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Showing papers on "Quadrature amplitude modulation published in 2021"


Journal ArticleDOI
TL;DR: A comprehensive analysis of the effects of wireless channel hostilities on the convergence rate of the proposed FEEL scheme is provided, showing that the hostilities slow down the convergence of the learning process by introducing a scaling factor and a bias term into the gradient norm.
Abstract: Federated edge learning (FEEL) is a popular framework for model training at an edge server using data distributed at edge devices (e.g., smart-phones and sensors) without compromising their privacy. In the FEEL framework, edge devices periodically transmit high-dimensional stochastic gradients to the edge server, where these gradients are aggregated and used to update a global model. When the edge devices share the same communication medium, the multiple access channel (MAC) from the devices to the edge server induces a communication bottleneck. To overcome this bottleneck, an efficient broadband analog transmission scheme has been recently proposed, featuring the aggregation of analog modulated gradients (or local models) via the waveform-superposition property of the wireless medium. However, the assumed linear analog modulation makes it difficult to deploy this technique in modern wireless systems that exclusively use digital modulation. To address this issue, we propose in this work a novel digital version of broadband over-the-air aggregation, called one-bit broadband digital aggregation (OBDA). The new scheme features one-bit gradient quantization followed by digital quadrature amplitude modulation (QAM) at edge devices and over-the-air majority-voting based decoding at edge server. We provide a comprehensive analysis of the effects of wireless channel hostilities (channel noise, fading, and channel estimation errors) on the convergence rate of the proposed FEEL scheme. The analysis shows that the hostilities slow down the convergence of the learning process by introducing a scaling factor and a bias term into the gradient norm. However, we show that all the negative effects vanish as the number of participating devices grows, but at a different rate for each type of channel hostility.

252 citations


Journal ArticleDOI
19 Mar 2021
TL;DR: In this article, power and bandwidth efficient modulation schemes for the next generation communication systems in details are surveyed and detailed study of star QAM, XQAM, and HQAM is presented.
Abstract: Communication system’s performance is sensitive to bandwidth, power, cost etc. There have been various solutions to improve the performance, out of them, one of the fundamental solutions over the years is design of optimum modulation schemes. As the research on beyond 5G heats up, we survey and explore power and bandwidth efficient modulation schemes for the next generation communication systems in details. In the existing literature, initially square quadrature amplitude modulation (SQAM) was considered. However, only square constellations are not sufficient for varying channel conditions and rate requirements, thus, efficient odd power of 2 constellations were introduced. For odd power of 2 constellations, rectangular QAM (RQAM) is most commonly used. However, RQAM is not a good choice and modified cross QAM (XQAM) constellation is preferred which provides improved power efficiency over RQAM due to its energy efficient two dimensional (2D) structure. The increasing demand for high data-rates has further encouraged research towards more compact 2D constellations which leads to hexagonal lattice structure based hexagonal QAM (HQAM) constellations. In this work, various QAM constellations are discussed and detailed study of star QAM, XQAM, and HQAM is presented. Generation, peak and average energies, peak-to-average-power ratio, symbol-error-rate, decision boundaries, bit mapping, Gray code penalty, and bit-error-rate of star QAM, XQAM, and HQAM constellations for different constellation orders are presented. Finally, a comparative study of various QAM constellations is presented which justifies the supremacy of HQAM over other QAM constellations for various wireless communication systems and a potential modulation scheme for future standards.

49 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented high modulated soliton power transmission interaction with optical fiber and optical wireless communication channels at flow rate of 40 Gbps and 20 km link range at the optical receiver.
Abstract: This paper has presented high modulated soliton power transmission interaction with optical fiber and optical wireless communication channels at flow rate of 40 Gbps and 20 km link range. The proposed modulation schemes are continuous phase frequency shift keying (CPFSK), Quadrature amplitude modulation (QAM), differential phase shift keying (DPSK), frequency shift keying (FSK), pulse amplitude modulation (PAM), minimum shift keying (MSK), and optical quadrature phase shift keying (OQPSK). CPFSK has presented better performance than other proposed modulation schemes for both optical fiber and optical wireless communication channels. The enhancement of optical signal/noise ratio at fiber/wireless channel, received electrical power and signal/noise ratio at optical receiver with increase of bits per symbol for different proposed modulation schemes except for CPFSK scheme. Therefore it is evident that CPFSK modulation scheme is more efficient and better performance than other modulation schemes for different communication channels. The obtained results are simulated with optisystem program version 13.

48 citations


Journal ArticleDOI
TL;DR: It has been shown via computer simulations that the GCIM-SM system has lower transmission energy, faster data transmission rate, and better error performance than DS-SS, SM, QSM, and CIM-SS systems.
Abstract: In this article, a high data rate and energy-efficient multiple-input multiple-output transmission scheme is considered by combining two popular and rational modulation techniques: spatial modulation (SM) and code index modulation-spread spectrum (CIM-SS). Since in the considered system, called generalized CIM-SM (GCIM-SM), incoming information bits determine modulated symbols, activated transmit antenna indices as well as their corresponding spreading code indices, data bits are conveyed not only by modulated symbols but also by the indices of the active antenna and spreading codes. Hence, a GCIM-SM scheme accommodates faster data rates while spending less transmission power and possessing better error performance compared to the conventional direct sequence spread spectrum (DS-SS), SM, quadrature SM (QSM), and CIM-SS systems. The mathematical expressions of the GCIM-SM system for bit error rate, throughput, energy efficiency, and the system complexity are derived to analyze the overall system performance. Besides, it has been shown via computer simulations that the GCIM-SM system has lower transmission energy, faster data transmission rate, and better error performance than DS-SS, SM, QSM, and CIM-SS systems. Performance analysis of the considered system was performed on Rayleigh block-fading channels for quadrature amplitude modulation technique.

