Paulo Monteiro - Academia.edu (original) (raw)

Papers by Paulo Monteiro

IntechOpen eBooks, Oct 30, 2019

The emerging fifth-generation mobile communications are envisaged to support massive number of de... more The emerging fifth-generation mobile communications are envisaged to support massive number of deployment scenarios based on the respective use case requirements. The requirements can be efficiently attended with ultradense small-cell cloud radio access network (C-RAN) approach. However, the C-RAN architecture imposes stringent requirements on the transport networks. This book chapter presents high-capacity and low-latency optical wired and wireless networking solutions that are capable of attending to the network demands. Meanwhile, with optical communication evolutions, there has been advent of enhanced photonic integrated circuits (PICs). The PICs are capable of offering advantages such as lowpower consumption, high-mechanical stability, low footprint, small dimension, enhanced functionalities, and ease of complex system architectures. Consequently, we exploit the PICs capabilities in designing and developing the physical layer architecture of the second standard of the next-generation passive optical network (NG-PON2) system. Apart from being capable of alleviating the associated losses of the transceiver, the proposed architectures aid in increasing the system power budget. Moreover, its implementation can significantly help in reducing the opticalelectrical-optical conversions issue and the required number of optical connections, which are part of the main problems being faced in the miniaturization of network elements. Additionally, we present simulation results for the model validation.

Digitally Mitigating Doppler Shift in High-Capacity Coherent FSO LEO-to-Earth Links

Journal of Lightwave Technology, Jun 15, 2023

Experimental Transmission of LTE Signal Using Visible Light Communications

In this paper we present an implementation of a Long-Term Evolution (LTE) signal transmission usi... more In this paper we present an implementation of a Long-Term Evolution (LTE) signal transmission using a visible light communications (VLC) setup. VLC is a novel technology that employs off-the-shelf LED lamps to offer high-speed wireless communication, specially at indoor environments, where reportedly the majority of wireless data traffic takes place. By using the optical wireless channel, we manage to transmit downlink LTE signals in distances of up to 3 m, while keeping an EVM lower than the limit compliant.

IEEE Access, 2022

With the rise of 5G and beyond, the ever-increasing data-rates demanded by mobile access are seve... more With the rise of 5G and beyond, the ever-increasing data-rates demanded by mobile access are severely challenging the capacity of optical fronthaul networks. Despite its high reliability and ease of deployment, legacy digital radio-over-fiber (RoF) technologies face an upcoming bandwidth bottleneck in the short term. This has motivated a renewed interest in the development of analog RoF alternatives, owing to their high spectral efficiency. However, unlike its digital counterpart, analog RoF transmission requires a highly linear transceiver to guarantee signal fidelity. Typical solutions exploited in recent research works tend to adopt the use of bulky benchtop components, such as directly modulated lasers (DML) and photodiodes. Although this provides a convenient and quick path for proof-of-concept demonstrations, there is still a considerable gap between lab developments and commercial deployment. Most importantly, a key question arises: can analog-RoF transceivers meet the 5G requirements while being competitive in terms of cost and footprint? Following this challenge, in this work we exploit the use of a low-cost commercial offthe-shelf (COTS) small form-factor pluggable (SFP) transceiver, originally designed for digital transmission at 1 Gbps, which is properly adapted towards analog RoF transmission. Bypassing the digital electronics circuitry of the SFP, while keeping the original transmitter optical sub-assembly (TOSA) and receiver optical sub-assembly (ROSA), we demonstrate that high-performance 5G-compatible transmission can be performed by reusing the key built-in components of current low-cost SFP-class transceivers. Particularly, we demonstrate error vector magnitude (EVM) performances compatible with 5G 64QAM transmission both at 100 MHz and 400 MHz. Furthermore, employing a memory polynomial model for digital pre-distortion of the transmitted signal, we achieve 256QAM-compatible performance at 100 MHz bandwidth, after 20 km fronthaul transmission.

Towards a Converged Optical‐Wireless Fronthaul/Backhaul Solution for 5G Networks and Beyond

Enabling VLC and WiFi Network Technologies and Architectures Toward 5G

Effects of diversity schemes and correlated channels on OWC systems performance

Journal of Modern Optics, Jul 28, 2017

Abstract The salient features and advantages of free-space optical (FSO) system are very appealin... more Abstract The salient features and advantages of free-space optical (FSO) system are very appealing for different applications in a number of communication network sectors. In spite of the advantages and diverse applications of FSO communication, its extensive use is hindered by the atmospheric turbulence-induced fading in real-life scenarios. Spatial diversity technique is one of effective means of mitigating turbulence-induced fading and, consequently, improves the system performance. In this paper, we study the spatial diversity schemes for mitigating turbulence-induced fading in the FSO communication systems using the bit error rate (BER) as a performance metric. The schemes considered are based on orthogonal space–time block codes and repetition codes (RCs). We derive simple approximate closed-form expressions for the error probability of the log-normal FSO links with intensity modulation and direct detection (IM/DD). Furthermore, we also investigate the effects of spatial correlation between the transmit apertures on the system performance. We achieve this using the exponential model for determining the correlations between the apertures. We observe that the proposed BER expressions are able to quantify the effects of spatial diversity schemes and spatial correlations on the system.

