| 1. |
- Lyu, Z., et al.
(författare)
-
Preamble-Free Synchronization Based on Dual-chirp Waveforms for Photonic THz-ISAC
- 2023
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213.
-
Tidskriftsartikel (refereegranskat)abstract
- The integrated sensing and communication (ISAC) systems based on the linear frequency modulation (LFM) waveforms have attracted substantial attention. However, existing routines suffer from additional synchronization preamble overhead, which limits both communication and sensing performance. This work, using the dual-chirp with opposite slopes, exploits a preamble-free synchronization scheme for the LFM-based ISAC. We first theoretically analyze the quasi-orthogonal property of the proposed dual-chirp LFM waveform and derive its achievable communication rate and range ambiguity function. A photonics-assisted proof-of-concept ISAC experiment is conducted in the 300 GHz frequency band, achieving a 20 Gbps data rate with a distinguished peak sidelobe ratio (PSLR) of up to 29.2 dB and 1.5 cm range resolution. More importantly, less than 0.5% synchronous power overhead is needed in our scheme. In addition, the performance trade-off induced by the data rate and amplitude ratio is validated in the experiment, which is in line with our theoretical analysis. Therefore, the proposed scheme provides a promising solution for synchronizing LFM-based future ISAC systems.
|
|
| 2. |
- Zhang, H., et al.
(författare)
-
30 m 64-QAM multicarrier photonic-wireless communication link in the 300 GHz band
- 2022
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9781510661264
-
Konferensbidrag (refereegranskat)abstract
- In recent years, terahertz communication has attracted extensive attentions due to its large bandwidth for supporting terabit-per-second capacity. Along with the rapid evolution of terahertz optoelectronic devices, remarkable achievements have been witnessed in developing photonic terahertz communication systems with large capacities. In fact, photonics-assisted terahertz communication systems have exhibited some advantages, for instance, bridging a seamless connection between the existing optical fiber network and wireless network, offering flexible carrier switching over a wide radio frequency range, as well as supporting easy implementation of high-order complex modulation formats and multicarrier multiplexing terahertz channels. However, due to high atmospheric propagation loss, limited terahertz component bandwidth and low terahertz emission power, achieving simultaneous transmission of single-lane data rates beyond 200 Gbps is still challenging based on a single pair of terahertz transceivers. In this work, by employing subcarrier (SC) multiplexing, high-order 64-ary quadrature amplitude modulation (64-QAM) format, well-defined digital signal processing (DSP) and wideband terahertz transceivers, a multicarrier terahertz photonic-wireless communication link operating in the 300 GHz band is proposed and experimentally demonstrated. At the transmitter side, a baseband pseudo-random binary sequence (PRBS-15) signal with a baud rate of 12 Gbaud is generated from an arbitrary waveform generator (AWG), and then modulated onto an optical carrier centered at 193.414 THz. The modulated optical signal is combined with three optical carriers centered at 193.7035 THz, 193.7165 THz, and 193.7295 THz, for multi-carrier THz generation at a uni-traveling carrier photodiode (UTC-PD) featuring large bandwidth (100 GHz), which consists of three SCs centered at 286.5 GHz, 299.5 GHz and 312.5 GHz, respectively. At the receiver side, we employ a Schottky diode mixer with high sensitivity to down-convert the three terahertz SCs into the intermediate frequency (IF) domain, with three IF signals cantered at 6.5 GHz, 19.5 GHz, and 32.5 GHz, respectively, which are then processed using home-made advanced DSP routine, including a linear adaptive equalizer, compensation algorithms of frequency offset and phase noise. In the experiment, a total line data rate of 216 Gbps (72 Gbps/SC ×3 SC) over a wireless distance of 30 m is successfully transmitted, and the performance of all three SCs can reach below the hard decision forward-error-correction (HD-FEC) with 6.25 % overhead, reaching an aggregated net transmission capacity of up to 202.5 Gbps. This achievement of single-lane simultaneous transmission of beyond 200 Gbps using a single pair of 300 GHz transceivers is considered a significant step towards next-generation wireless communications.
|
|
| 3. |
- Zhang, H., et al.
(författare)
-
Single-lane 200 Gbit/s photonic wireless transmission of multicarrier 64-QAM signals at 300 GHz over 30 m
- 2023
-
Ingår i: Chinese Optics Letters (COL). - : Optica Publishing Group (formerly OSA). - 1671-7694. ; 21:2
-
Tidskriftsartikel (refereegranskat)abstract
- Recently, wireless communication capacity has been witnessing unprecedented growth. Benefits from the optoelectronic components with large bandwidth, photonics-assisted terahertz (THz) communication links have been extensively developed to accommodate the upcoming wireless transmission with a high data rate. However, limited by the available signal-to-noise ratio and THz component bandwidth, single-lane transmission of beyond 100 Gbit/s data rate using a single pair of THz transceivers is still very challenging. In this study, a multicarrier THz photonic wireless communication link in the 300 GHz band is proposed and experimentally demonstrated. Enabled by subcarrier multiplexing, spectrally efficient modulation format, well-tailored digital signal processing routine, and broadband THz transceivers, a line rate of 72 Gbit/s over a wireless distance of 30 m is successfully demonstrated, resulting in a total net transmission capacity of up to 202.5 Gbit/s. The single-lane transmission of beyond 200 Gbit/s overall data rate with a single pair of transceivers at 300 GHz is considered a significant step toward a viable photonics-assisted solution for the next-generation information and communication technology (ICT) infrastructure.
|
|
| 4. |
- Zhang, Lu, et al.
