broacast radio part1

8/8/2019 Broacast Radio Part1

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Linda DoyleCentre for Telecommunications Value-Chain Research

Department of Electronic & Electrical EngineeringTrinity College, University of Dublin, Ireland

A Tour of Some Wireless and MobileCommunication Systems

BROADCAST RADIO-Part 1

Analogue broadcasting

AM1906

FM~1955(published: 1936)

The World of Broadcast Radio

AM and FM are traditional technologies with which weare familiar.

Radio networks are star shaped

Typically there is a powerful radio transmitter covering agiven area.

Outside of coverage area no reception

Radio receivers tend to be very cheap

Fixed, portable and mobile receivers The transmissions are in one direction

Armstrong & FM

Armstrong first got FM working in 1933. He showed it to RadioCorporation of America, who had most of his licenses, but they wereunimpressed.

RCA had at that point made vast investments in AM. All of their transmitters and all of the millions of radios that they had

sold used it. Radios were now commodities, and sold entirelybased on price, not quality.

RCA told itself that consumers didn't care what the music soundedlike from their radios, they just wanted to get it as cheaply aspossible.

They spent a couple of years evaluating the technique and thendeclined to license it.

http://world.std.com/~jlr/doom/armstrng.htm


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Armstrong Invented FM Radio

When he sought permission in 1935, however, to erect anexperimental FM station to demonstrate the unusual qualities of hisnew radio system, he ran into a stone wall.

The Federal Communications Commission (FCC) dismissed FM

out of hand as "a visionary development," and denied him a permit. The standard radio networks operating on AM or amplitudemodulation were equally indifferent. "Who needs a second methodof broadcasting?" they said.

It took Armstrong nearly five years to get his experimental stationconstructed, after threatening to take his invention to a foreigncountry.

FM ended up being given spectrum by the FCC in the 44-50 MHzband.

http://www.gm4jjj.co.uk/preamp/index.html

example of politics at play

In 1945 RCA and a block of other radio companies convinced theFCC to move the FM band from 44-50 MHz to 88-108 MHz, where itis today.

The nominal reason was to prevent "ionospheric disturbance", butno one was quite clear on what this was. The TV channel rightabove 50 MHz with its FM sound channel didn't seem to suffer fromit.

What it did do, though, was to immediately obsolete all thetransmitters and receivers that had been built. To add insult to injury,the FCC also voted to severely limit FM's broadcasting power, anddisallow radio relays from central stations to mountaintop antennas.Instead, the FM broadcasters had to send their material over AT&T's

coax cables at exorbitant rates. The overall, and intended, result was to cripple FM broadcasting.


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Microwavedata links, radio astronomy, remote sensing, advancedweapons systems, advanced security scanning

30300GHzEHFExtremely highfrequency

Wireless networking, satellite links, microwave links, satellitetelevision, door openers

330 GHzSHFSuper highfrequency

Broadcast television, amateur radio, mobile telephones, cordlesstelephones, wireless networking, remote keyless entry forautomobiles, microwave ovens

3003000 MHz

UHFUltra high frequency

FM broadcasting, amateur radio, broadcast television, aviation,30300MHzVHFVery high frequencyShortwave, amateur radio, citizens' band radio330 MHzHFHigh frequency

Navigational beacons, AM broadcasting, maritime and aviationcommunication

3003000 kHz

MFMedium frequency

AM broadcasting, navigational beacons30300kHzLFLow frequency

Directly audible when converted to sound (below ca. 20 kHz; orultrasoundotherwise)

330 kHzVLFVery low frequency

Directly audible when converted to sound, communication withmines

3003000 HzULFUltra low frequency

Directly audible when converted to sound, AC power grids (5060Hz)

30300HzSLFSuper lowfrequency

Directly audible when converted to sound, communication withsubmarines

330 HzELFExtremely lowfrequency

Long wave, Medium wave and Short wave can be used at times to refer toLF,MF and HF bands.

Human rights group broadcast 'pirate' radio show in Beijing

Updated Fri Aug 8, 2008 3:32pm AEST

A human rights group has broken China's tight control of the media bybroadcasting a radio show calling for freedom of expression in Beijing.

At 8.08am local time, the Paris based group Reporters Without Bordersbegan a twenty minute pirate broadcast on Beijing's airwaves.

