OOK Modulation Research Articles

Performance enhancement of hybrid diversity for M-ary modified pulse-position modulation and spatial modulation of MIMO-FSO systems under the atmospheric turbulence effects with geometric spreading

In this paper, we propose a novel model for hybrid spatial diversity of M-ary pulse position modulation (M-ary PPM) and spatial modulation (SM) with a multiple-input multiple-output (MIMO) links (i.e., optical receiver diversity) in a free-space optical (FSO) communication system under the atmospheric turbulence (AT) effects with geometric spreading (GS). In the proposed design, the spatial index modulator (SIM) and modified pulse position modulation (MPPM) schemes are combined to improve the system efficiency of the spatial diversity for the M-ary PPM modulated MIMO–FSO communication. In this work, we investigate and enhance the performance of the MIMO-FSO link using a digital pulse position modulation (DPPM) and on–off keying non-return-to-zero (OOK–NRZ). We propose a MIMO-based FSO link using spatial diversity and M-ary PPM modulation technique to compensate for the performance degradation due to geometric losses and atmospheric attenuation. Here, we have combined the N-SM with L-MPPM (N-SM/L-MPPM) and (M × N MIMO) to improve the system performance and provide high bandwidth and a higher throughput under the impact of the AT and GS. We analyze the GS impact on the performance of MIMO–FSO systems using SM over the Gamma–Gamma (GG) model. The performance is achieved by using the PPM technique, so the AT influences and fading are mitigated hence the ability to combat AT and the FSO link systems are enhanced sufficiently. Also, we improve the performance of the proposed link using a novel hybrid of SM/PPM and DPPM over GG to maximize the range and enhance the receiver sensitivity. Simulation results obtained for the bit-error-rate (BER) and average transmitted optical power for the DPPM and OOK modulation against various AT conditions are compared with the spatial diversity techniques and proved that both of the FSO systems based MIMO–SM/MPPM offers better performance in the receiver sensitivity and channel capacity. The obtained results show that the conjunction of the receiver diversity and SM/M-ary MPPM is a magnificent solution for mitigating the strong turbulence (ST) and GS effects. The proposed design provides an excellent optical signal-to-noise ratio (SNR) and high-sensitivity for the SIM/PPM-MIMO in the ST regime and GS. The numerical results report that the DPPM sensitivity improves about 10–11 dB at a distance of 2.5 km and the BER of 10−12 more than an equivalent OOK–NRZ modulation. The SIM/PPM-MIMO offers about 4 dB, 2 dB optical SNR improvements over without SIM/PPM-MIMO for the no turbulence and ST with GS for the FSO link, respectively. This work could be beneficial to the practical implementation of the hybrid spatial diversity for the SM/M-ary MPPM based MIMO-FSO links under the AT effects with GS.

Design of a Multipurpose Photonic Chip Architecture for THz Dual-Comb Spectrometers.

In this work, we present a multipurpose photonic integrated circuit capable of generating multiheterodyne complex Dual-Combs (DC) THz signals. Our work focuses on translating the functionality of an electro-optic tunable DC system into a photonic chip employing standard building blocks to ensure the scalability and cost efficiency of the integrated device. The architecture we analyze for integration is based on three stages: a seed comb, a mode selection stage and a DC stage. This final DC stage includes a frequency shifter, a key element to improve the final detection of the THz signals and obtain real-time operation. This investigation covers three key aspects: (1) a solution for comb line selection on GHz spaced combs using OIL or OPLL on photonic chips is studied and evaluated, (2) a simple and versatile scheme to produce a frequency shift using the double sideband suppressed carrier modulation technique and an asymmetric Mach Zehnder Interferometer to filter one of the sidebands is proposed, and (3) a multipurpose architecture that can offer a versatile effective device, moving from application-specific PICs to general-purpose PICs. Using the building blocks (BBs) available from an InP-based foundry, we obtained simulations that offer a high-quality Dual-Comb frequency shifted signal with a side mode suppression ratio around 21 dB, and 41 dB after photodetection with an intermediate frequency of 1 MHz. We tested our system to generate a Dual-Comb with 10 kHz of frequency spacing and an OOK modulation with 5 Gbps which can be down-converted to the THz range by a square law detector. It is also important to note that the presented architecture is multipurpose and can also be applied to THz communications. This design is a step to enable a commercial THz photonic chip for multiple applications such as THz spectroscopy, THz multispectral imaging and THz telecommunications and offers the possibility of being fabricated in a multi-project wafer.

