Oversampled Perfect Reconstruction Filter Bank Transceivers PDF Download

Author: Siavash Rahimi
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Languages : en
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Book Description
"Multicarrier modulation (MCM) is an efficient transmission technique for high data rate wired and wireless communications, where the channel bandwidth is divided into several subchannels with their own carriers. There are many different possible realizations for MCM systems, but with no doubt, orthogonal frequency division multiplexing (OFDM) has been the most prevalent solution in many current applications and standards. However, due to its use of a rectangular prototype filter, channel impairments such as narrowband interference (NBI) and carrier frequency offset (CFO) can greatly deteriorate the performance of OFDM. Moreover, future telecommunication networks call for higher data rate, increased bandwidth efficiency and flexibility in handling unsynchronized users. Filter bank multicarrier (FBMC) techniques have recently attracted considerable attention within the research community as a venue to fulfill these needs and potentially outperform the established OFDM in application areas such as dynamic spectrum access (DSA) and cognitive radio.In this context, we first propose a novel method for the design of discrete Fourier transform (DFT) modulated oversampled perfect reconstruction filter bank (OPRFB), for transmultiplexing application in MCM systems. The perfect reconstruction (PR) property is enforced by employing a parametric class of paraunitary matrices to form the transmit/receive polyphase filters of the transceiver system. Specifically, the polyphase filters are obtained by cascading special types of paraunitary matrices characterized by a limited set of design parameters. To reduce the number of these parameters, three different factorization methods are employed and compared. Through the optimization of these design parameters, the stop-band energy of the subband filters can be minimized which leads to improved spectral containment. Numerical results show that the proposed scheme leads to a clear advantage not only in additive white Gaussian noise (AWGN) and frequency selective channels, but also in the presence of channel impairments such as NBI or CFO. In particular, it is found that a significant reduction in the bit error rate (BER) can be achieved by employing the proposed scheme. Secondly, still in the context of single-user systems, we derive a data-aided joint maximum likelihood (ML) estimator of the CFO and the channel impulse response (CIR) for OPRFB transceiver systems operating over frequency selective fading channels. Then, by exploiting the structural and spectral properties of these systems, we are able to considerably reduce the complexity of the proposed estimator through simplifications of the underlying likelihood function. The Cramer Rao bound (CRB) on the variance of unbiased CFO and CIR estimators is also derived. The performance of the proposed ML estimator is investigated by means of numerical simulations under realistic conditions with CFO and frequency selective fading channels. The effects of different pilot schemes on the estimation performance for applications over time-invariant and mobile time-varying channels are also examined. The results show that the proposed joint ML estimator exhibits an excellent performance, where it can accurately estimate the unknown CFO and CIR parameters for the various experimental setups under consideration.Our third and final contribution deals with the extension of these newly proposed estimators to the multi-user case. More specifically, we consider the joint estimation of the CFO and channel equalizer coefficients based on the ML principle in the uplink of multi-user OPRFB (MU-OPRFB) systems. The performance of the proposed joint ML estimator is examined for various subband allocation schemes by means of numerical simulations. Also, different distributions of pilots over time are considered and their effects are investigated over mobile time-varying channels." --