Joint Estimation for Both AGC and DC Based on Distribution Function for OFDM Systems

In orthogonal frequency division multiplexing (OFDM) systems, automatic gain control (AGC) and direct current estimation (DCE) need to take longer time than the single carrier case. It is due to the fact that OFDM signals in the time domain appear as Gaussian distribution, therefore estimation errors in the AGC and the DCE will occur because of the clipping effect introduced by analog to digital converters (ADCs). Moreover, the AGC and the DCE will interfere with each other when operated separately, and generate larger estimate errors. This paper proposes a joint method for both AGC and DCE (AGC-DCE) based on distribution function for OFDM systems. The method overcomes the clipping effect of ADC and the interference between the separate operation of AGC and DCE. Simulation results demonstrate that only after one time adjustment, the proposed AGC-DCE method achieves less than 0.13 dB power estimate error and less than 71 mV DC estimate error, whereas the traditional method provides less than 20 dB and less than 550 mV estimate errors respectively. If the same estimate errors are reached, the estimate delay of the proposed AGC-DCE method is 33.3%-66.7% of that of the traditional method.