DIGITAL RADIO SYSTEM

1. AN AUDIO QUALITY
EVALUATION OF DIGITAL
RADIO SYSTEMS
GUIDED BY; PRESENTED BY;
MR. ANOOP CHANDRAN P ROJITH THOMAS
ASST. PROFESSOR MTECH-ECE
CAARMEL ENGG. COLLEGE CAARMEL ENGG. COLLEGE

2. SCOPE
• It is to provide a Broadcasting Standard for the Digital
Audio Systems designed for delivery of high quality
digital audio programme and data services for
mobile,portable and fixed reception from terrestrial or
satellite transmitters in the VHF/UHF as well as for
transmission through cable networks

3. INTRODUCTION
• Radio has changed the world of communication

during the last decade and even now remains
relevant in modern society.
• Nikola Tesla was the first to talk about utilizing these
signals for the use of communication.Macroni is the
first who introduced the radio system.
• Radio is the medium for communication. It transmits
message via Radio waves.And It is a communication
system based on broadcasting electromagnetic waves

4. • Mainly there are two types of radio systems;
a)Analog Radio System
b)Digital Radio System
• Major criteria for designing radio system is;
1)Audio Quality
2)Channel Capacity
• Radio is a democratic medium. So it has wide applications
in the field of Education,Entertainment,Medical,News and
even for Businesses also.

5. EXISTING SYSTEM
• The Existing System is Analog radio Systems
• They are divided into two;
>AM Radio Broadcasting Systems.
>FM Radio Broadcasting Systems.
• AM Broadcasting System is mainly divided into;
>Mid frequency:530 to 1600 KHz
>Short Wave 1 &2
SW1:2.3 to 7.0 MHz
SW2:7.0 to 22 MHz
• FM Radio Ranges from 88 to 106 MHz

6. EVALUATION OF EXISTING
SYSTEM
• Evaluation of analog radio system is mainly done for FM
system using MUSHRA Method.
• The Audio Quality for Analog Broadcasting systems are;
>FM :72% -Good
>SW2 :63% -Fair
>SW1 :60% -Fair
>MF :40% -Fair
• From this we can conclude that the audio quality of
analog system is not suitable for providing better
service.

7. DISADVANTAGES
• It has Transmission and Reception limitations.
• Due to increase in the usage of number of bands, the
congestion is occurs and it lead to the decline in
reception quality.
• It suffers to provide uniform reception quality
throughput.
• Insufficient use of spectrum; Spectrum Efficiency is low.
• It offers poor audio quality due to less Noise immunity.

8. PROPOSED SYSTEM
• In order to provide better quality of service, the digital
radio system is introduced.
• The digital radio transmitter compresses the audio
signals using an AUDIO CODEC and it transmits as bit
streams to the terminals
• And at receiver; the reconstruction of signal is occur
from bit streams.
• Digital system has capability to transfer through
terrestrial, satellite and even through cables.

9. ADVANTAGES
• More robust than analog and it can be transmitted
successfully at lower transmitter power.
• It uses Coded Multi carrier Modulation(PCM) in order
to provide improved reception quality.
• Provides wide coverage area with less implementing
cost.
• Spectrum efficiency is improved and also provide high
channel capacity.
• Introduction of data compression techniques help to
improve sound quality at low bit rates.

10. EVALUATION OF AUDIO QUALITY
• The evaluation is mainly for finding the mean audio
quality of all systems.
• In order for that; four terrestrial digital domestic radio
systems are considered. They are;
>DAB
>DAB+
>HD Radio
>T-DMB
• Each system has its own audio codecs.So,the audio
quality depends not only on the Bit Rate but also upon
the System type.

11. • Evaluation is at different bit rates in order to provide a
reference to determine Optimal Bit Rate for given
target audio quality.
• The Audio Quality adopted for each system are;
>DAB :MPEG-1 LAYER II(.mp2)
>DAB+ :HE-AAC v2(.aac)
>HD RADIO :HDC(.hd)
>T-DMB :MPEG-4 ER-BSAC(.mp4)
• In order to get accurate results, the evaluations has
setup in the same environment for all systems.
• The evaluation process is conducted in two phases
named as;
>PHASE-I >PHASE-II

12. EVALUATION SETUP
• Evaluation setup mainly consist of;
>Audio Samples
>Digital Radio Equipment
• The evaluation process are;
>Test Signal Acquisition.
>Subjective Evaluation Method(MUSHRA).
>Pre Screening And Post Screening.

