- 标题
- 摘要
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- 实验方案
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[IEEE 2018 IEEE 3rd Optoelectronics Global Conference (OGC) - Shenzhen (2018.9.4-2018.9.7)] 2018 IEEE 3rd Optoelectronics Global Conference (OGC) - Signal Quality Improvement in Optical PPM-CDMA Systems Based SIC Scheme
摘要： Optical pulse position modulation-code division multiple access (PPM-CDMA) system with an interference theoretically analyzed. Successive interference cancellation (SIC) scheme has the ability to suppress the overlapping between the users by subtracting the strongest one from the original received signals one by one until all users detected. Different optical codes have been used for the comparison purpose; results show that the system with SIC scheme using modified quadratic congruence codes has better performance than the system using modified prime code as signature codes. In addition, the system with SIC scheme significantly superior to the one without SIC scheme.
关键词： code division multiple access,optical communication,interference cancellation,pulse position modulation
更新于2025-09-23 15:22:29
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Outage and BER performances of indoor relay-assisted hybrid RF/VLC systems
摘要： In this study, the authors analyse the outage performance of the indoor relay-assisted hybrid radio frequency (RF)/visible light communication (VLC) systems. They derive closed-form expressions for the outage probability of the end-to-end signal-to-noise ratio. Then they obtain the optimal approximation parameter with optimising the outage probability using the differential evolution algorithm. Moreover, they analysed the average bit error rate (BER) performance of the hybrid RF/optical system using pulse position modulation method while assuming the timing error in synchronisation. Finally, they present some numerical results utilising the newly derived exact closed-form expressions.
关键词： pulse position modulation,hybrid RF/VLC,BER,differential evolution algorithm,relay-assisted,outage probability
更新于2025-09-23 15:21:21
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Analytic and simulative comparison of turbulent FSO system with different modulation techniques
摘要： In this paper, we characterize the performance of Intensity Modulation/Direct Detection (IM/DD) and coherent detection modulation techniques in free-space optical (FSO) communication system in terms of bit error rate (BER). The system of interest includes M-ary Pulse Position Modulation (M-PPM) in correspondence to IM/DD and M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) with respect to coherent detection. The system is subjected to weak turbulence regime of log-normal channel with scintillation index less than 0.75. Coherent techniques involve the amount of signal pulses transmitted in a particular time as the major component of their generation, except IM/DD which is a result of photon intensity, i.e. the number of photons forming a pulse. It is worth mentioning that in previous studies, the performance of IM/DD techniques had been evaluated in terms of photon-count fluctuation statistics and thus the impact of fading strength of channel on signal intensity was not discussed anywhere. In this work, an objective equivalence has been achieved between these two kinds of detection by deriving the BER expression of M-PPM in terms of probability density function of signal intensity, while considering fading strength, scintillation index, thermal noise and outage probability as system parameters for numerical analysis.
关键词： M-ary Pulse Position Modulation (MPPM),M-ary Phase Shift Keying (MPSK),M-ary Quadrature Amplitude Modulation (M-QAM),Intensity Modulation/Direct Detection (IM/DD),Scintillation index,Coherent detection
更新于2025-09-19 17:15:36
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Atmospheric turbulence mitigation using spatial mode multiplexing and modified pulse position modulation in hybrid RF/FSO orbital-angular-momentum multiplexed based on MIMO wireless communications system
摘要： In this paper, the capacity of a free-space optical (FSO) communication over radio frequency (RF) could potentially be increased by the simultaneous transmission of multiple orbital angular momentum (OAM) based on spatial mode multiplexing (SMM) as an additional effective degree of freedom (EDOF) and quadrature amplitude modulation (QAM). This paper describes using hybrid RF/FSO-OAM based on multiple-input multiple-output (MIMO)/SMM using M-ary modified pulse position modulation (MPPM) and spatial PPM (SPPM) for potentially enhancing capacity in wireless communication systems. We present an analytical system design concerning OAM multiplexing and MIMO/SMM processing in free space communications channel under atmospheric turbulence (AT). Here, we assume a new architecture that closes the gap in speeds between millimeter-wave (mm-wave) wireless and optical links. In this study, we highlight recent advances in the use of OAM multiplexing for high-capacity FSO and mm-wave communications. We have developed the MPPM in FSO communication over RF using the source Gaussian model and SMM by proposing a new version of hybrid SPPM and MPPM. The novelty approach presents performance enhancement of the acquisition, pointing, tracking position and AT mitigation of link. We propose to use SMM combined with OAM-QAM based MIMO communications system to mitigate both weak and strong turbulence distortions. Simulation results show that the capacity of OAM-based MIMO system outperforms the capacity of the conventional MIMO system when the propagation distance is larger than a specific threshold. The use of transmitter lenses could enhance the OAM beams with a larger mode spacing (MS) of 2 (OAM l +1, l +3, l +5, l +7 transmitted) shows a lower power penalty (PP) when the inter-channel crosstalk overwhelms a larger lateral displacement of about 2 mm. Using the lenses at the transmitter to focus OAM beams could reduce power loss and PP in OAM-based FSO links and that this improvement might be more significant for higher-order OAM beams and provide high power-efficiency. With a larger of the transmitter and receiver 8 cm, 10 cm aperture size respectively, the system with mode spacing of 2 (OAM l +1, l +3, l +5, l +7 transmitted) and mode spacing of 3 (OAM l +1, l +4, l +7, l +10 transmitted) of OAM beams based on MIMO should fulfill lower-power penalty of 2.2 dB, 3.4 dB, as respectively and could enhance system robustness under angular error but degrade tolerance of lateral displacement. The proposed system provides an excellent signal-to-noise ratio (SNR) for the capacity in the regime of strong atmospheric turbulence. In this way, the maximization of FSO communication and RF wide, the data capacity enhancement, and it is considered a massive solution in the bandwidth provision for future access networks. This work could be beneficial to the practical implementation of OAM-MIMO/SMM multiplexed RF/FSO links.
