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Publisher Copyright: Author In this paper, we compare in a new way the energy efficiencies of modulations that have been popular in ultra-low power (ULP) transmitters. The comparison considers how the choice of modulation affects the combined energy consumed per bit (EPB) by the carrier synthesizer and power amplifier (PA). The comparison includes on-off keying (OOK), binary phase-shift keying (BPSK), binary frequency-shift keying (BFSK), pulse-position modulation (PPM) and differential PPM (DPPM). The results suggest that using OOK, BPSK or BFSK can consume tens to hundreds of percents more energy per bit compared to PPM and DPPM. Furthermore, a new energy efficiency figure of merit (FOM) is derived for transmitters. It accounts for consumed power, output power, data rate, signal bandwidth and signal-to-noise ratio required by the utilized modulation. The FOM can be applied to various types of transmitters with numerous modulations. We also present a sub-100 W DPPM transmitter (TX) and a 3.2- W 2-axis gesture sensor interface, implemented in 0.18 m CMOS. The TX operates in the 433-MHz band, uses pulse shaping for improved spectrum and achieves a FOM of 189.7 dBJ/bit. The estimated uplink range is up to 1 kilometer

This paper proposes and implements an output-controllable efficiency-optimized wireless power transfer scheme using hybrid modulation. The key is to combine pulse frequency modulation (PFM) and on-off keying (OOK) modulation and to utilize feedback control. Among them, PFM is used for the output voltage regulation of the inverter to adjust the rectified output voltage on the receiver side, while OOK modulation is adopted to convert the load resistance to be close to the optimal resistance value so that the system efficiency can be effectively optimized. When the relationship between the input and output voltages reaches a ratio related to system parameters, it can be considered that the load resistance has reached the optimal state. Hence, the feedback output voltage is utilized to help convert the load resistance into an optimal value and only one voltage acquisition circuit is needed. In this paper, theoretical analysis and practical experimentation (using the LED lamp as a nonlinear load and the 102- resistance as a linear load) are both given to verify that the proposed scheme can help to maintain high system efficiency during the output voltage regulation process.

Backscatter communication holds potential for ubiquitous and low-cost connectivity among low-power IoT devices. To avoid interference between the carrier signal and the backscatter signal, recent works propose a frequency-shifting technique to separate these two signals in the frequency domain. Such proposals, however, have to occupy the precious wireless spectrum that is already overcrowded, and increase the power, cost, and complexity of the backscatter tag. In this paper, we revisit the classic ON-OFF Keying (OOK) modulation and propose Aloba, a backscatter system that takes the ambient LoRa transmissions as the excitation and piggybacks the in-band OOK modulated signals over the LoRa transmissions. Our design enables the backscatter signal to work in the same frequency band of the carrier signal, meanwhile achieving flexible data rate at different transmission range. The key contributions of Aloba include: i) the design of a low-power backscatter tag that can pick up the ambient LoRa signals from other signals; ii) a novel decoding algorithm to demodulate both the carrier signal and the backscatter signal from their superposition. We further adopt link coding mechanism and interleave operation to enhance the reliability of backscatter signal decoding. We implement Aloba and conduct head-to-head comparison with the state-of-the-art LoRa backscatter system PLoRa in various settings. The experiment results show Aloba can achieve 39.5-199.4 Kbps data rate at various distances, 10.4-52.4x higher than PLoRa.

We demonstrate 100-Gbaud on-off-keying (OOK) transmission driven at a low voltage using an electro-optic (EO) polymer modulator combined with a silicon Mach-Zehnder interferometer waveguide. Various types of organic- and polymer-based modulators have been reported to perform efficient EO modulation and high-speed data transmission at over 100 Gbaud. However, there are critical concerns regarding the practical application of polymer devices in terms of environmental stability. In particular, long-term thermal storage and stability during operation require improvements before EO polymer modulators can be applied in practical systems. We have developed an EO polymer with enhanced thermophysical stability and used it to fabricate an efficient EO polymer modulator. In this study we extend our earlier work on high-speed EO polymer modulators by performing fiber-link 100-Gbaud OOK transmission at various operating temperatures. A thermal stability test revealed that the EO polymer modulator can survive high-temperature exposure up to 110°C. Error-free signal transmissions over a distance of 2.0 km was successfully demonstrated with a driving voltage of 1.9 Vpp and a bit error rate below the 7% overhead forward error correction threshold. The driving voltage, bandwidth, bit error rate, and fiber-link performance of the device are presented.

