Testing c2k Mobile Stations Using a Digitally Generated Faded

Signal

Testing c2k Mobile Stations Using a Digitally Generated Faded

Signal

Agenda

Fading OverviewMitigationTest Methods

Overview of Presentation

Agenda

Fading OverviewMitigationTest Methods

Fading Presentation

Fading Overview

Tx/Rx Separation

Free space path loss Inverse square

Large Scale Path Loss

Rayleigh Distribution

Small Scale Path Loss

Short Time

Short Motion

Fading Overview

Free space path loss (log-normal)

average attenuation,exponentially proportional to distance

Time

MountainBuildings

Shadowing (diffraction)

secondary wavelets “wrap around” large objects

Signal level

Overview - Large scale

What is fading?

Why is it important?Enables engineers to test the receiver (BER/BLER) under realistic channel conditions

The effect of the environment on the Tx signal at the Rx

•Multipath – time delayed copies of the signal•Doppler shift – spreading of the spectrum•Attenuation – atmosphere reduces signal amplitude

Fading Overview

LOS

NLOS

NLOS

Multipath propagation

Doppler shift caused by angle of arrival relative to motion of receiver

Overview - Small scale

Fading Overview

QPSK Pilot Signal with no fade

QPSK Pilot Signal with deep Rayleigh fade

QPSK Signal in Rayleigh Deep Fade

Fading Overview

Delay time

Sig

nal s

treng

th

TX Im

puls

e

F0Coherence bandwidth

TmMax excess delay

Received Impulses

F0 ~ 1/Tm

Time spreading

FourierTransform

time frequency

1 32Symbols

1 Flat fading

Frequency selective

Fading Overview

fcfc - fd fc + fd

T0 ~ 1/fd

Time variance

Fd = Doppler spreadTo

Coherence time

1 32Symbols

1

Slow fading

Fast fading

FourierTransform

time frequency

0

Fading Overview• Reduced signal-to-noise ratio (SNR)

large scale, flat fading, slow fading• Intersymbol interference (ISI)

frequency selective fading• Must account for total fading margin in link budget analysis

Delay spread

Tu

Transmitter

Receiver

Time

Time

1 2 3

1 2 3

Tx

Rx

ISI causes symbol spreading

Agenda

Fading OverviewMitigation

Test Methods

Mitigation

Error correctioninterleaving and coding

Diversityin timein spacein frequency

Device design Rake receiver

Mitigation

Data

Effects of Direct Spreading

PN SequenceGenerator

PN SequenceGenerator

Demod

JammingSignal

Data

Agenda

Fading OverviewMitigation

Test Methods

Test Methods

fcfc - fd fc + fd

dc

d

cd

fff

ffff

fS <−

−−

∝2

1

1)(

• No line of sight • Deep fades separated by

half-wavelength on average• Worst-case scenario

ThresholdRayleigh

fc = carrier freq, fd = Doppler spread

Non-fade

periodFade

Test Methods

fcFc - fd Fc + fd

Fc + 0.7fdpathdirect Rician of arrival of angleRcθ

componentRicianofpoweroftcoefficienRcP

componentRayleighofpoweroft coefficienRyP

,

12

=

=

=

<−

−−+

−−

∝

wherefffif

]fθfc)δ[(fP

fffπf

PS(f)

dc

dRcRc

d

cd

Ry

• Rayleigh + direct path• Good for rural areas • K factor ratio between

direct path and NLOS paths

Rician

ν

α

ray

Test Methods

Rayleigh

Log-normal

Antenna displacement (or time)

Sig

nal p

ower

• Log-normal + Rayleigh fading

• Rayleigh represents small scale fading

• Log-normal represents large-scale fading

Suzuki

cdma2000 MS Fading Tests

Channel Section TestBroadcast

control channel

3.3.4 Demodulation performance in multipath fading

3.4.2 Demodulation performance in multipath fading

3.4.7 Demodulation performance in multipath fading with closed loop power control (FPC_MODE = '000' )

3.4.8 Demodulation performance in multipath fading with closed loop power control (FPC_MODE = '010' )

3.4.9 Demodulation performance in multipath fading with closed loop power control (FPC_MODE = '000' , '001' , and '010' )

3.4.10 Demodulation performance in multipath fading with closed loop power control (FPC_MODE = '000' ) and transmit diversity

3.4.11 Demodulation performance in multipath fading with closed loop power control (FPC_MODE = '010' ) and transmit diversity