Modulation Format Shifting Scheme for Optical Camera Communication

We propose and experimentally demonstrate a simple and elegant modulation format shifting (MFS) scheme by continuously changing the modulation formats between OOK and Manchester signal for optical camera communication (OCC) using a commercially available mobile phone. Leveraging the MFS scheme, extra data bits are delivered without reducing the pixel width of each bit, resulting in higher transmitted data rate. Meanwhile, multi-thresholding scheme is proposed for modulation format identification and signal decoding at the receiver. The experimental results demonstrate that the proposed MFS scheme can achieve a data rate of 8.16 Kbps with the bit error rate (BER) of $2.9\times 10^{-3}$ at the illuminance of 400 lux. In addition, compared with conventional OOK modulation, MFS scheme can remarkably improve the BER performance at the same data rate.

High-Speed Performance Evaluation of Graded-Index Multicore Fiber Compatible With Multimode and Quasi-single Mode Operation

A comprehensive study on the optical characteristics and high-speed transmission performance of a hexagonally arrayed seven-core fiber supporting both multimode transmission at 850 nm and quasi-single mode transmission at 1310 and 1550 nm are presented. We investigated its optical and transmission characteristics such as inter-crosstalk, modal bandwidth, chromatic dispersion, and misalignment tolerance. The results show that the multicore fiber (MCF) has a high bandwidth at 850 nm while remaining a comparable performance with standard single-mode fiber (SSMF) at 1310 and 1550 nm. The worst inter-core crosstalk is less than -43 dB over a 10 km-long MCF connected with a pairwise fanin/fan-out devices. The minimum effective modal bandwidth of 8.44 GHz·km is achieved with the MCF for multimode operation, while the chromatic dispersion of the MCF at 1550 nm only increases by 7% compared with that of SSMF. In experiment, we successfully performed the 7 × 25 Gb/s multimode transmission over a 300 meter-long MCF at 850 nm and quasi-single mode transmission over a 12.4 and 10 km-long fiber at 1310 and 1550 nm, respectively, with an OOK modulation format. There was no obvious degradation observed when all cores operated simultaneously. Moreover, we carried out 7 × 50 Gb/s PAM4 transmission over a 300 meter-long and 10 km-long MCF at 850 and 1310 nm, respectively, as well as 7 × 40 Gb/s PAM4 transmission over a 10 km-long MCF at 1550 nm. A BER which is well below the forward error correction (FEC) threshold (5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> ) was reached for different MCF links.

Spur Minimization Techniques for Ultra-Low-Power Injection-Locked Transmitters

Frequency multiplying wireless transmitters (TX) employing harmonic injection-locked technique benefit from high energy efficiency and less hardware complexity but largely suffer from reference spurs that violate the TX spectral specifications. This work proposes a self-aligned phase-locked loop (PLL) in conjunction with harmonic injection locking technique to achieve significantly improved spur performance under ultra-low-power (ULP) operations for sub-GHz IoT TXs. The on-chip type-I PLL calibrates the phase error in the ring oscillator (RO) in real-time and avoids large spurs induced from the frequency deviation in the harmonic injection locking. A compact zero power consumption twin-T notch filter for spur suppression is implemented within the PLL loop to tackle the rail-to-rail voltage jump that comes from the output of the phase detector (PD). Designed and fabricated in the TSMC 180 nm CMOS process, the proposed frequency multiplying TX occupies an active area of only 0.0413 mm2. The lowest power consumption with >3X improved energy-efficiency is observed while consistently achieving >62 dB spur suppression with −14 dBm output at 915 MHz. The TX supports OOK modulation with an average power consumption of $200.9~\mu \text{W}$ only at 3 Mb/s data rate achieving a normalized 66.97 pJ/bit energy efficiency.

