Capacity of MIMO-OFDM with Pilot-Aided Channel Estimation

An analytical framework is established to dimension the pilot grid for MIMO-OFDM operating in time-variant frequency selective channels. The optimum placement of pilot symbols in terms of overhead and power allocation is identified that maximizes the training-based capacity for MIMO-OFDM schemes without channel knowledge at the transmitter. For pilot-aided channel estimation (PACE) with perfect interpolation, we show that the maximum capacity is achieved by placing pilots with maximum equidistant spacing given by the sampling theorem, if pilots are appropriately boosted. Allowing for realizable and possibly suboptimum estimators where interpolation is not perfect, we present a semianalytical method which finds the best pilot allocation strategy for the particular estimator.