41 citations


Journal ArticleDOI
TL;DR: In this article, a simple approach based on photonic reservoir computing (P-RC) was proposed for modulation format identification in optical fiber communications. But the proposed technique utilizes very simple devices and thus offers a resource efficient alternative approach to MFI.
Abstract: We present a simple approach based on photonic reservoir computing (P-RC) for modulation format identification (MFI) in optical fiber communications. Here an optically injected semiconductor laser with self-delay feedback is trained with the representative features from the asynchronous amplitude histograms of modulation signals. Numerical simulations are conducted for three widely used modulation formats (on–off keying, differential phase-shift keying, and quadrature amplitude modulation) for various transmission situations where the optical signal-to-noise ratio varies from 12 to 26 dB, the chromatic dispersion varies from −500 to 500 ps/nm, and the differential group delay varies from 0 to 20 ps. Under these situations, final simulation results demonstrate that this technique can efficiently identify all those modulation formats with an accuracy of >95% after optimizing the control parameters of the P-RC layer such as the injection strength, feedback strength, bias current, and frequency detuning. The proposed technique utilizes very simple devices and thus offers a resource-efficient alternative approach to MFI.

39 citations


Journal ArticleDOI
TL;DR: This paper derives exact BER expressions under additive white Gaussian noise and Rayleigh fading channels for an arbitrary number of NOMA users and finds the optimal power assignment that minimizes the system's average BER for N=2 and 3 users cases.
Abstract: Non-orthogonal multiple access (NOMA) is a promising candidate for future mobile networks as it enables improved spectral-efficiency, massive connectivity and low latency. This paper derives exact and asymptotic bit error rate (BER) expressions under Rayleigh fading channels for NOMA systems with arbitrary number of users and arbitrary number of receiving antennas and modulation orders, including binary phase-shift keying and rectangular/square quadrature amplitude modulation. Furthermore, the power coefficients’ bounds, which ensure users’ fairness, and solve the constellation ambiguity problem, are derived for $N=2$ and 3 users cases with any modulation orders. In addition, this paper determines the optimal power assignment that minimizes the system’s average BER. These results provide valuable insight into the system’s BER performance and power assignment granularity. For instance, it is shown that the feasible power coefficients range becomes significantly small as the modulation order, or $N$ , increases, where the BER performance degrades due to the increased inter-user interference. Hence, the derived expressions can be crucial for the system scheduler in allowing it to make accurate decisions of selecting appropriate $N$ , modulation orders, and power coefficients to satisfy the users’ requirements. The presented expressions are corroborated via Monte Carlo simulations.

38 citations


Journal ArticleDOI
01 Jun 2021
TL;DR: A millimetre-wave modulator and antenna array for backscatter communications at gigabit data rates, created with inkjet printing, providing a bit rate of two gigabits per second and with a front-end energy consumption of only 0.17 pJ per bit.
Abstract: Future devices for the Internet of Things will require communication systems that can deliver higher data rates at low power. Backscatter radio—in which wireless communication is achieved via reflection rather than radiation—is a low-complexity approach that requires a minimal number of active elements. However, it is typically limited to data rates of hundreds of megabits per second because of the low frequency bands used and the modulation techniques involved. Here we report a millimetre-wave modulator and antenna array for backscatter communications at gigabit data rates. This radiofrequency front-end consists of a microstrip patch antenna array and a single pseudomorphic high-electron-mobility transistor that supports a range of modulation formats including binary phase shift keying, quadrature phase shift keying and quadrature amplitude modulation. The circuit is additively manufactured with inkjet printing using silver nanoparticle inks on a flexible liquid-crystal polymer substrate. A millimetre-wave transceiver is also designed to capture and downconvert the backscattered signals and route them for digital signal processing. With the system, we demonstrate a bit rate of two gigabits per second of backscatter transmission at millimetre-wave frequencies of 24–28 GHz, and with a front-end energy consumption of 0.17 pJ per bit. A microstrip patch antenna array and a single high-electron-mobility transistor, which are created with inkjet printing, can be used for backscatter communication at millimetre-wave frequencies, providing a bit rate of two gigabits per second and with a front-end energy consumption of only 0.17 pJ per bit.