An 800-MHz OOK transmitter for short-range Internet-of-Things (IoT) applications is presented in this letter. The OOK transmitter utilizes a microelectromechanical system (MEMS)-based RF oscillator for carrier frequency generation, leading to a hardware- and power-efficient architecture. The transmitter is implemented in a 180-nm CMOS process and delivers −12.4-dBm output power. The power consumption of the MEMS oscillator is only 0.24-mW with 126.3-dBc/Hz phase noise at 100-kHz offset and a figure-of-merit (FoM) of 210.5 dB due to the optimized high- $Q$ aluminum nitride (AlN) piezoelectric MEMS resonator. The transmitter can provide a 120-Mb/s data rate of OOK modulation with an energy efficiency of 5 pJ/bit by directly switching ON/OFF the power amplifier (PA). The 175-ns startup time of the MEMS-based oscillator can support very heavy duty-cycle transmitter operation, leading to ultralow average power consumption of 50 nW.

Photomultiplier tube (PMT) receiver is a promising solution for long-distance underwater wireless optical communication (UWOC) due to its characteristics of high gain, low noise, and large receiver area. However, the complex underwater environment leads to the dynamic change of the received optical intensity and impacts the stability and reliability of UWOC system using PMT. In this work, the bandwidth limitation and performance degradation of UWOC system caused by PMT saturation is experimentally observed and characterized for various optical intensity and PMT gain. A low-cost, high-integrated, and small-volume receiver control system and relevant adaptive control strategy are proposed to improve the stability and reliability of UWOC system by dynamically adjusting the received optical power and PMT gain according to the detected optical signal. The experiment results show that the dynamic range of UWOC received optical power can be extended to 68 dB (−63 dBm∼5 dBm) for 100 Mbit/s OOK modulation based UWOC system.

We consider optical camera communication (OCC) between a camera receiver with optical lenses and distributed transmitters. This article investigates the features of an OCC system when the periods of reception and transmission are slightly different from each other. We describe a received light signal model for the OCC system with on-off keying and regard the received signals generated from a probability distribution of a Gaussian mixture model. We obtain the parameters of the probability distributions by applying a variational Bayesian inference method and utilize them for channel estimation. In addition, we define cost functions and minimize them to demodulate the transmitted bit sequences. The demodulation procedure uses a maximum-likelihood sequence detection method, which can be implemented by the Viterbi algorithm and estimates a synchronization parameter by minimizing the cost functions. Our new demodulation method requires neither synchronization devices nor training sequences for estimating the parameters. Moreover, the receiver does not need the precise transmission period, which is difficult to know in advance in practical situations because of the frequency tolerance of the clock generator in the transmitter. To validate our developed method, we conducted numerical simulations and compared the results with those from an oracle estimator that knows the parameters other than the bit sequence in advance. We also experimented in a real setup situation, and the results show the efficiency of our developed method.

The energy efficiency of an inductive wireless power transfer (WPT) system will deviate from the possible peak value if the magnetic coupling of the transmitter and receiver coils or the load resistance changes. To achieve maximum-efficiency tracking regardless of coupling or load changes, on – off keying (OOK) modulation is used. However it has the issue of large surge current in the circuits during OOK modulation. The current overshoots of a series–series (SS) compensated WPT system at the startup stage might be much higher than the rated current. The current overshoots not only increase the stress on the power switch devices but also cause high voltage spikes across the windings and the resonant capacitors which is a challenge for insulation design. A soft-start scheme is proposed to address the current overshoot problem. The principle of the soft-start scheme can be essentially applied to WPT systems with different compensation topologies. The experimental results of a 3.3-kW prototype verify that the proposed soft-start scheme effectively suppress the current overshoots.

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 fan-in/fan-out devices. The minimum effective modal bandwidth of 8.44 GHz $\cdot$ 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 $\times\, 10^{-5}$ ) was reached for different MCF links.

