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Showing papers on "Frequency-division multiplexing published in 2019"


Journal ArticleDOI
TL;DR: This contribution provides guidelines for developing frequency comb sources in coherent fiber-optic communication systems by setting quantitative benchmarks for these characteristics and discussing tradeoffs in terms of transmission reach and achievable data rates.
Abstract: Laser frequency combs with repetition rates on the order of 10 GHz and higher can be used as multi-carrier sources in wavelength-division multiplexing (WDM). They allow replacing tens of tunable continuous-wave lasers by a single laser source. In addition, the comb's line spacing stability and broadband phase coherence enable signal processing beyond what is possible with an array of independent lasers. Modern WDM systems operate with advanced modulation formats and coherent receivers. This introduces stringent requirements in terms of signal-to-noise ratio, power per line, and optical linewidth which can be challenging to attain for frequency comb sources. Here, we set quantitative benchmarks for these characteristics and discuss tradeoffs in terms of transmission reach and achievable data rates. We also highlight recent achievements for comb-based superchannels, including >10 Tb/s transmission with extremely high spectral efficiency, and the possibility to significantly simplify the coherent receiver by realizing joint digital signal processing. We finally discuss advances with microresonator frequency combs and compare their performance in terms of flatness and conversion efficiency against state-of-the-art electro-optic frequency comb generators. This contribution provides guidelines for developing frequency comb sources in coherent fiber-optic communication systems.

82 citations


Journal ArticleDOI
TL;DR: New hybrid precoding schemes for the downlink transmission in a multiuser millimeter wave (mmWave) system over frequency selective channels are proposed and the correlation of subchannels is exploited to profoundly reduce the computational complexity.
Abstract: We propose new hybrid precoding schemes for the downlink transmission in a multiuser millimeter wave (mmWave) system over frequency selective channels. In the system, the multiantenna base station employs the fully connected architecture and uses orthogonal frequency-division multiplexing to serve multiple mobile users. We first propose an alternating minimization based hybrid precoding scheme by transforming the wideband hybrid precoding problem to a narrowband hybrid precoding problem. We then propose a beamforming-based hybrid precoding scheme by exploiting the correlation of subchannels to profoundly reduce the computational complexity. Numerical results are presented to demonstrate the advantages of our proposed schemes relative to two existing schemes, as well as to examine the impact of system parameters on the achieved performance.

49 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated a dual-polarization NFDM transmission with data modulation on the $b$ -coefficient, and compared the performance of the two polarizations in terms of Q-factor, spectral efficiency and correlation of sub-carriers.
Abstract: There has been much interest in the non-linear frequency-division multiplexing (NFDM) transmission scheme in the optical fiber communication system. Up to date, most of the demonstrated NFDM schemes have employed only single polarization for data transmission. Employing both polarizations can potentially double the data rate of NFDM systems. We investigate in simulation a dual-polarization NFDM transmission with data modulation on the $b$ -coefficient. First, a transformation that facilitates the dual-polarization $b$ -modulation was built upon an existing transformation in [M. Yousefi and X. Yangzhang, “Linear and nonlinear frequency-division multiplexing,” in Proc. Eur. Conf. Opt. Commun. , Dusseldorf, Germany, Sep. 2016, pp. 342-344]. Second, the $q_c$ - and $b$ -modulation for dual polarization were compared in terms of Q -factor, spectral efficiency (SE), and correlation of sub-carriers. The correlation is quantified via information theoretic metrics, joint and individual entropy. The polarization-multiplexed $b$ -modulation system shows 1-dB Q -factor improvement over $q_c$ -modulation system due to a weaker correlation of sub-carriers and less effective noise. Finally, the $b$ -modulation system was optimized for high data rate, achieving a record net data rate of 400 Gb/s (SE of 7.2 b/s/Hz) over $12\times 80$ km of standard single-mode fiber with erbium-doped fiber amplifiers. Based on the aforementioned simulation results, we further point out the drawbacks of our current system and quantify the error introduced by the transceiver algorithms and non-integrability of the channel

