Showing papers by "Gee-Kung Chang published in 2020"

Digital Pre- and Post-Equalization for C-Band 112-Gb/s PAM4 Short-Reach Transport Systems

Abstract: Insufficient system bandwidth and chromatic dispersion (CD) of fiber are major limitations for high-speed four-level pulse amplitude modulation (PAM4) direct detection systems. In this article, we investigate C-band 112-Gb/s PAM4 optical transport systems over 10-km and 20-km standard single-mode fiber (SSMF) transmission, which suffers from both bandwidth limitation and CD-induced power fading. Advanced digital signal processing techniques are proposed to handle those channel distortions. At the transmitter, a low-complexity $1+\alpha Z^{-1}$ finite impulse response (FIR) filter coarsely pre-compensates system bandwidth without a preliminary channel estimation. At the receiver, a modified feed-forward equalizer and decision feedback equalizer (FFE-DFE) is employed to compensate residual insufficient bandwidth and CD-induced power fading. Moreover, a novel multi-symbols joint decision is proposed for receiver-side FFE-DFE to mitigate symbol error propagation and correct possible previous error symbols. Experimental results show that the proposed pre-equalization technique exhibits a better transmission performance, which reduces bit error ratio (BER) from $3.3\times 10^{-3}$ to $5.5\times 10^{-4}$ for optical back to back transmission. As for 10-km transmission case, FFE-DFE with 5-symbols joint decision achieves a BER of $7.3\times 10^{-5}$ , which is better than the BER of $1.6\times 10^{-4}$ with ideal error-propagation-free FFE-DFE (EPF-FFE-DFE). Furthermore, for 20-km transmission scenario, FFE-DFE with 8-symbols joint decision achieves a BER of $6.0\times 10^{-4}$ , which is also a superior result than the BER of $9.1\times 10^{-4}$ with EPF-FFE-DFE.

Photonics-Aided Millimeter-Wave Technologies for Extreme Mobile Broadband Communications in 5G

Abstract: To meet the enhanced-mobile-broadband (eMBB) challenges in 5G, we have systematically explored the potential of the photonics-aided millimeter-wave (mm-wave) communication in terms of the wireless transmission capacity and distance it can accommodate. Enabled by various kinds of advanced multiplexing and digital-signal-processing (DSP) techniques, we have successfully achieved the significant enhancement of the wireless mm-wave signal transmission capacity from 100 Gb/s to 400 Gb/s, even to 1 Tb/s. Since our large-capacity (>100-Gb/s) experimental demonstrations typically have a very short wireless transmission distance of several meters, we have further explored the techniques for the extension of the wireless mm-wave signal transmission distance, and successfully achieved a series of field-trial demonstrations on photonics-aided long-distance (>100-m) wireless mm-wave signal transmission. We have realized the record-breaking product of wireless transmission capacity and distance, i.e., 54 Gb/s × 2.5 km.

Key Enabling Technologies for the Post-5G Era: Fully Adaptive, All-Spectra Coordinated Radio Access Network with Function Decoupling

Abstract: With the rapidly growing bandwidth demand for wireless applications, new system technologies related to post-5G are emerging. In this article, an all-spectra fully adaptive and coordinated radio access network (RAN) is reported and discussed. By employing a fiber-wireless integration and networking architecture, all data-carrying channels could be aggregated in the same fiber access infrastructure. This enables a coordinated RAN with function decoupling, in which lower RF, 5G New Radio (NR), sub-THz, and even lightwave are employed; also, different types of services are delivered depending on their physical layer properties. Promising scenarios are discussed, such as integrated access of wireless NR-free space optical (FSO) backhauling and indoor systems via visible light communication (VLC) and efficient NR beamforming aided by VLC positioning system. The former use case can enhance the network throughput and reliability. This is because both FSO and NR can support high channel capacity due to their abundant bandwidth. Meanwhile, with the advancement of novel DSP techniques, the stability of the NR-FSO link under diverse weather turbulences or suffering from burst mode interference can be enhanced. The latter scenario provides an alternative solution for high-speed data link and a simplified beam management via the VLC-aided positioning system. VLC can concurrently provide ubiquitous indoor illumination, data transmission, and positioning. With the help of artificial intelligence algorithms, a VLC-based precision positioning system can provide a location accuracy of less than 1 cm, and it is able to meet the narrow beam size of the NR beamformer in a 3D model. Therefore, it is foreseeable that an all-spectra function decoupled RAN can serve as a unified network platform to support all wireless applications while optimizing system throughput, channel condition, network coverage, and software/ hardware complexity for post-5G mobile data networks.

