Receiver design for OFDM in the presence of I/Q imbalance and amplifier nonlinearity

In this paper we study the joint estimation of channel and I/Q imbalance for OFDM in the presence of amplifier non-linearity. The presence of non-ideal behaviour at the transmitter and receiver in OFDM transmission systems can effect the estimation of both channel and data. The use of cost effective and miniaturized components such as local oscillators (LO) and direct conversion (DC) receivers can distort the signal. One approach is to allow low quality analog components and use signal processing to compensate for these impairments at the receiver. In this paper we analyze the effects of transmit/receiver amplifier nonlinearity in the presence of I/Q imbalance where amplifier nonlinearity is a serious impediment for higher order modulation systems. We also use two special training sequences to estimate the channel and amplifier non-linearity using the maximum likelihood (ML) criterion. (5 pages)