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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: [WAVEFORM MODULATED LOW RATE UWB SYSTEM - Proposal for 15.4a alt PHY]Date Submitted: [Jan., 2005]Source: [Soo-Young Chang] Company [California State University, Sacramento]Address [6000 J Street, Dept. EEE, Sacramento, CA 95819-6019 ]Voice:[916 278 6568], FAX: [916 278 7215], E-Mail:[[email protected]]

Re: [This submission is in response to the IEEE P802.15.4a Alternate PHY Call for Proposal ]

Abstract: [This document describes the waveform modulated UWB proposal for IEEE 802.15 TG4a.]

Purpose: [For discussion by IEEE 802.15 TG4a.]

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.

doc.: IEEE 802.15-05-0028-00-004a

Soo-Young Chang, CSUSSlide 1Submission

Jan. 2005 doc.: IEEE 802.15-05-0028-00-004a

WAVEFORM MODULATED LOW RATE UWB SYSTEM

- Proposal for 15.4a alt PHY-

Soo-Young ChangCalifornia State University

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

INTRODUCTION

• Use short duration impulses: purely processed in time domain, not in frequency domain– Simple concept– Simple digital processing Low complexity low cost– No components for processing frequency information (e.g. filter, o

sc., etc.)– High location accuracy and fast ranging with very short duration p

ulses– Stealth mode of operation possible with relatively small RF signat

ure by coding frequency subbands with orthogonal codes– Excellent co-existence capability due to adaptive frequency band u

sage

Jan. 2005


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PLAUSIBLE MYTHS

• Myth 1– ‘Low rate needs less power consumption.’ With high rates, low power consumption can be achieved.

• Myth 2– ‘Digital implementation needs more complexity and is not easily realizable with the

state-of-the art technologies.’ Digital implementation can be realized with less complexity and provide more

flexibility.• Myth 3

– ‘Higher frequency is not easy to manage or implement.’ Unless high power is not considered, digital processing method can be applied for

higher frequency band.• Myth 4

– ‘Since this technology was not realizable yesterday, today also it is not easy to realize.’

Since technologies advances rapidly, more sophisticated and conceptual ideas should be considered for future applications.

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

CONSIDERATIONS FOR LOW RATE UWB (1)

• Frequency band– Enjoy full frequency band assigned: 3.1 – 10.6 GHz in the US– Only max power spectral density is limited: Transmitted power is

proportional to the bandwidth– Pulse width is inversely proportional to bandwidth: more accurate ranging

possible for time based ranging– Large bandwidth entails low fading High rate sampling is needed To overcome this problem, new processing method should be devised

• Transmit power– Enjoy full power transmitted under frequency mask if waveforms have the

spectrum similar to frequency mask– Max power will be -41.3dBm/MHz*7500MHz = -2.54dBm = 0.5mW– More transmit power needs more power consumption ??? New waveform is needed to fit exactly to frequency mask

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

CONSIDERATIONS FOR LOW RATE UWB (2)

• Data rate– In TRD, “low rate” is suggested with expectation to reduce power consumption and

complexity/cost– Power consumption is mainly proportional to the time of signal transmission and processing– No need to reduce data rates if higher rates possible with the same cost/efforts

• with higher data rate, less probability of conflict with other transmissions for CSMA and higher success rate with ack

– More pulses may be transmitted for the same information with higher rates: more redundancy can be achieved

– The amount of information delivered is the key issue for any communication systems• The higher the data rate is, the less time it takes to deliver.

More sophisticated signal processing for higher rate is inevitable.• Full digital processing

– Provide full flexibility for any change in signal environments, system concepts and requirements

– May also be compatible with a variety of complex digital modulation schemes– Eliminate the cost and complexity of a down conversion stage Sophisticated digital signal processing technologies needed including high speed ADCs and

DACs with sampling rate > 1 Gsamples/sec

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

KEY CONSIDERATIONS

• Modulation/demodulation

• Source coding• Channel coding (FEC)

– ARQ not considered

• Interleaving• Pulse generation• Antenna• Multiple access

• Synchronization• LNA• Message relaying• Simultaneously

operated piconet (SOP)

