  Filter bank multi carrier (FBMC) is considered a competitive waveform
candidate for 5G that can replace orthogonal frequency division multiplexing
(OFDM). However, channel estimation (CE) is a big challenge in FBMC because it
suffers from intrinsic interference which is due to the orthogonality of the
subcarrier functions in the real field only. In this paper, we investigate a
proposed modified interference approximation scheme (M-IAM) by approximating
the intrinsic interference from the neighboring pilots to accommodate the
complex channel frequency and thus improving CE performance besides simplifying
its processing. The M-IAM scheme has larger pseudo pilot magnitude than other
conventional preamble schemes, namely the interference approximation method
(IAM) with its versions (IAM-C) and (E-IAM-C); in addition to the novel
preamble design (NPS). In addition, the proposed (M-IAM) scheme is
characterized by the lower transmitted power needed. The CE performance of the
M-IAM is investigated through 512 and 2048 subcarriers via different types of
outdoor and indoor multipath fading channels that are time-invariant such as
IEEE 802.22, IEEE 802.11, Rician, and additive white Gaussian noise (AWGN), as
well as time varying channels such as Rayleigh and Vehicular A (Veh-A).
Simulation results demonstrate that the proposed M-IAM scheme achieves a lower
bit error rate (BER), lower normalized mean square error (NMSE) and lower
peak-to-average power ratio (PAPR) over the conventional preamble schemes under
the aforementioned channel models. The proposed scheme has the advantage of
saving the transmitted power, a requirement that could match 5G low power
requirements.