13. AUDIO SAMPLES
• The audio samples used for test should be able to
recognize the performance difference between the
codecs and contain the realistic contents for the
digital radio services.
• Nine audio samples are used for evaluation and are
subdivided into different categories.
• The sample length for each sample is 10-15 seconds
and in stereo format with sampling frequency of 48
KHz.
• In HD Radio, it supports only the sampling rate of
44.1KHz.So audio samples with sampling rate of
44.1KHz were prepared from 48KHZ.

14. AUDIO SAMPLES USED IN EVALUATION
NAME TYPE CHARACTERISTICS
FEMALE,ENGLISH SINGING
SPEECH
MALE,KOREAN COLLOQUIAL STYLE
FEMALE ,ENGLISH LITERARY STYLE
POP MUSIC VOCAL,GUITAR,DRUM,KEYBOARD
MUSIC JAZZ WIND,BRASS,DRUM
CLASSICAL STRINGS,PERCUSSION,WIND
SPEECH+MUSIC MALE SPEECH,STRINGS,WIND.
PERCUSSIONS
MIXED SPORTS BROADCASTING FEMALE SPEECH,AUDIENCE SHOUTING
CHILDREN’S SONG,PERCUSSION,
SONGS+BACKGROUND SOUND EFFECT

15. DIGITAL RADIO EQUIPMENT
SYSTEM MANUFACTURE AND MANUFACTURER AND
ENCODER MODEL DECODER MODEL
DAB Factum Electronics PNP Network
MAP250E Technologies
PN3021P
DAB+ Factum Electronics PNP Network
MAP250E Technologies
PN3021P
HD Radio Broadcast Electronics Day Sequerra
Xpi 10 M4.0X
T-DMB Pixtree PNP Network
Pix VR-E11011 Technologies
PN3021P

16. TEST SIGNAL ACQUISITION
• The test signal for evaluation are acquired directly
from digital radio equipment.
• Audio signal is played from computer and transmitted
to audio encoder in the form of PCM through audio
interface equipment.
• The sampling rate is selected according to digital radio
system.
• Audio encoder compress audio signal to bit stream
and transmitted through wireless channel using
OFDM.
• In reciever,decoder converts bit streams to audio
signals and saved in computer as PCM format.

17. BLOCK DIAGRAM
DIGITAL
AUDIO RF
COMPUTER1 AUDIO
ENCODER TRANSMITTER
INTERFACE
OFDM
AUDIO RF
COMPUTER 2
DECODER RECEIVER

18. • In evaluation, the bits rate of encoder is set for
different values.
• Therefore,
4 bit rates X 4 Systems X 9 Samples=144 test signals
is used for evaluation.
• Test Bit Rates used for evaluation is ;
SYSTEMS DAB DAB+ HD RADIO T-DMB
64 24 24 48
BIT RATE 96 48 28 64
(Kbps) 128 64 64 96
192 96 96 128

19. SUBJECTIVE EVALUATION METHOD
• Subjective Evaluation is done by using MUSHRA
Method(Multiple Stimuli With Hidden Reference And
Anchor).
• It uses STEP ver.0.10 Program and which is provided by
Audio Research Lab(ARL).
• In this method, the grading system is provided with
each audio samples.
• In this method contains;
>REFERENCE AND HIDDEN REFERENCE SIGNAL.
>ANCHORS.
>TEST SIGNALS.

20. TESTING ENVIRONMENT

21. • In phase 1 test, evaluates the audio quality for each
system(evaluation of four bit rates of each system).
• On every trials each subjects(listeners) randomly
listens;
1 REF+1 HR+2 ANC+4 SIG(diff. bit rate)=8 SIGNALS
• So it conducts 4 system X 9 audio samples=36 trials.
• In Phase 2 test, evaluates the audio quality as a
function of four systems.
• On every trials each subjects(listeners) randomly
listens;
1 REF+1 HR+2 ANC+4 SIG(diff. system)=8 SIGNALS
• So it conducts 2 groupsX9 audio samples=18 trials.
• After each trial, the listener marks the grade.

22. PRE SCREENING AND POST SCREENING
• In order to provide a guaranteed audio quality
assessment, each listener must have a normal hearing
ability. So before main evaluation Pre-screening is
conducted.
• Nine different audio samples are impaired(processed)
using 3.5 and 7KHz LPF or an HE AAC v2 at 32kbps or
an HE-AAC V2 at 28 Kbps.
• Then participants first listen to the original sample and
after a short break again original and impaired signals.
Then they ask which is the original.
• This process continues for nine audio samples and pass
the test only when they give correct answer for 8 of 9.