• Localization function• Transmit only device

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

FREQUENCY PLAN

• Flexible enough to satisfy any frequency mask and to avoid any forbidden bands pulse waveforms can be adaptively tailored to any

frequency mask applied

• With FCC mask, 3.1GHz to 10.6 GHz full frequency band is used to enjoy more transmitted power 3.8 dB more power used than Gaussian pulse’s case in

the same frequency band 3.8 dB more margin for link budget

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

FREQUENCY SUBBANDS• Whole frequency band under FCC mask is divided into 4 groups

• Each group has 4 subbands

– BW of a subband = (10.6-3.1) GHz /16 = 469 MHz – Each subband has its own waveform

f

subband 1 subband 2 subband 3 subband 4

f

group 1 group 2 group 3 group 4

3.1 GHz 10.6 GHz

w21 w22 w23 w24base waveform

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

PULSE WAVEFORM OF SUBBAND• Pulse waveform shape

– Mathematical derivation/expression– Shape: duration: 9 ns– Spectrum: flat throughout whole band

• How can pulses be generated – Digital way? Overlapped with various delays

can be generated with relatively lower sampling rate DACs• 100 samples/waveform: • 16 waveforms/group for binary representation

81 waveforms/group for ternary representation• 1600 or 8100 sample information stored in ROM per group

1.6 or 8.1 Kbytes ROM needed to store waveform information if 8 bits/sample is adopted

• Generate waveforms using DACs which has a sampling rate of 1 Gsamples/sec – Analog way?

• No idea– 4 digital ways considered in this proposal

• How can delay devices for TX and RX be implemented? Cost/accuracy/step size are the key issues

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

TYPICAL PULSE WAVEFORM AND ITS SPECTRUM

• For each subband, there is one waveform which has flat spectrum as shown in the above.• Group i has four base waveforms: wi1, wi2 , wi3 , and wi4

• Group i has 16 waveforms: mi1, mi2, mi3, . . . , mi16

mij,=a* wi1 +b* wi2 +c* wi3 +d* wi4

where a, b, c, and d are determined by modulation method applied

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

time

am

plit

ud

e

-10 -8 -6 -4 -2 0 2 4 6 8 10-16

-14

-12

-10

-8

-6

-4

-2

0

2

frequencya

mp

litu

de

in d

B

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

POSSIBLE MODULATIONS

• OOK– Two levels: +1, -1

• Anti-podal: BPSK– Two levels: +1, -1

• OOK + Anti-podal– Three levels: +1, 0, -1

• n level modulation• nQAM

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

MODULATION/MA EFFICIENCY

• Energy or power efficient? joule/sec– Energy=power*time– Power limited by FCC mask

• Pmax=-41.3dBm/MHz*7500MHz=-2.54dBm=0.5mW To use more energy, more time needs to be transmitted totally related to time for UWB, BW>500MHz or fractional BW>20% of fc short duration pulses use multiple pulses for one bit (or symbol) need more power under frequency mask to have higher power power constrained with frequency mask for UWB case new waveform needed to have more transmitted power

• Spectrally efficient? bit/Hz– Not important for UWB because of plenty of bandwidth

• Time efficient? bit/sec– For higher rate, more important: for lower rate, less important more room for

flexibility for LR-WPAN– However, as bit duration increases, more power consumption may be required

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

MODULATION PROPOSED

• Proposed Mod (1)– 8 frequency bins are coded with an 8 bit Walsh code and represent

one bit using BPSK

• Proposed Mod (2)– 4 waveforms of a subgroup are mapped to 2 bit (quaternary) infor

mationex) m1,1(t) 00 m1,6(t) 01 m1,11(t) 10 m1,16(t) 11

– Each user sends information using one subgroup of each group

at one time 8 bit information is delivered– Each waveform is modulated by OOK or BPSK or OOK+BPSK

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

WAVEFORMS FOR EACH GROUP

f


3.1 GHz 10.6 GHz

m1,1(t)

m1,2(t)

m1,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m2,1(t)

m2,2(t)

m2,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m1,1(t)

m1,2(t)

m1,16(t)

m3,1(t)

m3,2(t)

m3,16(t)

m4,1(t)

m4,2(t)

m4,16(t)

