a d v a n c i n g w i r e l e s s t e s t

Testing the Radio Performance of Testing the Radio Performance of TETRA Terminals and Base StationsTETRA Terminals and Base Stations

44thth TETRA World Congress, Nice, 10 TETRA World Congress, Nice, 10thth December 2001 December 2001

Clive Rodmell Graham Stevens

Senior Principal Engineer Product Manager

2

a d v a n c i n g w i r e l e s s t e s t

Overview of PresentationOverview of Presentation

Understanding the impact of TETRA equipment performance on network operation

Examining the new radio performance requirements of TETRA compared with analogue systems

Analyzing the new challenges of testing TETRA equipment

Evaluating test solutions for TETRA

3

a d v a n c i n g w i r e l e s s t e s t

The Impact of TETRA Equipment Performance...The Impact of TETRA Equipment Performance...

Understanding the impact of TETRA equipment performance on network operation

Examining the new radio performance requirements of TETRA compared with analogue systems

Analyzing the new challenges of testing TETRA equipment

Evaluating test solutions for TETRA

4

a d v a n c i n g w i r e l e s s t e s t

TETRA is a RADIO network The radio link is the weakest link in the chain

TETRA Network OperationTETRA Network Operation

Validation

Proves the theory of network operation

Manufacture

Ensures individual equipment meet

requirements initially

Service

Ensures individual equipment continues to

meet requirements

Conformance

Proves the equipment design

5

a d v a n c i n g w i r e l e s s t e s t

Requirements for TETRA Network IntegrityRequirements for TETRA Network Integrity

Correct BS transmit power level for coverage required

Correct MS transmit power level as dictated by network

Adequate sensitivity of MS and BS receivers

Minimal interference caused to other users

Minimal susceptibility to signals from other users

Protection and maintenance of antennas and cables

6

a d v a n c i n g w i r e l e s s t e s t

The Impact of Poor Radio PerformanceThe Impact of Poor Radio Performance

Interference Excess power

Reduced coverage Inadequate power

Inadequate sensitivity

Retransmissions Increased response times

Reduced system capacity

Poorer quality speech and video

Failure to set up or maintain a call

7

a d v a n c i n g w i r e l e s s t e s t

New Radio Performance Requirements of TETRA... New Radio Performance Requirements of TETRA...

Understanding the impact of TETRA equipment performance on network operation

Examining the new radio performance requirements of TETRA compared with analogue systems

Analyzing the new challenges of testing TETRA equipment

Evaluating test solutions for TETRA

8

a d v a n c i n g w i r e l e s s t e s t

TETRA compared with Analogue systemsTETRA compared with Analogue systems

TETRA is a TDMA system

(Time Division Multiple Access)

TETRA is a DIGITAL system

TETRA is a CONTROLLED LINK system

9

a d v a n c i n g w i r e l e s s t e s t

216Scrambled Bits

14Bits

TrainingSequence

16Bits

216Scrambled Bits

14.2 msTypical slot

1 3 42 56.7 msTDMA Frame

Air Interface - TDMA IllustratedAir Interface - TDMA Illustrated

1.02 s1 3 182 4Multiframe

1 2 4 5 60 61.2 s3Hyperframe

10

a d v a n c i n g w i r e l e s s t e s t

TETRA Power Profile MaskTETRA Power Profile Mask

Transmitted power of a TDMA signal is BURSTY

Power is transmitted in short bursts

t 1 t 3

-70 dBc

+6 dB

0 dBc

+3 dB

of nominal power

1.5 dB-+

t 2

(time intervals not to scale)

11

a d v a n c i n g w i r e l e s s t e s t

Performance Requirements of a Performance Requirements of a TDMA SystemTDMA System

Power ramp up / down according to mask

Controlled profile to minimize interference Adjacent channel power due to switching

Timing of bursts must be correct

Power is attenuated between

bursts

Non-constant envelope

ActiveTimeslot

Power

-1 +1 Time+2

-70 dBc(MS)

Consequences of a bursty signal

12

a d v a n c i n g w i r e l e s s t e s t

Performance Requirements of the Performance Requirements of the Digital SystemDigital System

All transmitted signals are binary data Successful transmission and recovery of 1’s and 0’s

Requirements for Parametric measurements change

Vector accuracy replaces distortion for Tx measurements Vector Diagrams

Bit Error Rate (BER) replaces SINAD for Rx sensitivity RF Loopback

Synchronization of MS to BS frequency and timing

13

a d v a n c i n g w i r e l e s s t e s t

Vector AccuracyVector Accuracy

0.3R - Peak Vector Error(limit 30 %)

0.05R - Residual Carrier Leak Removed (limit 5 %)

RMS Vector Error limit 10 %

R

Q

I

14

a d v a n c i n g w i r e l e s s t e s t

Measuring sensitivity requires the use of BER measurements

Measuring Rx SensitivityMeasuring Rx Sensitivity

Test PortT1 SignalGenerator

RadioUnder Test

Bit ErrorRate meter

RF

MS BS

Static -112 dBm -115 dBm

Faded -106 dBm-103 dBm

15

a d v a n c i n g w i r e l e s s t e s t

UUT

Test Equipment

Tx

Rx

Returned patterns

Test patterns

RF Loop Back Test ConfigurationRF Loop Back Test Configuration

Optimized for manufacturing and service testing

Eliminates need for proprietary interfaces and test modes

16

a d v a n c i n g w i r e l e s s t e s t

TETRA radios operate at defined power ratings MS power level is variable in defined steps