关键词： Multiple-input multiple-output,Spatial mode multiplexing,Orbital angular momentum,Free space optical communications,Millimeter-wave communications,Modified pulse position modulation
更新于2025-09-04 15:30:14
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - E-band Impulse Radio Transceiver with 2-bit Pulse-Position Modulation
摘要： This paper presents a novel radio transceiver based on a 2-bit pulse-position modulation (PPM) system for E-band wireless communication systems. We propose a time-based modulation architecture for a wireless transceiver. This is a promising architecture for deep-submicron and nanoscale CMOS technology. The performance of the wireless transceiver can be enhanced as the speed of the CMOS circuit increases. The transmitter is composed of four circuit blocks: a pulse-position modulator, impulse generator, millimeter-wave bandpass filter, and power amplifier. The receiver is comprised of a conventional quadrature demodulator. The transmitter and receiver chipset is fabricated in 55-nm standard CMOS technology. In transceiver loop-back tests, a data rate of 7.0 Gb/s with repetition data and 4.6 Gb/s with pseudo-random bit sequence (PRBS) data are demonstrated.
关键词： point-to-point communications,wireless transceiver,E-band,pulse-position modulation,impulse radio
更新于2025-09-04 15:30:14
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Efficient Indoor Data Transmission with Full Dimming Control in Hybrid Visible Light / Infrared Communication Systems
摘要： We design a hybrid visible light (VL) and infrared (IR) data transmission scheme for indoor visible light communication (VLC) systems with multi-pulse position modulation (MPPM) dimming control. A low-power IR light-emitting diode (LED) is adopted to assist the VL downlink especially when the dimming level of VL is low. Both VL and IR orthogonal frequency division multiplexing (OFDM) signals are transmitted alternately during the “on” and “off” periods of MPPM dimming controlled pulses. In this way, MPPM “off” periods can be efficiently utilized to convey data information without affecting illumination level. This arrangement ensures reliable data transmission under all illumination conditions including dark scenario. Numerical results show that the additional IR link can always facilitate the use of low M-ary quadrature amplitude modulation (M-QAM) levels. The fluctuation of required M-QAM symbol rates caused by dimming control can also be mitigated. At low dimming levels, both the receiver sensitivity requirement for the VL link and the total required transmit power can be significantly alleviated while maintaining a constant data rate at BER < 10-3. Even with limited launching power, the proposed scheme can still extend dimming control range while achieving stable and reliable transmission quality effectively.
关键词： multi-pulse position modulation (MPPM),Visible light communication (VLC),infrared (IR) communication,dimming control,orthogonal frequency division multiplexing (OFDM),hybrid transmission
更新于2025-09-04 15:30:14
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[IEEE 2016 IEEE International Symposium on Circuits and Systems (ISCAS) - Montréal, QC, Canada (2016.5.22-2016.5.25)] 2016 IEEE International Symposium on Circuits and Systems (ISCAS) - A 800-Mb/s 0.89-pJ/b reference-less optical receiver with pulse-position-modulation scheme
摘要： A 800-Mb/s optical receiver based on pulse-position-modulation (PPM) scheme is presented. The proposed PPM receiver can recover the clock without any help of a reference clock or a forwarded clock. As a result, the number of wire and pin count is minimized. Moreover, the proposed receiver employs optical front-end circuits for fiber-optic communications which is optimized for low-power operation. The clock and data recovery (CDR) circuit is implemented with only a PLL and a sampling flip-flop to minimize the power consumption of the proposed receiver. A prototype chip is fabricated in 65-nm CMOS technology and dissipates 711 μW at 800-Mb/s data rate, achieving the power efficiency of 0.89 pJ/b. The measured jitter tracking bandwidth of the proposed receiver is about 10 MHz and the receiver sensitivity is measured to be -9.7 dBm for the BER of 10-12.
关键词： low-power,pulse position modulation (PPM),Clock and data recovery (CDR),optical front-end,reference-less receiver
更新于2025-09-04 15:30:14