32 citations



Journal ArticleDOI
TL;DR: In this paper, a geometric shaping (GS) strategy was proposed to design 8, 16, 32, and 64 -ary modulation formats for the optical fiber channel impaired by both additive white Gaussian (AWGN) and phase noise.
Abstract: In this article, we propose a geometric shaping (GS) strategy to design 8, 16, 32, and 64 -ary modulation formats for the optical fibre channel impaired by both additive white Gaussian (AWGN) and phase noise. The constellations were optimised to maximise generalised mutual information (GMI) using a mismatched channel model. The presented formats demonstrate an enhanced signal-to-noise ratio (SNR) tolerance in high phase noise regimes when compared with their quadrature amplitude modulation (QAM) or AWGN-optimised counterparts. By putting the optimisation results in the context of the 400ZR implementation agreement, we show that GS alone can either relax the laser linewidth (LW) or carrier phase estimation (CPE) requirements of 400 Gbit/s transmission links and beyond. Following the GMI validation, the performance of the presented formats was examined in terms of post forward error correction (FEC) bit-error-rate (BER) for a soft decision (SD) extended Hamming code (128, 120), implemented as per the 400ZR implementation agreement. We demonstrate gains of up to 1.2 dB when compared to the 64 -ary AWGN shaped formats.

30 citations


Journal ArticleDOI
TL;DR: In this article, a pilot-assisted self-coherent detection approach is proposed to overcome the effect of atmospheric turbulence in free-space optical communications, where the data is recovered by mixing a Gaussian local oscillator with a received Gaussian data beam.
Abstract: In free-space optical communications that use both amplitude and phase data modulation (for example, in quadrature amplitude modulation (QAM)), the data are typically recovered by mixing a Gaussian local oscillator with a received Gaussian data beam. However, atmospheric turbulence can induce power coupling from the transmitted Gaussian mode to higher-order modes, resulting in a significantly degraded mixing efficiency and system performance. Here, we use a pilot-assisted self-coherent detection approach to overcome this problem. Specifically, we transmit both a Gaussian data beam and a frequency-offset Gaussian pilot tone beam such that both beams experience similar turbulence and modal coupling. Subsequently, a photodetector mixes all corresponding pairs of the beams’ modes. During mixing, a conjugate of the turbulence-induced modal coupling is generated and compensates the modal coupling experienced by the data, and thus the corresponding modes of the pilot and data mix efficiently. We demonstrate a 12 Gbit s−1 16-QAM polarization-multiplexed free-space optical link that is resistant to turbulence. A transmission scheme for free-space optical communications is shown to be highly robust against turbulence.

29 citations


Journal ArticleDOI
TL;DR: In this paper, a chaotic optical coherent secure communication scheme was proposed and numerically investigated, which supports long-haul secure transmission for signals in advanced modulation formats, and a hybrid optical chaos system was designed with coordination of digital and analog signals.
Abstract: We propose and numerically investigate a chaotic optical coherent secure communication scheme, which supports long-haul secure transmission for signals in advanced modulation formats. A hybrid optical chaos system is designed with coordination of digital and analog signals. The hybrid entropy source provides a broadband analog optical chaos signal, which could serve as the carrier to load quadrature amplitude modulation (QAM) data. Simultaneously, a digital binary signal generated from the entropy source is transmitted to establish long-haul chaotic synchronization. Coherent detection is utilized at the receiver, and a digital signal processing (DSP) algorithm is adopted to reduce transmission distortion. A 5 Gbaud 16QAM signal is encrypted by a phase chaos carrier with the effective bandwidth of 5.8 GHz. A bit error rate (BER) below forward error correction (FEC) can be achieved after transmitting over 1600 km based on digital-signal-induced chaos synchronization technology. Optimal launch power is investigated to minimize nonlinear effects of transmission links. System security is guaranteed by the high dynamical complexity of the chaotic source and the sensitive time delay as the secret key.

Journal ArticleDOI
TL;DR: In this article, the authors established an analytical lower bound on the secret key rate of continuous-variable quantum key distribution with an arbitrary modulation of coherent states and showed that relatively small constellation sizes, with say 64 states, are essentially sufficient to obtain a performance close to a true Gaussian modulation and are therefore an attractive solution for large-scale deployment of continuous variable quantum key distributions.
Abstract: We establish an analytical lower bound on the asymptotic secret key rate of continuous-variable quantum key distribution with an arbitrary modulation of coherent states. Previously, such bounds were only available for protocols with a Gaussian modulation, and numerical bounds existed in the case of simple phase-shift-keying modulations. The latter bounds were obtained as a solution of convex optimization problems and our new analytical bound matches the results of Ghorai et al. (2019), up to numerical precision. The more relevant case of quadrature amplitude modulation (QAM) could not be analyzed with the previous techniques, due to their large number of coherent states. Our bound shows that relatively small constellation sizes, with say 64 states, are essentially sufficient to obtain a performance close to a true Gaussian modulation and are therefore an attractive solution for large-scale deployment of continuous-variable quantum key distribution. We also derive similar bounds when the modulation consists of arbitrary states, not necessarily pure.

Journal ArticleDOI
TL;DR: In this paper, a high-speed optical coherent receiver for optical communications based on Graphene-on-plasmonic slot waveguide photodetectors is presented.
Abstract: Graphene-based photodetectors have attracted significant attention for high-speed optical communication due to their large bandwidth, compact footprint, and compatibility with silicon-based photonics platform. Large-bandwidth silicon-based optical coherent receivers are crucial elements for large-capacity optical communication networks with advanced modulation formats. Here, we propose and experimentally demonstrate an integrated optical coherent receiver based on a 90-degree optical hybrid and graphene-on-plasmonic slot waveguide photodetectors, featuring a compact footprint and a large bandwidth far exceeding 67 GHz. Combined with the balanced detection, 90 Gbit/s binary phase-shift keying signal is received with a promoted signal-to-noise ratio. Moreover, receptions of 200 Gbit/s quadrature phase-shift keying and 240 Gbit/s 16 quadrature amplitude modulation signals on a single-polarization carrier are realized with a low additional power consumption below 14 fJ/bit. This graphene-based optical coherent receiver will promise potential applications in 400-Gigabit Ethernet and 800-Gigabit Ethernet technology, paving another route for future high-speed coherent optical communication networks. Graphene-based photodetectors have many advantages for applications. Here, the authors demonstrate a high-speed optical coherent receiver for optical communications based on graphene-on-plasmonic slot waveguide photodetectors.

