Bit error rate

In digital transmission, a bit error is a received bit of a data stream over a communication channel that has been altered by noise, interference, distortion or bit synchronization errors. The bit error rate, BER, is the number of bit errors per unit time, while the bit error ratio, also written BER, is the number of bit errors divided by the total number of transferred bits during a studied time interval. The ratio is a unitless performance measure, often expressed as a percentage, and the bit error probability is its expected value. For example, if 3 of 9 transmitted bits arrive wrong, the ratio is 0.333 or 33.3 percent. A related measure is the packet error ratio, where a packet counts as incorrect if at least one bit is wrong. The BER may be improved by a strong signal, a slow and robust modulation or line coding scheme, and channel coding such as forward error correction, and it can be evaluated analytically or by Monte Carlo computer simulation.