March 2009 doc.: IEEE 15-09-0166-01-0006 Project: IEEE P802.15 … · 2011. 7. 13. · March 2009...
Transcript of March 2009 doc.: IEEE 15-09-0166-01-0006 Project: IEEE P802.15 … · 2011. 7. 13. · March 2009...
doc.: IEEE 15-09-0166-01-0006March 2009
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: NICT Phy Solution: Part 1: Chirp Pulse Based IR-UWB Physical Layer
Date Submitted: 10 March, 2009
Source: Igor Dotlić and Ryuji Kohno, National Institute for Information and Communication Technology
Address: 3-4, Hikarino-oka, Yokosuka, 239-0847, Japan
Voice: +81-46-847-5066, FAX: +81-46-847-5431, E-Mail: [email protected], [email protected]
Abstract: Chirp Pulse Based UWB Physical Layer Proposal for Body Area Networks
Purpose: Response to “TG6 Call for Proposals” (IEEE P802.15-08-0811-02-0006)
Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for
Submission Dotlić and Kohno (NICT)Slide 1
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.
doc.: IEEE 15-09-0166-01-0006March 2009
NICT Phy Solution:
Part 1: Chirp Pulse Based IR-UWB
Physical Layer
Submission Dotlić and Kohno (NICT)Slide 2
Igor Dotlić and Ryuji Kohno
National Institute of Information and Communications Technology (NICT)
doc.: IEEE 15-09-0166-01-0006
Outline
• Motivation
• System principles
• System performance
March 2009
Submission
• System performance
• Conclusions
Dotlić and Kohno (NICT)Slide 3
doc.: IEEE 15-09-0166-01-0006
Motivation
• IR-UWB is a (strong) candidate for wearable BAN.
• Low power non-coherent IR-UWB systems are sensitive to MAI, NBI and interference from other IR-UWB.
March 2009
Submission
• Systems that are aspiring to be low power (differentially) coherent IR-UWB are still emerging and make significant compromise between system performance and power consumption.
• Is it possible to design a system that is coherent, performs close to the full Rake receiver and is low complexity and low power?
Dotlić and Kohno (NICT)Slide 4
doc.: IEEE 15-09-0166-01-0006March 2009
Submission
SYSTEM PRINCIPLES
Slide 5 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006March 2009
Why is linear chirp pulse signal like no other?
)(tf
maxf
K =∆f /T
• It de-spreads the chirp
in frequency without de-
Mixing two linear chirp pulses:
Submission Dotlić and Kohno (NICT)Slide 6
minf
∆fc
Tc
∆t Tc-∆t
Mixing
t
t
)(tV
Kc=∆fc/Tc
∆f=Kc∆t
in frequency without de-
spreading it in time.
• Timing does not to be
matched well in order to
get low-pass signal that
contains most of the
energy.
doc.: IEEE 15-09-0166-01-0006
Why is linear chirp pulse signal like no other?
(cont.)
Effects on multipath:
March 2009
X
)(tf
maxf
minf
∆fc
Tc
t
t
)(tV
Tc-Tc
Mixed signal energy
∆t
Channel response
main cluster
Submission Dotlić and Kohno (NICT)Slide 7
With proper choice of chirp parameters, for a given channel and optimum timing,
energy of the multipath signal will be mostly preserved after mixing and
concentrated in low frequencies where it ca be conveniently sampled.
From channel
)(tf
maxf
minf
∆fc
Tc
t
Receiver generator
TcTc ∆t
∆t
∆fc
-∆fc
∆f=Kc∆t
Mixed signal
bandwidth
doc.: IEEE 15-09-0166-01-0006
Chirp pulse generation non-idealities
robustness rationale
March 2009
)(tf
maxf
minf
2| ( ) |M f
Submission
• Non-idealities in chirp generation:
– Non-linearity and offset in chirp slope (Kc), carrier frequency offset,
as well as phase and amplitude modulations encountered in the channel widen
the spectra of tones after mixing.
– There is no need to have very good match in carrier frequency in order
to achieve phase coherence.
Dotlić and Kohno (NICT)Slide 8
minf
f
doc.: IEEE 15-09-0166-01-0006
Timing resolution relaxation rationale
In the worst case scenario
(single path), power in the
digital portion of the system
varies
March 2009
~ /R c
T T∆
In equivalent differentially
Submission
In equivalent differentially
coherent IR-UWB system with
short pulses, power would vary
~Rc
f T∆ ∆
Slide 9 Dotlić and Kohno (NICT)
Timing resolution necessary is
relaxed TB product of the used
chirp pulse times.
doc.: IEEE 15-09-0166-01-0006
Duty cycling (power saving) rationale
March 2009
Submission
• Duty-cycling is facilitated, both in Tx and Rx, through emitting symbols that consist of single long packet of energy instead of series of isolated short pulses.