Journal ArticleDOI
TL;DR: The proposed FSO transmission system with high-speed transmission capability is proposed by deploying orthogonal frequency division multiplexing (OFDM) to mitigate channel fading effects and improves the information rate and maximum transmission distance.
Abstract: The reliability and efficiency of free space optics (FSO) systems is significantly degraded by attenuation caused by different climate conditions and atmospheric turbulence. In this work, an FSO transmission system with high-speed transmission capability is proposed by deploying orthogonal frequency division multiplexing (OFDM) to mitigate channel fading effects. Further, we propose the hybridization of polarization division multiplexing (PDM) with CO-OFDM to improve the system capacity. We perform the bit error rate (BER) and optical signal to noise ratio (OSNR) comparative analysis of multi-level quadrature amplitude modulation (QAM) schemes, i.e., 4-QAM, 16-QAM, 32-QAM, and 64-QAM at 100, 120, 360, and 480 Gbps transmission rates, respectively. The obtained results reveal that the 4-QAM modulation scheme achieves the highest transmission range and the least OSNR requirement. In terms of spectral efficiency, 64-QAM shows the best performance. Also, the impact of different climate conditions on the system performance has been investigated. Through simulations, we demonstrate a successful transmission of 100 Gbps 4-QAM information at 15 km. Furthermore, we numerically investigated the increasing scintillation effect on the BER system performance. The proposed system not only reduces the channel fading but also improves the information rate and maximum transmission distance. The reported work can be considered for future FSO systems even in adverse climate conditions.

Journal ArticleDOI
TL;DR: In this article, a green 2×2 micro light-emitting diode (μ-LED) array with nanostructured grating patterns grown on a semipolar (20-21)-oriented gallium nitride (GaN) buffered layer on (22-43)-oriented sapphire substrate is specially transistor-outline can (TO-can) packaged with a sub-miniature-A (SMA) connector for high-speed data communication beyond 5Gbit/s.
Abstract: A green 2×2 micro light-emitting diode (μ-LED) array with nanostructured grating patterns grown on a semipolar (20-21)-oriented gallium nitride (GaN) buffered layer on (22-43)-oriented sapphire substrate is specially transistor-outline can (TO-can) packaged with a sub-miniature-A (SMA) connector for high-speed data communication beyond 5 Gbit/s. Through a specific design for suppressing the quantum-confined Stark effect (QCSE) in the green 2×2 μ-LED array with a low polarization-related electric field and flat quantum well band diagram, the green 2×2 μ-LED array exhibits a turn-on voltage of 2.5 V and output power of 0.3 mW at 1 A/cm2. The green 2×2 μ-LED array also reveals a wavelength shift from 543 nm to 537 nm smaller than that of conventional devices grown on c-plane buffered GaN substrate due to the inhibited QCSE. The 50 µm emission aperture of the green 2×2 μ-LED array ensures a lower capacitance for a larger −3 dB modulation bandwidth, which exhibits −1 dB power compression at a larger bias under high-speed operation, as it is less affected by the high resistance of the single μ-LED element. With a specific TO-can+SMA package, the green 2×2 μ-LED array exhibits maximal data rates exceeding 1.5 Gbit/s for the non-return-to-zero on–off keying format and beyond 5.02 Gbit/s for the bit-loaded discrete multitone (BL-DMT) format, which is very promising for optical wireless communication. As the sampling rate increases from 4 GSa/s to 16 GSa/s, the μ-LED array’s received signal-to-noise ratio (SNR) improves dramatically from 15.4 dB to 12.2 dB. The SNR remains about 15.4 dB, with a matching bit-error ratio (BER) of 2.7×10−3, whereas the 10-fold oversampling of the eight-ray quadrature amplitude modulation orthogonal frequency-division multiplexing (8-QAM OFDM) data stream with 16 GSa/s appears to reduce the SNR by −3 dB, resulting in a decoded BER of 3.3×10−3. The green 2×2 μ-LED array has demonstrated greater potential in data transmission beyond 5 Gbit/s using the BL-DMT algorithm for future applications in domains of visible light communication or optical wireless communication when packaged with handed mobile devices.

