UEC Tokyo

A New Concept of Baseband Radio

Yoshio KARASAWA

Advanced Wireless Communication research Center (AWCC)University of Electro-Communications (UEC Tokyo)

IEEE The 2009 Int. Conf. Advanced Tech. for Communications

UEC Tokyo

Presentation Topics

1. Baseband Signal vs Bandpass Signal

2. Wireless Baseband Transmission (WBT)

3. Experiment on Baseband RadioAdapting to Environmental Change

4. Radio Signal Processing Adaptive Arrayfor Terrestrial Digital TV Signalunder Multipath Environment

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Wireless Transmission Scheme

Information Information

Coding

Antenna(Tx)Mod.

Carrier(radiowave)

Multipleaccess

PropagationAntenna

(Rx) Demod.

Decoding

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Wireless Baseband Transmission

Information Information

Coding

Antenna(Tx) Propagation

Antenna(Rx)

Decoding

UWB-Impulse Radio(wireless impulse transmission)

Wireless waveform transmission

Carrier-less

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Modulatedsignal

Extreme of modulated signal

It is equivalentlya wireless basebandsignal.

CarrierInformation

(a)

(b)

Carrier

(c)

Information

Data Transmission Scheme

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freq.

fc-fc 0

Band-pass signal (real signal)

freq.

Baseband signal (complex signal)

Baseband Signal vs. Bandpass Signal

0

time

)()()( tsjtsts QI +=

)}({)( tsFfS =

time

)2sin()()2cos()(

)}(Re{)(

tftstfts

tsts

cQcI

RF

ππ −=

=

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freq.

0-B/2 B/2

B

Baseband signal- time domain: complex- freq. domain: complex

Wireless transmission signal- time domain: real- freq. domain: complex

freq.

B

0

B

-fc fc

B

0

B

-B/2 B/2

(a) Baseband signal

(b) RF signal transmission

(c) Baseband signal transmission

freq.

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The First Step:Wireless Baseband Transmission (WBT)

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?

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0 1-1

Power

Frequency f (x 1/T0)

1 0 1 0 0 1 1 1(a) Tx Data

(c) Power Spectrum

(b) ManchesterCoding

T0/2 Manchester coding(DC component is excluded.)

Data transmission rate: 1/2

Tx data

Wireless Transmission Scheme

2-2

T0

freq.

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Discorn Antenna (freq: 100MHz to 500MHz)TransmissionExperiment

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Generated Signal to be Transmitted (after Manchester Coding)

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Am

plitu

deA

mpl

itude

Transmitted

Received

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Data Detection

Error-free detection can be confirmed.

Receivedsignal

after Manchesterdecoding

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BER Characteristics of WBT

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Positive feature of WBT

GHz frequency signal can carry Gbit data.

Antenna size of (10cm)3 can realize 2.5Gbps transmission.(confirmed)

Antenna size of (1cm)3 can realize 25Gbps transmission.(estimated)

Problem to be solved

There is an substantial interference problem like UWB-IRdue to wide frequency band occupation.

Accordingly, this scheme restricts application fields very strictly.

Result

Possibility of WBT has been demonstrated.

Baseband Radio

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The Second Step: Baseband Radio

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Three Radios

Baseband Radio

Software-Defined Radio

Cognitive Radio

All functions are realized based on software

programming

Available resources areutilized flexibly

based on environmentrecognition

Radio signal is directly generatedbased on digital signal processing

without up conversion

Adaptive Communication

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Cognitive Radio (CR)

Access method

Modulation scheme

Frequency

Data rate

Ultimate Efficient Use of Radio FrequenciesAvoiding Radio Congestion

Cognitive Radio (CR)

“cognitive” Recognition, Process of Understanding

Adaptive radio system which can changeits system parameters autonomously,based on environmental sensing and intelligent judgement

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Baseband Radio

with Software-Defined Radio(*)and Cognitive Radio(**)functions

*) Kaleidoscopic change of configuration(reconfigurable)

**) Recognition of radio encironment(intelligent)

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Cognitive Radioavoiding Radio Traffic Congestionbased on Recognition of Radio Environment Change

frequency

Used in the primary service

CNR threshold

Availablefrequency bandto be used in CR

Other primary serviceband but not used now

CNRChannelcharacteristics

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Time-varyingPropagationEnvironment

TransmissionData

Coding &Modulation

Demod &Decoding

EnvironmentRecognition

0Freq.

