Chunxing Ni

PAPR Reduction of OQAM-OFDM Signals Using Segmental PTS Scheme With Low Complexity

In this paper, a novel segmental partial transmit sequence (S-PTS) scheme is proposed for the peak-to-average power ratio (PAPR) reduction in offset quadrature amplitude modulation based orthogonal frequency-division multiplexing (OQAM-OFDM) systems. The key idea of the S-PTS scheme is to divide the overlapped OQAM-OFDM signals into a number of segments, and then some disjoint subblocks are divided and multiplied with different phase rotation factors in each segment. Compared with the conventional PTS scheme directly employed in OQAM-OFDM sytems, the S-PTS scheme could offer better PAPR reduction with lower computational complexity.

Effect of PAPR Reduction on Spectrum and Energy Efficiencies in OFDM Systems With Class-A HPA Over AWGN Channel

In this paper, we mainly analyze the relations between peak-to-average power ratio (PAPR) reduction, spectrum efficiency (SE), and energy efficiency (EE) in orthogonal frequency division multiplexing (OFDM) systems, respectively. Through PAPR reduction, the efficiency of high power amplifier (HPA) could be substantially improved, and the nonlinear distortion noise caused by the HPA could also be significantly reduced. As a result, the SE and EE are increased with a total transmit power constraint over additive white Gaussian noise (AWGN) channel. Moreover, we derive the quantitative relations between PAPR reduction, SE, and EE, respectively. Simulation results show that the OFDM system with PAPR reduction could achieve higher SE and EE than the system without PAPR reduction.

A Novel Phase Offset SLM Scheme for PAPR Reduction in Alamouti MIMO-OFDM Systems Without Side Information

In this letter, a novel phase offset selected mapping (SLM) scheme is proposed to reduce the peak-to-average power ratio (PAPR) in Alamouti coded multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, and its key idea is that different phase rotation sequences are multiplied by their corresponding phase offsets at the transmitter. Moreover, a minimum Euclidian distance (MED) decoder at the receiver is proposed to recover the phase rotation sequences. Therefore, the proposed SLM scheme does not need to reserve bits for the transmission of side information, resulting in the increase of the data rate. Theoretical analysis and simulation results show that the proposed SLM scheme could offer good performances of both the bit error rate and PAPR reduction.

Joint PAPR Reduction and Sidelobe Suppression Using Signal Cancelation in NC-OFDM-Based Cognitive Radio Systems

It is well known that the high peak-to-average power ratio (PAPR) and large spectrum sidelobe power are two main drawbacks at the transmitter in noncontiguous orthogonal frequency-division multiplexing (NC-OFDM)-based cognitive radio (CR) systems. In this paper, we propose a novel signal cancellation (SC) method for joint PAPR reduction and sidelobe suppression in NC-OFDM-based CR systems. The key idea of the proposed method is to dynamically extend part of the constellation points on the secondary user (SU) subcarriers and add several SC symbols on the primary user (PU) subcarriers to generate the appropriate cancellation signal for joint PAPR reduction and sidelobe suppression. Then, the SC method formulates the problem of the joint PAPR reduction and sidelobe suppression as a quadratically constrained quadratic program (QCQP) to obtain its optimal cancelation signal. Moreover, we also propose a suboptimal SC (sub-SC) method to efficiently solve the QCQP optimization problem with low computational complexity. Simulation results show that the proposed SC method and the sub-SC method can provide both significant PAPR reduction and sidelobe suppression performances.

Energy-efficient NC-OFDM/OQAM-based cognitive radio networks

With the explosive growth of wireless multimedia applications and the demand for high data rate, improving the spectrum and energy efficiencies have been two most critical challenges for wireless communication networks under the background of limited spectrum and energy resources. Cognitive radio and OFDM/OQAM have emerged as two exciting technologies to solve the spectrum scarcity in future cellular networks; thus, energy-efficient communications have attracted increasing attention in cognitive radio networks. In this article, we consider how to make an energy-efficient physical layer design for non-contiguous (NC) OFDM/OQAM-based cognitive radio networks. Specifically, we propose a criterion on how to reduce the high PAPR of NC-OFDM/OQAM signals to achieve high power efficiency. The key idea of the proposed criterion is to jointly reduce the PAPR and suppress the sidelobe in NCOFDM/ OQAM-based CR systems. Extensive simulation results verify that the proposed criterion can provide both significant PAPR reduction and sidelobe suppression, resulting in prominent improvement of energy efficiency in NC-OFDM/OQAM-based cognitive radio networks.