44 citations


Journal ArticleDOI
TL;DR: These studies pave the way for the eventual realization of communication across a challenging water-air interface without the need for an interface relay, which is much sought-after for implementing a robust and large-coverage underwater-to-terrestrial internet-of-things.
Abstract: We experimentally demonstrated high-speed diffuse line-of-sight optical wireless communication across a wavy water-air-interface. The testbed channel was evaluated, in terms of data rate, coverage and robustness to the dynamic wave movement, based on the performance of different modulation schemes, including non-return-to-zero on-off keying (NRZ-OOK) and quadrature amplitude modulation (QAM)-orthogonal frequency division multiplexing (OFDM). Under the emulated calm water condition, 8-QAM-OFDM offers a data rate of 111.4 Mbit/s at the aligned position, while only 55 Mbit/s is achieved using NRZ-OOK. On the other hand, effective communication can still be maintained at a high data rate of 11 Mbit/s when the photodetector is off aligned laterally by 5 cm based on NRZ-OOK modulation, leading to a coverage of ~79 cm2. By utilizing OFDM modulation scheme, a data rate of 30 Mbit/s can be achieved up to 2.5-cm misalignment, leading to a coverage of ~20 cm2. Furthermore, in the presence of strong waves (15-mm wave height, causing a scintillation index of 0.667), 4-QAM-OFDM modulation showed a better resilience to channel instability than NRZ-OOK modulation. Our studies pave the way for the eventual realization of communication across a challenging water-air interface without the need for an interface relay, which is much sought-after for implementing a robust and large-coverage underwater-to-terrestrial internet-of-things.

40 citations


Journal ArticleDOI
TL;DR: A MIMO-OFDM approach based on random frequency- and time-division multiplexing is presented, enhanced by a multidimensional compressed sensing method that utilizes the information of multiple channels.
Abstract: In many applications, the direction of arrival information of the radar signal plays a decisive role in target localization. A multiple-input multiple-output (MIMO) radar allows to obtain the position of an object in space within one measurement frame. Recent research and publications verify the high potential of digital radar principles such as orthogonal frequency-division multiplexing (OFDM). In this letter, a MIMO-OFDM approach based on random frequency- and time-division multiplexing is presented. It is enhanced by a multidimensional compressed sensing method that utilizes the information of multiple channels. The approach is validated and compared to other MIMO-OFDM approaches using measurements of an experimental radar at 72.5 GHz.

39 citations


Journal ArticleDOI
TL;DR: In this paper, an angle domain carrier frequency offset (CFO) estimation approach was proposed for a downlink orthogonal frequency division multiplexing system from a base station to a high-speed train equipped with fully/partly calibrated massive uniform linear antenna array (ULA) in wireless environments with abundant scatterers.
Abstract: In this paper, we consider a downlink orthogonal frequency division multiplexing system from a base station to a high-speed train equipped with fully/partly calibrated massive uniform linear antenna-array (ULA) in wireless environments with abundant scatterers. Multiple Doppler frequency off- sets (DFOs) stemming from intensive propagation paths together with transceiver oscillator frequency offset (OFO) result in a fast time-varying frequency-selective channel. We develop an angle domain carrier frequency offset (CFO, a general designation for DFO and OFO) estimation approach. A high-resolution beamforming network is designed to separate different DFOs into a set of parallel branches in angle domain such that each branch is mainly affected by a single dominant DFO. Then, a joint estimation algorithm for both maximum DFO and OFO is developed for fully calibrated ULA. Next, its estimation mean square error performance is analyzed under inter-subarray mismatches. To mitigate the detrimental effects of inter-subarray mismatches, we introduce a calibration-oriented beamforming parameter and develop the corresponding modified joint estimation algorithm for partly calibrated ULA. Moreover, the Cramer-Rao lower bound of CFO estimation is derived. Both theoretical and numerical results are provided to corroborate the proposed method.

37 citations


Journal ArticleDOI
TL;DR: The proposed dual-polarization joint modulation schemes enables to exploit all the degrees of freedom for modulation (both polarizations and both spectra) provided by a single-mode fiber.
Abstract: Nonlinear distortion experienced by signals during their propagation through optical fibers strongly limits the throughput of optical communication systems. Recently, a strong research focus has been dedicated to nonlinearity mitigation and compensation techniques. At the same time, a more disruptive approach, the nonlinear Fourier transform, aims at designing signaling schemes more suited to the nonlinear fiber channel. In a short period, impressive results have been reported by modulating either the continuous spectrum or the discrete spectrum. Additionally, very recent works further introduced the opportunity to modulate both spectra for single polarization transmission. Here, we extend the joint modulation scheme to dual-polarization transmission by introducing the framework to construct a dual-polarization optical signal with the desired continuous and discrete spectra. After a brief analysis of the numerical algorithms used to implement the proposed scheme, the first experimental demonstration of dual-polarization joint nonlinear frequency division multiplexing modulation is reported for up to 3200 km of low-loss transmission fiber. The proposed dual-polarization joint modulation schemes enables to exploit all the degrees of freedom for modulation (both polarizations and both spectra) provided by a single-mode fiber.

