World Broadcasting Unions Digital Radio User Manual - page 62

DIGITAL RADIO GUIDE

TERRESTRIAL TRANSMISSION SYSTEMS - ISSUES

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Figure 4.21: End of the transition period

In summary, the full potential of the new digital plans will not be available until the

analogue switch off. 

In terms of propagation performance at L-Band using T-DAB, concern about the

efficiency of the 1.5 GHz Band has been largely removed as a result of extensive

technical evaluation and field measurements, mainly by Canada’s Communications

Research Centre (CRC). It was found that indoor reception at L-Band is comparable to

that achieved at VHF frequencies. The reason is that the shorter wavelength at L-Band

offsets the increased attenuation through walls at the lower VHF frequencies.

4.5.2

The Implications of Simulcasting

Whilst the benefits of digital broadcasting and the opportunities offered by this technology 

are clear to broadcasters, there is concern about the time and cost implications of the

transition from analogue to digital. Until the coverage from digital broadcasts matches

that from existing FM and AM services, it is unrealistic to cut existing transmissions and

disfranchise listeners. It could be some years before the new digital services provide

comparable coverage and a receiver base is established. Only then can the analogue

services be closed down.

The transition from analogue to digital is helped in many countries by cooperation

between public and private broadcasters, that jointly develop the necessary infra-

structure and create attractive new programmes, and suitable regulatory arrangements.

Examples of such cooperation exist in Canada, Sweden, the UK, France, Italy, etc.

(1)

HD Radio (IBOC)

IBOC transmission schemes are particularly well suited for ensuring a smooth

transition to digital services.  Since they are designed for compatibility with the

existing analog signals, there is little or no disenfranchisement of listeners at the

onset of service.  New receiver costs are minimised since much of the existing

circuitry can be shared by the analogue and digital portions of the receiver.  And

over time, as IBOC receiver penetration reaches a “critical mass,” individual