S = 1 i = 4, S = 2
Ttmin Tt
maxΔTs
Td
17th December 2009
Randel et al.Slide 14
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Exploiting prevalent high SNRs: symbol-length coding, contd.
Even higher data rates:• Introduce dips into
symbol• When introducing
several dips encode symbols onto relative position
• Example: time after beginning of symbol cluster
...
a)
Tc
Opt
ical
Pow
er
P0
Tt
...
b)
Opt
ical
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er
Td
tb te
tb1,i
te1,i
tb2,i
te2,i
tb3,i te3,i
t1,i+2 t2,i+2
Bits per symbol as a function of the cluster length for two “dips”
17th December 2009
Randel et al.Slide 15
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Summary and Conclusions
• Many avenues of increasing data rate (in lighting scenarios)
• Op to TG whether, how, and when to integrate into standard
• Happy to provide more details on request in January
17th December 2009
Randel et al.Slide 16
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
References
• Grubor et al., “Broadband Information Broadcasting Using LED-Based Interior Lighting,”J. Lightw. Technol., Vol. 26, 2008
• Randel et al., “Advanced Modulation Schemes for Short-Range Optical Communications,”J. Select. Top. Quant. Electr., submitted, 2009
17th December 2009
Randel et al.Slide 17
doc.: IEEE 802.15-09-0840-02-0007
Submission to IEEE 802.15 .7
Acknowledgment
The work resulting in the ideas presented here received partial funding from the European Commission's Seventh Framework Programme FP7/2007-2013 under grant agreement n° 213311, also referred to as OMEGA. The authors acknowledge the contributions of OMEGA colleagues. This information reflects the consortiums view, and the Commission is not liable for any use that may be made of any of the information contained therein.