37 citations


Patent
09 Aug 2019
TL;DR: In this article, a method and apparatus for determining a control resource set for remaining system information in a wireless communication system is provided, where a user equipment (UE) receives a configuration of control resource SET (CORESET) for RMSI via a synchronization signal (SS) block from a network.
Abstract: A method and apparatus for determining a control resource set for system information in a wireless communication system is provided. A user equipment (UE) receives a configuration of control resource set (CORESET) for remaining system information (RMSI) via a synchronization signal (SS) block from a network, and determines the control resource set for the RMSI according to the configuration. The SS block may include a physical broadcast channel (PBCH). A time and frequency location of a common search space (CSS) for the RMSI may be aligned with the SS block by at least one of time division multiplexing (TDM) or frequency division multiplexing (FDM).

31 citations


Journal ArticleDOI
TL;DR: The proposed RoFSO transmission system incorporating 4-QAM modulation demonstrates a successful transmission of 2 × 20 Gbit/s–40 GHz information over 104 km link range under clear weather conditions.
Abstract: This work is focused on the modeling and performance investigation of a 2 × 20 Gbit/s–40 GHz hybrid mode division multiplexing–orthogonal frequency division multiplexing-based radio over free space optics (RoFSO) transmission system under the influence of different weather conditions. The performance of the proposed system has been compared for 4-quadrature amplitude modulation (QAM), differential quadrature phase-shift keying, 16-QAM, and 32-QAM modulation schemes using error vector magnitude, optical signal-to-noise ratio requirement, and maximum link reach as the performance metrics. The results show that 4-QAM scheme demonstrates the best performance. The proposed RoFSO transmission system incorporating 4-QAM modulation demonstrates a successful transmission of 2 × 20 Gbit/s–40 GHz information over 104 km link range under clear weather conditions. Also, the maximum link range using the proposed system is reported as 4.52 km under light fog, 2.78 km under moderate fog, and 2.11 km under heavy fog conditions. Further, the performance of the proposed system has been compared with the previously reported literature which shows that the proposed system has a better figure of merit (information rate × transmission distance). The presented work can be used to implement a spectrum efficient, high-speed, long-haul information transmission system for future wireless networks.

31 citations


Journal ArticleDOI
TL;DR: A novel index-modulated non-orthogonal spectrally efficient frequency-division multiplexing (SEFDM) scheme is proposed, for the sake of reducing the effects of intercarrier interference while benefiting from SEFDM’s increased spectral efficiency.
Abstract: In this letter, we propose a novel index-modulated non-orthogonal spectrally efficient frequency-division multiplexing (SEFDM) scheme, in order to attain a higher bandwidth efficiency than the conventional orthogonal frequency-division multiplexing (OFDM) and SEFDM counterparts. More specifically, the recent index modulation concept is amalgamated with SEFDM, for the sake of reducing the effects of intercarrier interference while benefiting from SEFDM’s increased spectral efficiency. We also formulate a low-complexity log-likelihood ratio-based detection algorithm, which allows the proposed SEFDM to operate in the configuration of an arbitrarily high number of subcarriers. Our simulation results demonstrate that the proposed SEFDM scheme outperforms the conventional SEFDM and OFDM, especially in a low-rate scenario.

30 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed an enhanced OFDM-SNM scheme, which utilizes the flexibility of placing subcarriers to harvest a coding gain in the high SNR region.
Abstract: A novel modulation scheme termed orthogonal frequency-division multiplexing with subcarrier number modulation (OFDM-SNM) has been proposed and regarded as one of the promising candidate modulation schemes for next generation networks. Although OFDM-SNM is capable of having a higher spectral efficiency (SE) than OFDM with index modulation (OFDM-IM) and plain OFDM under certain conditions, its reliability is relatively inferior to these existing schemes, because the number of active subcarriers varies. In this regard, we propose an enhanced OFDM-SNM scheme in this paper, which utilizes the flexibility of placing subcarriers to harvest a coding gain in the high signal-to-noise ratio (SNR) region. In particular, we stipulate a methodology that optimizes the subcarrier activation pattern (SAP) by subcarrier assignment using instantaneous channel state information (CSI) and therefore the subcarriers with higher channel power gains will be granted the priority to be activated, given the number of subcarriers is fixed. We also analyze the proposed enhanced OFDM-SNM system in terms of outage and error performance. The average outage probability and block error rate (BLER) are derived and approximated in closed-form expressions, which are further verified by numerical results generated by Monte Carlo simulations. The high-reliability nature of the enhanced OFDM-SNM makes it a promising candidate for implementing in the Internet of Things (IoT) with stationary machine-type devices (MTDs), which are subject to slow fading and supported by proper power supply.