A TETRA radio determines optimum power level itself This requires measurement by MS of received signal

strength MS determines level and quality of signals from serving

and neighboring BS

30 mW

Performance required of a Performance required of a Controlled Radio LinkControlled Radio Link

MS power is optimized

Reduces interference

Increases battery life

17

a d v a n c i n g w i r e l e s s t e s t

TETRA’s co-existence with AnalogueTETRA’s co-existence with Analogue

TETRA system is very highly specified to avoid interference with analogue systems

In terms of both close to carrier and far from carrier emission

The following may cause interference to analogue radio channels

Adjacent Channel Power (ACP)

TETRA Power Ramping (Switching)

TETRA Transmitter Linearization

TETRA Transmitter Intermodulation

This has presented some CHALLENGES in TESTING

18

a d v a n c i n g w i r e l e s s t e s t

TETRA’s co-existence with AnalogueTETRA’s co-existence with Analogue

Analogue signals may cause interference in the TETRA Receiver Blocking Spurious Response Intermodulation Response

Measures performance in the presence of two strong interfering signals

Reference Sensitivity

WantedChannel

200kHz

-47 dBm

+3 dB

T1 T3

400kHz

T2

19

a d v a n c i n g w i r e l e s s t e s t

New Challenges of Testing TETRA Equipment New Challenges of Testing TETRA Equipment

Understanding the impact of TETRA equipment performance on network operation

Examining the new radio performance requirements of TETRA compared with analogue systems

Analyzing the new challenges of testing TETRA equipment

Evaluating test solutions for TETRA

20

a d v a n c i n g w i r e l e s s t e s t

Conventional Test Methods Unsuitable for TETRAConventional Test Methods Unsuitable for TETRA

Most conventional analogue test methods can not be used

Traditional power meter does not work for burst power

Traditional frequency meter does not work for DQPSK modulation

1 kHz distortion meter does not work for digital transmitter

1 kHz SINAD meter does not work for digital receiver

Conventional swept spectrum analyzer is inadequate

New Innovative methods are required

21

a d v a n c i n g w i r e l e s s t e s t

New Testing Challenges for TETRA TxNew Testing Challenges for TETRA Tx

Most TETRA Tx measurements

Must be TETRA filtered

>80 dB Require high dynamic range

Must be time-aligned

22

a d v a n c i n g w i r e l e s s t e s t

T3T2 T1

New Testing Challenges for TETRA RxNew Testing Challenges for TETRA Rx

Key RF Rx measurements: Sensitivity

Selectivity

Intermodulation Response

Spurious Response

Blocking

These tests require the use of: TETRA signal generator (T1)

One or two interfering signals TETRA interferer (T2)

CW interferer (T3)

Test system performance must be considerably better than the equipment under test Minimize influence on results

23

a d v a n c i n g w i r e l e s s t e s t

Evaluating Test Solutions for TETRA Evaluating Test Solutions for TETRA

Understanding the impact of TETRA equipment

performance on network operation

Examining the new radio performance requirements of

TETRA compared with analogue systems

Analyzing the new challenges of testing TETRA

equipment

Evaluating test solutions for TETRA

24

a d v a n c i n g w i r e l e s s t e s t

Interoperability Testing

Validation

R&D concentrate on a particular aspect

Manufacture

Fast and accurate

Service

Test functionality,

easily

Different stages of testing require different equipment

All testing requires specialized TETRA test equipment

Test Solutions for TETRATest Solutions for TETRA

Conformance

Comprehensive testing

25

a d v a n c i n g w i r e l e s s t e s t

Important Issues for Conformance TestingImportant Issues for Conformance Testing

Comprehensive radio equipment testing

RF Parametric

Protocol tests

Purpose is to prove to Users and Operators that radio equipment conforms to specification

Static

Dynamic

Using propagation simulator and Fading models

Automated system

26

a d v a n c i n g w i r e l e s s t e s t

Important Issues for ManufacturingImportant Issues for Manufacturing

All radio equipment is tested to a degree

Level of test is dependent on:

PASSED

Test 1 passed Test 2 passed Test 3 passed Test 4 passed Test 5 passed Test 6 passed

Design repeatability

Manufacturing process

Speed of testing required

Remote control of test equipment

Quality Control

Level of testing reduces as TETRA technology matures

27

a d v a n c i n g w i r e l e s s t e s t

Test Solutions for TETRA Equipment ManufactureTest Solutions for TETRA Equipment Manufacture

TETRA specific modulation analyzer for Tx measurements

High dynamic range

Accurate implementation of TETRA filter

Speed of test important

T1 or similar signals required for receiver testing

Dynamic (faded) receiver tests usually too time consuming

28

a d v a n c i n g w i r e l e s s t e s t

TETRA Installation and ServicingTETRA Installation and Servicing

Important issues

Ease of use of test equipment

Subset of measurements required for manufacturing

Test solution

RF Loopback eliminates special test connectors

Functional tests (registration, call set-up)

Give confidence that TETRA radio is dependable

29

a d v a n c i n g w i r e l e s s t e s t

IFR’s Support for TETRAIFR’s Support for TETRA

Support the TETRA standard

Actively involved in development of standards

ETSI EN 300 394-1 Radio Conformance Specification

TETRA Interoperability Profile (TIP)

Supply equipment for radio conformance testing

Supply equipment for interoperability testing

Participate in the Interoperability trials

Working with the radio manufacturers to provide Production Test solutions

Ensuring effective test equipment for service is available

30

a d v a n c i n g w i r e l e s s t e s t

and Finally .....and Finally .....

TestingEnsuresTrustReliabilityAvailability