Adaptive equaliser

An adaptive equaliser is an equaliser whose parameters are automatically and adaptively updated during the transmission of data. Equalisers are commonly used to compensate for the unequal frequency response of a transmission channel, e.g. to compensate for frequency selective fading in mobile communications.

An adaptive equaliser needs some information about the chracteristics of the transmission channel to adapt its parameters. In GSM a 26-bit training sequence is transmitted in the middle of each data burst. This provides the receiver with a set of bits whose values are known in advance and can be used to calculate the chracteristics of the transmission channel.