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Next generation passive optical networks (NGPONs) are progressing towards future generation optical access network solutions providing eminent bandwidth per user. The main drawback of NGPON based coexisting optical network is that multiple wavelength produces crosstalk as well as not all wavelengths are utilized. The proposed wavelength complements coding based NGPONs use multiple wavelengths to persist sum amplitude to eradicate the amplitude fluctuation convinced crosstalk to legacy NGPON signals. It also leads to no retrofitting as well as no code efficiency. A smooth 16 × 100Gbps hybrid mode division multiplexing and coherent-NGPON (C-NGPON) evolution on the basics of wavelength complement coding is designed and investigated. C-NGPON helps to reduces computational complexity and power consumption constraints. Also, probabilistically shaped quadrature amplitude modulation (PS-QAM) modulation is realized in C-NGPON as a key solution to embrace state-of-the-art coherent transponders. Obtained simulation results indicate that the designed integrated MDM/C-NGPON system can sustains higher 256/512 split ratio in downlink/uplink transmission in contrast the conventional passive optical networks (PONs). Moreover, for legacy PON wavelength coexistence with old as well as PON complement wavelengths, − 19 dBm received power in uplink as well as − 9 dBm in downlink can be attained. A high 20 dB optical to signal noise ratio is attained for PS 512-QAM than uniform-shaped 128 QAM providing low power penalty of 0.5 dB under 0.857 normalized generalized mutual information threshold. Additionally, the design offers a long-haul 250 km range considering 4.8 shaping factor. Eventually, it is depicted that this work realizes superiority over surviving designs with high throughput of 800 Gbps. [ABSTRACT FROM AUTHOR]

The future digital evolution poses challenges that need to be spectral and energy-efficient, as well as highly reliable and resilient. The non-orthogonal multiple access (NOMA) accomplishes massive connectivity, spectral efficiency, effective bandwidth utilization, and low latency. The proposed work involves the code domain NOMA scheme called Sparse Code Multiple Access (SCMA) which provides shaping gain through multi-dimensional constellation and the best performance in terms of bit error rate (BER). It achieves overloading of users through the non-orthogonal allocation of resources which enhances the spectral efficiency and serves more users. The shaping gain can be further improved by reducing the BER and enhancing the capacity of the channel through constellation shaping. This work employs a probabilistic-shaped (PS) constellation where each symbol is transmitted with different probabilities which achieves a reduction of average symbol power and forward error correction (FEC) through channel coding using polar codes which aid in energy efficiency. The output is two-dimensionally spread over Orthogonal Frequency Code Division Multiplexing (OFCDM) subcarriers to achieve a flexible transmission rate through a variable spreading factor. Computer simulations showed better BER performance under AWGN and Rayleigh channels with remarkable gain in SNR which paves the way for future applications in Fifth Generation (5G) beyond networks. [ABSTRACT FROM AUTHOR]

In this work, we present symbol error performance analysis of probabilistic shaping (PS) for wireless communications in noise-limited and fading channels. Two fading models considered are the Rayleigh and log-normal fading channels. The results are corroborated with simulation and compared with the conventional uniformly distributed input symbols. In all channel conditions, PS results in significant reductions in the SNR required to achieve a specific error probability compared to the conventional uniformly shaped symbols. For example, in a noise-limited channel, PS based quadrature amplitude modulation (QAM) signal results in SNR gains of 1.16 dB, 1.41 dB, and 1.52 dB compared to the uniformly distributed QAM symbols at equal entropy rates of 4, 6, and 8 bit/symbol and a symbol error ratio (SER) of $1\times 10^{-3}$ .

In this letter, we propose a novel and straightforward scheme for Q-band (33–50 GHz) millimeter-wave signal generation enabled by a Mach-Zehnder modulator (MZM)-based joint algorithm, which combines probabilistic shaping (PS) and precoding technology, to enhance the anti-interference ability of the transmission system. Based on the proposed scheme, we experimentally demonstrate the generation and transmission of 1.4-Gbaud 46-GHz PS-16-quadrature-amplitude-modulation (PS-16QAM) vector signals, showcasing improved bit-error-ratio (BER) in both standard single-mode fiber (SSMF) and wireless transmission cases. The proposed scheme exhibits a clear advantage in terms of nonlinear interference suppression and satisfies the hard-decision forward-error-correction (HD-FEC) threshold with a BER of 3.8 × 10−3 in radio-over-fiber (RoF) systems.