A Novel Multi-Block Tone Reservation Scheme for PAPR Reduction in OQAM-OFDM Systems

Due to the overlapping structure of the offset quadrature amplitude modulation-based orthogonal frequency-division multiplexing (OQAM-OFDM) signals, the peak-to-average power ratio (PAPR) in OQAM-OFDM systems cannot be efficiently reduced by existing PAPR reduction methods, which independently consider the PAPR reduction in each data block. In this paper, a novel multiblock tone reservation (MB-TR ) scheme is proposed for the PAPR reduction in OQAM-OFDM systems. The key idea of the MB-TR scheme is to exploit the overlapping structure of the OQAM-OFDM signals and jointly consider the adjacent data blocks to obtain the clipping noise. To effectively eliminate the peaks of the OQAM-OFDM signals, the MB-TR scheme generates the peak-canceling signal by employing the weighted least square algorithm to fit the waveform of the peak-canceling signal to the waveform of clipping noise. Simulation results and analysis show that the MB-TR scheme could offer better PAPR reduction with lower computational complexity than the clipping control tone reservation scheme directly employed in OQAM-OFDM systems.

Curve Fitting Based Tone Reservation Method with Low Complexity for PAPR Reduction in OFDM Systems

In this letter, a novel curve fitting based tone reservation (CF-TR) method is proposed to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems, and its key idea is to utilize the clipping noise introduced by clipping to generate an ideal peak-canceling signal. To effectively eliminate the peaks of the OFDM signal, the CF-TR method generates the peak-canceling signal by directly fitting the waveform of the peak-canceling signal to the waveform of clipping noise. The proposed CF-TR method obtains significant PAPR reduction with very few iterations, and only one IFFT operation is required at each iteration, resulting in dramatic reduction of the computational complexity.

Peak-to-average power ratio reduction in alamouti multi-input-multi-output orthogonal frequency division multiplexing systems without side information using phase offset based-partial transmit sequence scheme

In this study, a novel phase offset-based partial transmit sequence (PTS) scheme is proposed to reduce the peak-to-average power ratio (PAPR) in Alamouti coded multi-input-multi-output orthogonal frequency division multiplexing systems, and its key idea is that different phase rotation sequences are multiplied by their corresponding phase offsets at the transmitter. Moreover, a minimum Euclidean distance decoder is proposed to recover the phase rotation sequences at the receiver. The theoretical analysis and simulation results show that the proposed PTS scheme could offer good performances of both the bit error rate and the PAPR reduction without transmitting the side information, resulting in the increase of the data rate.

A Novel Adaptive Tone Reservation Scheme for PAPR Reduction in Large-Scale Multi-User MIMO-OFDM Systems

In this letter, a novel adaptive tone reservation (ATR) scheme is proposed for the orthogonal frequency division multiplexing-based large-scale multiuser multiple-input multiple-output systems to deal with the inherent peak-to-average power ratio (PAPR) problem. The key idea of the proposed ATR scheme is to iteratively perform the tone reservation (TR) scheme on the antenna with the maximum PAPR. Simulation results validate that the ATR scheme offers better PAPR reduction performance and lower computational complexity than the conventional TR scheme.

Novel 16-QAM and 64-QAM Near-Complementary Sequences With Low PMEPR in OFDM Systems

In this paper, we first propose a novel construction of 16-quadrature amplitude modulation (QAM) near-complementary sequences with low peak-to-mean envelope power ratio (PMEPR) in orthogonal frequency division multiplexing (OFDM) systems. The proposed 16-QAM near-complementary sequences can be constructed by utilizing novel nonlinear offsets, where the length of the sequences is n = 2m. The family size of the newly constructed 16-QAM near-complementary sequences is 8 × (m!/2) × 4m+1, and the PMEPR of these sequences is proven to satisfy PMEPR ≤ 2.4. Thus, the proposed construction can generate a number of 16-QAM near-complementary sequences with low PMEPR, resulting in the improvement of the code rate in OFDM systems. Furthermore, we also propose a novel construction of 64-QAM near-complementary sequences with low PMEPR, which is the first proven construction of 64-QAM near-complementary sequences. The PMEPRs of two types of the proposed 64-QAM near-complementary sequences are proven to satisfy that PMEPR ≤ 3.62 or PMEPR ≤ 2.48, respectively. The family size of the newly constructed 64-QAM near-complementary sequences is 64 × (m!/2) × 4m+1.