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.

In this letter, a 24-GHz high-isolation ON–OFF keying (OOK) modulator with reduced input impedance variation in a 65-nm CMOS technology is proposed. A modified magnetic coupled triple-cascode configuration with a series inductor and two shunt transistors, which can simultaneously improve the ON/OFF isolation and reduce the input return loss variation between the ON- and OFF-states, is designed and analyzed for the first time. Based on this configuration, the OOK modulator achieves a 45.7-dB ON/OFF isolation and maintains better than 10-dB return loss for both the ON- and OFF-states. In addition, a data rate of 3.3 Gbps is achieved.

Intercore crosstalk (ICXT) impaired weakly-coupled multicore fiber (MCF) systems using on-off keying (OOK) and direct-detection (DD) are experimentally assessed. The stochastic properties of the received bit amplitudes that depend on the relative propagation delay (skew) between two cores of the MCF and on the OOK bit-rate are discussed. For low skew×bit-rate ( $ 1): (i) the received amplitude of bits 0 or 1 of the interfered core are mainly characterized by two possible levels; (ii) when the short-term average crosstalk (STAXT) power increases (decreases), the fluctuations of the received amplitudes of bits 1 and 0 become larger (lower). For high skew×bit-rate ( $>>$ 1): (i) the received amplitudes of bits 0 and 1 present a noise-like behaviour; (ii) larger fluctuations of the received amplitudes of the OOK signal may not occur only for high STAXT powers. For both low and high skew×bit-rate, it is shown that the histogram of the received amplitudes of bits 1 or 0, and the histogram of the mean and variance of these amplitudes are reasonably well characterized by Gaussian distributions. Experimental results suggest that the rule of thumb to design emerging MCF applications with higher ICXT tolerance is to use cores with skew much longer than the symbol period.

This paper presents a G-band on-off -keying transmitter and a G-Band receiver in 65-nm bulk CMOS process. The proposed transmitter includes a high-efficiency push–push voltage-controlled oscillator (VCO) with body-bias and a switch-based modulator using the folded coupled-line topology. The benefits of the folded coupled-line in switch design are theoretically analyzed and proved. The receiver utilized a topology based on envelope detector and inverter-chain-based output buffer. The standalone VCO demonstrates a peak dc-RF efficiency of 4.1% at 209 GHz with 1.02 dBm output power. The switch-based modulator performs a minimum insertion loss of 1.6 dB with isolation better than 21 dB. The transmitter exhibits a maximum output power of −0.04 dBm at 208 GHz with 3% efficiency and a phase noise of −84.9 dBc at 1-MHz offset. The transmitter and receiver achieve 7.5-Gb/s errorless [bit error rate (BER) < 1 × 10−12] data rate with 1.73 pJ/b energy efficiency and 9 Gb/s with 1 × 10−4 BER in loop-back test. The results of both the transmitter/receiver and standalone components show competitive performances at the frequency over 200 GHz among the designs in CMOS process.

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.

Run-length limited (RLL) codes can facilitate reliable data transmission and provide flicker-free illumination in on-off keying-modulated visible light communication (VLC) systems. This letter proposes new RLL codes that can decrease error and achieve desirable brightness levels with high throughput. The flicker control and free distance of the proposed rate 2/3 RLL codes are extensively described. Extensive simulations evaluated the proposed RLL codes in forward error correction (FEC)-uncoded and FEC-coded VLC systems, demonstrating that the proposed RLL codes offer superior error performance when compared with rate 1/2 Miller and enhanced Miller codes.

In the paper, we present and investigate an integrated wavelength-division-multiplexing (WDM) free space optical (FSO) fiber access network for 51 km long-reach connection. Here, the proposed network architecture also can mitigate Rayleigh backscattering (RB) interferometric beat noise. We employ symmetric $4\times 10$ Gbit/s on-off keying (OOK) WDM-FSO downstream and upstream wavelengths for demonstration. According to the simulated and experimental results, the free space transmission length of 400 to 940 m can be achieved based on various WDM-FSO downstream signals and their corresponding power budget, when the wavelengths are without optical amplification.

