Physical Layer Simulations Research Articles

Efficient RMS Delay Spread-Based Physical Layer Abstraction Modelling for Enhanced 5G New Radio Performance Evaluation

Abstract— Nowadays, Fifth Generation-New Radio (5G-NR) is an important research area in telecommunication field. System level studies are essential to evaluate the performance of wireless systems and signaling techniques prior to practical deployment as well as to research purposes. System level studies of wireless systems involve many links between the base station and the user equipment, many modulations and coding schemes and many operation scenarios. Performing system level studies using detailed physical layer simulation using Link Level Simulator (LLS) is impractical and time consuming. Instead, physical layer abstraction models of wireless systems are used in system level studies. Therefore, this paper proposes a physical layer abstraction model for the 5G-NR cellular system following the Effective Signal to Interference plus Noise Ratio (ESINR) approach. The proposed abstraction model uses a novel Exponential ESINR Mapping (EESM) that involves two tunable parameters to model the Physical Downlink Shared Channel (PDSCH) of the 5G-NR system. The proposed model is validated against detailed LLS of the PDSCH. Novel equations are proposed to model the optimum values of the two tunable parameters of the EESM as a function of the RMS delay spread of the wireless channel for different modulation and coding schemes. The obtained results show that the performance - obtained using the proposed EESM abstraction model - is very close to the performance obtained from the detailed LLS. The run time of the abstraction model is independent of the size of the transport block data size. The abstraction model is 10 times faster than the detailed LLS for a transport block size of 3.1 kbits. This factor increases to 153 when the transport block size is increased to 57.376 kbits. The proposed equations for the EESM and its optimum two tunable parameters can be used as an accurate tool to evaluate the Block Error Rate (BER) and the throughput performance of PDSCH in NR wireless system for different environments.

Flexible PON systems enabling optical virtual private network and upstream channel upgrade

With the rapid growth of peer-to-peer (P2P) traffic in the access network, the capability to implement inter-optical network unit (ONU) communication (IOC) has become a fundamental requirement for the underlying passive optical network (PON). The conventional IOC is realized electronically on layer 2 or layer 3 and relies on the transfer operations in the optical line terminal (OLT), thus resulting in high transmission latency and excessive bandwidth consumption. To achieve an efficient IOC, the optical virtual private network (OVPN) is proposed to establish direct optical layer links among ONUs by adding some auxiliary optical components to the existing PON system. However, in previously reported OVPN schemes, the added devices are only used for IOC and cannot fulfill other network functions, which leads to poor flexibility. To improve the reconfigurability of the whole PON system, we present two simple modifications that can not only achieve a high-bandwidth OVPN but also increase the upstream channel capacity. The proposed schemes introduce a new wavelength as the OVPN channel to refrain from changing the physical configuration of the normal upstream and downstream. One scheme retrofits the optical line terminal (OLT) with a fiber Bragg grating (FBG) based reflection module, while the other employs an additional short-length distribution fiber for each ONU to redirect IOC traffic. In both schemes, optical switches (OSWs) are used to control the added OVPN wavelength and the original upstream wavelength so that the two wavelengths can transmit IOC traffic and upstream traffic flexibly. According to the states of OSWs, PON systems will form multiple working modes adapted to different network conditions. To evaluate the improvement in flexibility of wavelength usage, the throughput performances of proposed schemes were analyzed theoretically under varying offered loads and IOC traffic proportions. In addition, the feasibility of both schemes was verified through physical layer simulations, where the optical spectra and bit error rates (BERs) of signals on different wavelengths were investigated.

Impact of wideband wavelength conversion on the performance of optical networks

In this paper, it is proposed and numerically tested a 4 −THz guard-band-less integrated all-optical wavelength converter (iAOWC) with two four-wave mixing (FWM) stages. The nonlinear media used in each stage is a waveguide with a tellurite core that is buried into a SiO2 substrate. The core is shaped as two interleaved spirals connected in their centers by two arcs of a circle to minimize bend loss. The iAOWC can continuously shift a 4 −THz WDM bandwidth from the C- to the L-band and vice versa. In the physical layer simulations, 80×28−GBaud, as DP-QPSK and DP-16QAM, 50-GHz-WDM signals were propagated, respectively, through typical distances found in ultra-long-haul and long-haul transmission systems. For up to four wavelength conversions, the penalties imposed on the signals bit-error-ratios by the iAOWCs were negligible. In the network layer simulations, blocking probabilities were estimated in the CORONET and PANEUR topologies supposing an incremental traffic scenario. Physical layer results were fundamental for the parameters (route lengths, wideband conversion, and spectral shift) considered in the network layer analysis. All network links could carry up to 160 wavelengths that extended from C- to L-band. It is shown that by using an iAOWC with bandwidth of 4-THz instead of 1-THz, both with the same spectral shift capability, to match the blocking probabilities achieved with OEOWCs, this would lead to a reduction of 50% and 40% in the number of required devices for the CORONET and PANEUR topologies, respectively. Finally, this is the first time that it is reported a joint analysis of the physical and network layers regarding the impact of wideband wavelength conversion on the performance of optical networks, specially using an integrated all-optical device and under real-world traffic scenarios.