An Ultra-Low Power 2.4 GHz Transmitter for Energy Harvested Wireless Sensor Nodes and Biomedical Devices

We present a 2.4GHz ultra-low power energy-harvested narrowband transmitter (TX) for wireless sensing and biomedical devices. We used a 434 MHz RF energy for resonant cavity based wireless power transfer (WPT). An efficiency tracking loop maximizes the power transfer efficiency of WPT and achieves an efficiency of 11.5%. The TX comprises a voltage-controlled power oscillator (VCPO) and a loop antenna which is patterned over a flexible Parylene C substrate to achieve biocompatibility. The loop antenna acts as a radiator as well as an inductive element for the VCPO, eliminating a power amplifier stage and bulky off-chip matching network. The TX is designed for low active and sleep mode power consumption to support both continuous-data mode or deeply duty cycled burst-data mode of transmission. Implemented in 0.18 μm CMOS, the TX supports OOK and FSK modulations with the sleep mode power dissipation of 128 pW. Our active RF TX consumes an active-mode power of 70 μW at 10 Mbps while radiating -33 dBm of power, resulting in an energy efficiency of 7 pJ/bit, which is the best reported till date.

A SiPM-Based VLC Receiver for Gigabit Communication Using OOK Modulation

The growing demand for wireless communications services means that RF systems are increasingly unable to support user’s requirement. Consequently, there is a growing interest in using visible light communication (VLC), including interest in sensitive VLC receivers. Since they have the potential to detect single photons, silicon photomultipliers (SiPMs) could potentially be used to create the most sensitive possible VLC receivers. In this paper, results of experiments to determine the optimum bias voltage and dynamic range of an off-the-shelf SiPM are reported. Results are then presented which show that in 500 lux of ambient light this receiver supports data rates of more than 2 Gbps with a bit-error-rate (BER) of 10−3.

Development of an Underground Through-Soil Wireless Acoustic Communication System

The practical development of WUSN would benefit numerous applications, including online infrastructure monitoring, earthquake warning systems, and agricultural automation. However, stateof- the-art RF electromagnetic wireless systems are ineffective for communicating through-soil, due to extreme signal path losses from absorption and scattering in soil, even though the typical data requirements for such applications are modest, ranging from tens to hundreds of bps. In contrast, elephants, rodents and a wide variety of insects use acoustic waves for communicating through-soil, suggesting the viability of soil as a communication channel, and of acoustic waves as carriers. In this article, we demonstrate how soil can be used as a communication medium for wireless acoustic digital communication over distances up to 50 m at 20 bps data rates. By leveraging a physical model of the soil channel derived from its identified characteristics, then employing QPSK and OOK modulation and sparse decision feedback equalization schemes, and exploiting well-coupled and matched acoustic sources, wireless digital communication was successful in both laboratory and field experiments, illustrating the viability of sending application- specific data, ranging from binary sensor readings to low-resolution images.

A Power-Efficient Configurable FSK–OOK Transmitter with Scalable Data Rate for Wireless Medical Applications

This paper presents a 922 MHz power-efficient configurable frequency-shift keying–on–off keying (FSK–OOK) phase-locked loop (PLL)-based transmitter. The proposed transmitter works as a multimode structure with configurable data rate and output power. In OOK modulation, by duty cycle adjustment of input data and producing return-to-zero data (RZ-data) by a simple circuit, the data rate can be scaled with power consumption. This implies that any desired level of output power can be transmitted with different power consumption according to the power budget. The transmitter benefits from a new phase frequency detector, an improved charge pump and a low-power voltage-controlled oscillator. The proposed structure represents data rate of 0.24–2.4 Mb/s in OOK mode and 1.8 Mb/s in FSK mode, and it can deliver output power level from − 19.71 to 0.53 dBm. The efficiency of the transmitter at RZ–OOK modulation with data rate of 2.4 Mb/s and output power of 0.53 dBm is 57.25%. Also, the efficiency of transmitter in FSK modulation is 22.1%. The post-layout simulation results in 0.18 µm RF CMOS process are obtained and verify the effectiveness of the proposed circuit.

OpenCV 라이브러리 기반 FSK OCC 시스템의 성능 측정

With the development of semiconductor especially, nano technology, image processing is playing an important role in the multimedia display industry. It is also one of the most considered research topic which has been combined with the industrial production quickly with the on-chip integration. As an important step in optical camera communication (OCC) operation, image processing makes decision for the reliable system. There are some open-source computer vision libraries for image processing applications. One of the earliest libraries to be considered by many researchers is OpenCV. In this paper, we will propose a new OCC system based on frequency shift OOK modulation and evaluate the performance of proposed system based OpenCV library for a real time application on android smartphone scenario. From the measurement on consumption time, accuracy for every phase, we make a comparison with other implements to prove the efficiency of OpenCV library.