Free space optical (FSO) communication technology has become increasingly advanced with capabilities of high speed, high capacity, and low power consumption. However, despite the great potential of FSO, its performance is limited in a turbulent atmosphere. Atmospheric turbulence causes scintillation in the FSO propagated signals, leading to an increase in the bit error rate (BER) performance of the recovered signals at the receiver. In this paper, we demonstrate that the use of deep learning (DL) detection methods could overcome these limitations. We present a new detection method of on-off keying (OOK) modulated signals by using different models of DL over different strength FSO turbulent channels, without the need for prior knowledge of the parameters of the channel. The demonstrated DL decoders improve the performance of the FSO turbulent channel and decrease the power consumption. Moreover, the demonstrated DL models also work faster than maximum likelihood (ML) methods with perfect channel estimation decoders, with even slightly better performance because of the turbulence, thus enabling realization of FSO over turbulent atmospheric channels.

This letter presents the design of a 120-GHz wireless link. The link incorporates a 28-nm CMOS ON–OFF keying transceiver with on-chip antennas to launch the mm-wave signal into a flexible dielectric fiber. The flexible fiber is connected to a 3D-printed high-gain lens proposed to overcome the high free-space path loss to achieve a 15-dBm EIRP. The receiver consists of a low-noise amplifier with 24.9 dB of voltage gain and covers 42-GHz BW−3dB. An efficient self-mixing envelope detector demodulates the amplified signal back to baseband. Using the proposed flexible fiber and wireless topology, a data rate of 11 Gb/s is demonstrated and distance of 1 m is reached with a power consumption

Recent years have witnessed the conceptualization and development of light-to-camera communication (LCC). Various innovative modulation schemes are designed for throughput improvement. Nevertheless, the fundamental limits of LCC itself are still unknown from a theoretical perspective. In this paper, we present the LCC channel model to shed light on a question: how to improve the system performance under identical conditions of transmitting/receiving device and modulation scheme. We reveal the channel parameters of LCC that affect the formation of the signal layer and provide a design guideline for increasing the symbol rate. Moreover, we improve the demodulation performance by sampling judging points from the separated signal layer instead of detecting the widths of bands in capture images. To enhance the signal-to-noise ratio, we propose a short-time linear regression algorithm to filter out the noise from the signal layer. We build a hardware prototype with the simple ON-OFF keying to demonstrate the proposed channel model under various experiment settings. The results show that the system throughput reaches 8.2 kbps with a symbol rate of 25 kBd. We believe our techniques for symbol rate increasing and demodulation improvement can help other LCC systems improve their performance.

We demonstrate a high-efficiency silicon Mach-Zehnder modulator with U-shaped PN junctions. The depletion region of the U-shaped PN junction has a large overlap with the waveguide optical mode, leading to a low drive voltage. The calculated modulation efficiency is 0.33 V·cm at 0 V bias and 0.55 V·cm at −2 V bias. On-off keying (OOK) modulation and four-level pulse amplitude modulation (PAM-4) are achieved at 32 Gb/s and 64 Gb/s data rates under 2 V drive voltage, respectively. The bit error rate for the PAM-4 modulation is below the hard-decision forward error correction threshold of 3.8 × 10−3.

The probabilistic shaping scheme by Honda and Yamamoto (2013) for polar codes is used to enable power-efficient signaling for on–off keying (OOK). As OOK has a non-symmetric optimal input distribution, shaping approaches that are based on the concatenation of a distribution matcher followed by systematic encoding do not result in optimal signaling. Instead, these approaches represent a time-sharing scheme, where only a fraction of the codeword symbols is shaped. The proposed scheme uses a polar code for joint distribution matching and forward error correction which enables asymptotically optimal signaling. Numerical simulations show a gain of 1.8 dB compared to uniform transmission at a spectral efficiency of 0.25 bits/channel use for a blocklength of 65 536 bits.

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.

For coherent detection of ON-OFF keying (OOK) symbols in free-space optical (FSO) communications, the receiver requires the instantaneous channel fading coefficients. To accurately detect OOK symbols over FSO channels without requiring transmission of pilot symbols, in the first part of this letter, we propose an expectation-maximization (EM)-based sequence detection (SD) method with low implementation complexity which is shown to be particularly suitable for fast FSO communication systems. In the second part of this letter, to remove the error floor and to improve the accuracy of the proposed detector, by utilizing a source information transformation we propose an EM-based SD for this state which significantly outperforms than classical EM-based method.

