digital radio and tv systems part 1 v.2

Digital Radio and TV Systems Part 1 V.2

Course at FH Technikum Wien

DI Peter Knorr

25.07.2014 Digital Radio and TV Systems Part I Seite 2

1924 first radio transmission in Austria

How it all began


1955 first television transmission in Austria

How it all began


1972 colour television in Austria

How it all began


2006 – 2011 analog switch off – start of digital terrestrial television

DVB-T in Austria

How we developed digital TV


2013 start of second generation of digital terrestrial television DVB-T2

in Austria

Next generation of digital television


Digitalization of Broadcast in 2014


Definitions

Broadcast is a point to multipoint system


Definitions

Mobile Communication is a point to point system


Analog TV (Do you remember ?)

Ghosting (Multi path)

Weak signal Electrical Interference

Transmitter Interference

Source: www.rsm.govt.nz


Bandwidth (use of existing TV channels in VHF and UHF)

Simulcast with analog signals without interference

Robustness against multipath reception

Single frequency network

Portable and fixed reception

Technical requirements for a new terrestrial digital TV system:


Bandwidth (use of existing channels in VHF)

Robustness against multipath reception (also in mobile situations)

Single frequency network

Mobile, portable and fixed reception

Technical requirements for a new terrestrial digital radio system:


Developing of a digital broadcasting system

But 1966 no processor power was available to realize this system


Video compression formats

1991 MPEG 1

1994 MPEG 2

2001 MPEG 4 (H.264)

2013 H265 MPEG = Moving Pictures Expert Group

Developing of a digital broadcasting system

Audio compression formats

MPEG 1 Layer 1,2,3 (1989-1992)

AAC (1997), HE-AAC,

Extended HE-AAC (2013)

Dolby Digital Audio AC-3 (1990)

Dolby Digital Plus (E-AC-3) AAC = Advanced Audio Codec


A digital standard definition video signal (SDTV) has a data rate of 270 Mbit/s

(SDI format = CCIR 601))

A digital HDTV signal has a data rate > 1 Gbit/s (HD-SDI format)

An uncompressed digital audio signal has a data rate of approx. 1.5 Mbit/s

(Audio-CD)

This high bit rates can be transported between cameras and studios only on

short distances or via fibre optic (dark fibre technology).

A transport via broadcasting or mobile systems is only possible if the signals

are data reduced.

Why is data reduction (compression) of digital signals necessary ?


Source: uncompressed video signal SD = 270 Mbit/s (CCIR 601)

Compression to MPEG2 / 4 Video Elementary stream 2-15 Mbit

Source: uncompressed HD video signal HD-SDI = 1.485 Gbit/s

Compression to MPEG2 (~ 2o Mbit) or MPEG4 (~ 10 Mbit)

Video elementary stream 1.5 …7 (15) Mbit/s

Data reduction (compression) of digital video signals


MPEG Video Compression (Encoding):

Analysis of moving parts and fix parts of pictures

Group of picture (GOP)

I, B and P frames

An I frame indicates the

beginning of a GOP. The I frames

contain the full image and do not

require any additional

information to reconstruct it.

P and B frames contains

motion-compensated difference

information relative to previously

decoded pictures

Data reduction (compression) of digital video signals

GOP (Group of Pictures)

I-FrameIntra

Frame CodedPicture

B-FrameBidirectional

PredictedPicture

B-FrameBidirectional

PredictedPicture

P-FramePredicted

Picture

I-FrameIntra

Frame CodedPicture

Forward Prediction

Backward Prediction


Source: uncompressed audio signal form studio AES/EBU= 2 Mbit/s

or Audio-CD ~ 1.5 Mbit/s

Encoded audio bit rates:

MPEG, AAC: 16,32,64,128,160,192,256,384 kbit/s

Dolby Digital AC3: 448 kbit/s

Data reduction (compression = Encoding) of digital audio signals


MPEG-2 Audio compression (Encoding):

Audio compression by using Psycho Acoustic Model of Human Ear.

Perceptual Coding = Irrelevancy Reduction + Redundancy Reduction

It is found that the ear has a certain threshold of hearing. Below this the signals are

inaudible.

Data reduction (compression) of digital audio signals

Source: Wikipedia


MPEG-2 Audio Compression (Encoding):

Frequency Masking:

If a strong sound is present on one frequency (Masker) then weaker sounds close to it

may not be heard because the threshold of hearing is modified

Data reduction (compression) of digital audio signals

Source: Wikipedia


Multiplexing of Video, Audio and Data

VIDEOENCODER

AUDIOENCODER

MU

LTIP

LEXE

R

270 Mbit/sSDI

2 Mbit/sAES/EBU

Data (Teletext …)

5 Mbit/s

192 kbit/s

300 kbit/s

5,5 Mbit/sMPEG2-TS


Multiplexing of more MPEG-TS

Video 1

Video 2

Video 3

Audio 1

Audio 2

Audio 3

Data 1

Data 2

Data 3

MPE

G2-

Mul

tiple

xer

MPEG2-TS

Enco

der

Enco

der

Enco

der

Transport Stream Multiplex

PID=

0x10

0PI

D=0x

200

PID=

0x30

0PI

D=0x

400

PID=

0x50

0

PID=

0x60

0PI

D=0x

100

PID=Packet Identifier


MPEG2-TS structure

188 Byte

Payload = 184 Byte

Header4 Byte

Sync

Byt

e =

1 By

te

Tran

spor

t Err

or In

dica

tor

= 1

bit

Pack

et Id

entif

ier P

ID13

bit

188 Byte

Payload = 184 Byte

Header4 Byte

Sync

Byt

e =

1 By

te

Tran

spor

t Err

or In

dica

tor

= 1

bit

Pack

et Id

entif

ier P

ID13

bit

Reed SolomonError Protection

RS (204,188)

204 Byte

Transport stream specifies a container format encapsulating packetized elementary streams, with error correction and stream synchronization features for maintaining transmission integrity when the signal is degraded.


Synchronization problem

PCR, or Program Clock Reference, is fundamental to the timing recovery mechanism for MPEG2 transport streams. PCR values are embedded into the adaptation field within the transport packets of defined PIDs.