We experimentally demonstrate the transmission of multiorder quadrature amplitude modulation (QAM) millimeter wave (MMW) orthogonal frequency division (OFDM) signal at 28 GHz radio frequency (RF). To overcome these unfavorable channel properties such as high path loss, propagation loss, rain fading, etc., 5G MMW phased array antenna has been used. Meanwhile, probabilistic shaping (PS) technology is applied to extend transmission distance, and Volterra nonlinearity compensation (VNC) technology is used to alleviate the system nonlinearity. Using 5G MMW phased array antennas and technologies of PS and VNC, 6.72 Gbit/s 1024-QAM OFDM signal at 28 GHz can be transmitted over 55-m wireless distance in our experiment, satisfying the normalized general mutual information (NGMI) threshold of 0.83 with 25% soft-decision forward-error-correction (SD-FEC) overhead. To the best of our knowledge, this is the first time to demonstrate the transmission of multiorder QAM OFDM signal at 28 GHz RF using 5G MMW phased array antenna. [ABSTRACT FROM AUTHOR]

In this work, we study probabilistic shaping (PS) for optical wireless communications and apply the technique to wavelength division multiplexing (WDM) based visible light communication (VLC). The performance of the proposed scheme is validated with an experimental demonstration. The experimental set up uses lenses to collimate the light beam for triple LEDs. The system parameters of the WDM based VLC system are then optimised, the channel response measured, and PS based symbols are allocated to the individual orthogonal frequency division multiplexing (OFDM) subcarriers. For the channel conditions under consideration, PS resulted in a near Shannon capacity transmission rate of 10.81 Gb/s. Comparatively, the PS resulted in 25% higher transmission rate than the widely used adaptive bit-power loading algorithm under the same channel conditions. [ABSTRACT FROM AUTHOR]

We present a probabilistically shaped (PS) time-frequency-packing (TFP) wavelength-division multiplexing superchannel system employing higher order modulation (HoM) formats, with an objective to improve the spectral efficiency (SE). However, TFP systems suffer from inter-symbol interference (ISI) and/or inter-carrier interference (ICI). Additionally, the bandwidth limitations of the wavelength selective switches in the fiber link may cause severe ISI for the edge sub-channels (SCs) in a superchannel. Mitigation of such interferences is particularly challenging for HoM systems, since the implementation of the well-known turbo equalization schemes, such as the Bahl-Cocke-Jelinek-Raviv equalizer, is computationally challenging for larger constellations. In this paper, we investigate an expectation propagation based, computationally efficient, turbo decision feedback equalizer for ISI cancellation, in tandem with a parallel interference cancellation based ICI mitigation. By optimizing the parameters in the shaping and the packing dimensions, we show through our numerical results that the proposed PS-TFP superchannels enabling 1.8 Tbps data rates offer up to 1.05 dB packing gain over an unpacked system using the same modulation format, and a 1.15 dB shaping gain over an unshaped system that uses a lower modulation order to achieve the same SE.

We present a probabilistically shaped (PS) time-frequency-packing (TFP) wavelength-division multiplexing superchannel system employing higher order modulation (HoM) formats, with an objective to improve the spectral efficiency (SE). However, TFP systems suffer from inter-symbol interference (ISI) and/or inter-carrier interference (ICI). Additionally, the bandwidth limitations of the wavelength selective switches in the fiber link may cause severe ISI for the edge sub-channels (SCs) in a superchannel. Mitigation of such interferences is particularly challenging for HoM systems, since the implementation of the well-known turbo equalization schemes, such as the Bahl-Cocke-Jelinek-Raviv equalizer, is computationally challenging for larger constellations. In this paper, we investigate an expectation propagation based, computationally efficient, turbo decision feedback equalizer for ISI cancellation, in tandem with a parallel interference cancellation based ICI mitigation. By optimizing the parameters in the shaping and the packing dimensions, we show through our numerical results that the proposed PS-TFP superchannels enabling 1.8 Tbps data rates offer up to 1.05 dB packing gain over an unpacked system using the same modulation format, and a 1.15 dB shaping gain over an unshaped system that uses a lower modulation order to achieve the same SE. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate the transmission performance of the bit-loading discrete multi-tone (DMT) signal in intensity modulation and direct detection (IM-DD) system with a transmission distance of 2km and a net data rate of 108-Gb/s by two different shaping methods. A detailed comparison between the application of geometric shaping (GS) and probabilistic shaping (PS) in bit-loading DMT is presented. With continuous entropy loading for better channel fitting, probabilistically shaped bit-loading DMT achieves 1-dB receiver sensitivity gain compared to the conventional bit-loading DMT and outperforms geometrically shaped bit-loading DMT in the transmission experiment.