We address full-duplex relaying for optical wireless communication with stochastic and non-negligible self-interference at the relay node with on-off keying modulation. Assume a relay communication system with a source node, a relaying node, and a destination node, where there is no interference at the source and destination nodes, since they merely transmit or receive. We propose two full-duplex relay protocols, namely, the detect-and-forward relaying protocol and the decode-and-forward relay protocol. For the former, the relay node performs the symbol detection and forwards the detected symbols to the destination node, and for the latter, the relay node performs block decoding and forwards the re-encoded block to the destination node. We prove that for sufficiently high self-interference intensity, the achievable transmission rate of the full-duplex relay system can be lower than that of the half-duplex relay system without self-interference for the detect-and-forward relay protocol. We also prove that for the decode-and-forward relay protocol, the full-duplex relay system always has a larger transmission rate compared with the half-duplex relay system. This can be justified by the fact that, for the decode-and-forward protocol, the source-relay link adopts two codebooks in the scenarios with and without self-interference. The performance of the two proposed protocols is evaluated by the numerical results.

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.

An ideal Visible Light Communication (VLC) system should facilitate reliable data transmission at high throughputs, while also providing flicker-free illumination at the user-defined dimming level. In this spirit, we conceive a unary code aided dimming scheme for On-Off Keying (OOK) modulated VLC systems. The proposed unary-coded scheme facilitates joint dimming and throughput control, while relying on iterative decoding. It is demonstrated that the proposed unary-coded dimming scheme provides attractive throughput gains over its contemporaries and it is also capable of approaching the theoretical throughput limit. Furthermore, we design novel joint dimming-Forward Error Correction (FEC) coding schemes, which significantly outperform their compensation time dimming based counterparts in terms of the attainable Bit Error Rate (BER) performance as well as the throughput. Finally, in the quest for approaching the capacity, we also optimize our system using EXtrinsic Information Transfer (EXIT) charts and demonstrate an SNR-gain of up to 6 dB over the compensation time dimming based classic benchmarker.

Performances of high-speed switches operating as terahertz on–off-keying (OOK) modulators are reported. Two types of switches, a passive shunt switch and an amplifier switch, are fabricated using 0.25- $\mu \text{m}$ InP double heterojuction bipolar transistor (DHBT) technology. Small-signal tests show that the amplifier switch possesses superior on–off ratio, but the passive switch has broader bandwidth and smaller group delay ripples. A modulator test setup is built with 20-dB path loss between the transmitter and the receiver. The results indicate that carrier power levels of 14 dBm for the shunt switch and 8 dBm for the amplifier switch are required for 20-Gb/s OOK modulation with bit error rate (BER) of 10−2 at 290 GHz.

This paper proposes a frequency-domain OOK (F-OOK) modulation method which utilizes power detection of both a carrier and a sideband by modulating the carrier frequency with a pre-selected modulation template. Unlike the conventional OOK modulation, the carrier waveform in the time domain can be always present regardless of data pattern, thus offering a packet-level duty cycle operation without affecting overall spectrum occupation. Compared to the BFSK modulation, more efficient bandwidth control can be achieved for the same data rate with a symmetric FM template. The F-OOK signal is generated by a PLL based modulator in which only high-pass modulation is performed, which is different from the conventional two-point modulation, thus significantly relaxing design complexity. A prototype transmitter implemented in 65nm CMOS consumes 1.9mW from a 0.8V supply with a data rate of 750kb/s, achieving an energy efficiency of 2.5nJ/bit.

This letter proposes a new adaptive threshold modulation scheme, called chip averaging chaotic ON–OFF keying (CA-COOK). This new scheme is applied to non-coherent modulations in ultra-wideband direct chaotic communication. Mainly, the proposed method deals with the “estimation problem” caused by the bit energy variation of the chaotic carrier signal. This is completed by adopting the Cell Averaging Constant False Alarm Rate paradigm used in radar, and each bit period is divided into several chips, where one of those chips is bearing the information. Bit-error-rate performance in additive-white-Gaussian-noise, two-path Rayleigh, and IEEE802.15.4a office NLOS channel models, is analyzed and compared with well-known and challenging chaos-based communication systems. Simulation results show the effectiveness of the proposed CA-COOK.