MPEG2Encoder

Counter42 bit

MPEG2DecoderVideo, Audio Video, Audio

PCR intervalall

< 40 ms

PCR PCR

MPEG 2 - TS

STC = System Time Clock27 Mc

Counter

STC – 27Mc

NumericallyControlledOscillator


Additional Data in the MPEG-TS

MPEG-2 Program Specific Information PAT Program Association Table (list of all programs in the TS) PMT Program Map Table (contain information about programs) CAT Conditional Access Table

DVB SI Service Information NIT Network Information Table (info about name, RF parameter) SDT Service Descriptor Table BAT Bouquet Association Table (info about all services) EIT Event Information Table (Event info, EPG - program guide) TDT Time & Date Table (current time and date in UTC) TOT Time Offset Table (local time offset) RST Running Status Table (running status, delays ..) ST Stuffing Table


DVB Project

The DVB Project is an Alliance of about 200 companies, originally of European origin but now worldwide. Its objective is to agree specifications for digital media delivery systems, including broadcasting. It is an open, private sector initiative with an annual membership fee, governed by a Memorandum of understanding (MoU). The Members of the DVB project develop and agree specifications which are then passed to the European standards body for media systems, the EBU / CENELEC / ETSI Joint Technical Committee, for approval. The specifications are then formally standardised by either CENELEC or, in the majority of cases, ETSI.

Source: DVB Project


DVB Project developed a transport systems for digital broadcasting

Source: DVB Project www.dvb.org


DVB and other digital television systems

www.dvb.org


At the end we need a standard


DVB Workflow

Mathematical theory

Codingtheory

Digital processingtechniques U

nive

rsity

and

DVB

Pro

ject

wor

k ETSIStandard

Prototypetest

End productionRF

technology

IntegratedCircuit

technology


Basics of digital signal processing

Why broadcast needs digital transmission: Solve problems with multipath reception and other interference Better signal (picture and audio) quality and more robustness More information capacity (more TV or Radio programs over one

channel) Band width Power consumption (really ? – discussion), RF power, rack space Higher data security (encryption systems easier to integrate) User friendly (EPG, Scan, Data Services, Recording PVR, OTA Update)


Basics of Coding

Encode source information, by adding additional information, sometimes referred to as redundancy, that can be used to detect, and perhaps correct errors in transmission. The more redundancy we add, the more reliably we can detect and correct errors, but the less efficient we become at transmitting the source data


Signal processing before modulation

BasebandInterface

Energydispersal

ReedSolomonEncoding

TimeInterleaver

ConvolutionalCoder

Puncturing

MPEG2TS

FEC 1OuterCoder

FEC 2InnerCoder

Code Rate1/2...7/8

IQ



DVB-T and DVB-S use 2 coding algorithms : • Block Code = Reed Solomon Code • Convolutional Coding and Scrambling and Interleaving

Scrambler Reed SolomonCoder

TimeInterleaver

ConvolutionalCoder



Scrambler (energy dispersal) Use an algorithm that converts an input string into a seemingly random output string of the same length, thus avoiding long sequences of bits of the same value; in this context, a randomizer is also referred to as a scrambler. Time Interleaver Interleaving is widely used for burst error correction Example: Error-free code words: aaaabbbbccccddddeeeeffffgggg Interleaved: abcdefgabcdefgabcdefgabcdefg Transmission with a burst error: abcdefgabcd____bcdefgabcdefg Received code words after deinterleaving: aa_abbbbccccdddde_eef_ffg_gg


Basics of Coding

Block Code – Reed Solomon Reed-Solomon might well be the most implemented algorithm. Barcodes use it; every CD, DVD, RAID6, and digital tape device uses it; so do digital TV Reed-Solomon belongs to a family of error-correction algorithms known as BCH (Bose-Chaudhuri-Hocquenghem-Codes). It’s part of the FEC (Forward Error Correction) group. Reed-Solomon was introduced by Irving S. Reed and Gustave Solomon of MIT Labs in Polynomial Codes Over Certain Finite Fields, which was published in the Journal of the Society for Industrial and Applied Mathematics in 1960.


Basics of Coding

Reed Solomon code In DVB Reed Solomon Code (“Outer Coder”) can correct 8 Byte Errors or 58 continue bit errors in a codeword. In the MPEG-TS the RS-Coder add additional 16 checkbytes to the 188 Databyte RS (204,188)


Basics of Coding

Convolutional Coder (inner coding) Convolutionally encoding the data is accomplished using a shift register and associated combinatorial logic that performs modulo-two addition. • The Convolutional code is used over a noisy channel • The encoder is very simple to implement • But the decoding is quite complex • The basic code rate is ½ (called “Mother Code”) • The Viterbit algorithm is currently used for decoding

Modulo two


Basics of Coding

Convolutional Coder (inner coding) with puncturing Puncturing is the process of removing some of the parity bits after encoding with an error correction code. A pre-defined pattern of puncturing is used in the encoder. Then, the inverse operation, known as depuncturing, is implemented by the decoder

Source: rohde&schwarz


Bit Error Rate

The bit error rate or bit error ratio (BER) is the number of bit errors divided by the total number of transferred bits during a studied time interval. For example: 1 bit error in 100 transferred bits = 1/100 = 0.01 = 1E-2 = 1 * 10-2

The BER is 1E-2 Normally at the receiver input the BER is around 1E-2 The first FEC Decoder (Viterbi) should reach a BER at 2E-4 at the output. Than the Reed Solomon Decoder can reach a BER of 1E-11 called QEF (Quasi Error Free) – 1 bit error during a period of 1 hour !!


Bit Error Rate

DVB-SFrontend

ViterbiDecoder

ReedSolomonDecoder

MPEG2TS

FEC 2Outer

Decoder

BER<E-2 BER<2E-4than QEF

ispossible

BER<1E-11QEF

1 error/hour

MPEG2Decoder

FEC 1Inner

Decoder


Basics of digital Modulation

To transmit a signal over the air, there are three main steps: A pure carrier is generated at the transmitter The carrier is modulated with the information to be transmitted At the receiver the signal modifications or changes are detected and demodulated There are only three characteristics of a signal that can be changed over time: Amplitude Phase Frequency



AM – Amplitude Modulation In AM, the amplitude of a high-frequency carrier signal is varied in proportion to the instantaneous amplitude of the modulating signal

Source: Wikipedia



FM – Frequency Modulation In FM, the amplitude of the modulating carrier is kept constant while its frequency is varied by the modulating signal



PM – Phase Modulation In PM, the angle of the carrier wave is varied by the incoming signal



Amplitude and Phase Modulation together Polar Display A simple to view amplitude and phase is with the polar diagram. The carrier becomes a frequency and phase reference and the signal is interpreted relative to the carrier. Both are uses in digital communication systems.