Journal ArticleDOI
TL;DR: RIS-QRM improves the error performance of the additional bits delivered by the RIS without deteriorating the errorperformance of the bits modulated on the constellation symbol, as compared to ON/OFF-based RIS-aided schemes.
Abstract: Reflection modulation based on reconfigurable intelligent surface (RIS) is considered to be a promising information transfer mechanism without requiring any additional radio frequency chains. However, existing reflection modulation schemes consider manipulating the ON/OFF states of RIS elements, which suffers from power loss. In this paper, we propose a new scheme, called RIS-aided quadrature reflection modulation (RIS-QRM), for harvesting the reflection power based on an RIS-aided downlink multiple-input single-output (MISO) wireless system. To this end, RIS-QRM partitions RIS elements into two subsets for reflecting impinging signals into two orthogonal directions as well as passive beamforming and encodes its local data onto the element partition options. A closed-form expression for the unconditional pairwise error probability of RIS-QRM in Rician fading is derived assuming the maximum-likelihood detection. Moreover, we propose a low-complexity detection method with compromised performance for decoupling the joint search of the constellation symbol and the RIS element partition. Computer simulation results corroborate the effectiveness of RIS-QRM and validate the analytical results. It is shown that RIS-QRM is able to improve the error performance of the additional bits delivered by the RIS without deteriorating that of the bits carried on the constellation symbol, as compared to ON/OFF-based schemes.

Journal ArticleDOI
TL;DR: The obtained numerical results show that power assignment process at the transmitter for the superposition process and at the receiver for the SIC process should be performed meticulously because the power difference between the weakest and strongest users can be tremendous when the number of users or the modulation orders increase.
Abstract: This paper considers the power allocation for non-orthogonal multiple access (NOMA) users to enable using the successive interference cancellation (SIC) while providing reliable error performance. The derived closed-form expressions are applicable for arbitrary number of NOMA users each of which has a square or rectangular quadrature amplitude modulation (QAM) constellation with arbitrary order. The obtained numerical results show that power assignment process at the transmitter for the superposition process and at the receiver for the SIC process should be performed meticulously because the power difference between the weakest and strongest users can be tremendous when the number of users or the modulation orders increase. Moreover, the derived expressions can be used to reduce the computational complexity that is required to obtain the optimal power coefficients using brute force methods by significantly reducing the search space.

Journal ArticleDOI
TL;DR: A corner-inserted pilot pattern is proposed, which targets the low pilot overhead and satisfactory CE performance and an OTFS signal detector, leveraging the time-domain channel equalization, linear-complexity interference cancellation and delay-Doppler domain maximal ratio combining detection, is developed to retrieve the transmitted data symbols.
Abstract: Orthogonal time frequency space (OTFS) has shown to be a promising modulation technology that achieves the robust wireless transmission in high-mobility environments. The high mobility incurred Doppler effect in OTFS system, is represented as a continuous and relatively large band in the Doppler frequency. It yields the equivalent channel responses (ECRs) in the system change significantly within one symbol block, posing a challenge to channel estimation (CE) or tracking. In order to tackle this issue, in this paper, a set of transform-domain basis functions is designed to span a low-dimensional subspace for modeling the OTFS channel. Then, the CE can be performed by estimating a few projection coefficients of ECRs in the developed subspace, with training pilots. According to the individual transmission characteristic of OTFS signal, we propose a corner-inserted pilot pattern, which targets the low pilot overhead and satisfactory CE performance. Moreover, an OTFS signal detector, leveraging the time-domain channel equalization, linear-complexity interference cancellation and delay-Doppler domain maximal ratio combining detection, is developed to retrieve the transmitted data symbols. The simulations show the precisely estimated ECRs enable the detector to ideally demodulate 256-ary quadrature amplitude modulation signaling, under a velocity of 550 km/h at 5.9 GHz carrier frequency.

Journal ArticleDOI
TL;DR: To the best of the knowledge, this is the first time to employ the combination of partial response shaping and TCM technology in UWOC for high-speed long-reach transmission.
Abstract: In this paper, a joint digital signal processing (DSP) scheme including partial response shaping and trellis coded modulation (TCM) technology is proposed to mitigate the bandwidth limitation of the long-reach underwater wireless optical communication (UWOC) system. The similarity of spectral responses between the partial response filter and the communication system is utilized to suppress the enhancement of noise and distortion induced by the full-response feed-forward equalizer. A random interleaver and a precoder are applied to whiten the noise and distortion. In a laboratory experiment, the minimal required received optical power of -29.8 dBm (at a BER of $3.80 \times {10^{ - 3}}$ ) is realized at a data rate of 500 Mbps. In a standard swimming pool, the proposed system successfully achieves a data rate of 500 Mbps with a transmission distance up to 150 m, at which the total attenuation is measured to be 53.47 dB. Such a data rate, enabled by the proposed joint DSP scheme, is 8.0%, 9.2%, and 14.2% higher than those achieved by solely using partial response shaping scheme, TCM scheme, and least square equalization scheme, respectively. To the best of our knowledge, this is the first time to employ the combination of partial response shaping and TCM technology in UWOC for high-speed long-reach transmission.