A new binary frequency-shift keying (BFSK) waveform is suggested for continuous wave radar. It provides ideal periodic autocorrelation (PAC) when processed by a matched filter, and perfect periodic cross-correlation (PCC) when processed by a mismatched filter. Ideal PAC implies a uniform sidelobe level, whose ratio to the PAC peak is equal to the inverse of the code length. Perfect PCC implies zero sidelobes. BFSK is relatively spectrum efficient. Design details and processing issues are discussed.

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.

Space ionizing radiation impact on the on-orbit performance of 1550 nm on off keying, differential phase shift keying, and homodyne binary phase shift keying (BPSK) based optical intersatellite communication systems is studied in this paper. Essential optoelectronic devices involved in optical communication systems were irradiated by Co60 gamma ray to a total dose of 30 krad and the related ionizing radiation damage factors are obtained according to theoretical analyses. On this basis, ionizing radiation induced communication terminal degradation and system performance degradation are simulated. Subsequently, the ionizing radiation environment of four typical orbits is analyzed and the on-orbit performances of different intersatellite communication links are further obtained and discussed. The result shows the necessity of enhancing radiation protection of EDFAs, optical transmitters, and terminals located on GEO and HEO satellites, and it also shows the superiority of homodyne BPSK scheme against space ionizing radiation environment.

Dimming control is of vital importance for visible light communication (VLC) systems. Conventional dimmable transmission schemes based on compensation are spectrally inefficient. In this paper, we propose the use of two techniques, i.e., time-sharing and superposition, to construct spectral-efficient dimmable transmission schemes. For VLC systems with on–off keying (OOK) signaling, we present a general framework to construct dimmable transmission scheme by time-sharing among different dimming control codes. Arbitrary dimming target is achieved by adjusting the proportion of each dimming control code. We, then, give a practical construction of dimming control codes with semi-constant weight codes. We obtain optimal proportions of the semi-constant weight codes, which maximize the asymptotic spectral efficiency using linear programming. We also compute achievable rates of the proposed scheme under different dimming targets and different signal-intensity-to-noise-amplitude ratios. To achieve higher spectral efficiency ( $>$ 1.0 (b/s)/Hz), we present a dimmable multilevel transmission scheme based on superposition. In the proposed scheme, the first $\ell$ $-1$ levels adopt traditional OOK modulation, whereas the $\ell$ th level adopts the dimmable transmission scheme for OOK modulation. The transmitted signal is formed by superimposing modulated signals of the $\ell$ levels. Analysis shows that the proposed scheme achieves a higher spectral efficiency than the state-of-the-art schemes. Hence, it provides an attractive candidate for dimmable VLC systems with demanding spectral efficiency.

In this letter, we aim for maximizing the throughput of a visible light communication (VLC) system. Explicitly, we conceive a soft-in soft-out decoder providing soft feedback for the classic run length limited (RLL) codes, hence facilitating iterative decoding for exchanging valuable extrinsic information between the RLL and the error correction modules of a VLC system. Furthermore, we propose a unity rate code for our VLC system, which, hence, becomes capable of matching the ON–OFF keying capacity, while maintaining a flicker-free dimming value of 50%.

This letter investigates the performance of underwater optical wireless communication systems (UOWC) employing optical pre-amplification as well as multiple receivers to exploit the advantages of spatial diversity. Numerical results are further provided to evaluate the error performance of pre-amplified single-input multiple-output (SIMO) UOWC systems when onoff keying (OOK) modulation is utilized. Our results reveal that the proposed system configuration can indeed offer significant system performance enhancements in terms of the attainable bit error rate.