Source: Agilent



Different forms of modulation in polar form

Source: Agilent



In digital communication, modulation is often expressed in terms of I and Q. This is a rectangular representation of the polar diagram. The I axis lies on the zero degree phase reference, and the Q axis is rotated by 90 degrees.

Source: Agilent



Mapping for QPSK modulation

Serial toParallel

Conversion

I/QLook-Up

Table

I

Q

data bits

01101..

BIT 1 BIT 0 I Q 0 0 +1 +1 0 1 -1 +1 1 0 -1 -1 1 1 +1 -1



Why use I and Q ? Digital modulation is easy to accomplish with I/Q modulators. Most digital modulation maps the data to a number of discrete points on the I/Q plane. These are know as constellation points.

Source: Agilent transmitter receiver



Constellation points – constellation diagram – state diagram Each point is a “symbol”

QPSK 2 bit per symbol

16-QAM 4 bit per symbol

64-QAM 6 bit per symbol



Any fast transition in a signal will require a wide occupied bandwidth. Filtering of rectangular pulses allows the transmitted bandwidth to be reduced without losing the content of the digital data. In DVB we use a so called “Raised Cosine Filter”



Modulation format Theoretical bandwidth efficiency limits QPSK 2 bit/second/Hz 8PSK 3 bit/second/Hz 16 QAM 4 bits/second /Hz

32 QAM 5 bits / second /Hz

64 QAM 6 bits / second / Hz

But these figures cannot be achieved since they require perfect modulators, demodulators, filter and transmisssion paths. In real case of QPSK we need around 1,3Hz/Symbol A Symbolrate of 6 Msymb./sec. needs approx. 7,8 Mc Bandwidth



DVB Modulation

DVB-T QPSK, 16-QAM, 64-QAMDVB-T2 QPSK, 16-QAM, 64-QAM, 256-QAMDVB-S QPSKDVB-S2 QPSK, 8-PSK, 16-APSK, 32-APSK, DVB-C 16-QAM, 32-QAM, 64-QAM, 128-QAM, 256-QAMDVB-C2 16-QAM, 32-QAM, 64-QAM, 128-QAM, 256-QAM,

1024-QAM, 4096-QAMDAB+ DQPSKDRM 16-QAM, 64-QAMDRM+ QPSK, 16-QAM


dB Definition

The decibel (dB) is a logarithmic unit used to express the ratio between two values. The decibel confers a number of advantages, such as the ability to conveniently represent very large or small numbers, and the ability to carry out multiplication of ratios by simple addition and subtraction. For RF applications we use following formular: dB = 10 * Log (Power Output / Power Input) Example: Power Output: 100 Watt Power Input: 50 Watt dB = 10 * Log ( 100 / 50 ) = 10 * Log (2) = 3 dB


dB Definition

Other example: A DVB-T transmitter needs 7 dB less power for the same reception performance as an analog transmitter dB = 10 Log (P1/P2) 10dB/10

= P1/P2 107/10

= P1/P2 100.7

= P1/P2 = 5.01 Normally a strong analog TV transmitter had 20 kW. The same performance (reception) is possible with an 4 kW DVB-T Transmitter !


Time Domain vs. Frequency Domain

Source: Agilent Technologies


Frequency Domain measurement

Spectrum Analyzer


Time Domain measurement

Oscilloscope


DVB-T


DVB-T Facts

Constellation QPSK, 16-QAM, 64-QAM FEC CC + Reed Solomon Code Rate 1/2, 2/3, 3/4, 5/6, 7/8 Guard Intervall 1/4, 1/8, 1/16, 1/32 FFT Size 2K, 8K Scattered Pilots 8% of total Continual Pilots 2,6% of total Bandwidth 5,6,7,8 MHz Max. Bitrate 31,66 Mb/s Modulation COFDM


DVB-T Facts

Standard: ETS 300 744 Digital Video Broadcasting; Framing structure, channel coding and modulation for digital Terrestrial television (DVB-T) Modulation: COFDM = Coded Orthogonal Frequency Division Multiplex = multicarrier transmission C = Forward Error correction O = Orthogonal (no cross talk between carriers) FDM = information distributed over many subcarriers


Channel

Gaussian channel – direct line of sight between TX and RX (roof top antenna situation)


Channel

Rice channel – a dominant line of sight between TX and RX


Channel

Rayleight channel – no line of sight between TX and RX, many objects attenuate, reflect, refract and diffract the signal


DVB-T – Why we need a multicarrier transmission ?

8 MHz UHF Channel 8 MHz UHF Channel

f f

A (f)A (f)

ANALOG TVAll informationin one carrier

MulticarrierInformation spreadover many carriers

DVB-T: Information distributed over thousands of subcarriers Solving fading problems


DVB-T – Multicarrier modulation

Rather than carrying one data carrier on a single television frequency channel, COFDM works by splitting the digital data stream into a large number of slower digital streams, each of which digitally modulate a set of closely spaced adjacent subcarrier frequencies. In the case of DVB-T, there are two choices for the number of carriers known as 2K-mode or 8K-mode. These are actually 1,705 or 6,817 subcarriers that are approximately 4 kHz or 1 kHz apart. Each subcarrier is modulated. In this example with 16-QAM.

Channel bandwidthf

A (f)

f



Orthogonality condition: An OFDM signal consists of a number of closely spaced modulated carriers. Although the sidebands from each carrier overlap, they can still be received without the interference that might be expected because they are orthogonal to each another. This is achieved by having the carrier spacing equal to the reciprocal of the symbol period.

Source: rohde&schwarz



Orthogonality condition: f = 1 / t



But how we can produce thousands of orthogonal subcarriers ? In principle we need n I/Q modulators but this is not possible to realize. The IFFT (Inverse Fast Fourier Transform) at the transmitter side solve this problem. So we use numerical mathematic in a high integraded processor.



Before we produce thousand of subcarriers we add a FEC to the datastream. (OFDM COFDM) Each of the subcarriers transmit only a small part of the overall datastream. DEMUX: Serial to parallel conversion and interleaving Each of this bits packets goes to the mapper MAPPER: mapping for each subcarrier in Real- and Imaginary number (produce complex symbols in the Frequency Domain). Two lists with thousands of Real- and Imaginary numbers are the inputs for the IFFT IFFT: Transfer of the subcarrier (in the complex plane) from the Frequency Domain in the Time Domain. Filtering, I/Q-Modulation and D/A Conversion. A RF Modulator bring the signal on the RF Frequency


DVB-T – Guard Interval

The presence of ISI in the system introduces errors in the decision device at the receiver Output.



