An unified approach to equalization and echo cancellation in OQAM-based multi-carrier data transmission

Abstract

In this paper are presented methods for persubchannel equalization and echo cancellation in the OQAMbased parallel data transmission, which exploit the inherent T/2 AM signaling structure of the orthogonally frequencydivision multiplexed T/2-offset quadrature subchannel signals. The method of equalization on itself represents an alternative approach to the previously known one, whereas the method of echo cancellation gives potentially the only valid solution of this problem at the time being. The computationally efficient realization of echo cancellation is based on the conventional combination of poly-phase (PP) filtering and discrete Fourier transforms in realizing filter banks. The LMS algorithm convergence behavior has been analyzed by computer simulation, along with those of a two-step strategy to speed-up adaptation of the corresponding FIR adaptive structures.

Pilot-Based Synchronization and Equalization in Filter Bank Multicarrier Communications

“…To avoid the cross-connections between subchannels, an oversampled receiver filter bank structure with per-subcarrier FIR equalizers can restore the orthogonality of the subcarrier waveforms. This approach is followed in [33][34][35][36][37] and more recently with MMSE equalizers explicitly for FBMC/OQAM in [38].…”

“…(2) Assuming that {w i k,n } are known, the observation is a linear function of ψ and the optimum ψ can easily be calculated with the derivative of the expression in brackets in (35) with respect to ψ and setting the result to 0, yielding…”

Interference cancellation in coded OFDM/OQAM

“…The performance of iterative interference cancellation and FEC decoding was comparatively evaluated with the per-bin linear equalization of [8], using the indoor channel models developed for development of the IEEE 802.11n WLAN standard [17]. The equalization is performed for each subchannel as in regular QAM single-carrier, but by calculating only purely real and purely imaginary outputs at consecutive T/2 instants, and by adapting the complex coefficients at T/2 instants by using corresponding purely real and purely imaginary errors.…”

“…, and by using k k k (8) Due to the finite length duration in time and frequency of the impulse functions of the modulator and the channel, the received signal is the output of a linear matrix filter represented by real valued samples plus a white Gaussian noise, not accounted for after equation (4). The 3x1MISO model is described by the following relation (m replaced by n)…”

Multicarrier waveforms with I/Q staggering: uniform and nonuniform FBMC formats

“…The potential resilience of the staggered I/Q formats and the communication (multicarrier) waveforms based on them against the (kindred) co-channel interference has yet to be fully explored in terms of the per subchannel equalization in the WLF context [15,16]. The linear and nonlinear (DFE) MMSE equalization is directly applicable to the nonuniformly spaced subchannels of the FLO kind, while for the uniform and nonuniform TLO formats, the adequate oversampling at the output of the analysis filter bank might be needed.…”