A Full Field-of-View Self-Steering Beamformer for 5G mm-Wave Fiber-Wireless Mobile Fronthaul

Abstract: The upcoming new radio access allows ultra-high data rate using millimeter-wave (mm-Wave) frequencies, while it normally suffers from large path loss. To compensate for path loss, phased arrays for both the transmitter and receiver are used. The 5G new radio (NR) three beam management process proceeds as follows: The transmitted beam is first swept in the downlink direction from the remote radio unit (RRU) to the user equipment (UE), and then the uplink beam is aligned to determine which beam direction has the best reception quality, and vice versa . However, this sequential beam management requires that the RX must be able to perform both beam detection and steering across all the reception angles. Moreover, due to the narrow beamwidth of the phased array operation, a “quantum leap” performance improvement of the receiver operating at mm-Wave is required. In this article, a self-steering array beamformer (SSA-BF) receiving system is proposed, which is composed of a home-designed IC package with zero DC power consumption and a 4-element antenna array. We first conduct the measurement without the antenna, and the SSA-BF receiver shows a significant array factor enhancement with negligible SNR degradation over full field-of-view (FoV) (incidence angle = ±90°), <3 ms fast beam alignment time, and it can support enhanced mobile data-rate up to 10 and 7.8 Gb/s with 20x100 MHz carrier aggregation OFDM in back-to-back and over 25-km fiber transmission, respectively. Moreover, a broadside 3-dB beamwidth ±80° and broadband 17-36 GHz antenna is designed for the proposed SSA-BF receiver in a 5G fiber-wireless access. The SSA-BF receiving system with the 1 × 4 antenna array is designed at 28 GHz, and it shows the normalized array gain better than 3- and 6-dB degradation over broad FoV incidence = ± 68° and ± 85°, respectively. Without any external tuning controls, the proposed SSA-BF achieves the state-of-the-art autonomous beamforming for 6 Gb/s 64-QAM signal over 50-cm wireless distance, achieving a substantial array factor improvement. To the best of authors’ knowledge, this is the first demonstration of a high-speed switching SSA-BF receiver in a fiber-wireless integrated radio access as a true enabler for mm-Wave mobile fronthaul applications

Unified Performance Analysis of Hybrid FSO/RF System with Diversity Combining

Abstract: Hybrid free space optical (FSO)/radio frequency (RF) systems have been proved to be reliable links for high-data-rate wireless backhauls. In this paper, we present a unified performance analysis of the hybrid FSO/RF transmission system which transmits the identical data in both links and implements two popular diversity combining schemes, namely, selection combining (SC) and maximal ratio combining (MRC), in the receiver. Specially, for the FSO link, the Gamma-Gamma turbulence with pointing errors under heterodyne detection (HD) and intensity modulation/direction detection (IM/DD) is considered in our analysis while the general \k{appa}-{\mu} shadowed fading which unifies popular RF fading models is employed for the analysis of the RF link. As a result, unified closed-form expressions of outage probabilities and average bit error rates for different modulation schemes are derived. Analytical and Monte Carlo simulation results are provided to characterize the performance of the hybrid FSO/RF link which is compared to the single FSO link and the single RF link. The agreement between the analytical and simulation results confirms the unification of various FSO channels and RF fading scenarios into a single closed-form expression.