The purpose of the guard interval is to introduce immunity to propagation delays, ISI (Intersymbol Interference),echoes, reflections and frequency selective fading, to which digital data is normally very sensitive. In COFDM, the beginning of each symbol is preceded by a guard interval. As long as the echoes fall within this interval, they will not affect the receiver's ability to safely decode the actual data, as data is only interpreted outside the guard interval. Guard Interval is a proportion of the time there is no new data transmitted. This guard interval reduces the transmission capacity. In fact during the guard interval we transmit a small part of the next symbol.



COPY

Source: Rohde&Schwarz


Each frame consists of 68 DVB-T COFDM symbols

Four frames constitute one Superframe

Each symbol is composed of two parts: useful part and guard interval(1/4, 1/8, 1/16, 1/32).

Guard interval avoids ISI between symbols.

The choice of the guard interval depends on the maximum transmission distance.


MODE Symbol Guard Guard max. distanceDuration (µs) Interval Interval (µs) in km

2K 224 1/4 56 16,82k 224 1/8 28 8,42K 224 1/16 14 4,22K 224 1/32 7 2,18K 896 1/4 224 67,18K 896 1/8 112 33,68K 896 1/16 56 16,88K 896 1/32 28 8,4


Receiver(RX)

f1

f1


Example: GI = 224 µs (8K, ¼) 1 µs = 300m 300 x 224 = 67200m = 67,2 km


MFN = Multi Frequency Network

SFN = Single Frequency Network

DVB-T – MFN vs. SFN

f1 f2

f3

f1 f1

f1

MFN SFN


In order to set up one SFN network, three conditions have to be fulfilled.

DVB-T Transmitters belonging to one SFN cell shall radiate:

over the same frequency

at the same time

the same OFDM symbols

The first condition is easy to satisfy because all DVB-T transmitter will be configured

once to the required broadcast frequency. The next two conditions imply to provide

transmitter with extra information:

Synchronization

Transmission parameters

This is specifically the task of the Single Frequency Network (SFN) adapter.

SFN adapter will add to the TS stream all the information required by the transmitter

DVB-T – SFN (Single Frequency Network)


Synchronization and transmission information sent to the transmitter are

stored into one TS packet called MIP packet. DVB normalized ist PID to 0x15.

MIP = Megaframe Initialization Packet

The MIP Packet consist of:

Synchronization parameters (network delay, STS = Synchronization Time

Stamp)

Transmission parameter (bandwidth, FFT Mode, constellation, guard interval,

code rate)

Optional functions data (tx time offset, tx frequency offset, tx cell ID)

DVB-T – SFN Adapter – MIP Packet


But how is synchronization achieved ?

When talking about transmitters synchronization, two main synchronization criteria have to be

taken into account:

1. Temporal synchronization:

DVBT-Transmitters broadcasting synchronously, at the same time.

SFN adapter/MIP inserter aim to provide synchronization information

to transmitters based on one common clock reference: GPS

2. Frequency synchronization:

Transmitters broadcast exactly the same set of subcarriers.

The accuracy of 10 MHz (derived from 1PPS from the GPS signal) will

guarantee any transmitter belonging to one SFN cell to broadcast

exactly the same set of subcarriers (same frequency, no frequency shift)

DVB-T – SFN (Single Frequency Network)


DVB-T – Pilot carriers

In order to simplify the reception of the signal being transmitted on the terrestrial TV channel, additional signals are inserted in each block. Pilot signals are used during the synchronization and equalization phase, while TPS signals (Transmission Parameters Signalling) send the parameters of the transmitted signal and to unequivocally identify the transmission cell. The receiver must be able to synchronize, equalize, and decode the signal to gain access to the information held by the TPS pilots. The receiver analyse the pilot carriers (scattered and continual pilots) contained in the signal and calculate from these the linear distortion. After that a channel estimation is possible. The pilots are BPSK modulated at a boosted power level, 16/9 times greater than that used for the data and TPS symbols


DVB-T – Pilots

Continual pilots Fixed position in spectrum Fixed position in constellation diagram Used for automatic frequency control (AFC) They are located on the real axis (0 or 180 degrees) and have a defined amplitude The continual pilots are boosted by 3 dB compared with the average signal power


DVB-T – Pilots

Scattered pilots Variable position in spectrum Fixed position in constellation diagram “sweeping” over spectrum Used for channel estimation & correction They are located also on the I axis at 0 or 180 degrees and have the same amplitude as the continual pilots Each scattered pilot jumps forward by three carrier positions in the next symbol


DVB-T – TPS carrier

TPS carrier Fixed position in spectrum BPSK modulation Transmission parameter signaling (TPS) Fast information channel from TX to RX about the current

transmission parameter. All the TPS carriers in one symbol carry the same information. They are all either at 0 degrees or all at 180 degrees on the I axis. The TPS carriers keep the receiver informed about Mode (2K or 8K) Length of the guard interval (1/4, 1/8, 1/16, 1/32) Type of modulation (QPSK, 16QAM, 64QAM) and Code Rate Use of hierachical coding


DVB-T – Pilots and TPS carrier


DVB-T – Carriers position


DVB-T – Type of transmitter for digital terrestrial television

Transmitter transmit the signal over a defined RF channel f1 input ASI or IP (via microwave link, fiber or satellite) Transposer receive the signal from another TX on f1 and transmit the same signal on an another RF channel f2 Gap-Filler receive the signal from another TX on f1 and transmit the same signal on the same channel f1. A problem is the isolation between input/output antenna. Limitation of the output power at around 100W.


DVB-T – Transmission

After adding additional information to the datastream the modulator modulate the signal in COFDM.

DATA(MPEG TS)

Codi

ng (R

S+CC

)

Guar

d In

terv

al

MIP

pac

ket

Pilo

ts

TPS

carr

ier i

nfo

COFDM Modulation

Spectrum dvb-t signal


DVB-T – Spectrum and C/N (Carrier to noise)

C/N Noisefloor

Bandwidth


DVB-T – C/N vs. BER

Required C/N for dvb-t transmission to achieve a BER = 2 . 10-4 after the Viterbi decoder


DVB-T – „Cliff Effect“ in digital transmissions

If an error level exceeds the number of errors that can be corrected by the FEC design, then the system will fail dramatically. This leads to a behavior often dubbed the "cliff effect“ - a step function in performance that occurs when errors exceed the critical level. When the error level is below that critical level for which the FEC can compensate, a transmission will seem relatively error free, even in the presence of a large number of errors. Then, all of a sudden, things may go drastically wrong if the critical level is exceeded, the performance "falls off the cliff.“


„Cliff Effect“ in digital transmissions

Source: IfN Braunschweig


MER – Modulation Error Ratio

which is an indicator of noise, interferences or distortions on DVB-T/T2 signals

and is a figure of merit.

