Probability of bit errors as a function of SNR.
BER=P(bit error) vs Eb/N0: BPSK P_b=Q(√(2E_b/N₀)); QPSK same per bit; higher-order QAM needs more Eb/N0. Error-correcting coding gain shifts curves left. Waterfall curves; test with PRBS sequences. Target BER 10⁻⁶–10⁻¹².
Moving from BPSK to 16-QAM costs several dB in Eb/N0 for the same BER.
Bit error rate measures how often data is wrong, which determines whether a link is usable for a given application.
Probability of bit errors as a function of SNR.
Bit error rate measures how often data is wrong, which determines whether a link is usable for a given application.
The number of bit errors divided by the total number of bits transmitted, measured over a period.
It falls steeply as SNR rises, so a small SNR improvement can make a large difference in error rate.
Typical applications include specifying the BER target for a control network, comparing two coding schemes at the same SNR and estimating the retransmission rate for a wireless file transfer.
Study "Constellation diagrams" first (topic 81 of 101 in Signals, Control & Comms). It covers the groundwork this topic builds on.
Q-function. Coding gain. Packet error rate.
Moving from BPSK to 16-QAM costs several dB in Eb/N0 for the same BER.
The next topic is "Source coding", which builds directly on this one.
It is classed as Advanced in Signals, Control & Comms (topic 82 of 101). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Signals, Control & Comms.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.