Time-varying usable frequency bands

fL1 fH1 fH2fL2

Baseband Radio with Cognitive Radio Function

fL3 fH3

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Creation of Transmission Signal

Frequency band to be used in this communication

Data allocation in the data block: a

0 fmax

Kb/2 KbData to betransmitted

Re{IFFT(a)}Signal to be transmitted

Baseband OFDM

All null

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Data to be transmitted

0 0

0 KB/2

Block a

b = Re {IFFT (a)} Block b

DAC

KB

Block b Signal is directly transmittedfrom the antenna without up conversion.

Baseband OFDM

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Basic Experimental Configuration and Procedure

Rx dataTx data

DAC(FG)

PC

ADC(DSO)

Experiment procedure1 Environment recognition2 Channel sounding

(using pilot signal)3 Coding and Pre-distortion4 Data transmission5 Signal detection and analysis

DSO: Digital storage oscilloscopeFG: Function Generator

Sampling rate of DACin FG 250MHｚ

Resolution of DAC 14bitSampling rate of ADCin DSO 250MHｚ

Resolution of ADC 8bit

Performance of DAC & ADC

Discornantenna

Discornantenna

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Pre-Distortion

gain

frequency

Reference level

f1 f2

CN

R

frequency

Threshold level

f1 f2

Wanted CNR

f1 f2

CN

R

frequency

Channel characteristicsmeasured by pilot signal

Pre-distortedTx signal

Received signalwithout distortion

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0 20 40 60 80 100 120-220

-200

-180

-160

-140

-120

-100

-80

-60

周波数[MHz]

相対

利得

[dB

]

Frequency (MHz)

Rel

ativ

e po

wer

10dB

Tx data(full rangepilot

signal)

FG

PC

DSO

Discornantenna

Discornantenna

Full range channel monitoring

Allocated transmissionfrequency range

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-0.1 -0.05 0 0.05 0.1 0.15

-0.1

-0.05

0

0.05

0.1

Txpilot signal

FG

PC

DSO

Discornantenna

Discornantenna

0 20 40 60 80 100 120-240

-220

-200

-180

-160

-140

-120

-100

-80

-60

周波数[MHz]

相対

利得

[dB

]

Frequency (MHz)

Rel

ativ

e po

wer

(10

dB/d

iv)

16QAM

Pilot Signal Detection

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-25 -20 -15 -10 -5 0 5 10 15 20 25-20

-15

-10

-5

0

5

10

15

20

Pre-Distorted Tx SignalBased on the Pilot Signal Detection

0 20 40 60 80 100 120-180

-160

-140

-120

-100

-80

-60

-40

-20

0

20

周波数[MHz]

相対

利得

[dB]

Frequency (MHz)

Rel

ativ

e po

wer

(1

0 dB

/dv)

Txpilot signal

FG

PC

DSO

Discornantenna

Discornantenna

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-0.04 -0.02 0 0.02 0.04-0.04

-0.02

0

0.02

0.04

0 20 40 60 80 100 120-240

-220

-200

-180

-160

-140

-120

-100

-80

-60

周波数[MHz]

相対

利得

[dB]

Frequency (MHz)

Rel

ativ

e po

wer

(10

dB

/div

)Received signalafter pre-distortion

Txpilot signal

FG

PC

DSO

Discornantenna

Discornantenna

Successful transmission of 16QAMbased on “Baseband Radio”can be demonstrated!!