DVB-T – MER

Source: Agilent

A good MER at the transmitter site should have a MER>35 dB. MER, beside BER (C/N), is the primary parameter in a DVB transmission system as it provides information on transmission quality.


MER – Modulation Error Ratio

DVB-T – MER


DVB-T – Receiver

TunerFrontend A/D FFT

ChannelEstimation

DemuxDemapping

InnerInterleaver

RFInput

ReedSolomon

InnerDecoder

OuterInterleaver

OuterDecoder

De-Srambler

MPEG2-TS

ViterbiDecoder


Net Data Rate = 188/204 * Code Rate * log2 (m) * 1/(1+guard) * channel * const1

m: 5/6, 7/8

Guard: 1/4, 1/8, 1/16, 1/32

Channel: 1 (8MHz), 7/8 (7 MHz)

Const1 6.75 E+6 bit/s = 6.75 * 10+6 bit/s

Example: DVB-T in Vienna, Channel 24 = (CR 3/4, GI 1/4, 16-QAM)

Net Data Rate = 0.921 * 0.75 * 4 * 0.8 * 1 * 6.75E+6 = 14920200 = 14.9 Mbit/sek.

4(QPSK), 16(16QAM), 64 (64QAM)

log2(m): 2(QPSK), 4(16QAM), 6 (64QAM)

Code Rate: 1/2, 2/3, 3/4,

DVB-T – Net Data Rate


DVB-T2


DVB-T2 Facts

Constellation QPSK, 16-QAM, 64-QAM, 256 QAM FEC LDPC + BCH Code Rate 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 7/8

Guard Intervall 1/4, 19/256, 1/8, 19/128, 1/16, 1/32, 1/128

FFT Size 1K, 2K, 4K, 8K, 16K, 32K Scattered Pilots 1%, 2%, 4%, 8% of total Continual Pilots 0,35% of total Bandwidth 1.7, 5,6,7,8 MHz Max. Bitrate 50,34 Mb/s Modulation COFDM

Red: different to dvb-t


DVB-T vs. DVB-T2

Better coding systems based on DVB-S2 Outer FEC: BCH Coding – Inner FEC: LDPC Coding Rotated constellation More parameters (GI, CR, FFT Size, Pilots) PLP Technology Future Extension Frames (FEF) Transmission for mobile and stationary receivers Improved SFN performance

BCH=Bose-Chaudhuri-Hocquenghem LDPC=Low Density Parity Check Code


DVB-T vs. DVB-T2

DVB-T2 uses the same error correction coding as used in DVB-S2 and DVB-C2 => LDPC and BCH coding. The number of carriers, guard interval sizes and pilot signals can be adjusted, so that the overheads can be optimised for any transmission channel.

DVB-T2 can offer a much higher data rate than DVB-T

OR a much more robust signal


Shannon Law

Source: R&S


Coding DVB-T2

with the new coding 30% more net data rate is possible Additional we can use MPEG4 (half data rate to MPEG2). Example: DVB-T with ~ 15 Mbit to DVB-T2 with ~ 30 Mbit

BasebandScrambler

BCHCoder

LDPCCoder

BitInterleaver

outin


QEF DVB-T2

If the received signal is above the C/N threshold, the Forward Error Correction (FEC) technique adopted in the System is designed to provide a "Quasi Error Free" (QEF) quality target. The definition of QEF adopted for DVB-T2 is "less than one uncorrected error-event per transmission hour at the level of a 5 Mbit/s single TV service decoder", approximately corresponding to a Transport Stream Packet Error Ratio PER < 10-7 before the de-multiplexer.


Rotated constellation

Rotation of constellation diagram gives different projection points on I and Q axis for each constellation point instead of same projection point in case of non-rotated diagram. This can be used for soft decision

Source: Enensys, R&S


PLP

A PLP (Physical Layer Pipe ) is a logical channel that may carry one or multiple services. Each PLP can have a different bit rate and error protection parameters. For example, it's possible to split SD and HD services to different PLPs

Source: Enensys


Pilots in DVB-T2

Edge pilots Continual pilots Scattered pilots (8 different pilot pattern PP1-PP8) Frame closing pilots P2 pilots

Purpose of pilot insertion Channel estimation (and equalisation) Synchronisation Common Phase Error correction As a form of “padding”


T2-MI interface

Source: R&S


T2-MI interface (T2 Gateway)

BB frames, PLP => payload packed in BB frames and transmitted via PLPs

L1 signaling => DVB-T2 setup configuration data (e.g. FEC, interleaver, modulation of different PLPs

Timestamp => used for SFN synchronization FEF => Additional frame structure to transmit other T2 profiles

(e.g. T2-Lite) AUX => I/Q data, T2-MI packet type IA => used for configuration of individual transmitters T2-MI packets are encapsulated into DVB/MPEG transport stream packets using “data piping


DVB-T2 Spectrum

optimal DVB-T2 signal


DVB-T2 Spectrum

weak DVB-T2 signal


Terrestrial DVB-T/T2 distribution


Reception problems


RF attenuation in buildings

• distance between the transmitting aerial and the building • height of the transmitting aerial above the ground • the type of electromagnetic wave propagation • the construction and the width of the building • the number and the height of the floors • layers of the glass surfaces


Antenna types for DVB-T/T2 reception

Roof top antenna (Yagi) Indoor antennas


DVB-T/T2 transmit antennas

Seite 1

Digital Radio and TV Systems Part 2 V.1.1


DI Peter Knorr

Seite 2

DVB-S

25.07.2014 Digital Radio and TV Systems Part II

Seite 3

DVB-S

Condition:

gravitional force = centripetal force

D = 35780 km


A geostationary orbit is a circular orbit directly above the earth's equator

approximately 35,780 km above ground.

The geostationary orbit where the satellites are in is also called the

Clarke Belt, named after Arthur C. Clarke. He was a British scientist

who first proposed the idea of the geostationary orbit used by today's

satellites.

