Getting your BERs right

May 2, 2006.

Getting your Bit Error Ratios right

A unique feature of the digital DVB-T modulator MO-170 is the insertion of bit errors in different stages of the DVB-T modulation chain. This can help to check the accuracy of the BER estimation algorithms implemented in high-end professional receivers.

A Channel BER (CBER or BER before the Viterbi decoder) ranging between 7.6x10-6 and 1.25x10-1 is generated by modifying the sequence of bits at the input to the constellation mapper. Analogously, the MO-170 is able to generate a Viterbi BER (VBER or BER after Viterbi) going from 3.7x10-9 to 6.2x10-2 by properly processing the bits at the output of the Reed-Solomon encoder. The main advantage of this technique when compared with varying the C/N to get the desired CBER or VBER, is its high resolution and unparalleled accuracy.

BER measured by the TV EXPLORER field strength meter

QEF VBER insertion in the digital DVB-T modulator MO-170
QEF VBER insertion in the MO-170 and BER measured
by the TV EXPLORER field strength meter