Proceedings ArticleDOI
22 Apr 2019
TL;DR: This work proposes and analyze a radar communications (RadCom) approach to reduce this mutual interference while simultaneously offering communication functionality, and results indicate that radar interference can be significantly reduced, at no cost in radar accuracy.
Abstract: Commercial automotive radars used today are based on frequency modulated continuous wave signals due to the simple and robust detection method and good accuracy. However, the increase in both the number of radars deployed per vehicle and the number of such vehicles leads to mutual interference, cutting short future plans for autonomous driving and active safety functionality. We propose and analyze a radar communications (RadCom) approach to reduce this mutual interference while simultaneously offering communication functionality. We achieve this by frequency division multiplexing radar and communications, where communications is built on a decentralized carrier sense multiple access protocol and is used to adjust the timing of radar transmissions. Our simulation results indicate that radar interference can be significantly reduced, at no cost in radar accuracy.

Proceedings ArticleDOI
01 Apr 2019
TL;DR: Spect spectral efficiency is compared between OFDM signals, reputed SEF DM signals, and recently proposed RRC-SEFDM and PR- SEFDM signals to show that, at first, the maximum gain is achieved only with simultaneous introducing ISI and increasing the size of signal constellation, but at second, PR-SEfDM signals with optimal spectral pulses provide a significant gain in spectral efficiency.
Abstract: In the paper, we compared spectral efficiency between OFDM signals, reputed SEFDM signals, and recently proposed RRC-SEFDM and PR-SEFDM signals. The last three are different types of signals with non-orthogonal frequency division multiplexing, i.e. signals with intersymbol interference (ISI). All signals were modulated with QPSK and 16-QAM. For signals with ISI demodulation was performed by the suboptimal M-BCJR algorithm with $M=8$ paths survived at each step. For construction PR-SEFDM signals we used optimal spectral pulses with length $L = 12$ taps. The simulation results were shown that, at first, the maximum gain in spectral efficiency is achieved only with simultaneous introducing ISI and increasing the size of signal constellation. At second, PR-SEFDM signals with optimal spectral pulses provide a significant gain in spectral efficiency with respect to SEFDM signals and RRC-SEFDM signals at fixed energy consumptions and fixed complexity of the demodulation algorithm. Also, for QPSK and 16-QAM, with respect to OFDM signals our proposed PR-SEFDM signals provide up to 27% gain in spectral efficiency by additional expenses up to 0.6 and 1.3 dB respectively.

Patent
Akkarakaran Sony1, Luo Tao1
30 Jul 2019
TL;DR: In this article, phase-noise compensation tracking signals (PTRS) are transmitted using sets of resource blocks (RBs), where a frequency for each PTRS within the sets RBs is different from a frequency corresponding to a direct current (DC) tone.
Abstract: Methods, systems, and devices for wireless communication are described. In one example, phase-noise compensation tracking signals (PTRS) may be transmitted using sets of resource blocks (RBs), where a frequency for each PTRS within the sets RBs is different from a frequency corresponding to a direct current (DC) tone. In another example, a time-domain-based PTRS may be used, where a discrete Fourier transform (DFT)-spread-orthogonal frequency division multiplexing (DFT-s-OFDM) symbol may include a cyclic prefix and a PTRS inserted in the DFT-s-OFDM symbol. Additionally or alternatively, a guard-interval-based DFT-s-OFDM symbol may include a PTRS that replaces part or all of a guard interval. In some examples, subsets of tones used for PTRS across a system bandwidth may be transmitted using a scrambled modulation symbol, where at least one antenna port may be used for the transmission of PTRS.