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Evolution of Wireless Terminal

Digital Analogue

Environment recognitionavoiding frequency congection

All necessary functions are created by softwareprograming

Transmission signals are directlycreated by digital signal processing

Importance of RF circuittechnologies is keptforever.

- Wideband antenna- Antenna array (MIMO)- Tunable RF filter- Other RF circuits

Hardware TechnologySoftware-Defined Radio

Cognitive Radio

Baseband RadioWireless terminal

DA

C/A

DC

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Antenna Diversity

based on Radio Signal Processingfor Terrestrial Digital TV

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Terrestrial Digital TV Service in Japan

For reception in a vehicle, space diversity is indispensable.

for In-house reception (12-segment HDTV)

for mobile terminal (1-segment)(Existing analogue TV will be terminated

in July, 2011 in Japan)

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Specification of Digital TV (ISDB-T)

Bandwidth 5.572 MHzOFDM symbol period (Ts) 1,008 μsGuard Interval (TGI) 126 μsThe number of subcarriers 5,616The number of segments 13Primary Modulation 64QAM (HDTV)

QPSK (1-seg.)TV channel 27ch（NHK-G）、Carrier frequency 557.142857MHz

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Recording of radio signal (IF signal) directly to HDD in PC

Radio Tower

汎用パソコン

Radio signal Video signal

PC DVD

Continuous recording of 200MB/s (=100MS/s) can be done.

(Contents recording)

(Radio signalrecording:Total recording)

Total Recording

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“Radio Signal Processing” which processes IF signal directly without demodulation and detection.

Application of this scheme to the maximal ratio combining diversity scheme with subband signal processing for mobile reception of terrestrial digital TV broadcasting signal.

Adaptive Array based on Radio Signal Processing

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freq.

fc-fc 0

Band-pass signal (real-domain signal)

freq.

Baseband signal (complex-domain signal)

Baseband Signal Processing

Baseband Signal Processing and Radio Signal Processing

freq.

fc-fc 0

Radio Signal Processing

0

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Radio Signal Processing Adaptive Array

Adaptive digital signal processingusing RF or IF signalsbefore Demodulation and Detection

ADCRadioSignal

Processing

IFsignal

LocalOscillator

IF-to-BBconversionandDe-modulation

IF signal

IFsignal

TV tuner

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A4

A3

A2

A1

SB-MRC

000

IFFT

FFT

-

-

t = 0 t = TB

f = -fs/2 f = fs/2Signal band: S +(f)

Radio Signal Processing IF signal for antenna A1 (real-domain signal)(OFDM block Extracted symbol-by-symbol base)

Frequency domainanalysis

Combined signal

Copy & Paste(frequency-inverted and complex conjugated)

0Hz

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1 2 m M

1 2 m M

1 2 m M

1 2 m M

Divide signal frequency bandinto M small groups

Group m

R(m)

wm

A1

A2

A3

A4

Maximal-Ratio Combining with Subband Signal Processing

R(m): Correlation matrix

Obtaining the largest Eigen valueand its Eigenvector

The validityof the schemehas been confirmed throughfield experiments(off-line proc.)

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Antenna＃１

Antenna＃３

Antenna＃２

Antenna＃４

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Demonstration of MRC receptionbased on Radio Signal Processing

(omitted)

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0 5 10 15 20 25 30

0

0.2

0.4

0.6

0.8

1

CNR

Cum

ulat

ive

prob

abili

tyC

umul

ativ

e pr

obab

ility

CNR (dB)

Singleantennareception

2-elementDiversity

4-elementDiversity

CNR improvement

Service area improvement

Diversity Effects (Analyzed based on RSP)

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The Three Radios, again

Baseband Radio

Software-Defined Radio

Cognitive Radio

All functions are realized based on software

programming

Available resources areutilized flexibly

based on environmentrecognition

Radio signal is directly generatedor analyzed as if it is baseband

signal

Adaptive Communication