## Bit error rate vs symbol error rate

#### So far we have derived the probability of symbol error for a data system whereas in practice the user is more concerned with the probability of bit error for the communications link. For a binary system, bit and symbol error are identical as each symbol error corresponds to a single bit error. For M-ary systems (M > 2), however, this does not hold true. For example, the 8-ary ASK scheme shown here can convey three bits per symbol and may incur anything from one bit error to three bit errors for each incorrectly decoded symbol, depending on which symbol was mistakenly identified. |

#### In practice, some symbols are more likely to be detected in error than others, depending on how close or similar the symbols are to the correct symbol. Careful choice of bit pattern assignment to each symbol may thus help to minimize the number of bit errors occurring for every symbol error.

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