In this letter, we present a novel hybrid intensity modulation and direct detection communication system, which integrates asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and on-off keying (OOK) modulation schemes. First, the negative ACO-OFDM is proposed based on the conventional ACO-OFDM system to accommodate the on case with direct current in the OOK modulation, while the ACO-OFDM can match the off case in the OOK modulation. Therefore, the novel hybrid system combines the ACO-OFDM and OOK modulation schemes, while the signals can be recovered at the receiver to support the different qualities of service with high spectral efficiency and can be adapted to various receivers with different complexities. Simulation results are reported for the visible light channel and show that both the ACO-OFDM and OOK signals can be well recovered.

By combing Zn-diffusion and oxide-relief apertures with strong detuning (>20 nm) in our demonstrated short-cavity ( $\lambda $ /2) 850-nm vertical-cavity surface-emitting lasers (VCSELs), wide electrical-to-optical bandwidth (29–24 GHz), low-differential resistance ( $\sim 100~\Omega )$ , and (quasi) single-mode (SM) with reasonable output power ( $\sim 1.4$ mW) performances can be simultaneously achieved. Error-free ON–OFF keying transmission at 54-Gb/s data rate through 1-km OM4 multi-mode fiber can be achieved by using highly SM device with forward error correction and decision feedback equalization techniques. As compared with the reference device with a larger oxide-relief aperture and a multi-mode performance, the SM device exhibits lower bit-error rate ( $1\times {10}^{-5} $ versus $1\times {10}^{-2})$ at 54 Gb/s. This result indicates that modal dispersion plays more important role in transmission than that of output power does. We benchmark these results to an industrial 50-Gb/s SM VCSEL. It shows a higher bit-error-rate value $\sim 3.5\times {10}^{-3}$ versus $\sim 1.4\times {10}^{-4}$ under the same received optical power.

We propose a cost-effective multi-carrier generation technique which minimizes the passive optical access network (PON) costs. In this study replacement of laser array with multi-carrier source at optical line terminal (OLT) side in PON is addressed. With 25-GHz frequency spacing, the generated optical multi-carriers exhibit good tone to noise ratio (TNR) i. e. above 20dB, and least amplitude difference i. e. 1.5dB. At the OLT, multi-carriers signal based multiplexed differential phase shift keying (DPSK) data from all the channels each having 10Gbps for downlink is transmitted through 25km single mode fiber. While the transmitted information is retrieved at optical network unit (ONU), part of the downlink signal is re-modulated using intensity modulated (IM) on-off keying(OOK) for upstream transmission at 10-Gbps. Simulation results are in good agreement with the theoretical analysis, showing error free transmission in downlink and uplink with 10Gbps symmetric data rate at each channel. The received power, both for uplink and downlink transmission, is adequate for all channels at BER of 10−9 with minimum power penalties. Power budget is calculated for different splitting ratios showing excellent system margins for any unseen losses. The proposed setup provides a cost-effective way minimizing transmission losses, and providing greater system's margin in PON architecture.

Free-space optical communication using on–off keying (OOK) and source information transformation is proposed. It is shown that the source information transformation allows the proposed system to detect the OOK signal without requiring the knowledge of instantaneous channel state information and the probability density function (pdf) of the turbulence model. Analytical expressions are derived for the pdf of the detection threshold, and an upper bound is obtained on the average bit error rate (BER). Numerical studies show that the proposed system can achieve comparable performance to the idealized adaptive detection system, with a greatly reduced level of implementation complexity and a signal-to-noise ratio performance loss of only $1.8$ dB at a BER of $1\times 10^{-9}$ for a lognormal turbulence channel with $\sigma =0.25$ .

This paper presents the spectral analysis of OOK modulation with rectangular carrier and the expression that shows the behavior of this signal in the frequency domain is obtained. A graphical analysis is performed from the representation of the harmonics of the OOK wave with rectangular carrier, it permit make the conversion in OOK modulated signal with sinusoidal carrier. It checked how this approximation permit attenuate the problems in low frequency passive RFID system if is using the rectangular carrier in wireless power and communication. Further, is showed a converter circuit, this circuit was simulated and checked in practice.

