Low complexity multipath diversity through fractional sampling in OFDM

Orthogonal frequency division multiplexing (OFDM) enables low-complexity equalization and has been adopted in several wireless standards. However, OFDM cannot exploit multipath diversity without computationally complex coding and decoding. We show here that fractional sampling (FS) can improve the capacity and the diversity that an OFDM system can provide. We calculate the outage capacity of an FS-OFDM system to quantify the possible gains that FS offers. We also propose a low-complexity maximal ratio combining approach at each subcarrier for the FS-OFDM system, and argue that the diversity gains acquired through this approach are related to the frequency content of the transmit filter. We corroborate our approach with simulations.