Journal ArticleDOI
TL;DR: This paper investigates the performance of a hybrid receiver-based simultaneous wireless information and power transfer (SWIPT) two-way relay network over Nakagami-m faded channels and derived analytical expressions of outage probability and asymptotic OP are derived.
Abstract: In this paper, we investigate the performance of a hybrid receiver-based simultaneous wireless information and power transfer (SWIPT) two-way relay network over Nakagami- m faded channels. A hybrid receiver is adopted at the relay node that utilizes both the time switching (TS) and power splitting (PS) protocols for energy harvesting and information transmission. Amplify-and-forward relaying protocol is utilized at the relay node to process the information in half-duplex mode. In the considered network, impact of a practical non-linear power amplifier (NLPA) at the relay node is considered. Selection combining is performed at the destination node to utilize the direct-link and relay assisted signals. For the considered system, the analytical expressions of outage probability (OP) and asymptotic OP are derived over Nakagami- m faded channels for both the integer and non-integer value of m . The analytical expression of the system throughput and energy efficiency of the considered network are also derived. Further, the analytical expression of ergodic capacity is derived in terms of the Meijer-G function. By utilizing a cumulative distribution function based approach, analytical expressions of average symbol error rate (ASER) for general order hexagonal quadrature amplitude modulation (QAM), general order rectangular QAM, and 32-cross QAM schemes are derived. For different QAM constellations, a comparative ASER analysis is also illustrated. Furthermore, the impact of TS factor, PS ratio, energy conversion efficiency, NLPA, and threshold data-rates on the considered network is also highlighted. Finally, Monte-Carlo simulations are performed for validation of the derived analytical expressions.

Journal ArticleDOI
TL;DR: In this article, an effective method of underwater coherent optical wireless communication (UCOWC) with a simplified detection scheme is proposed, which provides a simple and effective approach to take advantage of coherent detection in underwater wireless optical communication, opening a promising path toward the development of practical underwater data transmission requirements on the capacity and transmission distance.
Abstract: In this paper, an effective method of underwater coherent optical wireless communication (UCOWC) with a simplified detection scheme is proposed. The proof-of-concept experiments with M-ary PSK have been conducted with a common laser used for the signal source and local oscillator (LO). The BER performance has been evaluated at different underwater channel attenuations and the maximum achievable attenuation length (AL) with a BER below the forward error correction (FEC) limit of 3.8×10-3 is investigated. The tested system offers data rates of 500 Mbps, 1 Gbps, and 1.5 Gbps with the BPSK, QPSK and 8PSK modulated signals, respectively. The corresponding maximum achievable attenuation lengths are measured as 13.4 AL 12.5 AL, and 10.7 AL. In addition, the performance degradation of the practical system with separate free running lasers for the signal and LO is also estimated. To the best of our knowledge, the UCOWC system is proposed and experimentally studied for the first time. This work provides a simple and effective approach to take advantages of coherent detection in underwater wireless optical communication, opening a promising path toward the development of practical UCOWC with next-generation underwater data transmission requirements on the capacity and transmission distance.

Journal ArticleDOI
TL;DR: 1-D features vector, extracted by projecting a 2-D asynchronous in-phase quadrature histogram (IQH), and the 2D IQH are proposed to achieve OPM in FMF-based network and simulation results show that the proposed 1D projection features vector provides better OPM results than those of the widely used asynchronous amplitude histograms (AAH).
Abstract: This article considers, for the first time, optical performance monitoring (OPM) in few mode fiber (FMF)-based optical networks. 1-D features vector, extracted by projecting a 2-D asynchronous in-phase quadrature histogram (IQH), and the 2D IQH are proposed to achieve OPM in FMF-based network. Three machine learning algorithms are employed for OPM and their performances are compared. These include support vector machine, random forest algorithm, and convolutional neural network. Extensive simulations are conducted to monitor optical to signal ratio (OSNR), chromatic dispersion (CD), and mode coupling (MC) for dual polarization-quadrature phase shift keying (DP-QPSK) at 10, 12, 16, 20, and 28 Gbaud transmission speeds. Besides, M-ary quadrature amplitude modulation (M = 8 and 16) is considered. Also, the OPM accuracy is investigated under different FMF channel conditions including phase noise and polarization mode dispersion. Simulation results show that the proposed 1D projection features vector provides better OPM results than those of the widely used asynchronous amplitude histogram (AAH) features. Furthermore, it has been found that the 2D IQH features outperform the 1D projection features but require larger number of features samples. Additionally, the effect of fiber nonlinearity on the OPM accuracy is investigated. Finally, OPM using the 2D IQH features has been verified experimentally for 10 Gbaud DP-QPSK signal. The obtained results show a good agreement between both simulation and experimental findings.

Journal ArticleDOI
TL;DR: In this article, the efficacy of nonlinearity compensation techniques, including both digital back-propagation and optical phase conjugation, for enhancing achievable information rates in lumped EDFA-and distributed Raman-amplified fully-loaded C-band systems is investigated considering practical transceiver limitations.
Abstract: Achievable information rates of optical communication systems are inherently limited by nonlinear distortions due to the Kerr effect occurred in optical fibres. These nonlinear impairments become more significant for communication systems with larger transmission bandwidths, closer channel spacing and higher-order modulation formats. In this paper, the efficacy of nonlinearity compensation techniques, including both digital back-propagation and optical phase conjugation, for enhancing achievable information rates in lumped EDFA- and distributed Raman-amplified fully-loaded C −band systems is investigated considering practical transceiver limitations. The performance of multiple modulation formats, such as dual-polarisation quadrature phase shift keying (DP-QPSK), dual-polarisation 16 −ary quadrature amplitude modulation (DP-16QAM), DP-64QAM and DP-256QAM, has been studied in C −band systems with different transmission distances. It is found that the capabilities of both nonlinearity compensation techniques for enhancing achievable information rates strongly depend on signal modulation formats as well as target transmission distances.

