Damian according to this ,there is no need of long sequence length to calculate BER.However in case of OFDm, in almost all the forum topics we say that due to long sequence length value of BER is either o error free and then abruptly decrease fimally to 1.By using BER DUT set, error in bits increase very quickly with even small distance.Is there any relation of ling sewuence length in OFDM ber? Ihave tried to write what i want to know.Hope you can also understand