On Pilot Grid Design for an OFDM Air Interface

In this paper, an analytical framework is established to dimension the pilot grid for OFDM in terms of overhead and power allocation. With the constraint that the receiver solely relies on pilot symbols for channel estimation, the capacity for OFDM over time-variant frequency selective channels is maximized. The authors show that the maximum capacity is achieved by placing pilots with maximum equidistant spacing given by the sampling theorem, if perfect interpolation is assumed and pilots are appropriately boosted. Allowing for realizable and possibly sub-optimum estimators where interpolation is not perfect, a semi-analytical best pilot allocation strategy is presented.