What is Bit Error Rate (BER) and how is it measured?

Bit Error Rate (BER) is the ratio of erroneously received bits to total transmitted bits, indicating digital communication quality. BER = Number of bit errors / Total bits transmitted. Typical acceptable BER: 10^-6 for voice, 10^-9 for data. BER depends on SNR, modulation scheme, and channel conditions. Measurement involves transmitting known patterns (pseudo-random sequences) and comparing received data. BER curves (BER vs Eb/No) characterize system performance and are used for link budget calculations.