This paper investigates Carrier Frequency Offset (CFO) estimation in the uplink of the Orthogonal Frequency-Division Multiple Access (OFDMA) systems with the interleaved subcarrier assignment. CFOs between the transmi...This paper investigates Carrier Frequency Offset (CFO) estimation in the uplink of the Orthogonal Frequency-Division Multiple Access (OFDMA) systems with the interleaved subcarrier assignment. CFOs between the transmitters and the uplink receiver will destroy orthogonality among different subcarriers, hence resulting in inter-carrier interference and multiuser interference. A two-stage frequency offset estimation algorithm based on subspace processing is proposed. The main advantage of the proposed method is that it can obtain the CFOs of all users simultaneously using only one OFDMA block. Compared with the previously known methods, it not only has a relatively low implementation complexity but is also suitable for random subchannel assignment.展开更多
This paper presents a novel carrier frequency offset estimation (CFO) algorithm for orthogonal frequency division multiplexing (OFDM)-based Wireless Local Area Networks (WLANs). Compared with previous approaches, this...This paper presents a novel carrier frequency offset estimation (CFO) algorithm for orthogonal frequency division multiplexing (OFDM)-based Wireless Local Area Networks (WLANs). Compared with previous approaches, this paper extends the whole frequency offset acquisition range by embedding a synthetic algorithm according to the preamble structure of WLANs symbols. The numerical results presented support the effectiveness of this algorithm by which the estimation error of the whole carrier frequency offset in the WLANs is effectively decreased.展开更多
Most of the blind Orthogonal Frequency Division Multiplexing (OFDM) Carrier Frequency Offset (CFO) estimators necessitate large number of samples to ensure the estimation accuracy. However, the number of samples can n...Most of the blind Orthogonal Frequency Division Multiplexing (OFDM) Carrier Frequency Offset (CFO) estimators necessitate large number of samples to ensure the estimation accuracy. However, the number of samples can not be selected too large because of the carrier offset drift. In this letter, a new closed form algorithm for blind OFDM CFO estimation in frequency-selective channel is proposed. This method utilizes the propagator obtained from data matrix and the diagonal loading technique, thus it has better performance even only using one or two OFDM blocks. Furthermore, the range of the CFO estimation which can be handled is overall transmission spectral. Simulation results confirm its effectiveness.展开更多
A protective synchronization scheme （ProSync） for the non-contiguous orthogonal frequency-division multiplexing （NC-OFDM） system is proposed in this paper, aiming to minimize the impact of cross-band interference ...A protective synchronization scheme （ProSync） for the non-contiguous orthogonal frequency-division multiplexing （NC-OFDM） system is proposed in this paper, aiming to minimize the impact of cross-band interference in opportunistic dynamic spectrum sharing networks. ProSync partly shrinks the preamble at the transmitter and exploits two multi-band filters at the receiver. By doing so, the potential interference suffered by NC-OFDM users, including both the cross-band interference and self interference, can be greatly reduced. Simulation results verify the effectiveness of ProSync, which is able to lower the carrier frequency offset （CFO） estimation error by up to 50%, compared with the traditional method.展开更多
As a novel one-atom-thick carbon allotrope,graphdiyne(GDY)has attracted wide interest in two-dimensional materials owing to its unique feature with a planar layer comprising sp2-and sp-hybridized carbon atoms and a di...As a novel one-atom-thick carbon allotrope,graphdiyne(GDY)has attracted wide interest in two-dimensional materials owing to its unique feature with a planar layer comprising sp2-and sp-hybridized carbon atoms and a direct natural bandgap.A high-quality saturable absorber(SA)based on GDY was successfully fabricated,and the nonlinear saturable absorption properties were investigated.A compact diode-pumped solid-state passively Q-switched laser based on the as-prepared GDY-SA could be operated at 2µm.The Q-switched laser delivered a maximum average output power of 1.29 W at a central wavelength of 1908.41 nm with up to 54.8%slope efficiency.A repetition rate of 91.58 kHz and single pulse energy of 23.08µJ were obtained.This work is the first application of GDY as an SA to generate all-solid-state pulsed lasers.These results indicate that GDY is a promising SA for solid-state pulsed lasers and has further application potential for ultrafast photonic devices in the 2-µm region.展开更多
基金the Specialized Research Fund for the Doctoral Program of Higher Education, China Ministry of Education (No.20030003039).