• Chirp pulse generator (founded both in Tx and Rx) is inherently duty cycled since it works in pulse regime.
• System is not peak-power limited but RMS power limited, which allows higher EIRP.
Dotlić and Kohno (NICT)Slide 10
doc.: IEEE 15-09-0166-01-0006
System block diagram
• Tx:
March 2009
Data
Submission
• Rx:
Dotlić and Kohno (NICT)Slide 11
D
doc.: IEEE 15-09-0166-01-0006
Notes on the system architecture
• System uses differentially phase modulated linear chirp pulses with relatively high TB product as symbols. Each pulse represents one symbol (there are no chips).
• Receiver is Quadrature Analog Correlating (QAC)
March 2009
Submission
• Receiver is Quadrature Analog Correlating (QAC) receiver (in specific configuration) found in both non-coherent and coherent IR-UWB solutions.
• Chirp generator is basically VCO with relatively linear tuning curve that works in pulse regime with linear ramp excitation (This technique of generation of chirp pulses is based on mature UWB VCO technology).
Dotlić and Kohno (NICT)Slide 12
doc.: IEEE 15-09-0166-01-0006
Notes on the system (cont.)
March 2009
-20
-15
-10
-5
0
Lev
el (
dB
)
Submission Dotlić and Kohno (NICT)Slide 13
The system uses chirp sweep of 550 MHz in order to fit
with high efficiency to narrower IEEE 802.15.4a
spectrum mask of about 600 MHz.
-500 -400 -300 -200 -100 0 100 200 300 400 500-40
-35
-30
-25
-20
Frequency (MHz)
Lev
el (
dB
)
IEEE 802.15.4a narrower UWB channel spectral mask
Chirp pulse ∆fc=550MHz, T
c=60ns
Chirp pulse ∆fc=580MHz, T
c=100ns
doc.: IEEE 15-09-0166-01-0006
Digital detection methods
• There are two symbol detection methods
that are considered.
1. Ordinary DPSK detection. i.e. “Symbol-
March 2009
Submission
1. Ordinary DPSK detection. i.e. “Symbol-
wise DPSK”.
2. “Digitally Differential Phase Shift
Keying (DDPSK)” i.e. “Sample-wise
DPSK”. (Suboptimal, but does not require
any channel vector estimation.)
Slide 14 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006March 2009
Submission
SYSTEM PERFORMANCE
Slide 15 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
Quantifying introduced concepts
• System multipath performance regarding
chirp pulse duration Tc and number of
samples per pulse.
March 2009
Submission
samples per pulse.
• Effects of the chirp pulse generation non-
idealities to the system performance.
• System BER performance with regard to
DPSK/DDPSK scheme and sampling
resolution used.
Dotlić and Kohno (NICT)Slide 16
doc.: IEEE 15-09-0166-01-0006
System multipath performance
IEEE 802.15.6 CM3
March 2009
η represents loss of energy
compared to ideal (i.e. “full
Rake”) receiver that
collects all multipath energy.
Submission Slide 17 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
System multipath performance. (cont.)
IEEE 802.15.6 CM4
March 2009
Submission Slide 18
TG6 CM4-1 TG6 CM4-2
Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
System multipath performance. (cont.)
IEEE 802.15.6 CM4 (cont.)
March 2009
Submission Slide 19
TG6 CM4-3 TG6 CM4-4
Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
System multipath performance (cont.)
IEEE 802.15.4a Channel Models
March 2009
Submission Slide 20
4a CM24a CM1
Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
System multipath performance (cont.)
IEEE 802.15.4a Channel Models (cont.)
March 2009
Submission Slide 21
4a CM3 4a CM4
Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
Notes on system multipath performance.
• Chirp duration higher than about 60ns does not significantly improve multipath performance.
• More than about 12 samples per pulse does not improve performance significantly.
March 2009
Submission
improve performance significantly.
• Regarding pulse duration both IEEE 802.15.4a 32ns time slot and its double – 64ns have their advantages.
• 32ns can allow lower duty cycle with some loss in multipath performance (about .5-1.5 dB depending on the channel model and number of samples used).
Slide 22 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
System robustness to chirp errors
Chirp slope (Kc) error Carrier frequency error
March 2009
Submission Slide 23 Dotlić and Kohno (NICT)
•Chirp slope error of 30% is acceptable
•Central frequency error of 100 MHz is still acceptable.
doc.: IEEE 15-09-0166-01-0006
System robustness to chirp errors (cont.)