Journal ArticleDOI
TL;DR: An electrical impedance tomography (EIT) system based on frequency division multiplexing (FDM) is proposed for real-time lung physiological imaging that allows the integration of 13 dedicated voltage sensing channels by combining data on-chip and sharing of ADC to alleviate area penalty caused by multi-channel.
Abstract: An electrical impedance tomography (EIT) system based on frequency division multiplexing (FDM) is proposed for real-time lung physiological imaging. The FDM technique allows the integration of 13 dedicated voltage sensing channels by combining data on-chip and sharing of ADC to alleviate area penalty caused by multi-channel. The EIT system-on-chip (SoC) is of the following features. 1) Early I/Q demodulation to relax the bandwidth requirement of analog front end and minimize the impact of motion artifacts and dc electrode offset. 2) Eliminates the need of adaptive gain control with constant inverted “U-shape” gain configuration to compensate amplitude variations across all channels. 3) FDM to combine 13 pairs of I/Q signals into two data streams for quantization using only two ΔΣ modulators. 4) Batch data recovery by Blackman window corrected fast Fourier transform without any digital filtering involved. 5) Lowest power consumption and smallest area occupation per channel reported to date. The EIT SoC occupies an area of 11.28 mm2 in 130-nm CMOS technology with a total power consumption of 1.53 mW under 1-V power supply. As a result, it generates lung EIT images at up to five frames per second.

Journal ArticleDOI
TL;DR: The simulation results surpass the proposed FGIS in giving superior improvement in both bit error rate (BER) and achievable rate ( achievable rate) compared with the state-of-the-art OFDM-LED index modulation schemes.
Abstract: In this letter, we propose a novel, fully generalized index-spatial (FGIS) light emitting diode (LED) modulation scheme for the optical MIMO-orthogonal frequency division multiplexing (OFDM) system. The fully generalized index-spatial (FGIS) is a spectrally efficient (SE) visible light communication (VLC) modulation scheme in which the LED indices are exploited in an innovative way to address, not only the OFDM signal time/frequency domain shaping problem but also to provide an additional spatial modulation (SM) domain. Compared to recent OFDM-LED index modulation schemes, FGIS achieves higher SE with lower number of LEDs. The simulation results surpass the proposed FGIS in giving superior improvement in both bit error rate (BER) and achievable rate ( $R$ ) compared with the state-of-the-art OFDM-LED index modulation schemes.

Journal ArticleDOI
TL;DR: The presented magnetic structure constitutes a prototype design of a passive circuit enabling frequency‐division multiplexing (FDM) in magnonic logic networks, verified that spin‐wave signals of different frequencies can be transmitted through the device simultaneously without any interaction or creation of spurious signals.
Abstract: Wave-based data processing by spin waves and their quanta, magnons, is a promising technique to overcome the challenges which CMOS-based logic networks are facing nowadays. The advantage of these quasi-particles lies in their potential for the realization of energy efficient devices on the micro- to nanometer scale due to their charge-less propagation in magnetic materials. In this paper, the frequency dependence of the propagation direction of caustic-like spin-wave beams in microstructured ferromagnets is studied by micromagnetic simulations. Based on the observed alteration of the propagation angle, an approach to spatially combine and separate spin-wave signals of different frequencies is demonstrated. The presented magnetic structure constitutes a prototype design of a passive circuit enabling frequency-division multiplexing in magnonic logic networks. It is verified that spin-wave signals of different frequencies can be transmitted through the device simultaneously without any interaction or creation of spurious signals. Due to the wave-based approach of computing in magnonic networks, the technique of frequency-division multiplexing can be the basis for parallel data processing in single magnonic devices, enabling the multiplication of the data throughput.

Journal ArticleDOI
TL;DR: The value iteration algorithm is used to find an asymptotically optimal energy harvesting and information transmission policy to optimize the long-term throughput and it is demonstrated that the proposed method outperforms the heuristic greedy method.
Abstract: This paper studies a wireless-powered sensor network, where a sensor harvests energy from a dedicated radio-frequency (RF) energy source and transmits information to an information sink using the harvested energy. Two working modes are considered; One is the frequency division multiplexing (FDM) mode in which the sensor harvests RF energy and transmits information simultaneously over orthogonal frequency bands. The other is the time division multiplexing (TDM) mode in which energy harvesting and information transmission are implemented in the same frequency band but in different time slots. The energy harvesting channel and the information transmission channel are assumed to follow the Rician and the Rayleigh distributions, respectively, and are discretized and modeled as finite-state Markov chains. We formulate the process of energy harvesting and information transmission as an infinite-horizon discounted Markov decision process. The value iteration algorithm is used to find an asymptotically optimal energy harvesting and information transmission policy to optimize the long-term throughput. In the asymptotically optimal policy of the FDM mode, the energy transmitted from the sensor in one slot is proved to be non-decreasing with the battery state of the sensor. By contrast, such monotonicity between the transmitted energy and the battery state does not exist in the asymptotically optimal policy in the TDM mode. Simulation results verify the above findings and demonstrate that the proposed method outperforms the heuristic greedy method.