文摘This paper investigates Carrier Frequency Offset (CFO) estimation in the uplink of the Orthogonal Frequency-Division Multiple Access (OFDMA) systems with the interleaved subcarrier assignment. CFOs between the transmitters and the uplink receiver will destroy orthogonality among different subcarriers, hence resulting in inter-carrier interference and multiuser interference. A two-stage frequency offset estimation algorithm based on subspace processing is proposed. The main advantage of the proposed method is that it can obtain the CFOs of all users simultaneously using only one OFDMA block. Compared with the previously known methods, it not only has a relatively low implementation complexity but is also suitable for random subchannel assignment.
基金Project supported by the National Natural Science Foundation of China (No. 2004012F33AA), and Education Foundation of Zhe- jiang Education Department (No. 20040125-66), China
文摘This paper presents a novel carrier frequency offset estimation (CFO) algorithm for orthogonal frequency division multiplexing (OFDM)-based Wireless Local Area Networks (WLANs). Compared with previous approaches, this paper extends the whole frequency offset acquisition range by embedding a synthetic algorithm according to the preamble structure of WLANs symbols. The numerical results presented support the effectiveness of this algorithm by which the estimation error of the whole carrier frequency offset in the WLANs is effectively decreased.
基金Supported by National Natural Science Foundation of China (No. 60172028)
文摘Most of the blind Orthogonal Frequency Division Multiplexing (OFDM) Carrier Frequency Offset (CFO) estimators necessitate large number of samples to ensure the estimation accuracy. However, the number of samples can not be selected too large because of the carrier offset drift. In this letter, a new closed form algorithm for blind OFDM CFO estimation in frequency-selective channel is proposed. This method utilizes the propagator obtained from data matrix and the diagonal loading technique, thus it has better performance even only using one or two OFDM blocks. Furthermore, the range of the CFO estimation which can be handled is overall transmission spectral. Simulation results confirm its effectiveness.
文摘A protective synchronization scheme （ProSync） for the non-contiguous orthogonal frequency-division multiplexing （NC-OFDM） system is proposed in this paper, aiming to minimize the impact of cross-band interference in opportunistic dynamic spectrum sharing networks. ProSync partly shrinks the preamble at the transmitter and exploits two multi-band filters at the receiver. By doing so, the potential interference suffered by NC-OFDM users, including both the cross-band interference and self interference, can be greatly reduced. Simulation results verify the effectiveness of ProSync, which is able to lower the carrier frequency offset （CFO） estimation error by up to 50%, compared with the traditional method.
基金financially supported by the National Natural Science Foundation of China (11974220, 61635012,61875138, 61961136001, and U1801254)the State Key Research Development Program of China (2019YFB2203503)
文摘As a novel one-atom-thick carbon allotrope,graphdiyne(GDY)has attracted wide interest in two-dimensional materials owing to its unique feature with a planar layer comprising sp2-and sp-hybridized carbon atoms and a direct natural bandgap.A high-quality saturable absorber(SA)based on GDY was successfully fabricated,and the nonlinear saturable absorption properties were investigated.A compact diode-pumped solid-state passively Q-switched laser based on the as-prepared GDY-SA could be operated at 2µm.The Q-switched laser delivered a maximum average output power of 1.29 W at a central wavelength of 1908.41 nm with up to 54.8%slope efficiency.A repetition rate of 91.58 kHz and single pulse energy of 23.08µJ were obtained.This work is the first application of GDY as an SA to generate all-solid-state pulsed lasers.These results indicate that GDY is a promising SA for solid-state pulsed lasers and has further application potential for ultrafast photonic devices in the 2-µm region.