Sparse Code Multiple Access (SCMA) is a promising non-orthogonal multiple access scheme owning to the shaping gain of its multi-dimensional codebook. Most of the existing designs of the codebook are based on geometric shaping (GS), while probabilistic shaping (PS) has important advantages in increasing channel capacity and reducing bit error rate. In this paper, an uplink SCMA codebook optimization algorithm which combines PS and GS is proposed. The algorithm adopts the bare bones particle swarm optimization algorithm based on maximizing the AMI. Based on the non-equiprobable codebook, a message passing algorithm with non-equalprobable distribution is introduced as the multiuser detection algorithm for SCMA scheme. We theoretically analyze the superiority of the codebooks combining PS and GS over others in terms of the average mutual information (AMI). Simulation results show that our proposed codebooks outperform the reference GS based codebooks under different overloading, different channels and different codebook sizes, and with the increase of overloading or codebook sizes, the gains are greater, which is up to 2.1dB gain in terms of block error rate performance. This observation also validates the theoretical analysis based on the AMI.

Research and development of Li-Fi (Light Fidelity) in Internet-of-things (IoT) has created significant interest among researchers. The low-cost version of standard color shift keying (CSK) modulation scheme having single photodetector (PD) at the receiver can become an alternative to on-off keying (OOK) in IoT sensor networks as an M -ary CSK modulation scheme provides log2M times more data rate than that of OOK. This work revolves around optimizing the constellation points of single PD based CSK (CSK-1PD) to achieve a more power-efficient modulation scheme. The optimization has been done with and without average white tone constraint for uniform and non-uniform (exponential, Maxwell-Boltzmann, Pareto) source distributions. The constellation design strategy is based on maximizing the minimum distance among the differently distributed symbols. In the case of non-uniform distributions, the constellations points have been optimized by geometrically shaping the points based on their probabilistic shaping (PS). The optimized constellation points (OCPs) of CSK-1PD without white tone constraint provide higher signal-to-noise ratio (SNR) gain at forward error correction (FEC) limit symbol error rate (SER) as compared with strict white tone constraint. Further, the strict white tone constraint has been relaxed by considering the whole white light region in the CIE 1931 chromaticity diagram as white tone. The OCPs for uniform data with relaxed white tone constraint achieves SNR gain similar to without white tone constraint. However, for probabilistically shaped symbols, the SNR gain achieved from OCPs improves from strict white tone constraint but remains less than the without white tone constraint. A novel method to utilize an additional RGB LED at the transmitter side has been proposed and designed to maintain any white tone light in the white light region without degrading the maximum achieved SNR gain.

A bi-directional photonics-aided millimeter-wave (MMW) transmission system at E-band is proposed in this article, which can be applied in future mobile networks. Only one pair of horn antennas are adopted in the experiment to support symmetrical wireless signal transmission. The center frequency of the downlink and uplink is set as 73.5 and 83.5 GHz, respectively, to avoid the interference effect. Moreover, the probabilistic shaping (PS) technique is used to adapt transmission rate and improve system capacity under a limited SNR. The time-domain Volterra series based equalizer effectively compensates the nonlinear distortion induced by the photoelectric devices. Based on the experimental results, the proposed full-duplex MMW-RoF system can support OFDM truncated PS (TPS)-4096QAM signal transmission, whose entropy is 10 bits/symbol/Hz. We set the probability of the outermost points to zero and the generated TPS-4096QAM signal is actually a PS-1936QAM one. The system simultaneously allows 7 Gbaud TPS-4096QAM signal downlink and uplink transmission over 2 m wireless distance, satisfying the NGMI threshold at 0.83. Moreover, the bi-directional 7 Gbaud PS-1024QAM signal transmission distance can be extended to 13.4 m when we adopt a higher NGMI threshold at 0.67. So the total rate of our proposed bi-directional transmission system is achieved to 100 Gbit/s. We also investigate the BER performance with different modulation formats. Such a system is a promising solution for future high-speed backhaul networks with multiple modulation format requirements. [ABSTRACT FROM AUTHOR]