Machine learning-aided LiDAR range estimation

Optics Letters, Mar 31, 2023

Automotive light detection and ranging (LiDAR) requires accurate and computationally efficient ra... more Automotive light detection and ranging (LiDAR) requires accurate and computationally efficient range estimation methods. At present, such efficiency is achieved at the cost of curtailing the dynamic range of a LiDAR receiver. In this Letter, we propose using decision tree ensemble machine learning models to overcome such a trade-off. Simple and yet powerful models are developed and proven capable of performing accurate measurements across a 45-dB dynamic range.

Time-Frequency Range Estimation Method for Pulsed LiDAR

IEEE Transactions on Vehicular Technology, Feb 1, 2023

Sub-6 GHz Multi-Band Multi-Carrier Remote Unit Based on RFSoC

In this paper, a flexible Remote Unit (RU) with real-time modulation of 5G-like Orthogonal Freque... more In this paper, a flexible Remote Unit (RU) with real-time modulation of 5G-like Orthogonal Frequency Division Multiplexing (OFDM) signals, capable of transmitting in the sub-6 GHz band, is presented. This architecture is capable of multi-carrier transmission, with the present implementation being able to transmit up to 3 distinct carriers and the overall architecture being only limited by the number of transmission chains implemented. The results show a maximum Error Vector Magnitude (EVM) of 4.7%, with Adjacent Channel Power Ratio (ACPR) above 47 dBc.

Photonic instantaneous frequency measurement system based on complementary E/O modulation

Opto-Electronics and Communications Conference, Jul 4, 2011

ABSTRACT A novel photonic approach to realize the instantaneous microwave frequency measurement w... more ABSTRACT A novel photonic approach to realize the instantaneous microwave frequency measurement with digital output is proposed and demonstrated experimentally. Based on the power fading function of a double-sideband modulated microwave signal transmitting in a dispersive fiber channel, the microwave frequency to digital code mapping can be realized in a multi-channel system where each channel is configured with a predetermined amount of dispersion. The coding process involved here is similar to that of the photonic analog-to-digital conversion. The principle of the system is discussed in detail. An experiment is carried out, in which the frequency identification with 4-bit quantization levels in 17.5 GHz measurement range is demonstrated. The measurement range and the resolution are discussed theoretically and numerically.

Highly Reliable Outdoor 400G FSO Transmission Enabled by ANN Channel Estimation

Optical Fiber Communication Conference (OFC) 2022, 2022

Using an ANN channel estimator, we experimentally demonstrate an outdoor 400G FSO-link with slow-... more Using an ANN channel estimator, we experimentally demonstrate an outdoor 400G FSO-link with slow-fading prediction and compensation. A transmission reliability of more than 99% is obtained after 3-hour BER measurements.

Coherent interference 2R regeneration of Optical CDMA based on MZI SOA

Optical code division multiple access (OCDMA) is attractive for the next-generation broadband mul... more Optical code division multiple access (OCDMA) is attractive for the next-generation broadband multiple access networks due to its beneficial features. These include full asynchronous transmission, low latency access, soft capacity on demand, protocol transparency, ...

Microwave and Optical Technology Letters, 2007

between the CDR and ground plane. This shift in the resonant frequency was about 0.5%. Figure sho... more between the CDR and ground plane. This shift in the resonant frequency was about 0.5%. Figure shows the measured return loss of several antennas. It is clearly seen that proposed antenna has a wider impedance bandwidth. For comparison, the design parameters and corresponding measured data of reference, 1 and proposed antenna is listed in Table . The measured E-and H-plane radiation patterns of the wide aperture-coupled feed CDRA are illustrated in Figure . The pattern were measured at the two resonant mode f ϭ 5.09 and 5.27 GHz. Two resonant modes have similar broadside radiation patterns and this might be because of the symmetry presence of the slot with CDRA. The radiation patterns at the two frequencies do not fully match each other because of different operating modes at the operating frequencies, but these patterns are still good enough for some wireless applications. Additionally, the proposed antenna gain is about 7.9 dBi. A simple design CDRA with wide aperture-coupled for broadband applications has been proposed. This antenna is very simple to design and has the advantage of being able to be printed on a single layer, thus allowing reduced weight and cost. The microstrip feed-line with fork-like tuning stub can provide good impedance matching and bandwidth enhancement. The obtained impedance bandwidth covers the required WLAN bandwidth (5150 -5350 MHz) and the proposed antenna also shows good roadside radiation characteristics.