Delay-aware Cellular Traffic Scheduling with Deep Reinforcement Learning

Abstract: Radio access network (RAN) in 5G is expected to satisfy the stringent delay requirements of a variety of applications. The packet scheduler plays an important role by allocating spectrum resources to user equipments (UEs) at each transmit time interval (TTI). In this paper, we show that optimal scheduling is a challenging combinatorial optimization problem, which is hard to solve within the channel coherence time with conventional optimization methods. Rule-based scheduling methods, on the other hand, are hard to adapt to the time-varying wireless channel conditions and various data request patterns of UEs. Recently, integrating artificial intelligence (AI) into wireless networks has drawn great interest from both academia and industry. In this paper, we incorporate deep reinforcement learning (DRL) into the design of cellular packet scheduling. A delay-aware cell traffic scheduling algorithm is developed to map the observed system state to scheduling decision. Due to the huge state space, a recurrent neural network (RNN) is utilized to approximate the optimal action-policy function. Different from conventional rule-based scheduling methods, the proposed scheme can learn from the interactions with the environment and adaptively choosing the best scheduling decision at each TTI. Simulation results show that the DRL-based packet scheduling can achieve the lowest average delay compared with several conventional approaches. Meanwhile, the UEs’ average queue lengths can also be significantly reduced. The developed method also exhibits great potential in real-time scheduling in delay-sensitive scenarios.

135-GHz D-Band 60-Gbps PAM-8 Wireless Transmission Employing a Joint DNN Equalizer With BP and CMMA

Abstract: In this article, a novel scheme to effectively mitigate the nonlinear impairments in a PAM-8 radio-over-fiber (ROF) delivery is proposed by a joint deep neuron network (J-DNN) equalizer, which has more superiority in terms of good training accuracy, satisfactory tracking speed, and over-fitting suppression compared with a typical deep neuron network (DNN) equalizer. Our proposed J-DNN equalization scheme is mainly based upon back-propagation (BP) algorithm and blind cascaded multi-modulus algorithm (CMMA), which can be trained via two steps including DNN initialization and DNN optimization. By using the proposed J-DNN equalizer, 60-Gbps PAM-8 signal generation and transmission over 10-km SMF and 3-m wireless link at 135-GHz can be achieved. For the digital signal processing (DSP) at receiver, comparisons between CMMA equalizer, DNN equalizer, and J-DNN equalizer are demonstrated. The results indicate that J-DNN equalizer has a much better BER performance in receiver sensitivity than the traditional CMMA, and an improvement of receiver sensitivity can be achieved as much as 1 dB compared with a DNN equalizer at the BER of 3.8 × 10−3. To the best of our knowledge, this is the first time to propose a novel joint DNN equalizer, which is promising for the development in integrated microwave photonics and microwave/millimeter-wave photonics for 5G applications and beyond.

Performance Enhancement of Optical Comb Based Microwave Photonic Filter by Machine Learning Technique

Abstract: Machine learning technique is employed to design a microwave photonic filter (MPF) consisting of an optical comb generator and a phase modulator (PM), to realize centralized management of radio signal delivery in optical networks. The proposed comb generator successfully generates up to 103 optical carriers with adjustable wavelength spacing and number of optical carriers. It exhibits large tunability, flat band response and high tone-to-noise ratio. Thus, the proposed optical comb-based filter is capable to provide flexible tunability with respect to its center frequency and 3-dB bandwidth. In our experimental setup, different wavelength spacing settings and number of optical carriers are fed into the PM for modulation and their corresponding frequency responses are measured by a network analyzer. The experimental data have been analyzed to correlate with the simulation results and theoretical predictions. Besides, a subcarrier multiplexing (SCM) technique can be applied to a multi-user optical system incorporating the proposed filter since its frequency response is varied by the accumulated dispersion. After measuring the characteristic of the proposed filter, a set of frequency responses is collected and fed into the convolutional neural network (CNN) model to obtain the inverse mapping between frequency response to the wavelength spacing and fiber length. As a result, the well-trained model can successfully predict the wavelength spacing and fiber length with high accuracy.