Seite 4

DVB-S


Geostationary orbit • difficult to achieve • more launch performance needed • no service to polar regions (highest latitude 71°) • satellite first inserted in inclined elliptical transfer orbit • Orbital perturbations (Sun, Moon, radiation pressure of

the sun)

Coverage by GEO

Seite 5

Satellite orbital position

Example:

SES Astra

Longitude

19,2° East

Vienna:

48° 12‘ N

16° 22‘ E


Seite 6

SES Satellite Fleet


Seite 7

Satellite footprint


Source: SES

Seite 8

DVB-S Uplink - Downlink


Seite 9

Satellite Uplink Station


Seite 10

Polarisation

An electromagnetic wave consists of

electric field

magnetic field

Polarisation is the orientation

of the electric (E) vector in an

electromagnetic wave, frequently

horizontal or vertical.


Seite 11

Satellite transponder

A satellite channel is called transponder, because it is a separate

transceiver or repeater.


Seite 12

LNB – Low Noise Block Converter

The LNB is a combination of low-noise

amplifier, frequency mixer, local oscillator

and IF amplifier. It receives the microwave

signal from the satellite (10.7-12.75 GHz)

collected by the dish, amplifies it, and

downconverts the block of frequencies to a

lower block of intermediate frequencies (IF

= 950 2150 MHz).

This downconversion allows the signal to

be carried to the indoor satellite TV receiver

using a relatively cheap coaxial cable.


Source text: Wikipedia

Seite 13

Satellite parabol antenna types


Source: Wikipedia

Seite 14

Azimuth - Elevation

Azimuth


ASTRA 19.2° Vienna: Azimuth =176°; Elevation = 34,64°

Elevation

Seite 15

Elevation


Offset satellite antenna

Elevation

Seite 16

Elevation


Elevation for location Vienna

Seite 17

Signal level vs. modulation


DVB-T/T2 distance < 100km, high power TX, channel estimation possible Modulation in Amplitude + Phase (256-QAM)

DVB-C/C2 distance ~ some km, Line-amplifier (high signal level), channel characteristic constant Modulation in Amplitude + Phase (4096-QAM)

DVB-S/S2 distance 36000km Downlink, channel unknown because of weather conditions (rain, clouds) only Phase modulation (QPSK, 8PSK …)

Seite 18

Free-space path loss


c = Speed of light = 300 000 km/s = 3 x 108 m/s Frequency f in Hz Wavelenght λ in m C = λ . f Free space path loss in vacuum F: F = 20 log (4 π d / λ) Unit: dB Example for satellite receive path: d = 36 000 km = 36 000 * 103 m f = 14 GHz = 14 x 109 Hz => λ= 3 x 108 / 14 x 109 = 0,0214 m F = 20 log (4 x 3,14 x 36 000 x 103 / 0,0214) = 206 dB (but this is without atmospheric attenuation calculations)

Seite 19

Attenuation on satellite links


Atmospheric propagation degradation on satellite links • Cloud and fog • Rain attenuation • Oxygen attenuation • Water vapour • Atmospheric clouds

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DVB-S Modulation


QPSK Spectrum

Seite 21

Amplifier – back off


In case of digital modulation it is not possible to operate an amplifier at saturation. A „backoff“ at about 3dB or more is necessary to reach the linear range. This is done to avoid that the intermodulation products originating from the input carrier signal raise over a certain level, causing excessive interference in the adjacent bands.

Seite 22

DVB-S Modulation

Same data block diagram as DVB-T


Seite 23

DVB-S Net data rate


Formular: Net data rate = Symbolrate * 2 (QPSK) * FEC * (1/RS) Example: Astra satellite channel 117 Symbolrate = 22 Msymb./sec. FEC = 5/6, RS (204,188) 1/RS = 0.92 Net data rate = 22 * 2 * 0.8333 * 0.92 = 33.79 Mbit/sec. Symbolrate 22 Msymb./sec. = 44 Mbit/sec. (QPSK) means 10.21 Mbit/sec. for coding

Seite 24

DVB-S BER vs. Eb/No


Example: Eb/N0 = C/N – 2,2 dB for QPSK, FEC = 5/6

Seite 25

Eb/No


Eb/N0 (the energy per bit to noise power spectral density ratio) is an important parameter in digital communication. It is a normalized signal-to-noise ratio (SNR) measure, also known as the "SNR per bit". It is especially useful when comparing the bit error rate (BER) performance of different digital modulation schemes without taking bandwidth into account. Eb = Energy required per bit of information N0 = thermal noise in 1Hz of bandwidth R = system data rate BT= system bandwidth SNR = (Eb/N0) * (R/BT)

Seite 26

DVB-S2


Seite 27

DVB-S2


DVB-S 1994 DVB-S2 2003 New optimized FEC (LDPC + BCH coding) used in DVB-S2. Later exactly the same coding in DVB-T2 and DVB-C2 30% higher data rates than in DVB-S Designed for Broadcast and commercial use like DSNG

Seite 28

DVB-S2 Modulation


Phase modulation (consumer) QPSK (consumer) 8-PSK (consumer) 16APSK (for commercial use) 32APSK (for commercial use)

Seite 29

Robustness DVB-S vs. DVB-S2


Minimum C/N - Fall of the Cliff Test results from Rohde&Schwarz - HUMAX DVB-S2 ST

DVB-S DVB-S2, QPSK DVB-S2, 8PSK CR C/N (dB) CR C/N (dB) CR C/N (dB) 1/2 2.5 1/2 1.3 3/5 9.1 2/3 4.3 3/5 2.3 2/3 8.8 3/4 5.3 2/3 3.1 3/4 9.1 5/6 6.4 3/4 4.1 5/6 9.6 7/8 7.1 4/5 4.7 8/9 10.9

5/6 5.3 9/10 11.2 8/9 6.3 9/10 7.3

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Conditional Access (CA)


To protect a DVB transmission, the DVB standard integrates into its broadcasting infrastructure an access control mechanism, commonly known as Conditional Access, or CA. To avoid confusion, the DVB-CA specification uses the terms scrambling and descrambling to mean the encrypting and decrypting of TV contents

Seite 31

Scrambling (used in all DVB systems)


Free to air (no scrambling) Free to view (scrambled but after registration free) Pay TV (scrambled with monthly costs) Systems: with Smard Card Cardless

Seite 32

Scrambling (used in all DVB systems)


Seite 1



DI Peter Knorr

Seite 2

DVB-C/C2

25.07.2014 Digital Radio and TV Systems Part III

Seite 3

DVB-C/C2


Seite 4

DVB-C


No concatenated codes (DVB-T, DVB-S) Only Reed Solomon – no convolutional coder (no channel estimation necessary because of robust channel characteristic cable)

Seite 5

DVB-C


SMATV: Satellite master antenna television distribution system

TDT: Transparent digital transmodulation

Seite 6

DVB-C


Prior to modulation, the I and Q signals shall be square-root raised cosine filtered. The roll-off factor is 0,15.

