  Universal filtered multi-carrier (UFMC) systems offer a flexibility of
filtering arbitrary number of subcarriers to suppress out of band (OoB)
emission, while keeping the orthogonality between subbands and subcarriers
within one subband. However, subband filtering may affect system performance
and capacity in a number of ways. In this paper, we first propose the
conditions for interference-free one-tap equalization and corresponding signal
model in the frequency domain for multi-user (MU) UFMC system. Based on this
ideal interference-free case, impact of subband filtering on the system
performance is analyzed in terms of average signal-to-noise ratio (SNR) per
subband, capacity per subcarrier and bit error rate (BER) and compared with the
orthogonal frequency division multiplexing (OFDM) system. This is followed by
filter length selection strategies to provide guidelines for system design.
Next, by taking carrier frequency offset (CFO), timing offset (TO),
insufficient guard interval between symbols and filter tail cutting (TC) into
consideration, an analytical system model is established. New channel
equalization algorithms are proposed by considering the errors and
imperfections based on the derived signal models. In addition, a set of
optimization criteria in terms of filter length and guard interval/filter TC
length subject to various constraints is formulated to maximize the system
capacity. Numerical results show that the analytical and corresponding optimal
approaches match the simulation results, and the proposed equalization
algorithms can significantly improve the BER performance.
