hello all,
On what basis people decide targeted BER, like many system designers prefer 10^-12 in most of the cases, and i heard old TV and small length communication people preferred even 10^-20. I have some understanding on BER like total invariance of the noise relation to some specific number, but would like to know fundamental reason behind choosing BER target?

Thanks,
Raj.

In some transmission standards BER can relate to the possibility of a reliable link.  For example BlueTooth LE has a BER=0.1%.  This represents a packet error rate of ~30%, about the maximum error to maintain a link.  In other words, for every 3 packets sent, 2 should be received.