Source: R&S

Seite 7

DVB-C


Main target: It should be possible to receive a Mux from a satellite transponder with e.g a bandwidth of 33 MHz and transfer the TS stream direct without conversion into a cable RF channel with a bandwidth of 8 MHz. Satellite: QPSK, 27.5 Msymb./sek., FEC= ¾ Net bit rate = 38.01 Mbit/sek. DVB-C net bit rate: ld(m) * symbol rate * 188/204 6 Bit/Symbol (64-QAM) * 6.9 Msymb./sek. * 188/204 = 38.15 Mbit/sek.

Seite 8

DVB-C


Frequency Identification Channel 47 - 68 MHz Band I HF und VHF I C2 ... C4 87 - 108 MHz Band II VHF II FM 108 - 174 MHz Midband MB S2 ... S10 174 - 230 MHz Band III VHF III C5 ... C12 230 - 300 MHz Superband SB S11 ... S20 300 - 470 MHz Hyperband HB S21 ... S38 470 - 622 MHz Band IV UHF IV C21 ... C39 622 - 862 MHz Band V UHF V C40 ... C69

Seite 9

DVB-C


Internet over cable infrastructure EuroDOCSIS DOCSIS = Data Over Cable Service Interface Specification

Seite 10

DVB-C


Spectrum of DVB-C signals

Seite 11

DVB-C2


Based on DVB-S2/T2

COFDM with 4k Mode (4096 carrier), short guard

intervals because of short reflections.

Subcarrier distance 2.232 kHz

FEC with LDPC like T2/S2

Multiple TS and GS (generic streams)

Single and multiple PLP

Modulation QSPK 4096 QAM

Variable coding and modulation

Seite 12

DVB-C2


3 type of interleaver (bit, time and frequency) Pilots like T2 (edge, continual and scattered) Broadband signals possible (e.g. 32 MHz)

Sony DVB-C2 Demodulator chip

Seite 13

DVB-C/C2 Signal level vs. analog TV


Source: Fischer R&S

Seite 14

DVB-C2


Seite 1



DI Peter Knorr

Seite 2

DAB+

25.07.2014 Digital Radio and TV Systems Part IV

Seite 3

DAB / DAB+


History: Digital radio is one of the 'older' forms of new digital media. Research Project Eureka-147 (1987) Digital Audio Broadcasting (DAB) The MPEG-1 Audio Layer II ("MP2") codec was created as part of the EU147 project DAB was the first standard based on orthogonal frequency division multiplexing (OFDM) modulation technique, which since then has become one of the most popular transmission schemes for modern wideband digital communication systems. First DAB digital radio broadcasts in September 1995 (BBC, NRK).

Seite 4

DAB


ETSI Norm (February 1995) ETS 300 401

Radio Broadcasting Systems; Digital Audio Broadcasting (DAB) to mobile, portable

and fixed receivers

Seite 5

DAB


Problems with FM Multipath fading (reflections from buildings, vehicles); very

large variations in signal strength over distances of ~ 1m Interference (from equipment, vehicles and other radio

stations)

Seite 6

DAB / DAB+


The Eureka 147 system comprises three main elements Source Coding: MUSICAM Audio Coding = MP2 ( by Philips,

IRT, CCETT ) Masking Pattern Universal Sub-band Integrated Coding And Multiplexing Since 2011 DAB+ with a new audio compression format: HE AAC+ V2

Transmission coding & multiplexing Channel Coding: Convolution, Puncturing, Freq & Time interleaving COFDM Modulation

Seite 7

DAB


additional frequencies in L-Band (1.4 GHz)

Seite 8

DAB Frequency planning


Source: Komm Austria

Seite 9

DAB Receiving side


Home receivers (Hifi tuners, kitchen radios, clock radios, portable stereo systems)

Car radios Portable receivers, mobile phones, tablets PC-based receivers (USB device) Monitor receivers for network monitoring

Fixed – portable – mobile Indoor = Outdoor

Seite 10

DAB DAB+


An upgraded version of the DAB system was released in February 2007, which is called DAB+. DAB is not forward compatible with DAB+, which means that DAB-only receivers will not be able to receive DAB+ broadcasts. DAB+ is approximately twice as efficient as DAB due to the adoption of the AAC+ audio codec, and DAB+ can provide high quality audio with as low as 64kbit/s.

Reception quality will also be more robust on DAB+ than on DAB due to the addition of Reed-Solomon error correction coding.

Seite 11

DAB DAB+


Source: Fraunhofer

Seite 12

DAB+


Transmitting guiding information such as the spectral envelope of the original input signal or additional Information to compensate for potentially missing high-frequency components.

Audio format HE AAC+ v2 High efficiency advanced audio coding version 2 SBR (Spectral band replication)

Source: EBU

Seite 13

DAB+


PS (Parametric stereo) In the encoder, only a Monaural downmix of the original stereo signal is coded after extraction of the Parametric Stereo data. Just like SBR data, these parameters are then embedded as PS side information in the ancillary part of the bit-stream. In the decoder, the monaural signal is decoded first. After that, the stereo signal is reconstructed, based on the stereo parameters embedded by the encoder.

Source: EBU

Seite 14

DMB – Digital Multimedia Broadcasting


DMB is a video and multimedia technology based an DAB(DAB+). It offer new services such mobile TV, traffic and safety information, interactive programmes, data information and other applications. DMB is a broadcast technology and not a streaming

technology meaning congestion is eliminated in the case of many simultaneous viewers (seen i.e. during the Olympics and FIFA World Cup)

DMB requires less power (battery usage) than streamed services

DMB requires less spectrum commitment than other mobile TV standards, which typically use 6-8 MHz blocks

Source: worlddab.org

Seite 15

DMB – Digital Multimedia Broadcasting

Multimedia content to be delivered without the risk of network congestion

DMB also enables reception while moving at high speeds.(>300km/h) Existing DAB transmitter networks can be to be adapted to carry

these new services Both DMB and DAB services to be accessed on the same receiver DMB is an open International Standard A wide range of TV and interactive services to be broadcast

simultaneously on the same multiplex: − video services − DAB and DAB+ radio services − file downloading (podcasting) − electronic programme guide − slide show − broadcast website (BIFS)


Source: worlddab.org

Seite 16

DAB

Four audio modes are provided:

Mono

Dual channel (two mono)

Stereo

Joint stereo

Audiobitrates: 16 – 384 kbit/sec.