Forward traffic

channel

Test Methods

Test Methods

AWGNGenerator

BTS Emulator

Tx

Rx

Tx/Rx

MSUnder Test

Channel Simulator Σ

cdma2000 MS Receiver Testing standard setup

Test Methods

1 1 1 (8 km/h, 2 paths)

2 1 3 (30 km/h, 1 path)

3 1 4 (100 km/h, 3 paths)

4 2 1 (8 km/h, 2 paths)

5 2 3 (30 km/h, 1 path)

6 2 4 (100 km/h, 3 paths)

Channel Simulator Configuration Number

Radio ConfigurationCase

Parameter Units Test 1 Test 2 Test 3Îor/Ioc dB

dB

(1): -16.1 (1): -13.5 (1): -11.5(2): -16.1 (2): -13.5 (2): -11.5(3): -17.2 (3): -16.0 (3): -15.2

ÎocdBm/

1.23MHData Rate bps

(1): 6.8 (1): 9.4 (1): 11.4

(2): 6.8 (2): 9.4 (2): 11.4(3): 5.7 (3): 6.9 (3): 7.7

Channel Simulator

Configuration

-63

dB

8

-7

(1): BC 5 and 11; (2): BC 0, 2, 3, 7, 9, 10 and 12; (3): BC 1, 4, 6 and 8.

9600

dB

1

orc

IEPilot

or

cI

E Traffic

t

bN

E Traffic

1 2 3 4 5 6Band Classes0, 2, 3, 5, 7, 9, 10, 11 and 12Band Classes1, 4, 6 and 8

2 2 1 3 2 1

0 0 N/A 0 0 N/A

N/A N/A N/A -3 N/A N/A

0 0 0 0 0 02 2 N/A 2 2 N/A

N/A N/A N/A 14.5 N/A N/A

Channel Simulator Configuration

0 3

Parameters

8 30 30 100

100 0 3

Number of Paths

8 14 30

Delay from Path 3 to

Vehicle Speed [km/h]

Path 2 Power (Relative to Path 1) [dB]

Path 3 Power (Relative to Path 1) [dB]

Delay from Path 1 to Delay from Path 2 to

Verify that the FER stays below a certain value under standard channel simulation

conditions

Example test 3.4.2 Demodulation of Forward Traffic Channel in multipath

Test Methods

Add AWGN

ADC

Loss

Measure output power

Add noise

Measure total power

Average

RF In Digitized sample

Add fading

Loss

DAC

RF Out

RayleighLog-normal

Rician

Errors from conversion loss increase uncertainty

Adding calibrated noise is difficult and time-consuming

Conversion Loss and Noise Calibration

Process must be repeated for any change in power!

Test Methods

• Reconfigurable FPGA technology• Intuitive user interface

•Test Set or•Signal Generator

• Digital connectivity• ease of use and error reduction

Digital bus

1) Test Set or Signal Generator generates baseband signal.

2) Baseband waveform is sent to PC over digital bus

3) Signal is faded and AWGN is added in PC4) Baseband signal is sent back to Test Set for

upconversion to RF

RF

DUTAll digital fading simulator

Test MethodsAll digital – calibrated and integrated noise

ConventionalRF Fader

AWGN Source

Power Meter

Power Meter

Power MeterRF Output

Faded RF Signal with AWGN

Combiner

DirectionalCoupler

DirectionalCouplers

Signal Source

Digital bus

Test SetPC

old method

new method

TestingPreconfigured setups for major cell standards

Test Methods

Baseband Studio for FadingFade real-time signals coming from 8960

High Speed Digital Bus

DUT

Faded signals to DU

T

RF

8960 Series 10 Test Set with W-CDMA and cdma2000 Lab Applications

Fading with call processing

References

•Bernard Sklar; Rayleigh Fading Channels in Mobile Digital Communication Systems Part I: Characterization; IEEE Communications Magazine; July 1997

•Bernard Sklar; Rayleigh Fading Channels in Mobile Digital Communication Systems Part II: Mitigation; IEEE Communications Magazine; July 1997•Theodore Rappaport; Wireless Communications: Principles and Practices; Prentice Hall PTR; 1996

•Victor Shtrom, Jose Tellado, A. Paulraj; Designing MIMO systems for reliable coverage in non-LOS wireless links; RF Design; October 2002

•Wally Rasmussen; Simulating the Complex Multipath Signal Conditions of the Mobile Radio Environment; Hewlett-Packard Wireless Communications Symposium; 1993

•www.howstuffworks.com

For more information, please visit

www.agilent.com/find/basebandstudio