Abstract :
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 by sampling at a rate higher than the symbol
rate, which is also known as fractional sampling (FS), one can improve
the diversity that the wireless channel can provide in an
OFDM system.We propose maximal ratio combining at each subcarrier
for the FS-OFDM system, argue that the diversity gains
acquired through this approach are related to the spectral shape
of the pulse and its excess bandwidth, and derive analytical bit
error and symbol error rate expressions for our scheme. We also
explore extensions to differentially encoded systems that do not
require channel status information at the receiver, multiple-input
multiple-output (MIMO) systems that exploit space diversity, and
low peak-to-average (PAR) options such as zero-padded (ZP) and
cyclic-prefix only (CP-only) transmissions.We corroborate our approach
with simulations.