Seite 17

DAB


The DAB transmission system combines three channels

MSC (Main service channel)

FIC (Fast information channel)

Synchronization channel

Each channel supplies data from different sources and these

data are provided to form a transmission frame

Seite 18

DAB


MSC (Main service channel) – use to carry audio, PAD and

data service components.

The MSC is a time-interleaved data channel divided into

a number of sub-channels which are individually

convolutionally coded, with equal or unequal error

protection

PAD (Programme Associated Data): text, label, name of

the song, the artist and the genre of music, slide show

Seite 19

DAB


FIC (Fast information channel)

The FIC is limited in capacity but is capable of supplying

information to a receiver faster than the main service channel

allows. This is possible because the FIC is not subjected to the

time interleaving part. Convolutional coding protection level is

permanently fixed (CR = 1/3).

In order to achieve an acceptable error performance, FIC

information is repeated regularly.

Seite 20

DAB


Synchronization channel – used internally within the

transmission system for basic demodulator functions like AFC

(automatic frequency control), AGC (automatic gain control)

and a phase reference.

Seite 21

DAB


Seite 22

DAB - Frequency interleaving


prevend fading causing burst errors

Source: Mike Brookes

Seite 23

DAB - Transmission frame


Source: ETSI

Seite 24

DAB - Transmission frame


Seite 25

DAB - MSC


The MSC is made up of Common Interleaved Frames (CIFs). The CIF contains 55 296 bits. The smallest addressable unit of the CIF is the Capacity Unit (CU), comprising 64 bits. Therefore, the CIF contains 864 CUs. The MSC is divided into sub-channels. Each sub-channel shall occupy an integral number of consecutive CUs and is individually convolutionally encoded. Each sub-channel consist of audio service components and data elements. Gross bit rate: 864 CU * 64 bit = 55296 bit in 24ms 2.304 Mbit/sec. There are two transport modes in the MSC: the stream mode (multiples of 8 kbit/s). Deliver data

transparently from source to destination (audio) packet mode for data service components

Seite 26

DAB – MSC


Seite 27

DAB - Modes


Mode I: Is specially intented for single frequency network

(SFN). Has a long guard interval for the absorption of multi-

path reflections. Used in VHF band.

Mode II: have a wider carrier spacing, better for mobil.

Optimal for small SFN networks. Used in L-Band < 1.5 GHz

Mode III: for satellite < 3 GHz

Seite 28

DAB - Modes


Parameters Mode I II III

Application SFN Terrestrial Satellite Frame duration ( Tf ) 96 ms 24 ms 24 ms Symbol duration ( Ts ) 1 ms 250 μs 125 μs Guard interval ( Tg ) 248 μs 62 μs 31 μs No. of symbols / frame (J) 76 76 153 No. Of carriers / symbol (N) 1536 384 192 Carrier spacing (fs ) 1 kHz 4 kHz 8 kHz Bandwidth (fw ) 1536 kHz 1536 kHz 1536 kHz Max. frequency (fm ) 250 MHz 1GHz 2GHz

Seite 29

DAB - Doppler effect


Example: v = 100 km/h = 27,7m/sec. C = 3 * 108 m/s F = 200 MHz = 200 * 106 Hz Δ f = 18,5 Hz

Christian Doppler

Seite 30

DAB Modulation ∏/4 DQPSK


Example Mode I:

COFDM Multicarrier

1536 carrier

Carrier spacing 1 kHz

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∏/4-DQPSK Differential quaternary phase shift keying


Seite 32



From symbol to symbol the carrier phase change 45 degree. Only +/- 45° and +/- 135° phase shift no 180° phase shift necessary Phase information from the PRS (Phase reference symbol)

Source: Rohde&Schwarz Wikipedia

Seite 33

DAB Spectrum


Source: Jim‘s Aerials

Seite 34

DAB Multiplex calculations


DAB offer different error protections =

UEP (unequal error protection)

One frame has 864 CUs.

Each service is transported in a SC (service channel) with a

capacity of n CUs.

It is possible that each subchannel has a specific error

protection

The sum of all SC must be < 864 CUs

Seite 35

DAB Multiplex calculations


Seite 36

DAB Applications



Seite 37

DAB Applications


Source: DAB Principles & Applications

Seite 38

DAB Applications


MOT (Multimedia Object Transfer Protokoll)

specifies a transmission protocol, which allows to broadcast various

kinds of data using DAB. It is tailored to the needs of Multimedia

services and the specific constraints given by the broadcasting

characteristics of the DAB system. After reception this data can be

processed and presented to the user (text, pictures, video or audio

sequences)

DLS (Dynamic Label Segment)

Supplementary data services in text form (up to 128 characters)

running alongside the DAB or DAB+ radio programme. Similar to

RDS on FM radio.

Seite 39

DAB Applications


IP over DAB

Tunneling of IP datagrams over DAB. The tunnelling is to be done by

encapsulating the IP datagrams into the MSC data groups. The IP

tunnelling through DAB is unidirectional.

TMC (Traffic Message Channel)

The Traffic Message Channel (TMC) was originally designed for

transport in the narrow-band Radio Data System (RDS) services in FM

broadcast.

DAB enables TMC messages to be carried in a much faster and bitrate-

efficient way. DAB-TMC has a cycle time that is much shorter than RDS-

TMC and the transmission is over the FIC channel.

Seite 40

DAB Applications


TPEG (Transport Protocol Expert Group) TPEG-RTM: Road Traffic Message Application TPEG-PTI: Public Transport Information RTM – Road Traffic Messages TEC – Traffic Event Compact TFP - Traffic Flow Prediction PTI – Public Transport Information PKI – Parking Information SPI – Speed Limit Information BSI – Bus Service Information WEA – Weather POI – Points of Interest CTT – Congestion and Travel Time

Seite 41

DAB Applications


PAD (Programme Associated Data)

Used to describe data embedded into an audio stream such

as DLS or Slideshow which is related to the programme

being broadcast at that time.

NPAD (Non Program Associated Data)

Data – transmit together with the DAB ensemble

digital radio and tv systems part 1 v.2

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