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

SUBGROUPS FOR EACH GROUP

f


3.1 GHz 10.6 GHz

m1,1(t) m1,6(t)

m1,11(t) m1,16(t)

m2,1(t) m2,6(t)

m2,11(t) m2,16(t)

m3,1(t) m3,6(t)

m3,11(t) m3,16(t)

m4,1(t) m4,6(t)

m4,11(t) m4,16(t)

m1,4(t) m1,7(t)

m1,10(t) m1,13(t)

m2,4(t) m2,7(t)

m2,10(t) m2,13(t)

m3,4(t) m3,7(t)

m3,10(t) m3,13(t)

m4,4(t) m4,7(t)

m4,10(t) m4,13(t)

m1,2(t) m1,8(t)

m1,9(t) m1,15(t)

m2,2(t) m2,8(t)

m2,9(t) m2,15(t)

m3,2(t) m3,8(t)

m3,9(t) m3,15(t)

m4,2(t) m4,8(t)

m4,9(t) m4,15(t)

m1,3(t) m1,5(t)

m1,12(t) m1,14(t)

m2,3(t) m2,5(t)

m2,12(t) m2,14(t)

m3,3(t) m3,5(t)

m3,12(t) m3,14(t)

m4,3(t) m4,5(t)

m4,12(t) m4,14(t)

SG1

SG2

SG3

SG4

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

BASE WAVEFORM FOR ONE GROUP

0 1 2 3 4 5 6 7 8 9 1000.20.40.60.81

1.21.41.61.82

Frequency( GHz.)

amplitude

+

+

+

t (ns)0 4

• For four subbands – assuming each has 1 GHZ BW– If smaller BW, larger pulse width

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

EXAMPLES OF WAVEFORMS

m1,5(t) m1,12(t) m1,16(t)

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

CORRELATIONS

• # of samples = 180 # of samples = 90

• Correlation ratio = autocorrelation/crosscorrelation

correlation

correlation ratio

w11 w12 w13 w14

w11 0.020984

1/1

0.0012155

17.264/9.7396

2.2562×10-5 930.05/3957.3

3.4173×10-6

6140.6/9681.8

w12 0.0012155

17.264/9.7396

0.020984

1/1

6.8651×10-6

305.66/106.69

2.2562×10-5

930.05/3957.3

w13 2.2562×10-5

930.05/3957.3

6.8651×10-6

305.66/106.69

0.020984

1/1

0.0012155

17.264/9.7396

w14 3.4173×10-6

6140.6/9681.8

2.2562×10-5

930.05/3957.3

0.0012155

17.264/9.7396

0.020984

1/1

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

DATA RATES• 1 Mbps max with 100% overhead Tb = 1/2 Mbps = 500 ns

• Pulse width = 9 ns Duty cycle = 2 %

Mod type # of waveforms

/subgroup

# of bits/symbol duration

symbol duration

(ns)

Data rate w/100% overhead

(Mbps)

Mod (1)

BPSK

4 2 500 2

Mod (2)

OOK or BPSK

16 8 500 8

500 ns 500 ns

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

MULTIPLE ACCESS (1)

• Possible MAs considered– Frequency hopping (FH)

among groups• Not efficient because of

uncertainty of FCC’s ruling on FH so far and less usage of power

– TDMA• Less time efficient

– Direct-sequence (DS) CDMA

• Less time efficient and more complex

f

t

Group 1

Group 2

Group 3

Group 4

16 frequency bins

time domain bins

t4t2 t3t1 t5

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

MULTIPLE ACCESS (2)

• For each subband, one base waveform exists – 16 base waveforms:

w11(t), w12(t), w13(t), w14(t), w21(t), . . . . , w43(t), w44(t)

– Each waveform is almost orthogonal to each other

• Each group has – 16 waveforms for mod (1) or 81 waveforms for mod

(2)• m1,1=0, m1,2= w1, m1,3= w2, . . . . , m4,16= w13+ w14+ w15+ w16

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

MULTIPLE ACCESS (3)• Correlation

where : kth sample of ith waveform of a subband for N samples

– Ratio of correlations = autocorrel/crosscorrel for various N values– Orthogonality holds for sinusoidal waveforms with some conditions

(Orthogonality condition, refer to next slide), but the waveforms used here are not sinusoidal with some envelope

• At receiver, a processing procedure can be used to make pure sinusoidal for a period

– mij*mij=(a* wi1 +b* wi2 +c* wi3 +d* wi4 )(a* wi1 +b* wi2 +c* wi3 +d* wi4)where mij is the waveform transmitted and mij is the waveform generated at RX

– After integrate for a one waveform duration, only autocorrelation terms remain– Orthogonality can hold at RX during detection

• What is the best sampling frequency such that orthogonality can be achievable?

)(ksi

)()( *

1

kskslationcrosscorre j

N

ki

2

1

*

1

)()()( ksksksationautocorrelN

kii

N

ki

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

ORTHOGONALITY OF SINUSOIDS

• A key property of sinusids is that they are orthogonal at different frequencies. That is,

• This is true whether they are complex or real, and whatever amplitude and

phase they may have. All that matters is that the frequencies be different. Note, however, that the sinusoidal durations must be infinity.