Journal ArticleDOI
TL;DR: In this article, the authors jointly address user scheduling and precoder/combiner design in the downlink of a wideband millimeter-wave communications system, and propose an algorithmic solution based on the linear successive allocation, which greedily allocates streams to different users and computes the corresponding precoders and combiners.
Abstract: This paper jointly addresses user scheduling and precoder/combiner design in the downlink of a wideband millimeter-wave communications system. We consider the orthogonal frequency-division multiplexing modulation to overcome the channel frequency selectivity and obtain a number of equivalent narrowband channels. Hence, the main challenge is that the analog preprocessing network is frequency flat and common to all the users at the transmitter side. Moreover, the effect of the signal bandwidth over the uniform linear array steering vectors has to be taken into account to design the hybrid precoders and combiners. The proposed algorithmic solution is based on the linear successive allocation, which greedily allocates streams to different users and computes the corresponding precoders and combiners. By taking into account the rank limitations imposed by the hardware at transmission and reception, the performance loss in terms of achievable sum rate for the hybrid approach is negligible. The numerical experiments show that the proposed method exhibits excellent performance with reasonable computational complexity.

Journal ArticleDOI
TL;DR: The proposed superresolution, yet low-complexity method for compensating for motion-induced Doppler frequency offset in multicarrier acoustic communication systems based on orthogonal frequency-division multiplexing (OFDM) provides excellent performance at low computational cost.
Abstract: This paper addresses the problem of compensating for motion-induced Doppler frequency offset in multicarrier acoustic communication systems based on orthogonal frequency-division multiplexing (OFDM). In mobile acoustic systems, Doppler effect can be severe enough that the received OFDM signal experiences nonnegligible frequency offsets even after initial resampling. To target these offsets, a superresolution, yet low-complexity method based on a stochastic gradient approach is proposed. The method relies on differentially coherent detection that keeps the receiver complexity at a minimum and requires only a small pilot overhead. Differential encoding is applied across carriers, promoting the use of a large number of closely spaced carriers within a given bandwidth. This approach simultaneously supports frequency-domain coherence and efficient use of bandwidth for achieving high bit rates. While frequency synchronization capitalizes on differentially coherent detection, it can also be used as a preprocessing stage in coherent receivers without creating undue complexity. Using simulation, as well as the experimental data transmitted over a 3–7-km shallow-water channel in the 10.5–15.5-kHz acoustic band, we study the system performance in terms of data detection mean squared error and bit error rate, and show that the proposed method provides excellent performance at low computational cost. Such advantages are of paramount importance for practical implementation of high data rate acoustic OFDM systems.

Journal ArticleDOI
TL;DR: 10 Gbps 32-QAM-OFDM/FBMC/UFMC/GFDM system performance for high-layer split ultra-DWDM-PON-based fronthaul using a radio-over-fiber technique and the crosstalk interference between two adjacent channels of the same modulation scheme, as a function of their electrical frequency span for downlink application is evaluated.
Abstract: The current constant growth in mobile networks’ traffic demands caused by the popularization of cloud and streaming services on personal devices, requires architectural changes so as to fulfill all new 5G mobile network requirements. Cloud access radio network (C-RAN) architecture in combination with the massive deployment of small cell antenna sites have recently been proposed as a promising solution but will be demanding for high-capacity mobile fronthaul links. An efficient way for performing that connectivity is to make use of the dense wavelength multiplexing passive optical network (DWDM-PON) infrastructure. In this context, orthogonal frequency division multiplexing (OFDM) has been extensively explored as a potential candidate. Nevertheless, the main drawback of OFDM is its high out-of-band radiation. In order to overcome that drawback, new 5G multicarrier waveforms (FBMC, UFMC, and GFDM) have recently been proposed. In this paper, we experimentally assess and compare 10 Gbps 32-QAM-OFDM/FBMC/UFMC/GFDM system performance for high-layer split ultra-DWDM-PON-based fronthaul using a radio-over-fiber technique. The performance has been done in terms of spectral efficiency, peak-to-average power ratio, spectral density, and receiver sensitivity. In particular, intensity-modulation with direct-detection and quasi-coherent-detection have been considered. In order to improve the multicarrier system energy efficiency, the effect of using a hard clipping technique over transmitted signals is also studied. Finally, we evaluated the crosstalk interference between two adjacent channels of the same modulation scheme, as a function of their electrical frequency span for downlink application.

