Offset Quadrature Amplitude Modulation (OQAM)-Based FBMC
Abstract:
Next-generation communication systems have to comply with very strict requirements for increased flexibility in heterogeneous environments, high spectral efficiency, and agility of carrier aggregation. This fact motivates research in advanced multicarrier modulation (MCM) schemes, such as filter bank-based multicarrier (FBMC) modulation. This paper focuses on the offset quadrature amplitude modulation (OQAM)-based FBMC variant, known as FBMC/OQAM, which presents outstanding spectral efficiency and confinement in a number of channels and applications. Its special nature, however, generates a number of new signal processing challenges that are not present in other MCM schemes, notably, in orthogonal-frequency-division multiplexing (OFDM). In multiple-input multiple-output (MIMO) architectures, which are expected to play a primary role in future communication systems, these challenges are intensified, creating new interesting research problems and calling for new ideas and methods that are adapted to the particularities of the MIMO-FBMC/OQAM system. The goal of this paper is to focus on these signal processing problems and provide a concise yet comprehensive overview of the recent advances in this area. Open problems and associated directions for future research are also discussed.
Abstract:
This paper introduces filter bank multicarrier (FBMC) as a potential candidate in the application of massive MIMO communication. It also points out the advantages of FBMC over OFDM (orthogonal frequency division multiplexing) in the application of massive MIMO. The absence of cyclic prefix in FBMC increases the bandwidth efficiency. In addition, FBMC allows carrier aggregation straightforwardly. Self-equalization, a property of FBMC in massive MIMO that is introduced in this paper, has the impact of reducing (i) complexity; (ii) sensitivity to carrier frequency offset (CFO); (iii) peak-to-average power ratio (PAPR); (iv) system latency; and (v) increasing bandwidth efficiency. The numerical results that corroborate these claims are presented.
METHOD FOR ADAPTIVE COUNTERACTING CROSSTALK IN DSL SYSTEMS
Abstract:
This paper presents filtered multitone (FMT) modulation techniques as a potential candidate for counteracting crosstalk interference in digital subscriber line (DSL) systems. We also analysis the importance of these techniques in the context of filter bank-based systems for very high-speed DSL (VDSL) systems. This paper focuses on redundant precoder schemes with non-uniform equalizer filter banks, which provide an outstanding spectral efficiency for multicarrier systems. The introduction of these redundant precoder filter banks provides more degree of freedom to compensate the induced crosstalk at the equalizer. In addition, the proposed algorithms allow more flexible carrier aggregation and provide a property of self-equalization with reduced crosstalk challenges. The goal of this paper is to focus on nonlinear multicarrier signal processing problems, such as crosstalk, and to provide an iterative and adaptive method of mitigating these challenges. Some simulation results that validate the proposed algorithms are presented.
Introduction
Abstract:
A technique for using jointly precoder and equaliser schemes for digital subscriber lines (DSL) is presented. The methods utilize analysis filter bank as precoder before modulation and transmission of signals. The performance of this joint transmission scheme is analysed and compared with that of a conventional transceiver, with no preprocessor, on some design rules. It is found that the crosstalk (NEXT) impairment can be counteracted using redundant precoder schemes in addition to adaptive decision-feedback equalizers (DFEs). This method offers more flexibility over using fixed precoder scheme with minimum mean square equalizer (MMSEs). However, the results indicate that adaptive based DFE equalizer can be used to counteract precursor intersymbol interface (ISI) without substantial performance constraints. This leaves the equalizer with the opportunity to compensate the effects of additive interference and postcursor crosstalk.