Non-Orthogonal Uplink Services Through Co-Transport of D-RoF/A-RoF in Mobile Fronthaul

Abstract: To efficiently support multiple services with diverse requirements in data capacity, latency, and connectivity in the fifth-generation (5G) communication system and beyond, various mobile fronthaul solutions, including digital and analog radio-over-fiber (RoF), will be considered. We propose a non-orthogonal multiplexing scheme for multiservice uplink transmissions in mobile fronthaul, where in-band analog RoF (A-RoF) signals can be transmitted with digital RoF (D-RoF) signals simultaneously, resulting in high spectrum resource utilization. The demultiplexing is fulfilled by exploiting different characteristics of the D-RoF and A-RoF signals in the time-domain and it can be implemented with analog signal processing, providing low processing complexity and processing delay. The proposed scheme is experimentally demonstrated to achieve the joint transmission of the D-RoF and A-RoF signals over a shared mobile fronthaul through 20-km standard single mode fiber (SSMF). Experimental results show that in-band A-RoF signals from 2–10 GHz can be co-transmitted with D-RoF 10 GBaud NRZ-OOK signals, with the signal-to-interference-plus-noise ratio (SINR) enhanced by the demultiplexing module. Both received D-RoF and A-RoF signals can achieve bit error ratio (BER) lower than the 7% hard-decision forward-error correction (FEC) threshold.

Impact of laser flicker noise and linewidth on 64 to 96 Gbaud/DP-nQAM metro coherent optical links

Abstract: We experimentally investigate the impact of laser flicker noise and linewidth on 64 Gbaud/DP-64QAM, 96 Gbaud/DP-32QAM and 64 or 96 Gbaud/DP-16QAM links. To give a more practical viewpoint, the examined flicker noise closely follows that of an industry forum (OIF 400ZR). We have found that higher modulation order (e.g., 64QAM) is sensitive to phase noise from the linewidth and flicker noise, even in the back to back case. Significant optical signal to noise ratio (OSNR) and cycle slip rate penalties can also be observed with a transmission distance $ {\gt} {200}\;{\rm km}$>200km for both 64QAM and 32QAM signals, which mainly comes from equalization-enhanced phase noise. Moreover, with the increasing of transmission distances, the effective linewidth of a tunable laser with a higher flicker noise and higher linewidth (210 KHz) increases significantly, while it remains unchanged for an external cavity laser (ECL) with 47-kHz linewidth. The result indicates the importance of more stringent flicker noise and linewidth requirement for future ultrabaud rate transmissions.

The Impact of Local Oscillator Frequency Jitter and Laser Linewidth to Ultra High Baud Rate Coherent Systems

Abstract: Through theoretical analysis and simulation, we investigate the system impact due to a sinusoidal jitter tone and the resultant local oscillator (LO) laser linewidth requirement in ultra-high baud rate and long distance coherent optical systems. We also carried out experiments in 64 Gbaud, dual-polarization (DP)-16 QAM systems to verify the theoretical analysis and simulation. We have also obtained a jitter interference tolerance mask to qualify LO lasers. A jitter tone with a frequency lower than ∼1 MHz has a higher tolerance since it generally causes constant frequency or phase shift, which can be tracked by a receiver DSP. For a jitter tone with a frequency higher than ∼1 MHz, the tolerance becomes much tighter since the tone will affect laser lineshape and induce equalizer-enhanced phase noise (EEPN). Consequently, a jitter tone in the higher frequency region could severely affect the system performance. Theoretical analysis and numerical result illustrate that EVM2 due to the effect of laser linewidth and a sinusoidal jitter tone is proportional to the weighted sum of $[ \Delta u \times B_{s}\times \text{L}] $ and $[ \Delta f_{pp}\times B_{s}\times \text{L}] ^{2}$ , where Δν is the laser linewidth, $B_{s}$ is the baud rate, $\Delta f_{pp}$ is the laser peak-to-peak frequency deviation due to a sinusoidal jitter tone, and L is the fiber transmission length. This result is applicable for all orders of QAM constellations. The implication to future 100 Gbaud and beyond systems is delineated.

