Multipath channels, simulation and more

May 2, 2006.

Fixed/mobile multipath channels, SFN/MFN simulation and more (OP-170-E option)

COFDM was the modulation chosen for digital terrestrial TV broadcasting because of its superior performance in dynamic and static multipath channels.

A novel feature in the digital DVB-T modulator MO-170 is the possibility of simulating channels with up to 5 echoes (plus the main path) of variable attenuation (0 to 40 dBc in 0.1 dB steps), delay (0 to 445 ms), phase (0º to 359.9º with resolution of 0.1º) and Doppler frequency (zero for fixed channels and ranging between -830 Hz and +830 Hz in 0.1 Hz steps for mobile channels).

Amplitude and phase of fixed Ricean channel F1 simulated with the MO-170
Amplitude and phase of fixed Ricean channel F1
simulated with the MO-170

Among other applications, the channel simulator can be successfully used to simulate the following scenarios:

  • Pre-echoes in a SFN or, in general, any power delay profile found in practice in single (MFN) & multiple transmitter (SFN) networks.
  • Static channels corresponding to roof-top fixed and portable reception. In particular, good 6-ray approximations can be generated for the F1 and P1 channels defined in Appendix B of document ETSI EN 300 744. Other 6-path profiles are those defined in Appendix K.2 of document ETSI TR 101 290.
  • Mobile channels with pure Doppler shift. An example of this is the 0 dB echo profile proposed in Appendix K.3 of document ETSI TR 101 290.

The channel simulator may be used in conjunction with the C/N generator to evaluate the performance of a DVB-T system for a pre-defined multipath channel as a function of the amount of additive noise present in the channel.

Multipath interference outside the guard interval in digital terrestrial broadcasting
Multipath interference outside the guard interval in digital terrestrial broadcasting