Introduction
Earlier we have discussed various video broadcasting techniques with different protocols of DVB organization. But not yet any audio broadcasting we discussed. We were using Analog FM Radio which was not efficient due its limitations less number of stations, multi-patch fading and Noise. Then the solution came Digital Audio Broadcasting.
So today in this article we will cover the a Audio Broadcasting Technique with its working which is known as DAB.
What Is DAB ?
DAB stands for Digital Audio Broadcasting. DAB is a standard for broadcasting of high quality digital audios for audio receivers. The equipment used to receive this digital audio is called Digital Radio. The DAB standard was initiated in 1980. So it is also known as Digital Radio Broadcasting.
DAB have significant advantages over the Analog FM Radios. It prove us high quality audios, without interference with maximum number of stations as compared with Analog FM Radios. Which results good user experience.
Working Of Digital Audio Broadcasting
To understand the working of Digital Audio Broadcasting there are two main factors which we need to understand. These factors are ,
(1) Spectrum Bandwidth
(2) Audio Codecs
(3) Modulation Technique
(1) Spectrum Bandwidth
In UK the Spectrum Bandwidth is from 217.5 to 230 MHz. Which contains 7 slots each with 1.55 MHz. Where a single frequency can carry multiple audio channels.
While bandwidth allocated for delivery of digital radio from satellite is from 1467 to 1492.
(2) Audio Codecs
DAB uses the Audio Codec of MPEG-1 Audio Layer 2. It is also known as MP2.
While a more advanced standard of DAB is called as DAB+ , due to its high efficiency than its previous standard DAB.
DAB+ is more efficient than its previous standard because of two things quality and number of stations. So DAB+ uses the AAC+ codec which provides good audio quality. On the other hand DAB+ allows us for more number of stations than DAB standard.
(3) Modulation Technique
Digital Audio Broadcasting uses the COFDM Modulation Technique. Where COFDM stands for Coded Orthogonal Frequency Division Multiplexing. This modulation technique resists the audio signal from interference.
It have 1500 different carriers. Which have the spectrum of 1.5 MHz. These carriers are very close to one another. To reduce the interference between these carriers, the signal is done orthogonal to each other. where each carrier is defined with bit-rate which they carries.
Now the modulating signal that is audio signal is spreaded on these carrier waves which carries little bit of this data. As we explained small data rate is carried out by these carriers. So if there is any kind of interface is found in the signal then it can be recovered easily.
The advanced digital radio receivers comes up with small display. Which shows the scrolling text with image. It shows the general news , weather news and playing track.
Conclusion
Digital Audio Broadcasting Standard is an improved standard of Traditional Analog FM Radio for delivery of high quality digital audios to Digital Radio Equipments.
Intitially the cost of digital radio receivers were very high. Because it was costly for manufactures due to requirement of large development programs. The manufactures used the multi-chip which again was costly for digital audio receivers. Also it made bulky to digital audio receivers.
After sometime a special kind of chip were developed which reduced the cost of digital audio receiver. It also reduced the size of these receiver. Which made is convenient for users.
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reference : dab eureka