Power line communication (PLC) utilizes power lines for the purpose of electronic data transmission. Differential binary phase shift keying (DBPSK) is a popular modulation scheme proposed in the PLC standards like G3, PRIME, and IEEE P1901.2. This letter provides the performance evaluation of a PLC system assuming DBPSK modulation under the combined effect of Nakagami- $m$ background noise and impulsive noise. We utilize a simple, yet accurate approximation available in literature to derive the probability density function of the sum of two Nakagami- $m$ random variables. Closed-form expressions of the analytical average bit error rate and the outage probability of the system are derived. Validity of the derived analytical expressions is closely verified by simulated results.

Nanoscale electromechanical wireless communication with on-off keying in the very high frequency (VHF) band (30–300 MHz) is studied for a receiver using a carbon nanotube (CNT). Previous studies on this topic have only considered continuous wave (CW) on-off keying which suffers from spectral widening due to sharp changes in the signal. Effects of the inter-symbol interference (ISI), the co-channel interference, and the adjacent channel interference on the received signal statistics have not been analyzed. The rise- and fall-times associated with the filtering of the incoming signal by the mechanical frequency response of the receiver’s CNT have also been ignored. In this paper, Fourier-series based modeling and statistical analysis of decision variables are performed. The results and modeling in this study enable performance evaluation of CNT based receivers with an arbitrary number of interfering signals with arbitrary pulse shapes, and fully incorporates the transient signal components. Received signal statistics under interference are derived using the developed model. Numerical results are presented for Hanning pulse and trapezoidal pulse (which includes rectangular pulses corresponding to CW as a special case). The required guard intervals between pulses to mitigate ISI, required frequency separation between channels, and required spatial separation of co-channel networks (frequency reuse distance) are shown. These results show that large frequency reuse distance is required, limiting efficient spectrum utilization. However, the ISI and adjacent channel interference can be controlled more easily with a proper selection of parameters.

We demonstrate the demodulation of a multi-Gb/s ON–OFF keying (OOK) signal on a 96 GHz carrier by utilizing a 250-nm graphene field-effect transistor as a zero bias power detector. From the eye diagram, we can conclude that the devices can demodulate the OOK signals up to 4 Gb/s.

Free-space optical communication links operating over lognormal turbulence channels using on-off keying (OOK) are studied in this paper. Such systems can suffer from irreducible error floors that result from the use of demodulation with fixed and unoptimized detection thresholds. The resulting error floors are analyzed for the general case of low- and high-state offsets (i.e., finite extinction ratios). An electrical signal-to-noise ratio (SNR) optimized detection system is applied. The system uses the electrical SNRs to implement adaptive detection thresholds and eliminate the error floors. The system can accommodate operation with finite extinction ratios, as it uses the method of moments and maximum likelihhod estimation techniques to estimate the low- and high-state offsets and electrical SNR. Numerical results show that the SNR gap between the electrical-SNR-optimized detection system and the adaptive detection system is 2.3 dB at a bit-error rate of $10^{-5}$ without a state offset. The SNR gap increases to 4.5 dB with a state offset of $\xi =0.2$ .

This letter presents the high-data rate performance of a 7-Gb/s resonant tunneling diode (RTD)-based on-off keying (OOK) oscillator core with a heterojunction bipolar transistor (HBT) switch design. It is found that the integrated HBT switch improves the data rate of the RTD OOK oscillator IC by minimizing the RC delay time in the previous direct driving oscillator design. The fabricated OOK oscillator IC shows an energy efficiency of 0.71-pJ/b which is the best value reported to date to the authors’ knowledge in a related frequency range.

This letter reports an integrated ultrawideband impulse radio design. The proposed radio applies a combination of frequency-shift keying and ON–OFF keying to realize intrinsic clock and data recovery as well as asynchronous wireless communication. The transmitter uses frequency-hopping and duty-cycling methods to achieve ultrawide bandwidth. Both of the transmitter and the receiver are fabricated on IBM 0.18- $\mu \text{m}$ CMOS process. The chip core area is 0.031 mm2 for the transmitter and 0.017 mm2 for the receiver. The measured power consumption is 2.89mW for the transmitter and 5.4mW for the receiver at the data rate of 3Mb/s. The sensitivity at $1.3\times 10^{-3}$ bit error rate, 2.5Mb/s, and 10.42-ns pulsewidth is −60dBm.