23. • 22 listeners applied for evaluation test and one failed
the pre screening. So the remaining 21 listeners were
selected for final participation.
• After PHASE 1 test, a Post Screening test was
conducted in order to ensure a fair assessment of
quality.
• By analyzing of evaluation result of each listener, the
listeners who are believed to make consistent grading
and appropriate quality discrimination are selected.
• Six listeners failed in post screening, therefore
evaluation results of 15 were collected and statistical
analysis is performed for each subject data.

24. EVALUATION RESULTS
A.PHASE 1 TEST
• This figure shows the mean audio quality of each
system as a function of bit rates.

25. • It helps us to determine necessary bit rate for a given
target audio quality for each sub system.
• The quality of DAB at 64 and DAB+ at 24 kbps are
low. The reason is for this is encoders used are
optimized for higher bit rates.
• And also HD Radio at 96 kbps does not show
expected quality; the reason might be the non
optimized encoder.
B.PHASE 2 TEST
• It is to confirm evaluation consistency of PHASE 1.
• Two groups of similar audio quality were determined
from all of the members in each system.
> MID QUALITY >HIGH QUALITY

26. TEST SIGNAL SET IN A SINGLE TRIAL OF PHASE 1 AND 2
SYSTEM DAB DAB+ HD Radio T-DMB
64 24 24 48
96 48 48 64
BIT RATE
(Kbps) 128 64 64 96
192 96 96 128
- Test Signal for Phase 1 test.
- Test Signal for Phase 2 test.
GROUP OF TEST CASES USED IN PHASE 2 TEST
GROUP DAB DAB+ HD Radio T-DMB
MID QUALITY 128Kbps 48Kbps 48Kbps 64Kbps
HIGH QUALITY 192Kbps 96Kbps 96Kbps 128Kbps

27. • The mean audio quality of each groups;

28. C.ANALYSIS
• Comparing audio quality of the systems that was in
two phases.
• If the two grades of a system are in the range of
equality, then evaluation consistency between two
phases are guaranteed.
• The results of comparison is as;

29. • This unsatisfactory condition are occur due to;
>MUSHRA method measures the relative quality
among the test signals in each trial.
• In First Case: HD radio(High Quality Group)
>Each signals in the phase 2 test are higher value
signals in the PHASE 1.
>It can be explained as;

30. • In Second Case: T-DMB(Mid Quality Group)
>Each signals in the phase 2 test are higher value
signals in the PHASE 1.
>It can be explained as;
• This difference is occur due to relatively large
difference in their evaluation setup.

31. • From this; the mean audio quality of system is given
as;
FM
• DAB 128,HD RADIO 48,DAB+ 48,HD RADIO 64 provide
better audio quality than FM.
• DAB 64,T-DMB 96,DAB+ 96,T-DMB 128,DAB 192 can
provide better audio quality like CD.

32. CONCLUSION
• Subjective audio quality of 4 digital systems are
evaluated using MUSHRA METHOD using nine audio
samples.
• Evaluation process consist of two phases. Phase 1 is
for evaluating quality on the basis of function of bit
rates. Phase 2 is for evaluating on the basis of
functions of system.
• The results are compared and finally mean audio
quality is calculated.
• This results can be used as a reference to determine
the optimal channel capacity for a given target audio
quality.

33. REFERENCE
• F.HOFMANN,C.HANSEN AND W.SCHAFER,”DIGITAL RADIO
MONDIALE (DRM) DIGITAL SOUND BROADCASTING IN THE AM
BANDS , ”IEEEE TRANS. BROADCAST.,VOL.49,NO.,PP.319-328,
SEP . 2003.
• RADIO BROADCASTING SYSTEMS: DIGITAL AUDIO
BROADCASTING TO MOBILE , PORTABLE AND FIXED RECEIVERS ,
ETSI EN 300 401 VER 1.4.1.JAN 2006.
• “METHOD OF SUBJECTIVE ASSESSMENT OF INTERMIDATE
QUALITY LEVEL OF CODING SYSTEMS”,ITU-R BS.1534,2003.
• “SUBJECTIVE TRAINING EVALUATION PROGRAM”,ARL 2004.
• “EBU EVALUATION OF MULTICHANNEL AUDIO CODECS”,EBU
2007.
• “EBU LISTENING TEST ON INTERNET CODECS”,EBU TECHNICAL
REVIEW 2000.