(författare)
-
Hybrid fiber–THz fronthaul supporting up to 16384-QAM-OFDM with the delta-sigma modulation
- 2022
-
Ingår i: Optics Letters. - : Optica Publishing Group (formerly OSA). - 0146-9592 .- 1539-4794. ; 47:17, s. 4307-4310
-
Tidskriftsartikel (refereegranskat)abstract
- With the progress of high-capacity radio access networks, ultra-dense small cells are rapidly being deployed in urban areas. As a result, the deployment of a large number of optical fibers in urban areas becomes a severe issue. In this Letter, we propose a hybrid fiber–terahertz (THz) mobile fronthaul system supporting flexible and high-order wireless signal transmission with the delta-sigma modulation. The photonic THz transmission is used as the seamless extension of fiber-based fronthaul in small cells. A 20-Gbit/s digital fiber–THz fronthaul system is experimentally demonstrated to validate the proposed scheme, with 10-km optical fiber transmission and 300-GHz wireless relay. Carrier aggregation of up to 10 40-MHz and 60-MHz 5G-new radio (5G-NR) channels at the radio carrier frequency of 3.9 GHz is reported. The design of quantization noise suppressed delta-sigma modulation enables the system to transmit orthogonal frequency division multiplexing (OFDM) modulation up to 16384 order quadrate amplitude modulation (QAM) mapping with the error vector magnitude (EVM) below 0.5%.
|
|
| 5. |
- Zhang, L., et al.
(författare)
-
Quantum Noise Secured Terahertz Communications
- 2023
-
Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - : Institute of Electrical and Electronics Engineers Inc.. - 1077-260X .- 1558-4542. ; 29:5
-
Tidskriftsartikel (refereegranskat)abstract
- The terahertz communications display an important role in high-speed wireless communications, the security threat from the eavesdroppers in the terahertz communications has been gaining attention recently. The true randomness in the physical layer can ensure one-time-pad encryption for secured terahertz communications, however, physical layer security schemes like the quantum key distribution methods suffer from device imperfections that limit the desirable signal rate and link distance. Herein, we present the quantum noise secured terahertz wireless communications with photonic terahertz signal generation schemes. With the high-order diffusion algorithms, the signal is masked by the quantum noise ciphers to the eavesdroppers and cannot be detected because the inevitable randomness by quantum noise measurement will cause physical measurement errors. In the experiment, we demonstrate 16 Gbits-1 quantum noise secured terahertz wireless communications with the conventional optical communication realms and devices, operating at 300 GHz terahertz frequency. This quantum noise secured terahertz communication approach is a significant step toward high-security wireless communications.
|
|
| 6. |
- Zhang, X., et al.
(författare)
-
Why Do Bamboo Parenchyma Cells Show Higher Nanofibrillation Efficiency than Fibers : An Investigation on Their Hierarchical Cell Wall Structure
- 2022
-
Ingår i: Biomacromolecules. - : American Chemical Society. - 1525-7797 .- 1526-4602. ; 23:10, s. 4053-4062
-
Tidskriftsartikel (refereegranskat)abstract
- The cell walls of parenchyma cells and fibers in bamboo are both highly lignified with secondary thickening. However, the former were found to have much higher nanofibrillation efficiency than fibers via both protocols of ultrasonication and high pressure homogenization. To elucidate the inherent mechanism, detailed comparisons of chemical composition, cell morphology, cell wall density, pore structures, and structural organization of cell wall polymers were performed on native and pretreated cell walls of both parenchyma cells and fibers. Chemical compositional analysis showed that fibers have much higher cellulose (49.8% to 35.5%) but lower xylan content (21.1% to 36.2%) than parenchyma, while their lignin contents were similar (24.9% vs 22.9%). Polarized FTIR further revealed clear differences in the structural organization of polymers between the two types of cells, with all the polymers of fibers being more orderly assembled than those of parenchyma cells. The compact arrangement of polymers in the fibers was also supported by the much higher cell wall density (1.52 vs 1.28 g/cm3) and lower porosity (0.007 vs 0.013 cc/g after chemical pretreatments), as compared to the parenchyma cells. The study provides evidence that the anatomical characteristics of huge cavity-wall ratio, higher cell wall porosity, and less ordered arrangement of cell wall matrix polymers (mainly lignin) in parenchyma cells contribute to their higher nanofibrillation efficiency compared to fibers.
|
|
| 7. |
- Åstlund, L, et al.
(författare)
-
4H- 6H-SiC UV photodetectors
- 2012
-
Ingår i: Phys. Status Solid. ; c9:7, s. 1680-2
-
Tidskriftsartikel (refereegranskat)
|
|