Journal ArticleDOI
TL;DR: The issue of the phase and amplitude mismatches at the virtual array elements due to the scalable radar architecture is addressed and a calibration solution is introduced in this article.
Abstract: A scalable four-channel multiple-input multiple-output (MIMO) radar that features a modular system architecture and a novel frequency-division multiplexing approach is presented in this article. It includes a single 30-GHz voltage-controlled oscillator (VCO) for the local oscillator signal generation, four cascaded 120-GHz transceivers with a frequency quadrupler, and on-board differential series-fed patch antennas. The utilized uniform antenna configuration results in 16 virtual array elements and enables an angular resolution of 6.2°. The vector modulators in the transmit (TX) paths allow the application of complex bit streams of second-order delta–sigma modulators easily generated on a field-programmable gate array (FPGA) to implement single-sideband (SSB) modulation on the TX signals resulting in orthogonal waveforms for the MIMO operation. Only one phase-locked loop and no digital-to-analog converter is required. The waveform diversity also allows the simultaneous transmission of the TX signals to reduce the measurement time. The application of the SSB modulation on the frequency-modulated continuous-wave MIMO radar requires only half of the intermediate frequency bandwidth compared with the double-sideband modulation. The issue of the phase and amplitude mismatches at the virtual array elements due to the scalable radar architecture is addressed and a calibration solution is introduced in this article. Radar measurements using different numbers of virtual array elements were compared and the digital-beamforming method was applied to the results to create 2-D images.

Journal ArticleDOI
TL;DR: Generalized space–time–frequency index modulation is proposed for conveying extra information with the aid of the space, time, and frequency indices and is capable of providing higher transmission rate than the classic OFDM-based GSTSK.
Abstract: Generalized space–time–frequency index modulation (GSTFIM) is proposed for conveying extra information with the aid of the space, time, and frequency indices. GSTFIM subsumes the concept of generalized space–time shift keying (GSTSK), which flexibly activates $Q^{\prime }$ out of $Q$ dispersion matrices, and the orthogonal frequency-division multiplexing (OFDM) with index modulation. The transceiver architecture of the proposed GSTFIM is outlined. GSTFIM is capable of providing higher transmission rate than the classic OFDM-based GSTSK. It also outperforms the classic OFDM-aided GSTSK in terms of the bit-error-probability.

Journal ArticleDOI
TL;DR: In this article, a dual-polarization joint nonlinear frequency division multiplexing (NFDM) modulation scheme was proposed to exploit all the degrees of freedom for modulation (both polarizations and both spectra) provided by a singlemode fiber.
Abstract: Nonlinear distortion experienced by signals during their propagation through optical fibers strongly limits the throughput of optical communication systems. Recently, a strong research focus has been dedicated to nonlinearity mitigation and compensation techniques. At the same time, a more disruptive approach, the nonlinear Fourier transform (NFT), aims at designing signaling schemes more suited to the nonlinear fiber channel. In a short period, impressive results have been reported by modulating either the continuous spectrum or the discrete spectrum. Additionally, very recent works further introduced the opportunity to modulate both spectra for single polarization transmission. Here, we extend the joint modulation scheme to dual-polarization transmission by introducing the framework to construct a dual-polarization optical signal with the desired continuous and discrete spectra. After a brief analysis of the numerical algorithms used to implement the proposed scheme, the first experimental demonstration of dual-polarization joint nonlinear frequency division multiplexing (NFDM) modulation is reported for up to 3200 km of low-loss transmission fiber. The proposed dual-polarization joint modulation schemes enables to exploit all the degrees of freedom for modulation (both polarizations and both spectra) provided by a single-mode fiber (SMF).

Journal ArticleDOI
TL;DR: By introducing full-duplex relaying, this paper is able to achieve a higher end-to-end capacity, as long as the power of the residual self-interference can be mitigated to an appropriate level.
Abstract: In this paper, we propose a full-duplex relay-assisted orthogonal frequency-division multiplexing (OFDM) with index modulation system, in which a complete transmission from source to destination is forwarded by a full-duplex decode-and-forward relay. By introducing full-duplex relaying, we are able to achieve a higher end-to-end capacity, as long as the power of the residual self-interference can be mitigated to an appropriate level. To investigate the proposed system, we assume that the maximum-likelihood detection is adopted at both relay and destination for decoding the received OFDM block. Then, we derive or approximate the average outage probability, block error rate, and end-to-end capacity in a closed form. All analyses are verified by numerical results generated by Monte Carlo simulations and comparisons between half-duplex and full-duplex relaying schemes are also provided to show the performance superiority of the proposed system.