A Simplified Radio-Over-Fiber System for Over 100-km Long-Reach n-QAM Transmission

Abstract: A simplified and cost-effective architecture is proposed and experimentally demonstrated with a millimeter wave (MMW) signal over fiber and free-space wireless transmission. The distributed feedback (DFB) laser is operated in optimized settings after measuring its characteristics and thus the 6 Gbps 64–quadrature amplitude modulation (64-QAM) signal can be successfully transmitted after 20- and 50-km fiber and 1-meter wireless transmission with EVM of 5.98% and 6.87%, respectively. Moreover, the EVM of 10.8% over 100-km long reach is also achieved with the 32-QAM modulation format and data rate of 5 Gbps. The experimental results show that the proposed direct modulation scheme can satisfy applications in metro and rural areas.

D-Band mm-Wave SSB Vector Signal Generation Based on Cascaded Intensity Modulators

Abstract: We proposed and experimentally demonstrated a novel and simple method to realize D-band millimeter-wave (mm-wave) single-sideband (SSB) vector signal generation using cascaded one single-drive Mach-Zehnder modulator (MZM) and one push-pull MZM. After the first MZM driven by a radio frequency (RF) signal of 20-GHz, an optical frequency comb (OFC) with six flat carriers was successfully generated. Using the subsequent push-pull MZM driven by 10-GHz SSB vector signals and a photodiode (PD) for detection, we finally generated D-band SSB vector mm-wave signals at frequencies of 130-GHz and 150-GHz, respectively. The experimental results are well consistent with theoretical and simulation analysis. Based on the proposed scheme, 4-Gbaud generated D-band quadrature phase shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) mm-wave signals were transmitted over 10-km/25-km single-mode-fiber (SMF) and 1-m wireless links. The bit-error-rate (BER) performance can reach less than 7% hard-decision forward-error-correction (FEC) threshold of 3.8 × 10−3.

Combining Efficient Probabilistic Shaping and Deep Neural Network to Mitigate Capacity Crunch in 5G Fronthaul

Abstract: We experimentally demonstrate a capacity-approaching transmission in 5G fronthaul utilizing PS-PAM8 and DNN. An 80-Gb/s over 20-km SSMF transmission performance is realized with a beyond 7.3-dB gross gain over uniform PAM modulations with linear post-equalization.

Experimental Demonstration of C-Band 112-Gb/s PAM4 over 20-km SSMF with Joint Pre- and Post-Equalization

Abstract: We demonstrate C-band 112-Gb/s PAM4 over 20-km transmission with pre- and post-equalization. Pre-filter coarsely pre-compensates system bandwidth at transmitter while FFE-DFE with erasure technology jointly post-compensates residual bandwidth limitation and dispersion-induced power fading at receiver.

