Conference Paper

Wireless OFDM-OQAM with a Small Number of Subcarriers

Univ. degli Studi di Palermo, Palermo
DOI: 10.1109/WCNC.2008.38 Conference: Wireless Communications and Networking Conference, 2008. WCNC 2008. IEEE
Source: IEEE Xplore

ABSTRACT Orthogonal frequency division multiplexing based on offset quadrature amplitude modulation (OFDM-OQAM) is a multicarrier signaling technique which trades off robustness for spectral efficiency when compared to conventional OFDM with a cyclic prefix. In this paper, a novel matrix model for passband OFDM-OQAM signaling with a small number of subcarriers over a multipath frequency selective fading channel is presented. Specifically, in OFDM-OQAM a frequency selective channel is divided into many smaller but still frequency selective overlapping channels, so approximating the frequency response of a subchannel by the channel frequency response sampled at the subcarrier frequency may be inadequate. Channel effects may be better characterized if the frequency response of each subchannel is represented as a Taylor expansion at the subcarrier frequency. Simulation results show how the matrix model implemented by means of this approximation is a suitable model for OFDM-OQAM with a small number of subcarriers.

1 Bookmark
 · 
87 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel equalization structure for filter bank based multicarrier (FBMC) based modulations is proposed in this paper. The equalizer architecture is derived by assuming that the number of carriers is asymptotically large, and it consists of multiple parallel stages that are linearly combined on a per-subcarrier basis. The traditional single-tap per-subcarrier equalizer is obtained as a special case of the proposed architecture when the number of stages is fixed to one. An analytical characterization of the output signal to noise plus distortion ratio is provided, which can be used in practice to fix the number of parallel stages of the equalizer in order to obtain a certain performance level at the minimum complexity. Both simulations and analytical predictions indicate that high performance gains can be obtained with respect to more conventional FBMC equalization approaches. Furthermore, the proposed architecture is also shown to present important advantages in terms of computational complexity when compared with classical FBMC equalization architectures.
    IEEE Transactions on Signal Processing 07/2013; 61(14):3592-3606. · 3.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Channel estimation in multicarrier systems employing filter banks with offset quadrature amplitude modulation (FBMC/OQAM) is known to face challenges related to the interference effect intrinsic to these systems. Most of the methods reported thus far rely on the assumption of (almost) flat subchannels - implying a low frequency selective channel - to more easily tackle this problem. Others, more recent ones, relax this assumption but they either depend on a model for the channel or they concentrate on per-subchannel estimation and often require long training sequences. This paper revisits this problem by proposing a method that makes no assumption on the channel frequency selectivity, while using a very short preamble for training. The latter is optimized with respect to the channel estimation mean squared error. The superiority of the proposed method over classical ones is demonstrated via simulation results for both mildly and highly frequency selective channels.
    ICASSP 2014 - 2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP); 05/2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: Filter bank-based multicarrier (FBMC) techniques have attracted a lot of interest in the last decade as a competitive alternative to the long established OFDM, particularly in wireless applications. Their potential stems from their increased ability to carrying a flexible spectrum shaping together with a major increase in spectral efficiency and robustness to synchronization requirements, features of fundamental importance in future mobile networks. A particular type of FBMC, the so-called FBMC/OQAM system, consisting of pulse shaped OFDM carrying offset QAM (OQAM) symbols, has received increasing attention due to, among other features, its potential for maximum spectral efficiency. It suffers, however, from an inherent inter-carrier/inter-symbol interference that complicates signal processing tasks such as channel estimation. The goal of this paper is to concisely present the state-of-the-art in channel estimation for FBMC/OQAM, putting emphasis on the problems that are still open and outlining related on-going research. Preamble-based channel estimation is given special attention in the realistic scenario of highly frequency/time selective channels and some new results are reported in this context.
    2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP); 05/2014

Preview

Download
6 Downloads