Journal ArticleDOI
Abstract: We demonstrate a broadband and continuously tunable 1×4 optical beamforming network (OBFN), based on the hybrid integration of indium phosphide (InP) components in the silicon nitride (Si3N4) platform. The photonic integrated circuit (PIC) comprises a hybrid InP-Si3N4 external cavity laser, a pair of InP phase modulators, a Si3N4 optical single-sideband full carrier (SSBFC) filter followed by four tunable optical true time delay lines (OTTDLs), and four InP photodetectors. Each OTTDL consists of eight cascaded thermo-optical micro-ring resonators (MRRs) that impose tunable true time delay on the propagating optical signals. The OBFN-PIC is designed to facilitate the steering of a microwave signal with carrier frequency up to 40 GHz over a continuous set of beam angles. We evaluate the performance of the OBFN-PIC to handle and process microwave signals, measuring the link gain, the noise figure (NF), and the spurious-free dynamic range (SFDR) parameters. Moreover, we assess its beamforming capabilities assuming that the OBFN-PIC is part of a wireless system operating in the downlink direction and feeds a multi-element antenna array. Using microwave signals at 5 and 10 GHz with quadrature amplitude modulation (QAM) formats at 500 Mbaud, we evaluate the performance of the OBFN-PIC under various configurations. We show that error-free performance can be achieved at both operating frequencies and for all the investigated beam angles ranging from 45° to 135°, thus validating its potential for high-quality beamforming performance.

Journal ArticleDOI
TL;DR: In this article, an all-optical aggregation and de-aggregation scheme between one 8-ary quadrature amplitude modulation (8QAM) signal and three binary phase shift keying (BPSK) signals is proposed and theory simulated based on nonlinear effects in high nonlinear fiber (HNLF).
Abstract: An all-optical aggregation and de-aggregation scheme between one 8-ary quadrature amplitude modulation (8QAM) signal and three binary phase shift keying (BPSK) signals is proposed and theory simulated based on nonlinear effects in high nonlinear fiber (HNLF). In this scheme, the input 8QAM signal is de-aggregated into three BPSK signals by deploying self-phase modulation (SPM), cross-phase modulation (XPM), four wave mixing (FWM) and parameter amplification (PA) effect. Firstly, an improved amplitude compression loop (ACL) is designed based on SPM effect to convert 8QAM signal into quadrature phase shift keying (QPSK) signal. A degenerate phase sensitive amplifier (PSA) based on FWM effect is used to decompose QPSK signal into the first two BPSK signals (BPSK-1 and BPSK-2). The third BPSK signal (BPSK-3) can be extracted from the probe light modulated in its phase by the input 8QAM signal thanks to XPM and PA effect. Secondly, BPSK-3 is converted into an atypical on-off keying (OOK) signal through a 1-bit delay interference (DI). BPSK-1 and BPSK-2 are recombined into one QPSK signal through a coupler. Finally, the recombined QPSK signal and the atypical OOK signal are aggregated into one 8QAM signal by using XPM and PA effect. The error vector magnitude (EVM) and bit error ratio (BER) of the 8QAM and BPSK signal before and after de-aggregation and aggregation are calculated to analyse the performance of the scheme. The scheme can be applied in the network node to connect different networks which explore to use 8QAM and BPSK signal respectively.

Journal ArticleDOI
TL;DR: In this paper, the authors present a wideband mmWave receiver front-end that covers the frequency range from 43 to 97 GHz, supporting the operation in the major parts of the V-, E-, and W-bands.
Abstract: This article presents a wideband millimeter-wave (mmWave) receiver front-end that covers the frequency range from 43 to 97 GHz, supporting the operation in the major parts of the V-, E-, and W-bands. The front-end incorporates a passive mixer-first topology to achieve high linearity and wideband performance. The front-end adopts I/Q generation at the RF port, using a coupled-line coupler (CLC), rather than at the local oscillator (LO) port to mitigate the crosstalk of the overlapping I/Q LO signals especially present at high frequencies. The CLC at the RF input facilitates ultrawide band input matching. The front-end implements the multi-gate gm3 cancellation technique at the IF amplifiers to preserve the linearity and provide gain at the IF section. Image rejection capabilities using a current mode transformer-based IF 90° coupler are implemented on chip and demonstrated with measurements. The front-end prototype is fabricated on the GlobalFoundries 22-nm FD-SOI CMOS process and it demonstrates an ultra-wideband performance across the frequency range 43–97 GHz (2.25:1 bandwidth) with image rejection of up to 32 dB, IIP3 of 1.6–5.2 dBm, and gain of 15 dB. The implementation used is low-IF topology with 3.8-GHz IF frequency and 1-GHz bandwidth. Furthermore, the measurement results show that the front-end supports high-speed modulated signals of up to 6-Gbps 64QAM modulation data.

