One of the most important features of a DVB-T receiver is the performance of the RF front-end, principally consisting of a tuner and the COFDM demodulator. The ability to successfully deliver the video and audio elementary streams to the user is the acid test that fuels return rate and churn. Good receiver sensitivity is of paramount importance as the DVB-T signal coverage is still marginal across much of Europe, compounded by inefficient legacy analogue antennae serving many consumer households. The low antennae gain of increasingly popular mobile devices is also a challenge for receiver designers. With much Europe's spectrum consisting of a mix of analogue and digital channels combined with multi-path effects from single frequency networks (SFN), the successful reception of a channel is hampered by multiple impairments. Up until now, front-end receiver performance has been typically validated through limited lab testing to specifications and patchy field test measurements.
DVB-T RF Front End Validation
Typically receivers are validated in lab conditions to RF test specifications such the UK D-Book 5.0, the Scandinavian NorDig 1.03 and sometimes E-Book or the Italian DGTVi requirements. However, these specifications usually test only one type of signal impairment such as an echo or interferer at any one time. Real field conditions are often a combination of impairments, such as fading, impulse noise, echoes and multiple interferers. The wide variation of complex waveforms that are actually encountered in the field cannot possibly be modelled with normal lab tests.
Specifications are designed to set minimum performance criteria, and in practice there is a wide variation of receiver performance amongst compliant receivers as the bar is set quite low. Also the test specifications only really call for "spot" tests on performance. For example, the UK D-Book only requires sensitivity tests for each mode on the bottom, middle and top channels, allowing receivers with sub-standard performance on un-tested channels to pass and subsequently fail at those frequencies in the field. The reality is that some apparently specification-conformant receivers will fail to install all the channels in the consumer premises, and may be returned to the retailer.
The conventional approach to augmenting these lab tests has been to field test receivers.