Spectral Precoding Techniques for OFDM and OFDMA
Date Issued
2014
Date
2014
Author(s)
Chen, Wei-Chang
Abstract
Spectrally precoded orthogonal frequency-division multiplexing (OFDM) and its multiple access extension (OFDMA) are useful rectangularly pulsed OFDM and OFDMA signaling formats for they exploit high spectral compactness and frequency diversity characteristics. This thesis aims at exploring more on spectrally precoded OFDM and OFDMA. In the first part of the thesis, two new spectral precoders of the largest precoding rate are developed in order to provide improved spectral compactness and reduce implementation complexity, respectively, for OFDMA using cyclic prefix and interleaved subcarrier allocation (IOFDMA) and OFDM using zero padding (ZP-OFDM). Specifically, a new correlative precoder is developed and shown to minimize the dominant spectral coefficient among all correlative precoders of the largest precoding rate and thus can construct IOFDMA and ZP-OFDM signals providing extremely high spectral compactness. Besides, a multiple-stage spectral precoding technique is proposed to construct low-complexity orthogonally precoded IOFDMA and ZP-OFDM with power spectral sidelobes decaying as f^{-2L-2} for L>1, where L is the number of stages. The corresponding orthogonally precoded IOFDMA and ZP-OFDM signals conveying independent zero-mean data are respectively shown to provide the same power spectrum as existing orthogonally precoded IOFDMA and ZP-OFDM signals of the largest precoding rate, while requiring much less complexity. In the second part of this thesis, the cancellation-subcarrier-based (CS-based) spectral precoding scheme is proposed for OFDMA. In the scheme, the subcarriers allocated to a user are divided into two parts, namely, data subcarriers and cancellation subcarriers. The data subcarriers are used to transmit data symbols and the cancellation subcarriers are used to transmit precoded symbols and endow the resulting OFDMA signals with extremely small power spectral sidelobes decaying as f^{-2L-2} for L>1. When the number of cancellation subcarriers is assigned, the proposed CS-based spectrally precoded OFDMA signals are shown to provide comparable power spectral compactness to existing CS-based OFDMA signals while giving comparable or much smaller average redundant power on cancellation subcarriers.
Subjects
正交分頻多重存取
正交分頻多工
頻域預編碼
頻譜旁波壓抑
頻譜緊密度
子載波分配
消除子載波
最小冗餘能量
Type
thesis
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