Multi-Carrier 5G-Compliant DML-Based Transmission Enhanced by Bit and Power Loading

IEEE Photonics Technology Letters, Jun 15, 2020

The introduction of 5G enhanced mobile broadband (eMBB) services has brought unprecedented bit-ra... more The introduction of 5G enhanced mobile broadband (eMBB) services has brought unprecedented bit-rate demands to the optical transport infrastructure, which can hardly be supported through cost-effective digital fronthauling solutions. This opens up a whole new opportunity for bandwidth-efficient radio-over-fiber (RoF) analog fronthaul transmission, which avoids the well-known bandwidth multiplication issue associated with the digitization of radio signals. Using a low-cost directly-modulated laser (DML) with less than 3 GHz bandwidth and a standard PIN photodetector, we demonstrate the transmission of a carrier-aggregated 5G downlink signal over up to 25 km of single-mode fiber (SMF). Resorting to the use of intermediate-frequency-over-fiber (IFoF), we enable the transmission of 5G-compatible signals composed of up to 12 aggregated 400 MHz component carriers (CCs), resulting in a total radio bandwidth of 4.8 GHz, corresponding to >300 Gbps CPRI-equivalent downlink data-rate. 5G-compliant EVM performance across all CCs is achieved through the optimization of power and bit loading between component carriers, enabling an aggregated end user data-rate of 15.6 Gbps.

Optical wireless communication for future broadband access networks

We present experimental results on ergodic channel capacity of single input single output (SISO) ... more We present experimental results on ergodic channel capacity of single input single output (SISO) free-space optical (FSO) communication link. Furthermore, we present simulation results on bit error rate (BER) performance of M-ary quadrature amplitude modulation (M - QAM) considering the average received irradiance. In the simulation, effects of different parameters such as constellation size, wavelength and the refractive index which can be helpful in the adoption of adaptive modulation scheme are analyzed on system performance for different operating conditions.

Optics Communications, May 1, 2017

In this paper, we present experimental results on channel characterization of single input single... more In this paper, we present experimental results on channel characterization of single input single output (SISO) free-space optical (FSO) communication link that is based on channel measurements. The histograms of the FSO channel samples and the log-normal distribution fittings are presented along with the measured scintillation index. Furthermore, we extend our studies to diversity schemes and propose a closed-form expression for determining ergodic channel capacity of multiple input multiple output (MIMO) FSO communication systems over atmospheric turbulence fading channels. The proposed empirical model is based on SISO FSO channel characterization. Also, the scintillation effects on the system performance are analyzed and results for different turbulence conditions are presented. Moreover, we observed that the histograms of the FSO channel samples that we collected from a 1548.51 nm link have good fits with log-normal distributions and the proposed model for MIMO FSO channel capacity is in conformity with the simulation results in terms of normalized mean-square error (NMSE).

Iet Optoelectronics, Aug 1, 2008

The use of return-to-zero (RZ) formats is proposed to enhance the dispersion tolerance of intensi... more The use of return-to-zero (RZ) formats is proposed to enhance the dispersion tolerance of intensitymodulated carrier-unsuppressed (IM-CUs) optical single sideband (oSSB) systems. The performance of these systems, employing electrical dispersion compensation (EDC), is accessed using unipolar and polar RZ signalling formats, and compared with common non-return-to-zero (NRZ). Simulation results at 10.7 Gb/s reveal that oSSB systems with EDC using both NRZ and unipolar RZ signalling formats are limited to low extinction ratio (ER) values. However, the use of polar RZ allows increased ER and transmission distances, because of higher inter-symbol interference tolerance and the absence of discrete spectral tones. Considering a minimum ER of 9 dB and resort to forward error correction schemes, polar RZ allows single-channel error free transmission over 1400 km of standard single-mode fibre, substantially improving the 980 km obtained for NRZ with ER of 6 dB. Dense wavelength-division multiplexing transmission was also assessed, retrieving improved resilience of IM-CUs oSSB polar RZ.

Impact and compensation techniques of laser phase noise in ultra-dense coherent access networks

The purpose of this paper is to provide a performance comparison between two carrier phase recove... more The purpose of this paper is to provide a performance comparison between two carrier phase recovery (CPR) algorithms used to mitigate the impact of the laser phase noise in an ultra-dense wavelength-division multiplexing passive optical network WDM-PON (UDWDM-PON) scenario. The algorithms used in this work are the classic non-data-aided (NDA) phase estimation (PE) algorithm based on Viterbi & Viterbi (V&V) method, and another one based on data-aided (DA) technique which makes use of pilot symbols. The performance of the algorithms is numerically assessed for Quadrature Phase Shift Keying (QPSK) and Differential QPSK (DQPSK) modulations formats. The obtained results show that the linewidths of the optical network unit (ONU) and optical line terminal (OLT) lasers play an important role in the system performance. It is shown that fine laser linewidths ofΔν.Ts = 3×10-4 are required in order to obtain low penalties.

Using time-adaptive probabilistic shaped 64QAM driven by a simple SNR prediction algorithm, we de... more Using time-adaptive probabilistic shaped 64QAM driven by a simple SNR prediction algorithm, we demonstrate >450 Gbps transmission over a 55-m free-space optics link with enhanced resilience towards rainy weather conditions. Through continuous measurement over 3-hours, we demonstrate ∼40 Gbps average bit-rate gain over unsupervised fixed modulation.