361 research outputs found
Efficient implementation of filter bank multicarrier systems using circular fast convolution
In this paper, filter bank-based multicarrier systems using a fast convolution approach are investigated. We show that exploiting offset quadrature amplitude modulation enables us to perform FFT/IFFT-based convolution without overlapped processing, and the circular distortion can be discarded as a part of orthogonal interference terms. This property has two advantages. First, it leads to spectral efficiency enhancement in the system by removing the prototype filter transients. Second, the complexity of the system is significantly reduced as the result of using efficient FFT algorithms for convolution. The new scheme is compared with the conventional waveforms in terms of out-of-band radiation, orthogonality, spectral efficiency, and complexity. The performance of the receiver and the equalization methods are investigated and compared with other waveforms through simulations. Moreover, based on the time variant nature of the filter response of the proposed scheme, a pilot-based channel estimation technique with controlled transmit power is developed and analyzed through lower-bound derivations. The proposed transceiver is shown to be a competitive solution for future wireless networks
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.Peer ReviewedPostprint (author's final draft
Conjugate-Root Offset-QAM for Orthogonal Multicarrier Transmission
Current implementations of OFDM/OQAM are restricted to band-limited symmetric
filters. To circumvent this, non-symmetric conjugate root (CR) filters are
proposed for OQAM modulation. The system is applied to Generalized Frequency
Division Multiplexing (GFDM) and a method for achieving transmit diversity with
OQAM modulation is presented. The proposal reduces implementation complexity
compared to existing works and provides a more regular phase space.
GFDM/CR-OQAM outperforms conventional GFDM in terms of symbol error rate in
fading multipath channels and provides a more localized spectrum compared to
conventional OQAM.Comment: 4pages, revised version submitted to IEEE WC
Dual-Polarization OFDM-OQAM Wireless Communication System
In this paper we describe the overall idea and results of a recently proposed
radio access technique based on filter bank multicarrier (FBMC) communication
system using two orthogonal polarizations: dual-polarization FBMC (DP-FBMC).
Using this system we can alleviate the intrinsic interference problem in FBMC
systems. This enables use of all the multicarrier techniques used in
cyclic-prefix orthogonal frequency-division multiplexing (CP-OFDM) systems for
channel equalization, multiple-input/multiple-output (MIMO) processing, etc.,
without using the extra processing required for conventional FBMC. DP-FBMC also
provides other interesting advantages over CP-OFDM and FBMC such as more
robustness in multipath fading channels, and more robustness to receiver
carrier frequency offset (CFO) and timing offset (TO). For DP-FBMC we propose
three different structures based on different multiplexing techniques in time,
frequency, and polarization. We will show that one of these structures has
exactly the same system complexity and equipment as conventional FBMC. In our
simulation results DP-FBMC has better bit error ratio (BER) performance in
dispersive channels. Based on these results, DP-FBMC has potential as a
promising candidate for future wireless communication systems.Comment: 1.This paper is accepted to be published in IEEE Vehicular Technology
Conference (VTC) FALL 2018. 2.In this new submitted version authors have
revised the paper based on the VTC FALL reviewers comments. Therefore some
typos have fixed and some results have change
Preamble-Based Channel Estimation for CP-OFDM and OFDM/OQAM Systems: A Comparative Study
In this paper, preamble-based least squares (LS) channel estimation in OFDM
systems of the QAM and offset QAM (OQAM) types is considered, in both the
frequency and the time domains. The construction of optimal (in the mean
squared error (MSE) sense) preambles is investigated, for both the cases of
full (all tones carrying pilot symbols) and sparse (a subset of pilot tones,
surrounded by nulls or data) preambles. The two OFDM systems are compared for
the same transmit power, which, for cyclic prefix (CP) based OFDM/QAM, also
includes the power spent for CP transmission. OFDM/OQAM, with a sparse preamble
consisting of equipowered and equispaced pilots embedded in zeros, turns out to
perform at least as well as CP-OFDM. Simulations results are presented that
verify the analysis
Alamouti OFDM/OQAM systems with time reversal technique
Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude
Modulation (OFDM/OQAM) is a multicarrier modulation scheme that can be
considered as an alternative to the conventional Orthogonal Frequency Division
Multiplexing (OFDM) with Cyclic Prefix (CP) for transmission over multipath
fading channels. In this paper, we investigate the combination of the OFDM/OQAM
with Alamouti system with Time Reversal (TR) technique. TR can be viewed as a
precoding scheme which can be combined with OFDM/OQAM and easily carried out in
a Multiple Input Single Output (MISO) context such as Alamouti system. We
present the simulation results of the performance of OFDM/OQAM system in SISO
case compared with the conventional CP-OFDM system and the performance of the
combination Alamouti OFDM/OQAM with TR compared to Alamouti CP-OFDM. The
performance is derived by computing the Bit Error Rate (BER) as a function of
the transmit signal-to-noise ratio (SNR)
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