Journal ArticleDOI
TL;DR: A novel topology multi-stage noise-shaping (MASH) delta-sigma modulator is proposed for 20-km digital mobile fronthaul (MFH) in this article and a newly designed feedback unit is combined with a traditional fourth-order sturdy MASH structure to enhance the noise-Shaping capacity.
Abstract: A novel topology multi-stage noise-shaping (MASH) delta-sigma modulator is proposed for 20-km digital mobile fronthaul (MFH) in this article. In the proposed MASH structure, a newly designed feedback unit is combined with a traditional fourth-order sturdy MASH structure to enhance the noise-shaping capacity. The detailed comparison between the conventional fourth-order single delta-sigma modulator (SDSM) and the proposed new topology MASH is presented in a 512/1024 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) transmission system with the bandwidth of 1.125 GHz. The OFDM signal is quantized to two bits by SDSM/MASH analog-to-digital conversion (ADC), and this digitized signal is transmitted over 20-km single mode fiber (SMF) in 20-Gbaud 4-level pulse amplitude modulation (PAM4) intensity modulation direct detection (IM/DD) system. The signal to noise ratios (SNRs) of the retrieved OFDM signal utilizing the proposed new topology MASH and the fourth-order SDSM ADCs are 38.7dB and 34.5dB, respectively. In the case of 1024-QAM PAM4 system, the error vector magnitude (EVM) floors of the proposed new topology MASH and the conventional fourth-order SDSM schemes are 1.64% and 1.96% over 20-km SMF transmission at off-line digital signal processing (DSP) reception, and 1.2 dB receiver sensitivity improvement is achieved.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a data detection algorithm and a corresponding VLSI design for massive multiuser (MU) multiple-input-multiple-output (MIMO) wireless systems.
Abstract: In this article, we propose a novel data detection algorithm and a corresponding VLSI design for massive multiuser (MU) multiple-input–multiple-output (MIMO) wireless systems. Our algorithm uses alternating direction method of multipliers (ADMM)-based infinity-norm-constrained equalization and is called ADMIN. ADMIN is an iterative algorithm that outperforms linear detectors by a large margin when the ratio between the numbers of base-station (BS) and user antennas is small. In the first iteration, ADMIN computes the linear minimum mean-square error (MMSE) solution, which is sufficient when the ratio between the numbers of BS and user antennas is large. We develop time-shared and iterative VLSI architectures for LDL-decomposition-based soft-output ADMIN supporting 16- and 32-user systems. We present application-specific integrated circuit (ASIC) designs for 16–64 antenna base stations in 28-nm CMOS that supports up to 64 quadrature amplitude modulation (QAM). The 16-user ADMIN ASIC achieves 303 Mb/s while dissipating 85 mW. The 32-user ADMIN ASIC achieves 287 and 241 Mb/s while dissipating 121 and 135 mW for 32 and 64 BS antennas, respectively. ADMIN has also been implemented on a Xilinx Virtex-7 field-programmable gate array (FPGA) and is compared with state-of-the-art massive MIMO data detectors.

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TL;DR: In this article, a gradient-free training method based on the cubature Kalman filter was proposed for non-differential channel models and the autoencoder was employed to perform geometric constellation shaping on differentiable communication channels.
Abstract: Training of autoencoders using the back-propagation algorithm is challenging for non-differential channel models or in an experimental environment where gradients cannot be computed. In this paper, we study a gradient–free training method based on the cubature Kalman filter. To numerically validate the method, the autoencoder is employed to perform geometric constellation shaping on differentiable communication channels, showing the same performance as the back-propagation algorithm. Further investigation is done on a non–differentiable communication channel that includes: laser phase noise, additive white Gaussian noise and blind phase search-based phase noise compensation. Our results indicate that the autoencoder can be successfully optimized using the proposed training method to achieve better robustness to residual phase noise with respect to standard constellation schemes such as Quadrature Amplitude Modulation and Iterative Polar Modulation for the considered conditions.

Journal ArticleDOI
TL;DR: In this article, a new rate aware congestion control (RACC) mechanism has been proposed which defines three levels of congestion based on which the data rate, throughput, overhead and the delay.
Abstract: The sensor nodes in wireless sensor networks (WSNs). inherit low processing, shorter range and low power features with the miniature size to offer wireless transmission. Therefore, in order to fulfil the long-time data sensing need, several Quality of Service (QoS) parameters such as: lesser delay, higher throughput and packet delivery ratio (PDR) with minimum overhead must to be improved. In recent years extensive research efforts have been made to ameliorate these parameters to achieve optimum QoS. However, the rate adaptation and congestion control in WSNs are still least explored areas. The traffic congestion in WSNs is the main reason that results in higher delay and low throughput. In this paper, a new rate aware congestion control (RACC) mechanism has been proposed which defines three levels of congestion based on which the data rate, throughput, overhead and the delay. RACC at the transport layer, improves congestion by source rate regulation at the specific hotspot areas. Further, RACC has been applied to different modulation schemes like: 16 QAM (Quadrature Amplitude Modulation), BPSK (Binary Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying) to test the optimum modulation scheme for the proposed approach. The testing is done to ensure the that the data can be sent to the longer distant sensors using appropriate modulation technique suitable for the congestion model (RACC). The simulation outcomes in NS2 tool confirms the improvement of RACC over existing techniques (Delay-aware congestion control protocol (DACC) and Joint energy replenishment and load balancing (J-ERLB)) in WSNs. The overall improvement for RACC over existing techniques follows an improvement percentage 17% for throughput parameter, for packet delivery ratio, it is 8.35%, while for normalized routing overhead it shows 0.56% and for MAC Overhead, average end to end delay, and average remaining energy it shows 0.64%, 2.04% and 59.28% improvement respectively.