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Digital Audio Broadcasting


 

What is DAB?

DAB stands for Digital Audio Broadcasting and is a method for the terrestrial digital transmission of radio signals. DAB allows for a much more efficient use of frequency spectrum than traditional analogue radio. Instead of just one service per frequency as is the case on FM, DAB permits up to nine (or more) services on a single frequency. 

The interference that commonly disturbs analogue reception, which is caused by radio signals bouncing off buildings and hills, is eliminated with DAB signals.  Since DAB automatically selects the strongest regional transmitter, reception is much clearer.

DAB is broadcast on terrestrial networks and consumers are able to receive services, with a selection of over 1000 different devices.  Since DAB was originally designed for mobility, consumers have the added advantage of listening to services in the car and while on the move.  

 

Benefits of DAB

In spite of the variety of additional services, DAB receivers are simple and easy-to-use.

Success of DAB

There are now over 320 different DAB receivers commercially available. 30 countries have regular DAB services on air, and more than 12 million DAB receivers have been sold worldwide.

Present Status in Pakistan:

In Pakistan the VHF \ UHF bands identified for DAB are already occupied by different services mostly by Analog Terrestrial Broadcasting (174 ~ 240 MHz / 1452 ~ 1492 MHz ) of PTVC & STN etc, whereas most of the Sound Broadcasting Radio Stations are operating in the FM band 87.5 ~ 108 MHz .

 

DIGITAL VIDEO BROADCASTING - TERRESTRIAL (DVB-T)

INTRODUCTION:

Digital Terrestrial Broadcasting is an implementation of digital technology to provide a greater number of channels i.e. 4 to 8 TV programs and other data services in a single carrier/channel of 6, 7 or 8 MHz bandwidth. It also provides better quality of picture and sound using aerial broadcasts to conventional antenna (or aerial) instead of satellite dish or cable connection. Digital broadcast is transmitted on radio frequencies through the airwaves that are similar to standard analog television, with the primary difference being the use of multiplex transmitters making possible the transmission \ reception of high quality multiple streaming and interactive programs on a single frequency carrier \ channel.

DVB STANDARDS:

In addition to DVB-T other DVB standards are also available for different technologies / platforms i.e. DVB-H, DVB-S, DVB-C.

DVB IDENTIFIED BANDS:

According to ITU-R Recommendation, DTB should fit in the channels intended for analog transmission of 6, 7 or 8 MHz bandwidth in the VHF/UHF bands. The most suitable bands for DVB transmission are the VHF\UHF band III , IV & V (174~230 MHz, 470 ~ 960 MHz).

ITU SUPPORT FOR TRANSITION FROM ANALOGUE TO DIGITAL:

Considering the advantages of digital broadcasting, ITU is engaged in facilitating the transition from analogue to digital. ITU has developed frequency plans for digital terrestrial broadcasting (the GE06 Plans) for Region 1 and the Islamic Republic of Iran. Countries are to implement these plans by 17 June 2015, except for some developing countries, which have until 17 June 2020 to make the transition. Through various projects, ITU is helping developing countries and least developed countries to make this transition smooth.

INTERNATIONAL PRACTICES & MARKET DEPLOYMENT:

DVB-T services are on air in more than 78 countries and most successful markets where DVB-T is launched are: UK, Germany, France, Spain, Italy, India, Iran, UAE, Sri Lanka, Malaysia and Australia. Moreover more than 100 countries in Europe, Africa and the Middle East have signed the ITU GE06 agreement and all the signatories to this agreement will ultimately deploy DVB-T.

PRESENT STATUS IN PAKISTAN:

In Pakistan the VHF\UHF bands identified for DVB-T are already occupied by different services mostly by Analog Terrestrial Broadcasting 160 MHz (174 ~230 MHz and 502 ~ 598 MHz, 20 Channels) by the PTVC & STN in Pakistan, while private sector is relying on satellite delivery platform for broadcasting the content.

 

Digital Multimedia Broadcasting (DMB)

 

Digital Multimedia Broadcasting (DMB) is a video and multimedia technology based on DAB. It offers a wide range of new innovative services, such as mobile TV, traffic and safety information, interactive programmes, data information and many other applications.  DMB is currently the world's most successful mobile TV standard, with over 8 million devices sold.  Countries in Europe and Asia have implemented commercial services.

 

Since DMB  is based on the globally used digital audio broadcasting (DAB) core standard, DMB devices are always backwards compatible and can receive not only DMB multimedia services but also DAB audio services. On the broadcaster side, this means that the conventional DAB transmission system can be used for DMB transmission by simply adding a DMB video encoder to the existing DAB system

 

Benefits of DMB

 

DMB demands less spectrum commitment than other mobile TV standards, which typically use 6-8 MHz blocks.  In contrast, DMB can offer both TV and radio services within a multiplex of just 1.5 MHz.  Whilst this spectrum would deliver a range of approximately 7 DMB services, extra services can be made available simply by adding further multiplexes. 

DMB has the further benefit of being broadcast in Band III or L-Band, where higher powers give rise to broader and more comprehensive coverage.  Other mobile TV standards must use UHF Bands IV or V.  As a result, transmitter powers are low and coverage areas from a single transmitter are typically small.  However, since DMB is in Band III and L-Band higher powers give rise to broader and more comprehensive coverage.