A CDMA-based high-speed multi-access VLC system with OOK modulation

An overall bit rate of 625 Mb/s real-time multi-access VLC system is presented in this paper. In order to decrease the effect of ambient light and deal with the non-linearity of LED, we propose a new algorithm to get orthogonal codes which is suitable for OOK modulation. By employing a single white LED and three photo diodes, three users are provided access to the VLC system individually at the same time. A data frame and CRC32 are adopted to realize a reliable and continuous data interaction between Ethernet and VLC system. All the numerical calculations are implemented by FPGAs so as to provide a practical high-speed transmission.

A 60-GHz 3.0-Gb/s Spectrum Efficient BPOOK Transceiver for Low-Power Short-Range Wireless in 65-nm CMOS

This paper presents a 60-GHz transceiver for low-power high-speed short-range wireless using the proposed binary-phase on-off keying (BPOOK) modulation scheme. The proposed BPOOK wireless transceiver transmits radio frequency (RF) signal with amplitude modulated on and off by input baseband data, and meanwhile, the phase is changing between 0° and 180°. The BPOOK transceiver achieves doubled spectral efficiency compared with OOK modulation and binary-phase-shift keying (BPSK) modulation. It also cancels the intrinsic local-oscillator feed through (LOFT) issue in the OOK modulation. The BPOOK RF signal can be demodulated by employing low-power square-law envelope detector incoherently. The transceiver is fabricated in a standard 65-nm CMOS technology. A data rate of 3.0 Gb/s is achieved while consuming a power of 100 mW from 1-V supply. The incoherent receiver has a sensitivity of −46 dBm. The core area of the transceiver is 1.56 mm2.

Photonic-based integrated sources and antenna arrays for broadband wireless links in terahertz communications

This paper analyzes integrated components for ultra-broadband millimeter-wave wireless transmitters enabling the 5 G objective to increase the wireless data rates 10× to 100×. We have pursued the photonic-based approach to generate the millimeter-wave carrier (≈97 GHz in this paper) through photomixing. We have achieved up to 10 Gb s−1 data rate using an OOK modulation format (to reduce latency) and either direct detection (DD) or coherent detection. We show that coherent detection enables a sensitivity improvement of 17 dB over DD. We also demonstrate in this work that such improvement can be achieved using as the transmitter a novel integrated antenna array—the self-complementary chessboard array. This avoids the use of complex coherent schemes at the receiver, enabling simple DD for ultra-broadband links.

Low Rate VLC Receiver Design Using NCP302 Voltage Detector for IoT/IoL Connected Smart Homes

The Internet of Things (IoT) and Visible Light Communication (VLC) is opening up new services in lighting industry by integrating sensory network features in addition to standard illumination functionality. In this progressive developments, the next generation lighting devices for smart homes are capable to sense the environmental conditions and transfer the captured data through lights to gateway controller to access remotely. The smart home environmental sensor information’s are few kbps only so VLC systems need to built-in with low rate light connectivity to transfer data to the gateway. To provide error free communication, the quality of a received light signal is important to be considered when designing an VLC receiver. Therefore, this paper proposes the design of robust low rate IoL receiver design using NCP302 voltage detector for micro controller to adapt the IoT/IoL front end module for system integration. To evaluate the proposed system performance, the Arduino UNO based IoT/IoL controller designed with lighting, sensors and lights connectivity interfaces. The experimental result shows that the robust interference rejection is feasible on proposed VOL receiver and possible to have an error-free communication up to 10 kbps at a low SNR using OOK modulation.

Design and feasibility study of human body communication transceiver based on FDM

The body area networks (BAN) are built by many wearable sensors to record, monitor or control the vital signals within the human body continuously. Human body communication (HBC) is a novel physical layer method to implement the BAN with low power consumption, low radiation, and strong anti-interference. However, the most existing HBC rarely consider the situation in which multiple sensors transmit data at the same time. The aim of this paper is to investigate the feasibility of frequency division multiplexing for human body communication multiplex data transmission. The signal was injected into the human body, and the human channel gain was measured by the spectrum analyzer. Two frequency signals were selected with smaller gain to design the transceiver. The transmitter used OOK modulation technology to design each functional unit, and the receiver recovered the original signal with a non-coherent demodulation method. The experimental results show that after the dual signals were transmitted through the human body, the receiver could recover the original signal correctly. In both static and dynamic situations, even if the transmission rate was as high as 115.2 kb/s, the bit error rate was only 10-4. The frequency division multiplexing scheme can be selected for multi-channel data transmission in human body communication.