Using FM transmitters they broadcast a twenty minute show on FM radiodenouncing China's censorship and control of the media and freeexpression.

It's unknown how many people were able to listen to the program.

The press freedom group says it was the first radio station notcontrolled by the government to broadcast in China since the

Communist Party took power in 1949.

Wireless, not just broadcast radio can of course play this kind of role in general

DAB

The latest trend in the world of radio broadcasting hasbeen a move away from analogue to digital radio

We talk about DAB now digital audio broadcast

The acronym DAB (Digital Audio Broadcasting) issynonymous with the Eureka 147 standard.

here is our first mention of a standard

DAB


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What is DAB?

DAB is a digital radio broadcasting system that through theapplication ofmultiplexing and compression combines multipleaudio streams (and non-audio) together for transmission.

Uses MPEG audio coding for compression Uses orthogonal frequency division multiplexing (OFDM) which is

robust in a multipath environment for transmission. [note: It was thefirst standard to include OFDM, which since then has become one ofthe most popular transmission schemes for modern wideband digitalcommunication systems]

When OFDM is used in conjunction with channel coding techniques,it is described as Coded Orthogonal Frequency Division Modulation(COFDM). This is what happens in a DAB system.

This combination of the compression, coding and OFDM is whatreally defines DAB.

compression- MPEG

MPEG -MovingPicture Experts Group

The term refers to the family of digital video compression standardsand file formats developed by the group.

There are also MPEG standards for audio compression MPEG-1 Audio Layer II is actually the standard of interest for DAB

DAB uses the MPEG Audio Layer II system to achieve acompression ratio of 7:1 without perceptible loss of quality. Thissystem is modelled on the working of the human ear, and retainsonly the audible components of the sound.

For the system to be viable the data ratehas to be considerably reduced from thatof a standard CD. The digital radio systemadopted reduces the data rate down to 128kbits / sec, a sixth of the bit rate for asimilar quality linearly encoded signal. Toachieve these reductions the incomingaudio signal is carefully analysed. It isfound that the ear has a certain thresholdof hearing. Below this the signals are notheard.

Additionally if a strong sound is presenton one frequency then weaker soundsclose to it may not be heard because thethreshold of hearing is modified. By

analysing the incoming audio and onlyencoding those constituents that the earwill hear the significant reductions can bemade.

http://www.radio-electronics.com/info/broadcast/dab/what-is-digital-audio-broadcasting-tutorial.php

multiplexing

More than one programme of the radio station can betransmitted at the one time from a given transmitter

Note if you listen to RTE 1 on FM they sometimes splitinto two simultaneous programmes but to get the parallelprogramme you have to tune to a different frequency(e.g. Religious Services)

In DAB you use multiplexing to combine the differentaudio services

DATA can be multiplexed as well

multiplexing allows for data as well

DAB can carry text and images as well as sound, and allreceivers will be equipped to handle non-audio data.

All but the smallest will be able to display at least two 16-character lines of text, allowing programmeselection by name or programme type, and enablingbroadcasters to transmit programme-associated datasuch as album title, song lyrics, or contact details.

Additional services, such as traffic information andsports, weather or stock market news feeds, arepossible. Transmission of full colour images possible.

128

128

128

128

128

128

128

128

128

DAB

Multiplex

'Bouquet'

DAB stereo audio at 128kbpsup to 9 services per multiplex

typical configuration


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COFDM for dealing with multipath reminder - OFDM

some details

The bandwidth of the signal is 1.5MHz

Much wider than the narrowband AM and FM signals

The number of subcarriers in the OFDM signal is over1500

The multiplexed audio and data streams will each havebeen error coded to give the robust performance

required.

Last Slide Explained

FIC: Fast Information Channel, which carries control and serviceinformation.MSC: Main Service Channel, which carries the audio and data

services.Multiplexer: A device which combines all audio and data services

for modulation and transmission.OFDM: Orthogonal Frequency Division Multiplexing, the modulation

technique which helps avoid multi-path fading in mobilecommunications.