Rate Redundancy and Entropy Allocation for PAS-OFDM Based Mobile Fronthaul

Abstract: From the perspective of an experimentalist, we discuss the comparison framework that ensures the same information rate in probabilistic shaping (PS) signals. Theoretically, the information rate can be tuned by adjusting the target entropy, scaling the signal bandwidth and adjusting FEC code rate. In practice, the information rate tuning should be based on the hardware feasibility (e.g., DAC resolution, available analog bandwidth, cost of rate adaptation). Adjusting a constellation entropy rate without considering FEC redundancy will cause an over-estimation of the PS system performance gain. To avoid the over-estimation issue, the modified pre-FEC threshold for PS signal is also proposed to estimate the system performance accurately. The modified pre-FEC threshold is obtained from the FEC code rate of PS signal. Moreover, we experimentally investigated the adaptive entropy allocation scheme in a millimeter-wave analog radio over fiber fronthaul using the modified pre-FEC threshold. By grouping the subcarriers into PS units and using the same QAM order, the proposed scheme can reduce the required data frame length as well as the processing complexity. Notably, this method requires neither dynamic FEC coding rate nor bandwidth adjusting method. Up to 2.5-dB power margins and a smoother pre-FEC performance among PS units are achieved in a frequency selective fading channel. If the modified FEC threshold were not used, it would induce up to 0.7-dB over-estimation in the received sensitivity. This indicates the importance of employing the proposed methods for comparison when FEC is used in combination with PS.

Modulation Format Shifting Scheme for Optical Camera Communication

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

Low-complexity equalizer with a hybrid decision scheme for 50 Gb/s/λ PAM4-PON using a low-cost 10 G receiver.

Abstract: In this Letter, we experimentally demonstrate a 50Gb/s/λ four-level pulse amplitude modulation-based passive optical network system with a 10 G class receiver. A memory polynomial equalizer (MPE) combined with a decision feedback equalizer (DFE) is applied to eliminate channel distortions in the system. To further improve the performance of the MPE-DFE, for the first time, to the best of our knowledge, a low-complexity hybrid decision scheme (HDS) is proposed, which consists of single-symbol decision (SSD) and multi-symbol decision (MSD). The SSD is exactly the conventional hard decision based on minimum Euclidean distance, whereas MSD is based on a simplified maximum likelihood detection principle with M-algorithm. In terms of complexity, MSD requires 19.1% more multiplications than SSD, but the symbol number of MSD only accounts for less than 20% of the total signal frame when the received optical power is greater than -27dBm. Experimental results show that the proposed MPE-DFE with HDS achieves a 0.7 dB and 1.3 dB sensitivity gain compared with conventional SSD, and up to 35.4 dB and 31.4 dB link power budget, regarding the forward error correction threshold of 10-2 and 10-3, respectively.

User-specific power level allocation optimization for OFDM-NOMA in a multi-user RoF system.

Abstract: In this Letter, we propose a digital signal processing (DSP) -aided technique to optimize the power ratio among users for orthogonal frequency division multiplexing (OFDM) -based non-orthogonal multiple access (NOMA) in an integrated optical fiber and millimeter wave (mmWave) wireless communication system. In this way, a central or distributed unit can leverage the proposed techniques to maintain the uniformity of the signal-to-noise ratios (SNRs) among subcarriers without requiring any channel information feedback. The proposed mechanism can facilitate the power allocation management by treating all subcarriers equally as an independent channel. As an illustration, multiple NOMA scenarios, in which a near user with 10 km fiber transmission and far user with either longer fiber distance or additional wireless propagation, are experimentally investigated. Experimental results demonstrate that when the conventional OFDM-NOMA without the proposed DSP-aided technique is used, the optimal power ratios vary rapidly when the subcarrier quality index changes due to high-frequency fading in a mmWave radio over fiber (RoF) system, whereas, by using the proposed techniques, including both orthogonal circulant matrix transform and discrete Fourier transform, the optimal power ratios on all effective subcarriers are optimized at the same level and the users’ performance is significantly improved.

Joint Optimization of Processing Complexity and Rate Allocation through Entropy Tunability for 64-/256-QAM Based Radio Fronthauling with LDPC and PAS-OFDM

Abstract: We experimentally demonstrate LDPC coded PAS-OFDM 64-/256-QAM signals in radio fronthauls. Through entropy allocation by adjusting the complexity and signal bandwidth, tunable power margins gain up to 3 dB and relaxed process latency are achieved.