Performance investigation of MLR optical WDM network based on ITU-T conforming fibers in the presence of SRS, XPM and FWM

This article investigates the performance degradation of a mixed line rate (MLR) optical wavelength division multiplexing network in the presence of the combined FWM, XPM and SRS effects. For performance evaluation a novel mathematical model is developed which evaluates the results in terms of quality-factor. Further, the simulations are performed (i) based on the optical frequency grid defined by the ITU-T Recommendation G.692, and (ii) considering the ITU-T compliant optical fibers viz., G.652, G. 652D, G. 653, G. 654, G.655, and LEAF. The obtained results show that among the various considered fibers and modulation format configuration cases, irrespective of spacing between the channels (i) SMF (G.652) and DSF (G.653) fibers provide the best and the worst performances, respectively, and (ii) a combination of the central channel transmitting at 40 Gbps using the duo-binary modulation format with adjacent channels transmitting at 10 Gbps using OOK modulation format, provides the best performance. However, with increase in spacing between the channels, the performance is enhanced owing to mitigation of the deleterious non-linear effects. Overall, the results clearly show that choice of the data rate of both, the central channel and its adjacent channel has a major effect on the MLR network performance.

All-Optical Logic Gates Devices based on SPP Coupling between Graphene Sheets

The aim of this work is to propose all-optical logic gates based on surface plasmon polaritons (SPP's) coupling among spatially separated graphene sheets. This model consists of graphene nanoribbons embedded in silica (SiO 2 ) substrate place ina distance such that allow an efficient coupling between the plasmonic modes of the waveguides. It was numerically analyzed the propagation´s behavior of the SPP modes in an interferometric device as function of the chemical potential and geometrical parameters in order to obtain the AND/OR/XOR logic gates for OOK modulation.

Sensor/Antenna Interface IC for Implantable Biomedical Monitoring System

An interface IC for medical implants is implemented by using RF techniques of carrier synthesis and wireless powering. An external RF signal at 1.608 GHz is shared by an RF-dc converter and an injection-locked divide-by-four circuit, where most of the RF energy goes to the former for RF energy harvesting and the rest of it serves as the injection signal for the latter to generate a low-phase-noise carrier at 402 MHz. Through an on-chip digital control unit and a successive approximation register analog-to-digital converter, biomedical signal in digital form can be obtained and then used to control the bias voltages of a power amplifier (PA) to perform the OOK modulation for wireless transmission. It requires an input level of 8 dBm to operate the chip. The 402-MHz carrier exhibits a phase noise of −136.7 dBc/Hz at an offset frequency of 1 MHz and the PA delivers an output power of −19.7 dBm.

Using a Single VCSEL Source Employing OFDM Downstream Signal and Remodulated OOK Upstream Signal for Bi-directional Visible Light Communications

In this work, we propose and demonstrate for the first time up to our knowledge, using a 682 nm visible vertical-cavity surface-emitting laser (VCSEL) applied in a bi-directional wavelength remodulated VLC system with a free space transmission distance of 3 m. To achieve a high VLC downstream traffic, spectral efficient orthogonal-frequency-division-multiplexing quadrature-amplitude-modulation (OFDM-QAM) with bit and power loading algorithms are applied on the VCSEL in the central office (CO). The OFDM downstream wavelength is remodulated by an acousto-optic modulator (AOM) with OOK modulation to produce the upstream traffic in the client side. Hence, only a single VCSEL laser is needed for the proposed bi-directional VLC system, achieving 10.6 Gbit/s OFDM downstream and 2 Mbit/s remodulated OOK upstream simultaneously. For the proposed system, as a single laser source with wavelength remodulation is used, the laser wavelength and temperature managements at the client side are not needed; and the whole system could be cost effective and energy efficient.

Generalized Blind Detection of OOK Modulation for Free-Space Optical Communication

For optimal detection of ON – OFF keying symbols in free-space optical (FSO) communication, the receiver requires the instantaneous channel fading coefficient. In this letter, to increase the bandwidth efficiency of the FSO channel, we propose a blind data detection method, i.e., without requiring transmission of any training symbols. The proposed blind detection is a two-step method that performs block-by-block detection. Simulation results show that the proposed receiver can achieve a significantly lower bit-error-rate performance compared with the existing blind methods in the context of FSO communications. In addition, the proposed blind method has a simple structure, which makes it particularly suitable for fast FSO communications.