Packet Mux: Combines several 'service components' (stock-marketupdates, weather forecasts, paging messages, etc.) into a single

data service for transmission.Packet Demux: Deconstructs the single service data into separate

services upon reception.

frequencies set aside for DAB

Band III: DAB frequency band 174240 MHz L-Band: DAB frequency band 14521492 MHz


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A network of DAB transmitters

DAB gives substantially higher spectral efficiency,measured in programmes per MHz and pertransmitter site, than analogue communication.

Apart from the multiplexing we spoke about earlierwhere multiple stations can be transmitted by the onetransmitter, the various transmitters can all operate onthe same frequency SINGLE FREQUENCYNETWORK (SFN)

SFN transmission can be considered as a severe form ofmultipath propagation.

So?

1. Improved end-user features (can contain non audioinformation)

2. Reception quality3. More stations (because it is more spectrallyefficient)

4. Variable bandwidth5. Less pirate interference

But?

1. Implementation choices leading to Sound quality issues

2. Currently limited coverage

3. Expense of the receivers

4. Expense of the system as more transmitters required(though overall have read comments on electricitysavings)

5. More power needed for the receiver (hence batteries donot last as long)

6. Compatibility we have not looked at new DABstandards, DAB+ the scene is not so settled

The Story with RTE

RT has indicated to the Department ofCommunications that it will have a DAB networkcovering the South East corridor, making DABaccessible to 52% of the population, by the end of2010.

The terrestrial DAB frequencies set aside for Irelandseem to be at 174-223 and 223-230 MHz.


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DAB Trial, Block 12c

Transmission sites:Three Rock 10kW ERPClermont Carn 5kW ERPSpur Hill - 5kW ERPWoodcock Hill - 5kW ERP

Coverage is predicted for 1.5mabove ground.

Reciption threshold is:48 dBuV/m outdoor car radio57 dBuV/m indoor kitchen radio64 dBuV/m pocket radio

Mixed signals on digital radio

Saturday, March 22nd, 2008 JOHN COLLINS IRISHTIMES 21/03/2008

RT WILL cease broadcasting on medium wave (MW) nextMonday just as it expands its digital radio service to cover almosthalf the population. This week the State broadcaster extended itstrial of digital radio technology to Cork and Limerick, making it

available to 44 per cent of the population.

Based on the Digital Audio Broadcasting (DAB) standard, the trialbroadcasts include seven new RT digital radio servicesincluding a childrens radio service and a dedicated news headlinechannel, as well as content from commercial broadcasters.

However, some industry observers have wondered if the Statebroadcaster is backing the right technology, particularly in light of itsstatutory obligation to broadcast to the Irish abroad. Brian Greene, adigital media consultant, says killing MW to fund DAB is a crazymove by RT because DAB has a short range while MW canbe picked up by listeners in the UK.

page 1

For its part, RT maintains that its services are available on the SkyDigital platform and over the web. According to JP Coakley, RT Radioshead of operations, the broadcaster will save 1.5 million in annual runningcosts by shutting down MW, of which 1 million relates to electricitycosts. Coakley says the MW infrastructure had an immediate need toinject circa 2.4 million in capital as the installation is reaching the end of itsnatural life. The savings will not just fund DAB but a number of onlineprojects, improvements to FM broadcasting and additional programmingresources, according to Coakley. That said, national DAB has to stand as aseparate business and rationale - its about an industry moving together toprovide the next generation of radio to the listener, rather than just whatRT can fund on its own, says Coakley.

The replacement that RT is proposing for MW is long wave (LW). RTinstalled a new LW transmitter in 2007, which also supports broadcasting ina newer digital technology called Digital Radio Mondiale (DRM).

page 2


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However, Greene maintains that because DRM is more efficient, ithas to be broadcast at a lower power. As a result, an Algerian radiostation also broadcasting on LW252 is causing interference withRTs signal.

Coakley concedes Tipaza in Algeria interferes with LW252 at nightin London and parts of southeast England, but points out that MW isnot available at all in London.

This month Greene wrote to Cathal Goan, director-general of RT,raising questions about the broadcasters transmission planning andmove to digital.

He also questions just how successful DAB has been in the UK,despite the fact that well over five million receivers have been soldthere and the format dominates sales of kitchen, portable and clockradio sales.

page 3

some DAB recordings

http://www.briangreene.com/bhg/2008/03/

This person has a blog that comments on RTE and itsDAB system

but- sound quality???