• For length sampled sinusoidal signal segments exact orthogonality holds only for the hamonics of the sampling rate-divided-by- , i.e., only for the frequencies

• These are the only frequencies that have a whole number of periods in samples

• Ex. N=100 for 4 ns pulse duration, fs=25 GHz– fk=k*25*10**9/100=2.5*10**8*k=0.25*k GHz– For any integer k, fk can be determined center frequencies of each subband can

be determinedhttp://ccrma.stanford.edu/~jos/r320/Orthogonality_Sinusoids.html

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

MAPPING FREQUENCY BINS TO WALSH ENCODED SYMBOLS

Jan. 2005


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MUTIPLE ACCESS (4)

• A orthogonal set of 8 8-bit Walsh codes is used– Max autocorrelation, min (or zero) crosscorrelation each other– One code consists of 8 frequency domain bins– Minimal Hamming distance of this code set is 4

• One frequency bin error can be corrected while three bin errors can be detected; works as an ECC code; increases robustness

• 8 SOPs case– For one user, one code is assigned– One time domain bin is occupied by two codes

• Each code represents one bit; one time domain bin represents two bits; one time domain bit deliver two bits

• 64 SOPs case– For one user, two codes (16 bits) are assigned– One time domain bin is occupied by two codes

• two codes represent one bit; one time domain bin represents one bit; one time domain bit deliver one bit

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

TRANSMITTER STRUCTURE

• Simple structure with impulse radio concept– FEC encoder

– Interleaver

– Pulse generator

– Modulator

– Antenna

Data manipulator

modulator

Pulse generator

Data in

antenna

Source codingChannel codinginterleaving

This part can be realized using digital processing

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

TRANSMITTER BLOCK DIAGRAM

ROM, group 1

ROM, group 2

ROM, group 3

ROM, group 4

DAC

DAC

DAC

DAC

waveform transformer




data manipulator

S/P converter

encodinginterleavingencryption

input data

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

RECEIVER STRUCTURE• Simple receiver structure

– Antenna - Pulse generator

– LNA - Location processor

– Demodulator

– Data detector

– De-interleaver

– Channel decoder

– Synchronizer

demodulatorData

De-manipulator

Pulsegenerator

SynchInformation

retriever

antennaLNA

Data out

detector

location

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

RECEIVING BLOCK

waveform conditioner

ADC correlator

ROM

LNA

6 bit Flash

correlation

pulsegenerator

receivedsignal correlation

Time correlator concept

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

LINK BUDGET ANALYSIS

• AWGN and 0 dBi gain at TX/RX antennas assumed. Fc=5.73GHz

Parameter Value Value Value

Information Data Rate 1 Mb/s 2 Mb/s 1 Mb/s

Average TX Power -2.54 dBm -2.54 dBm -2.54 dBm

Total Path Loss

(49.15dB@1m + L2)

77.14 dB

(@ 30 meters)

67.60 dB

(@ 10 meters)

67.60 dB

(@ 10 meters)

Average RX Power -79.68 dBm -70.14 dBm -70.14 dBm

Noise Power Per Bit -114 dBm -111 dBm -114 dBm

RX Noise Figure 8 dB 8 dB 8 dB

Total Noise Power -106 dBm -103 dBm -106 dBm

Required Eb/N0 6.25 dB 6.25 dB 6.25 dB

Implementation Loss 2.5 dB 3.0 dB 2.5 dB

Link Margin 17.57 dB 23.11 dB 22.61 dB

RX Sensitivity Level -97.25 dBm -93.25 dBm -92.75 dBm

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

mailto:49.15dB@1m

WHY THIS PROPOSAL?

• More transmit power used under frequency mask– More margin: at least 3 dB more by using full power under any frequency-power

constraints with waveforms adaptive to frequency mask Spectrally efficient / more received signal power More chance to intercept signals

• Very simple architecture– Directly generated pulse waveforms using ROM– Processing in digital methods

• No need to have analog devices, i.g., mixers Los, integrator, etc. low cost / low power consumption

• High location accuracy– Wider bandwidth for each waveforms narrower pulse width more accurate location information

• High adaptability to frequency, data rate, transmit power requirements high scalability in frequency, data rate, system configuration, waveform, etc.

Jan. 2005


doc.: IEEE 802.15-05-0028-00-004a

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