Rostom Zakaria

A Novel Filter-Bank Multicarrier Scheme to Mitigate the Intrinsic Interference: Application to MIMO Systems

Filter-bank multicarrier (FBMC) transmission system was proposed as an alternative approach to orthogonal frequency division multiplexing (OFDM) system since it has a higher spectral efficiency. One of the characteristics of FBMC is that the demodulated transmitted symbols are accompanied by interference terms caused by the neighboring transmitted data in time-frequency domain. The presence of this interference is an issue for some multiple-input multiple-output (MIMO) schemes and until today their combination with FBMC remains an open problem. We can cite, among these techniques, the Alamouti scheme and the maximum likelihood detection (MLD) with spatial multiplexing (SM). In this paper, we shall propose a new FBMC scheme and transmission strategy in order to avoid this interference term. This proposed scheme (called FFT-FBMC) transforms the FBMC system into an equivalent system formulated as OFDM regardless of some residual interference. Thus, any OFDM transmission technique can be performed straightforwardly to the proposed FBMC scheme with a corresponding complexity growth compared to the classical FBMC. First, we will develop the FFT-FBMC in the case of single-input single-output (SISO) configuration. Then, we extend its application to SM-MIMO configuration with MLD and Alamouti coding scheme. Simulation results show that FFT-FBMC can almost reach the OFDM performance, but it remains slightly outperformed by OFDM.

Maximum likelihood detection in spatial multiplexing with FBMC

In FBMC transmission systems, the bit rate is maximized when OQAM modulation is employed. One of the characteristics of this modulation is that the received data symbols are accompanied by interference terms, which complicates the application of ML techniques in optimal decoders. Two approaches are proposed to cope with this situation. The first one exploits the MMSE estimation of the interference terms and it introduces no additional delay. In the second one, the interference terms are calculated from past, present and future data symbols, either already decided or estimated. The gains provided by these approaches, with respect to MMSE, are assessed and illustrated by simulation.

On Maximum Likelihood MIMO detection in QAM-FBMC systems

Multi-carrier modulation and especially CP-OFDM is widely used nowadays in several radio communications. However, FBMC is a potential alternative to CP-OFDM since it does not require cyclic prefix, and thus, it has a higher spectral efficiency. One of the characteristics of FBMC is that the received data are accompanied by a two dimensional inter-symbol interference term (2D ISI), which complicates MIMO techniques when combined with optimum detection. In this paper we consider the association of FBMC with the multiple-input multiple-output (MIMO) technique focusing on the spatial data multiplexing (SDM), and we investigate the use of Maximum Likelihood (ML) detection. We propose modified FBMC schemes based on inserting null data among QAM symbols to reduce, in this way, the overlapping of the symbols.1

MIMO Signal Processing in Offset-QAM Based Filter Bank Multicarrier Systems

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.

A novel FBMC scheme for Spatial Multiplexing with Maximum Likelihood detection

FBMC transmission system was proposed as an alternative approach to OFDM system since it has a higher spectral efficiency. One of the characteristics of FBMC is that the demodulated transmitted symbols are accompanied by interference terms caused by the neighboring transmitted data in time and frequency domain. The presence of this interference is an issue for the Maximum Likelihood (ML) implementation when we consider a Spatial Multiplexing MIMO system. In this paper, we will propose a new FBMC scheme and transmission strategy in order to avoid this interference term. This proposed scheme (called FFT-FBMC) transforms the FBMC system into an equivalent system as simple as OFDM. First, we will develop the FFT-FBMC in the case of SISO configuration, and then, we extend its application to Spatial Multiplexing MIMO configuration with Maximum Likelihood detection.1

Intrinsic interference reduction in a filter bank-based multicarrier using QAM modulation☆

Abstract The offset QAM-based filter-bank multicarrier (FBMC/OQAM) has recently attracted a lot of research interest thanks to its high spectral efficiency. The data in the FBMC/OQAM are carried by real-valued symbols transmitted at each half period ( T / 2 ). At the receiver side, the received symbols are corrupted by pure imaginary intrinsic interference terms which prevent the application of some well-known schemes such as Alamouti coding and maximum likelihood (ML) detection in spatial multiplexing (SM) systems. Receiver schemes with interference cancellation are not always effective, due to error propagation. Interference cancellation can be effective when the signal-to-interference ratio is beyond a certain threshold. In this paper, we propose reducing the intrinsic interference power by modifying the conventional FBMC/OQAM system by transmitting QAM data symbols instead of OQAM ones. Consequently, the real orthogonality condition is no longer satisfied. On the other hand, we can show that, by using receivers based on iterative interference cancellation, we can successfully remove the intrinsic interference. We test the proposed FBMC/QAM in both schemes: 2 × 1 Alamouti coding scheme and 2 × 2 SM with ML detection. The bit-error rate performance is assessed and illustrated by Monte Carlo simulations.

Partial ISI cancellation with viterbi detection in MIMO filter-bank multicarrier modulation

In this paper we deal with the presence of the intrinsic intersymbol interference (ISI) in the filter-bank multicarrier systems. Indeed, the received data symbols are accompanied by interference terms, which complicate the detection in a maximum likelihood (ML) sense in the spatial multiplexing scheme. Detection schemes with ISI estimation and cancellation are not always effective due to the error propagation. We propose a receiver based on a partial ISI cancellation followed by the Viterbi detector. A simple tentative detector is first used to cancel partially the ISI. We show that under some conditions the ISI cancellation is effective and the performance converges to the optimum one.

On ISI cancellation in MIMO-ML detection using FBMC/QAM modulation

In this paper, the filter-bank multicarrier (FBMC) system is considered, and we deal with the presence of the inherent intersymbol interference (ISI). Indeed, the transmitted data symbols in FBMC are OQAM (Offset QAM) modulated, and the received data symbols are corrupted by inherent interference terms which complicate the detection in a maximum likelihood (ML) sense in the spatial multiplexing scheme. Detection schemes with ISI estimation and cancellation are not always effective due to the error propagation. We propose in this paper to modify the conventional FBMC system by transmitting QAM data symbols instead of OQAM ones in order to reduce the inherent interference. Then, we propose a receiver based on ISI estimation and cancellation. A simple tentative detector is first used to attempt to cancel the ISI before applying the ML detection. We show by simulation that with the proposed FBMC/QAM system, the ISI cancellation is effective and the performance converges to the optimum one.

Resource Block-Level Power Allocation in Asynchronous Multi-Carrier D2D Communications

This letter focuses on weighted sum rate maximization with filter bank multi-carrier (FBMC) and orthogonal frequency division multiplex (OFDM) multi-carrier modulations for asynchronous device-to-device (D2D) communications. The main difficulty in power allocation with asynchronous multi-carrier transmissions is that inter-channel interference (ICI) depends on subcarriers, whereas power values should be optimized with resource block (RB) granularity. In this letter, we show that the weighted sum rate maximization problem can be solved at RB level, while still considering ICI, and that the power allocation algorithm solving this problem is distributed and leads to its global optimum. Moreover, FBMC achieves higher data rates than OFDM, thanks to its lower ICI spread.

On the impact of the prototype filter on FBMC sensitivity to time asynchronism

This paper investigates the impact of the prototype filter on the sensitivity of the FBMC system to timing synchronization errors. A global evaluation of the average error rate has been made for OFDM and two FBMC systems using PHYDYAS and IOTA prototype filters. This evaluation has been performed taking into account different parameters: the timing error range, the guard band length and the load factor of the network. The validity of the simulation results will be verified by comparison with those obtained with the analytical expressions.