The reason why they're using insufficient bit rate levels isdue to DAB using the inefficient MP2 audio codec, whichneeds to be used at bit rate levels of at least 192 kbps toprovide good audio quality -- FM provides an audio qualitywhich is equivalent to 192 - 224 kbps MP2. Unfortunately,98% of all of the stereo stations on DAB in the UK areusing a bit rate level of 128 kbps, hence the audio qualityis poor.

SOURCE:http://www.digitalradiotech.co.uk/dab/incompetent_adoption_of_dab.htm

From The Guardian:-

Is DAB radio the next Betamax?

John Plunkett guardian.co.uk, Tuesday January 29 2008

aside

Sony's Betamax video standard was introduced in 1975,followed a year later by JVC's VHS. For around adecade the two standards battled for dominance, withVHS eventually emerging as the winner.

http://www.mediacollege.com/video/format/compare/betamax-vhs.html

ORhttp://www.guardian.co.uk/technology/2003/jan/25/comment.comment

Digital audio broadcasting (DAB) may end up to radio what Betamaxwas to video, warns a report published today.

The report, by media and telecoms specialist Enders Analysis, saidthe launch of the second national commercial digital radio multiplex,headed by Channel 4, might exacerbate the problems rather thansolve them, and warned that media regulatorOfcom would face apublic outcry if DAB failed.

Enders Analysis added that the high cost of DAB transmissionand slow growth in revenue had combined to undermineconfidence in the new medium and led to the closure of a string ofnational digital stations.

Today's report urged the radio sector to "stop continually beating itschest in public about the wonders of DAB and instead partake in anhonest industry debate about the future of the platform".


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"The exodus of stations from the DAB platform is starting to look likea stampede," said the Enders report, written by Grant Goddard.

"With three of the largest radio groups having reduced theircommitment to the DAB platform in recent months, their stationshaving been replaced by a mix of ethnic, religious and non-commercial broadcasters, the future health of the DAB platformmust be under question."

Goddard's report ends with a chilling prediction from RichardWheatley, the chief executive of the Local Radio Company, toanalysts last month: "DAB is the Betamax of radio."

National digital stations that have closed include GCap Media'sCore, UBC's Oneword and Virgin Radio's Groove. GCap's Chill andFun Radio have also been scaled back, while Virgin scrapped plansfor a new national digital station, Virgin Radio Viva.

The report said the launch of digital stations such as Polish RadioLondon, Rainbow Radio and BFBS Radio, owned by the BritishArmed Forces, had worrying echoes of the decline of the AMwaveband at the end of the last century.

"The DAB platform of 2008, particularly in London, is already starting toresemble the AM platform of 1998, suggesting that DAB might have alreadybeen written off by the sector as a means to reach the 'mass market'audiences that national advertisers desire from the medium," it added.

Goddard said the launch of the second national commercial digitalmultiplex, headed by Channel 4, was unhelpful at a time when the first - runby Digital One - was struggling to fill its capacity.

"Channel 4 is faced with the task of imminently launching a brand new DAB

multiplex in the middle of a snowstorm around the future of the wholeplatform," his report stated.

"By the end of 2007, it was evident that the 'masterplan' for DAB which theradio industry had clung to since the mid-1990s was simply not going towork.

"The closure of two longstanding national digital-only stations - Core andOneword - combined with reductions in the service of several other digitalbrands helped to crystallise the problems: too much spectrum, notenough consumer hardware takeup, and not enough enthusiasm forDAB from listeners or advertisers."

` Goddard said the issue of DAB overcapacity had to be "urgentlyresolved" by Ofcom, Digital One, Channel 4 and transmissionbusiness Arqiva. He added: "Put bluntly, can the UK commercialradio sector really support two DAB multiplexes?

"Ofcom faces a public outcry if the DAB platform were to fail, withowners of the 6.45 million DAB receivers sold to date demandinga refund of their purchases (remember ITV Digital?)."

A working group on the future of digital radio set up by theDepartment for Culture, Media and Sport was due to meet for thefirst time this week.

http://newsgroups.derkeiler.com/Archive/Uk/uk.tech.broadcast/2008-01/msg00940.html

broacast radio part1

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