Kc non-linearity, same in TX and
Rx
Kc non-linearity, different sign in TX and Rx
March 2009
Submission Slide 24 Dotlić and Kohno (NICT)
•Non linearity is modeled as 3rd order polynomial.
•30% Non-linearity is acceptable.
doc.: IEEE 15-09-0166-01-0006
Ordinary DBPSK detection versus
DDBPSK with 10 samples per symbol
March 2009
Submission
DBPSK DDBPSKSlide 25 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
Ordinary DQPSK detection versus
DDQPSK with 10 samples per symbol
March 2009
Submission
DQPSK DDQPSKSlide 26 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
NBI resistivity of the system regarding
sampling resolution.
Eb/N0=30 dB, 0.98 Msps (Processing gain
27 dB), DDBPSK
March 2009
•The system fully utilizes processing gain
in NBI resistance.
Submission Slide 27 Dotlić and Kohno (NICT)
in NBI resistance.
•The system does not have a problem of
saturation of low-resolution ADCs with
NBI, like some others do, 2 bits are more
than enough here.
•Most of processing gain effect to
NBI, both in TDMA and CDMA
(spreading in frequency and low-
pass filtering) is already achieved
before ADC.
doc.: IEEE 15-09-0166-01-0006
Comparison to differentially coherent
short pulse IR-UWB system• Benchmark short
pulse IR-UWB system uses QAC with single sample per chip (pulse).
• It uses single (ideally
March 2009
Performance
loss
Chirp pulse
UWB
Benchmark
short pulse
IR-UWB
Multipath
performance
compared to
-1 to -4 -6 to -12
Submission
• It uses single (ideally strongest) multipath component.
Dotlić and Kohno (NICT)Slide 28
compared to
full RAKE
(dB)
Pulse shape
distortion in
the channel
(dB)
Up to -.5 -3 to -6
Overall
performance
loss (dB)
-1.5 to -4.5 -9 to -18
doc.: IEEE 15-09-0166-01-0006
Link budgetFactor Symbol (unit) Value
Tx power P_Tx (dBm) -14
Path Gain 1m
(3m)
Pg (dB) -63 (-58)
Tx antenna gain G_Tx (dBi) 0
Rx antenna gain G_Rx (dBi) 0
Multi-path gain Mp (dB) -2
Pulse shape L_pl (dB) -0.3
March 2009
•For Pe calculation
DDBPSK with 2 bit ADC
and 10 samples per symbol
is used.
•For the same sampling
Submission Slide 29
Pulse shape
degradation
L_pl (dB) -0.3
Timing jitter L_jitt (dB) -0.1
Noise figure Nf (dB) 7
Noise density N0 (dBm) -174
Effective power at
detection 1m (3m)
P_det (dBm) -79.4 (-74.4)
Bit rate R_b (Mbps) 0.98
Eb/N0 1m (3m) Eb/N0 (dB) 27.7 (32.7)
Eb/N0 for Pe=1e-
6
Eb/N0 _req (dB) 14
Link margin Lm (dB) 13.7 (18.7)
Dotlić and Kohno (NICT)
•For the same sampling
characteristics other
modulation/detection
methods have +/- 2 dB
variation in the link
margin.
doc.: IEEE 15-09-0166-01-0006March 2009
Submission
CONCLUSIONS
Slide 30 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
Conclusions
• The system main advantages are:
– Multipath performance that is about 1-3 dB lower than one of full Rake receiver.
– Coherent operation with timing resolution requirement that is close to non-coherent short pulse IR-UWB (can be same as sampling period).
– Low sampling resolution necessary (2 bits are enough).
– Low sampling rate (about 10 times symbol rate.)
March 2009
Submission
– Low sampling rate (about 10 times symbol rate.)
– Inherent robustness to error in chirp generation.
• The system is full-blown coherent IR-UWB with:
– high NBI resistance.
– high MAI resistance (expected).
– Other IR-UWB radios interference resistance (expected).
• The system, especially receiver can be easily reconfigured to be used in other IR-UWB schemes.
Slide 31 Dotlić and Kohno (NICT)
doc.: IEEE 15-09-0166-01-0006
Conclusions (cont.)
• Probable proposed system characteristics:
– For 0.98 Mbps data rate system, we can propose system
with Tc of 64 ns and 8 samples per pulse with 1 or 2
bits sampling resolution and DDBPSK.
March 2009
Submission
bits sampling resolution and DDBPSK.
– Higher data rates may use Tc either of 32 ns or 64 ns
with somewhat more sophisticated digital part of the
receiver: e.g. 3 bits of resolution and 12 samples per
pulse and DQPSK (There is still wide range of
possibilities.)
Slide 32 Dotlić and Kohno (NICT)