Entropy Allocation Optimization for PS-OFDM With Constellation Partitioning Based Modeling

Abstract: We propose and experimentally demonstrate an entropy (bits/symbol) allocation scheme for orthogonal frequency division multiplexing (OFDM) signal in a millimeter wave (mmW) over optical fiber fronthaul link. Under the condition of additive white Gaussian noise (AWGN) channel, a closed-form expression between the symbol error rate (SER) of probabilistically shaped quadrature amplitude modulation (QAM) signal and signal-to-noise ratio (SNR) is derived. With a fixed averaged target entropy of the overall signal frame, we use a projected mirror descent algorithm to maximize the averaged SER of the channels based on the pre-measured SNR information. The gradient information is estimated by finite difference using the modeling result. Experimental results in a fiber-mmW converged system validate the proposed method, which allocates more entropy for higher SNR regions compared to a simple scheme that allocates the entropies proportionally based on Shannon's formula. It yields a smoother NGMI and can meet the 0.86 NGMI threshold over the operation frequencies, while uniform QAM signal and Shannon formula based algorithm fails the threshold requirement. Up to 1.8-dB and 0.6-dB received optical power (ROP) gain are achieved as compared with uniform QAM signal and signal with Shannon formula-based allocation, respectively. Compared with the uniform signal, up to 0.7-bits/symbol GMI improvement is also demonstrated.

RF Fading Circumvention using a Polarization Modulator for Supporting W-Band RoF Transport from 85 to 95 GHz

Abstract: RF fading in an RoF system is circumvented by managing the frequency notch through the control of a polarization modulator. W-band signals centralized at 90 GHz with 10GHz operation bandwidth are fully utilized with stable EVM performance.

New radio access technologies for 5G with enhanced network reliability and channel capacity

Abstract: The explosive growth of mobile applications, e.g., ultra-high definition video streaming, virtual reality/augmented reality (VR/AR) wearables, incurs lots of changes in 5G network of its reliability, coverage, transmission throughput and received quality of service (QoS). Therefore, to make 5G a reality, Fiber-Wireless Integration and Networking (FiWIN) is the key architecture in serving such diverse user scenarios, which provides a comprehensive network design for signal delivery. In this paper, some of the great challenges in 5G mobile fronthaul and the possible solutions will be discussed. In particular, we will review the recent breakthroughs in the FiWIN research center of the digitally spreading OFDM, polarization division multiplexing (PDM) radio-over-fiber (RoF), and beamforming enhanced mobile fronthaul. From the network perspective, by employing the 5G new radio and dense small cells deployment, the 5G wireless environment could become sophisticated, and the unexpected interference would cause a significant received performance declination. In this case, a spreading OFDM exhibit a superior received performance over the typical OFDM is considering as a promising signal format. While, the photonic-aided RoF system greatly simplified the 5G small cell hardware design. In order to maintain that beneficial feature, a self-polarization PDM scheme may be applied in mobile fronthaul for increasing the channel capacity and network coverage. The narrow beam-width property of 5G new radio reduces the tolerance of antenna misalignment. To address such issue, we will present the future-proof experiment of the fiber-wireless integration network with a 1-by-4 beamforming receiver with full reception angles (±90o) and signal waveforms transparency.

Demonstration of Pattern Division Multiple Access With Message Passing Algorithm for Multi-Channel mmWave Uplinks via RoF Mobile Fronthaul

