DAB is immune to the sort of interference that can make listening to today's conventional AM or FM radio less than satisfying. If you listen to FM in your car, you will hear distant hisses and pops and short blackouts as you drive along. These disturbances are caused by multipath interference, which occur when the FM signal bounces off buildings, trees and hills and arrives at your receiver out of phase with the main signal, confusing the transmission. What is basically happening is that in multipath reception inter-signal interference occurs, i.e. signals adjacent in time overlap each other due to the signal components arriving at different times.
But DAB is revolutionary because inside the receiver is a computer which sorts through the countless multipath signals and other distortions to enhance the main signal. It simply sorts out the main signals and ignores any reflections that it may be receiving. Another consequence of multipath reception is that direct and reflected signal components reach the receiver at different times. (Source: www.radi-tmc.com/dabqa.htm) Another function that DAB employs is Forward Error Correction. For each useful bit of data DAB transmits 1 1/3 bits of data. This extra data makes it possible to reconstruct the transmitted bit sequence in the receiver, even if part of it is disrupted during transmission
The best part is that DAB is flexible. Supposing that normally six stereo program channels, can be transmitted in a DAB ensemble at a time, some programs will require less audio data (for e.g. talk shows or news broadcasts) while some will require more data (for e.g. music or concerts). The DAB can be easily adjusted to suit the requirements. Secondly the number of channels in a DAB ensemble can even depend on the time of day; for instance, on Saturday afternoon a stereo channel could be divided into a special sports channel and a further mono channel for news (demand specific broadcasting). This means that the overall data rate available in DAB is flexibly distributed over various program channels, and even the number of program channels per DAB ensemble is flexible.
