Unified out-of-band emission reduction with linear complexity for OFDM

© 2014 IEEE. This paper proposes a unified out-of-band emission (OOBE) reduction framework with linear complexity for orthogonal frequency-division multiplexing (OFDM) systems. Unlike conventional spectral precoding approaches which use orthogonal precoding matrixes, this framework composes cancellation signals from the linear combinations of data symbols and minimizes the average OOBE power with a general least-squares solution. A joint frequency domain cancellation subcarrier and data domain cancellation symbol allocation scheme is also proposed for discrete Fourier transform precoded OFDM, by which the overall signal processing complexity of the OFDM transceiver is further reduced without impact on other system performance. The advantages of the proposed scheme is verified both analytically and by simulation as compared with some well-known low-complexity OOBE reduction schemes

Time-Domain N-continuous GFDM

Generalized frequency division multiplexing (GFDM) has been a candidate multicarrier scheme in the 5th generation cellular networks for its flexibility of transmitter filter in time and frequency. However, for the circularly shaped transmitter filter, GFDM provides limited performance gain of sidelobe suppression. In this paper, we propose a scheme, called time-domain N-continuous GFDM (TD-NC-GFDM), to reduce the discontinuities caused by the GFDM transmitter filter and achieve promising sidelobe suppression gain. Based on time-domain N-continuous orthogonal frequency devision multiplexing (TD-NC-OFDM), TD-NC-GFDM signal can be obtained by superposing a smooth signal in the time domain. The smooth signal is linearly combined by basis signals in a new basis set related to GFDM transmitter waveform. To eliminate the interference caused by the smooth signal, two solutions are proposed. Firstly, a signal recovery algorithm for reception is adopted at the cost of high complexity. Thus, secondly, to simplify the TD-NC-GFDM receiver, a low-interference TD-NC-GFDM is proposed by redesigning the basis signals. A soft truncation of the basis signals in TD-NC-GFDM is given to design the basis signals in the low-interference TD-NC-GFDM. Then, the smooth signal is aligned with the beginning of the GFDM symbol and is added in the front part of the GFDM symbol. Moreover, for a big number of GFDM subsymbols, theoretical analysis proves that the signal-to-interference ratio (SIR) in TD-NC-GFDM is much higher than that in TD-NC-OFDM. Simulation results shows that TD-NC-GFDM can obtain significant sidelobe suppression performance as well as the low-interference TD-NC-GFDM, which can achieve the same BER performance as the original GFDM.Comment: single column, 19 pages, 10 figure

Performance Analysis of a Low-Interference N-Continuous OFDM Scheme

This paper investigates two issues of power spectrum density (PSD) and bit error rate (BER) of an N-continuous orthogonal frequency division multiplexing (NC-OFDM) aided low-interference time-domain scheme, when the smooth signal is designed by the linear combination of basis signals truncated by a window. Based on the relationship between the continuity and sidelobe decaying, the PSD performance is first analyzed and compared, in terms of the highest derivative order (HDO) N and the length of the smooth signal L. Since the high-order derivative of the truncation window has the finite continuity, the N-continuous signal has two finite continuities, which may have different continuous derivative orders. In this case, we develop a close PSD expression by introducing another smooth signal, which is also linearly combined by other basis signals, to explain the sidelobe decaying related to N and L. Then, in the context of BER, considering the multipath Rayleigh fading channel, based on the effect of the delayed tail of the smooth signal to the received signal, we provide a procedure for calculating the BER expressed in the form of an asymptotic summation.Comment: 7 pages, 6 figure

Mask-compliant orthogonal precoding for spectrally efficient OFDM

Orthogonal precoding constitutes a powerful technique to reduce spectrum sidelobes of multicarrier signals. This reduction is bought at the cost of introducing precoder redundancy, which results in some throughput loss and additional precoding/decoding complexity. When the goal is to meet some spectral emission mask constraints, it is desirable to avoid unnecessary sidelobe suppression in order to keep precoder redundancy at a minimum. In this context, we introduce a general framework under which we develop a novel Lagrange multiplier-based mask-compliant orthogonal precoder design targeting minimal redundancy. We also adapt to this framework two previously proposed designs based on spectral notches and minimum out-of-band emission, respectively, to explicitly incorporate mask constraints. Simulation results are provided to show the effectiveness of the proposed designs under different practical masks for multicarrier wireless systems.Agencia Estatal de Investigación | Ref. TEC2016-76409-C2-2-RAgencia Estatal de Investigación | Ref. BES-2017-080305Agencia Estatal de Investigación | Ref. PID2019-105717RB-C21Xunta de Galici

WN: COGNET: Cognitive radio networks based on OFDM

Issued as final reportNational Science Foundation (U.S.