Abstract: Orthogonal multiple access (OMA) such as orthogonal frequency division multiple access (OFDMA) has been the predominant access technology adopted by the current generation of mobile communication Representing an evolutionary step in radio access networks, non-orthogonal multiple access (NOMA) is considered to be a promising technology to meet the goals of increased capacity, enhanced flexibility, and reduced latency Pattern division multiple access (PDMA) is a NOMA scheme using resource-element mapping as the multiple-access signature in the symbol level This article introduces PDMA in a millimeter-wave (mmWave) radio access system with systematic experimental demonstration One key advantage of PDMA is that it can facilitate advanced parallel interference cancellation (PIC) in the decoding process A message passing algorithm (MPA) is developed and implemented in this article to enhance the decoding performance of PDMA A novel PDMA system integrated with MPA is experimentally demonstrated in a multi-user mmWave radio access system that uses radio-over-fiber (RoF) mobile fronthaul, achieving reduced sensitivity penalty and improved modulation spectral efficiency compared to conventional power-domain NOMA (PD-NOMA) with successive interference cancellation (SIC) Experimental results show that PDMA is capable of supporting disparate channel conditions, adapting to various patterns, and providing improved system flexibility

Intelligent Bandwidth Allocation for Latency Management in NG-EPON using Reinforcement Learning Method

Abstract: A novel intelligent bandwidth allocation scheme in NG-EPON using reinforcement learning is proposed and demonstrated for latency management. The capability of the proposed scheme is verified under both fixed and dynamic traffic loads.

Unified Performance Analysis of Hybrid FSO/RF System With Diversity Combining

Abstract: Hybrid free space optical (FSO)/radio frequency (RF) systems have been proved to be reliable for high-data-rate wireless backhauls. In this article, we present a unified performance analysis of the hybrid FSO/RF transmission system which transmits identical data in both links and implements two popular diversity combining schemes, namely, selection combining (SC) and maximal ratio combining (MRC), in the receiver. Specially, for the FSO link, the Gamma-Gamma turbulence with pointing errors under heterodyne detection (HD) and intensity modulation/direction detection (IM/DD) is considered in our analysis while the general κ - μ shadowed fading which unifies popular RF fading models is employed for the analysis of the RF link. As a result, unified closed-form expressions of outage probabilities and average bit error rates for different modulation schemes are derived. A preliminary extension of the RF link to multi-input–multi-output (MIMO) transmission is also analyzed. Analytical and Monte Carlo simulation results are provided to characterize the performance of the hybrid FSO/RF link which is compared to the single FSO link and the single RF link. The agreement between the analytical and simulation results confirms the unification of various FSO channels and RF fading scenarios into a single closed-form expression.

Hybrid W-Band/Baseband Transmission for Fixed-Mobile Convergence Supported by Heterodyne Detection with Data-Carrying Local Oscillator

Abstract: A novel architecture with data-carrying local oscillator was proposed and demonstrated, supporting co-transmission of 35.39-Gbps W-band OFDM at 85-GHz and 10.9-Gbps OOK signals. Sensitivity penalty induced by interference as low as 0.5 dB was experimentally validated.

Wide FoV Autonomous Beamformer Supporting Multiple Beams and Multi-Band Operation for 5G Mobile Fronthaul

Abstract: An autonomous beamformer covering 24-37 GHz for fiber-wireless network demonstrates multi-beam and multi-band signal transmission with wide-FoV (110o-180o) self-steering beam-tracking/-forming over a 10-km fiber and 56-cm wireless link for future dynamic 5G-NR fronthaul applications.

Optical comb generator with flat-topped spectral response using one electroabsorption-modulated laser and one phase modulator

Abstract: We experimentally demonstrated a novel structure for generating an optical frequency comb source for multicarrier modulation in an optical transmission system. In the proposed scheme, the integration of an electroabsorption-modulated laser cascaded with a phase modulator is employed, both of which are driven and synchronized via a common sinusoidal radio frequency signal. The optimal operating range defined as a spectral flatness with less than 3-dB power fluctuation can be obtained through numerical simulation. Using the proposed scheme, we can achieve 10 flat-topped and frequency-locked optical carriers with a 12.5-GHz frequency spacing. On–off-keying intensity-modulated signals with 3.125 and 12.5 Gb / s are transmitted error-free over 20 km standard single-mode fiber utilizing the proposed optical frequency comb source for an optical wavelength-division multiplexing transmission system.