In telecommunications, Filter Bank Modulation (FBM), also known as Multicarrier Modulation (MC), is a Frequency-division multiplexing transmission technique. This technique is generally used in digital high-data rate communication systems.

Multicarrier modulations idea was born in 1957 by M.L. Doelz^[1]. The baseline idea was quite simple. The high data-rate sequence is split into a series of K parallel low data-rate sequences. Following the FDM principle, the total bandwidth available is partitioned in K non-overlapping sub-channels. The sub-channels digital sequences are modulated with a digital modulation (e.g. PSK or QAM) and the obtained signals are summed together to yield the transmitted signal. If the sub-channel number is sufficiently high, the transmission medium frequency response is quasi-flat for each sub-channel. Thus, the equalization process can be simplified. A MC scheme is practically implemented with a filter bank structure. Oppositely from conventional FB theory, where an analysis bank is followed by a synthesis bank, in FBM the two banks are swapped. The transmitter is implemented with a synthesis bank and the receiver is implemented with an analysis bank.

Mathematically, the transmitted signal is expressed as

${\displaystyle x(nT)=\sum _{k=0}^{K-1}\sum _{\ell =0}^{L-1}a^{(k)}(\ell NT)g(nT-\ell NT)e^{i2\pi nk/K))$,

where L is transmitter block size (in symbols) and g(nT) is the transmitter prototype pulse impulse response. At the receiver, the m-th received symbol in the i-th sub-channel is written as

${\displaystyle z^{(i)}(mNT)=\sum _{n}x(nT)h(mNT-nT)e^{-i2\pi ni/K))$,

where h(nT) is the receiver prototype pulse impulse response.

Generally, the filtering operations in the filter banks exploit the linear convolution operator. In 1997 a new idea has come: replace the linear convolution with the circular convolution. Cyclic filter banks have been introduced by Vaidyanathan.^[2] This new concept has been used to build a new type of multicarrier systems. Commons cyclic FBM schemes are CB-FMT, COQAM, SC-FDMA and GFDM.

Cyclic Block Filtered Multitone Modulation is the cyclic-version of conventional Filtered Multitone Modulation, a multicarrier scheme proposed by G. Cherubini in 2000 for VHDSL.^[3] CB-FMT has been proposed by A. Tonello in 2008.^[4] In CB-FMT the prototype pulses have high frequency domain confinement and the banks are orthogonal.

Cyclic Offeset-QAM is the cyclic-version of Offeset-QAM. In OQAM, the complex symbol is split into the real and the imaginary part. Furthermore, real and imaginary parts are staggered in time-domain between adjacent sub-channels. This idea was was conceived in 1967 by B.R. Saltzberg.^[5] The cyclic implementation has been proposed in 2014 by P. Siohan.^[6]

Single-carrier FDMA is born to improve OFDMA (multi-user version of OFDM). SC-FDMA scheme has been introduced by Myung, Junsung and Goodman in 2006 and it allows to reduce the peak-to-average power ratio.^[7]

Generalized FDM is born to generalize the SC-FDMA scheme with pulse shaping. The scheme was introduced by Fettweis in 2009.^[8] Initially, the scheme was proposed for UHF TV bands.

Category:Radio modulation modes Category:Digital signal processing