With the increasing demand of bandwidth, a higher capacity communication system is required for short-reach optical link. Intensity modulation/direct detection (IM-DD) is considered as a reasonable method, due to its low cost and power consumption. In the aspect of digital signal processing (DSP), discrete Fourier transform-spread (DFT-s) precoding can be used to reduce peak to average power ratio (PAPR) and average the noise among the subcarriers. In addition, probabilistic shaping (PS) turns out to further increase the system capacity. We experimentally demonstrated a 200 Gbit/s single λ dual band DMT transmission with a spectrum efficiency (SE) of 6.29 bit/s/Hz. The achievable information rate (AIR) of the proposed dual band signal increases about 30 Gbit/s compared with that of single band signal. Moreover, single-sideband (SSB) signal and signal with guard band are implemented to mitigate the frequency selective fading of optical fiber chromatic dispersion (CD). The performance of these two methods are quite closed for short reach transmission. Considering the signal-signal beat interference (SSBI) introduced by the SSB signal, an extra Volterra filter is applied in DSP. Besides, an extra optical filter is required to generate the SSB signal. [ABSTRACT FROM AUTHOR]

In this letter, a novel physical layer encryption method based on digital chaos is proposed for the security in high-speed intensity modulation and direct detection (IM/DD) discrete multi-tone (DMT) transmission system. In the proposed encryption scheme, a random interleaving method is used, which further enhances the ability to encrypt the quadrature amplitude modulation (QAM) constellation and improves the transmission performance. In addition, probabilistic shaping (PS) technique is also cascaded into the encrypted transmission system for the first time. Adopting the proposed algorithm, we experimentally demonstrated the transmission of 100-Gbit/s encrypted 64QAM and PS-64QAM DMT signals over 2-km standard single-mode fiber (SSMF). [ABSTRACT FROM AUTHOR]

In this article, we analyze the performance of probabilistic shaping (PS) color shift keying (CSK) modulated visible light communication (VLC) systems. Specifically, we have considered three variants of CSK with respect to receiver structure, namely CSK with one photodetector (PD), CSK with three PDs, and CSK with one avalanche PD. For shaping the CSK input symbols, four different source distributions are considered viz., uniform, exponential, Maxwell–Boltzmann, and Pareto. The article comprises of developing algorithms to obtain the optimum probability order for maximizing the received signal-to-noise ratio (SNR) gain. The proposed systems have been analyzed for computational complexity. Furthermore, the closed-form expressions for symbol error rate (SER) have been derived for the proposed PS-CSK schemes. It has been observed that proposed PS-CSK schemes provide different SNR gain for different source distributions at a given SER. The results show that PS based on Pareto distribution gives the best performance gain at unity achievable information rate among all considered source distributions. [ABSTRACT FROM AUTHOR]

In this article, a 5 × 25-GBaud wavelength division multiplexing passive optical network (WDM-PON) is reported and experimentally demonstrated with each channel carrying a low-density parity check- (LDPC-) coded probabilistic shaping 4-ary pulse amplitude modulated signal (PS-PAM4). In such a splitter-based WDM-PON system, 8-point 3-bits/symbol PAM8 is mapped into 4-point PAM4 by adoption of a many-to-one mapping scheme, which enables improved receiver power sensitivity and increased spectral efficiency, compared with the uniformly-distributed PAM4. Different from the typical constant composition distribution matching method for PS, no shaping codes or PS overheads are needed in our PS-PAM4 signal which is to be encoded and decoded in a LDPC-based bit-interleaved coded modulation iterative decoding (BICM-ID) system for the compatibility with the forward error correction (FEC) applied in most of the optical transponders currently. In the BICM-ID system, the extrinsic messages are delivered circularly between the PS de-mapper and the LDPC decoder to deal with PS many-to-one mapping ambiguity. The experimental results strive to make the WDM-PON system better spectrum efficiency, as well as superior receiver power sensitivity and fiber nonlinear effect tolerance, thus maximizing the input power at the optical line terminal and economic efficiency of the system due to ampler loss budget provided for the legacy optical distribution networks. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate the transmission performance of the bit-loading discrete multi-tone (DMT) signal in intensity modulation and direct detection (IM-DD) system with a transmission distance of 2km and a net data rate of 108-Gb/s by two different shaping methods. A detailed comparison between the application of geometric shaping (GS) and probabilistic shaping (PS) in bit-loading DMT is presented. With continuous entropy loading for better channel fitting, probabilistically shaped bit-loading DMT achieves 1-dB receiver sensitivity gain compared to the conventional bit-loading DMT and outperforms geometrically shaped bit-loading DMT in the transmission experiment. [ABSTRACT FROM AUTHOR]

