System and method for estimating phase offset in a communication system

A system for estimating phase offset between a local oscillator and a transmitted input signal in a communication system, the transmitted signal comprising a number of symbols each having an associated phase, the system comprising:

• a differential detector stage for receiving a transmitted input signal, the differential detector stage having an input and an output;
• a phase compensation stage for compensating for phase errors in an output signal from the differential detector stage, the phase compensation stage having an output;
• a decision-based rotation stage couplable to the outputs of the differential detector stage and the phase compensation stage, the decision-based rotation stage having an output signal having a phase, the decision-based rotation stage being arranged to rotate the output signal from the differential detector stage so that the phase of the signal output from the decision-based rotation stage is within a predetermined amount of a predetermined phase angle, the decision-based rotation stage being arranged to rotate the output signal from the differential detector stage based on a decision made using the output signal from the phase compensation stage;
• an accumulation stage couplable to receive and accumulate the output signal from the decision-based rotation stage for a number of symbols in the transmitted input signal, the accumulation stage having an output;
• and
• a normalization stage couplable to the output of the accumulation stage for receiving an accumulated output signal therefrom, the normalization stage being arranged to normalize the accumulated output signal to produce a normalized output signal;
• the normalized output signal corresponding to the phase offset of two successive symbols caused by the frequency offset and the phase offset between a local oscillator and a transmitted input signal;
• the phase compensation stage having a further input to which the phase offset is applied to compensate the phase of a subsequently received symbol in the transmitted input signal.