Journal ArticleDOI
TL;DR: When multiple physical layer pipes are used, the feasibility of the implementation and memory use aspects are discussed, and the performance analysis in comparison with other multiplexing techniques that ATSC 3.0 offers is shown.
Abstract: This paper presents implementation and memory use aspects for layered division multiplexing (LDM) technology defined in the next generation terrestrial broadcast standard, called advanced television systems committee (ATSC) 3.0. As LDM becomes a new method that combines multiple broadcast contents, its practical considerations on transmitter and receiver implementations as well as memory usages are described in this paper. When multiple physical layer pipes are used, the feasibility of the implementation and memory use aspects are discussed, and the performance analysis in comparison with other multiplexing techniques that ATSC 3.0 offers is shown.

Journal ArticleDOI
TL;DR: In this paper, a unified data communication and radar sensing system for mm-wave applications with extended coverage is proposed and experimentally demonstrated, in which the superheterodyne optical carrier suppression (HeteroOCS) is used to up-convert the intermediate frequency (IF) OFDM signal to the mm wave band in the central office (CO).
Abstract: A unified data communication and radar sensing system towards millimeter-wave (mm-wave) applications with extended coverage is proposed and experimentally demonstrated. In the unified system, the transmission and reception of mm-wave signals are implemented by microwave photonics technologies, and the orthogonal frequency division multiplexing (OFDM) signal is employed for communications and radar sensing simultaneously. The superheterodyne optical carrier suppression (HeteroOCS) is used to up-convert the intermediate frequency (IF) OFDM signal to the mm-wave band in the central office (CO). The optical mm-wave signal is transmitted to the remote antenna units (RAUs) via optical fibers. The echo signal is received by the RAU which is remotely connected to the CO by an analog photonic link based on a polarization modulator (PolM). In the transmitter and receiver links, the chromatic dispersion of optical fibers is overcome by the HeteroOCS and the PolM, respectively. The baseband units (BBU) centralized in the CO is used to process the radar sensing signal. A pre-delayed trigger signal is proposed to overcome the fiber length limitation. A proof-of-concept experiment is performed. Two targets with distances of 1.64 m and 3.40 m are successfully detected separately. The communication function of the system is also verified. 1 m wireless transmission of 1.56 Gb/s data rate is achieved below the forward error correction limit.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the peak-to-average power ratio (PAPR) problem in orthogonal frequency-division multiplexing systems and proposed an efficient PAPR reduction technique, where clipping noise can be flexibly controlled and filtered inside the transmitter passband, allowing to control the transmitted signal quality per PRB.
Abstract: In this correspondence paper, we study the peak-to-average power ratio (PAPR) problem in orthogonal frequency-division multiplexing systems. In conventional clipping and filtering based PAPR reduction techniques, clipping noise is allowed to spread over the whole active passband, thus degrading the transmit signal quality similarly at all active subcarriers. However, since modern radio networks support frequency multiplexing of users and services with highly different quality-of-service expectations, clipping noise from PAPR reduction should be distributed unequally over the corresponding physical resource blocks (PRBs). To facilitate this, we present an efficient PAPR reduction technique, where clipping noise can be flexibly controlled and filtered inside the transmitter passband, allowing to control the transmitted signal quality per PRB. Numerical results are provided in 5G new radio mobile network context, demonstrating the flexibility and efficiency of the proposed method.

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TL;DR: An Φ-OTDR system based on the ultra-weak fiber Bragg grating array and the frequency-division-multiplexing (FDM) scheme is proposed, which can offer wider FRB as well as the enhanced visibility characteristic.

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TL;DR: It is demonstrated that the correlation among the NFT channels is universal and can be exploited to maximize transmission throughput and proposed noise model showing that end-to-end noise can be modelled as the accumulation of noise associated with each segment of optical communication.
Abstract: There is a fundamental limit on the capacity of fibre optical communication system (Shannon Limit). This limit can be potentially overcome via using Nonlinear Frequency Division Multiplexing. Dealing with noises in these systems is one of the most critical parts in implementing a practical system. In this paper, we discover and characterize the correlations among the NFT channels. It is demonstrated that the correlation is universal (i.e., independent of types of system noises) and can be exploited to maximize transmission throughput. We propose and experimentally confirm a noise model showing that end-to-end noise can be modelled as the accumulation of noise associated with each segment of optical communication which can be dealt with independently. Also, each point noise can be further decomposed into different components, some of which are more significant (and even dominating) than others. Hence, one can further approximate and simplify the noise model by focusing on the significant component.