A 5 × 100-Gb/s discrete-Fourier-transform spread (DFT-spread) discrete multi-tone wavelength division multiplexing passive optical network (DMT-WDM-PON) employing low-density parity-check (LDPC) coded probabilistic shaping 16-ary quadrature amplitude modulation (PS-16 QAM) is proposed and experimentally demonstrated. We first introduce PS-16 QAM mapping scheme with 16-point constellation reshaped from 32 symbols into splitter-based DMT-WDM-PON. The DMT-WDM-PON employing PS-16 QAM can achieve superior receiver power sensitivity (RPS) and enhanced spectral efficiency (SE) compared with the unshaped one. Compatible with the forward error correction (FEC) implemented in most of the optical transponders today, an optimized bit-interleaved coded modulation iterative decoding (BICM-ID) system based on LDPC coding is proposed to encode the PS-16 QAM DMT signal without any extra shaping codes or overheads. Then the labeling optimization with the assistance of extrinsic information transfer (EXIT) chart is investigated, in which the extrinsic messages are transferred between the PS demapper and the LDPC decoder for retrieving the PS-16 QAM DMT signal. Furthermore, the experimental results show that 1.5-dB RPS improvement and 2-dB fiber nonlinear effect tolerance enhancement are respectively realized over a 20-km standard single-mode fiber (SSMF) link by using joint applications of DFT-spread scheme and PS-16 QAM mapping in proposed DMT-WDM-PON system, which can thus provide abundant system loss budget for the legacy optical distribution networks (ODNs). [ABSTRACT FROM AUTHOR]

We investigate and compare the performance of star-shaped 16-ary quadrature amplitude modulation (Star-16QAM) and square-shaped 16QAM (Square-16QAM) in the probabilistic shaping (PS) and uniform schemes with coherent detection. With the help of PS technology, the bit error ratio (BER) improvement achieved in the PS-Star-16QAM scheme is greater than that of the PS-Square-16QAM when compared with the uniform schemes in our numerical simulation and experiment. Therefore, the PS-Star-16QAM shows superiority over the PS-Square-16QAM in terms of the BER improvement.

We experimentally demonstrate the photonics-aided wireless transmission of 4 × 4 multiple-input multiple-output probabilistic shaping 64-ary quadrature-amplitude-modulation (PS 64QAM) millimeter-wave signals at D-band (110–170 GHz) over 3.1-m distance with a total bit rate of 1.056 Tb/s and a bit-error ratio under 4 × 10−2. The employment of advanced digital-signal-processing techniques, including probabilistic shaping, the Nyquist shaping, and look-up-table predistortion, significantly improves the transmission capacity and distance as well as the system performance. To the best of our knowledge, this is the first time to realize >1-Tb/s millimeter-wave signal wireless delivery. [ABSTRACT FROM AUTHOR]

As we know, probabilistic shaping (PS), as a typical one of modulation format optimization technologies, becomes a promising technology and attracts more and more attention, because of its higher transmission capacity and lower computation complexity. In this paper, we experimentally demonstrated a reliable 8 Gbaud-rate delivery of polarization multiplexed PS 16-QAM single carrier signal in a MIMO radio-over-fiber system with 20-km SMF-28 wire link and 2.5-m wireless link at 60 GHz. The BER performance of PS 16-QAM signals at different baud rate was also evaluated. What is more, PS 16-QAM was also experimentally compared with uniform 16-QAM, and it can be concluded that PS 16-QAM brings a better compromise between effectiveness and reliability performance and a higher capacity than uniform 16-QAM for the radio-over-fiber system. [ABSTRACT FROM AUTHOR]

• In this paper, a photonic-aided heterodyne coherent detection fiber and W-band MM-wave converged system is experimentally demonstrated. • This is the first time that PS and PE are applied in W-band MMW fronthaul system. • By employing above method, the BER of 8 Gbaud 16-QAM OFDM signal can improve from 1.65 × 10−2 to 4.4 × 10−3 when they are delivered over 25 km SSMF and 4-m wireless. In this paper, an 85 GHz MM-wave signal is demonstrated in the fiber and MM-wave converged system in W-band. It is known to us, this is the first experimental demonstration that the pre-equalizaiton (PE) and probabilistic shaping (PS) techniques are applied to the fiber and MM-wave converged system. BER of 4.4 × 10−3 is achieved by using those method after 4-m wireless transmission and 25-km Standard single mode fiber (SSMF). [ABSTRACT FROM AUTHOR]