Spectral Efficiency Evaluation of an NR-Based 5G Terrestrial Broadcast System for Fixed Reception

LTE-based 5G terrestrial broadcasting, standardized in 3GPP Release 16, allows broadcasters to reach cellular devices. In this paper, toward the development of a future terrestrial broadcast system in Release 18 or later called 5G-Advanced, a specification for New Radio (NR) based 5G terrestrial broadcasting is presented for a 6 MHz-channel raster, which is used in current digital terrestrial television broadcasting. The transmission performance is evaluated in physical layer simulations. In particular, the spectral efficiency is evaluated and compared with a second-generation DTTB system at a required carrier-to-noise ratio (CNR) of 20 dB in a fixed-reception scenario with a rooftop receiving antenna. The evaluation in an additive white Gaussian noise channel indicates that the spectral efficiency of NR-based 5G terrestrial broadcasting can be improved by 0.83 (bps/Hz) by enhancing the code length of low density parity check code, the carrier modulation scheme, guard band ratio, and cyclic prefix ratio from what available so far in Release 16. Furthermore, when frequency interleaving is incorporated, the spectral efficiency is increased by 0.75 (bps/Hz) in a short echo channel with a desired-to-undesired signal power ratio of 0 dB. The introduction of time interleaving increases spectral efficiency by 0.97 (bps/Hz) in an impulsive interference channel with a carrier-to-interference signal power ratio of -20 dB. For each interleaving, the increase in spectral efficiency tends to be higher as the required CNR increases.

WDM equipped universal linear optics for programmable neuromorphic photonic processors

Non-von-Neumann computing architectures and deep learning training models have sparked a new computational era where neurons are forming the main architectural backbone and vector, matrix and tensor multiplications comprise the basic mathematical toolbox. This paradigm shift has triggered a new race among hardware technology candidates; within this frame, the field of neuromorphic photonics promises to convolve the targeted algebraic portfolio along a computational circuitry with unique speed, parallelization, and energy efficiency advantages. Fueled by the inherent energy efficient analog matrix multiply operations of optics, the staggering advances of photonic integration and the enhanced multiplexing degrees offered by light, neuromorphic photonics has stamped the resurgence of optical computing brining a unique perspective in low-energy and ultra-fast linear algebra functions. However, the field of neuromorphic photonics has relied so far on two basic architectural schemes, i.e., coherent linear optical circuits and incoherent WDM approaches, where wavelengths have still not been exploited as a new mathematical dimension. In this paper, we present a radically new approach for promoting the synergy of WDM with universal linear optics and demonstrate a new, high-fidelity crossbar-based neuromorphic photonic platform, able to support matmul with multidimensional operands. Going a step further, we introduce the concept of programmable input and weight banks, supporting in situ reconfigurability, forming in this way the first WDM-equipped universal linear optical operator and demonstrating different operational modes like matrix-by-matrix and vector-by-tensor multiplication. The benefits of our platform are highlighted in a fully convolutional neural network layout that is responsible for parity identification in the MNIST handwritten digit dataset, with physical layer simulations revealing an accuracy of ∼94%, degraded by only 2% compared to respective results obtained when executed entirely by software. Finally, our in-depth analysis provides the guidelines for neuromorphic photonic processor performance improvement, revealing along the way that 4 bit quantization is sufficient for inputs, whereas the weights can be implemented with as low as 2 bits of precision, offering substantial benefits in terms of driving circuitry complexity and energy savings.

Throughput modeling of cellular network systems with spatial precoding

The paper discusses wireless cellular radio communication systems along highways using Multiple-input Multiple-output (MIMO, multiple transmit / receive antennas) technologies, in particular spatial multiplexing and diversity reception, and also proposes a model for assessing the potential gains in a multi-antenna system from MIMO, which takes into account the multipath of the channel and the relative orientation of the antennas. The work was carried out by transferring the results of the calculated correlation matrix from stochastic channel model into the physical layer simulator of the cellular system protocol. A methodology for evaluating the performance of multi-antenna systems using spatial multiplexing for roadside cellular networks has been developed. The correlation properties of the channel between the antennas of the two roadside units (RSU), each of which has two perpendicular linearly polarized antennas and a user terminal with the same two orthogonally polarized antennas, have been investigated. A prediction scheme for the type of correlation matrix has been developed, which makes it possible to more accurately set the correlation matrix in simulators of the physical layer. The obtained results showed that for properly designed systems the throughput will be close to the throughput of low spatial correlation, and the case of high correlation proposed by the standard does not need to be modeled. It is also shown that the channels between Tx / Rx pairs that undergo similar polarization changes (the same relative spatial rotation of the antennas) will be strongly correlated, which must be taken into account when developing MIMO systems.

Physical and MAC layer simulation of IEEE 802.15.4c protocol in transformer terminal unit

IEEE 802.15.4c protocol is suitable for large-scale process control applications with ultra-low complexity, low cost and low power consumption. It is particularly suitable for wireless communication standard used in TTU (transformer terminal unit). Based on the introduction of IEEE 802.15.4c protocol, the physical and MAC (media access control) layer simulation program of IEEE 802.15.4c protocol in TTU is written in MATLAB. In the program, the Gaussian noise with different SNRs (signal-to-noise ratios) is used to simulate noise of signal, and the spread spectrum O-QPSK (offset-quadrature phase shift keying) is used to modulate signal. Based on this, the process of signal generation, signal transmission and signal reception is simulated. The influences of SNR, threshold of sliding autocorrelation method and order of filter on BER (bit error rate) are investigated. The results reveal that the BER of simulation is significantly lower than the theoretical value, and the former is only about 2/5 of the latter when the SNR varies from -2 dB to 6 dB. The threshold of sliding autocorrelation method has a big influence on BER. The threshold corresponding to the minimum BER ranges from 0.4 to 0.6. The order of filter has little influence on BER.

Modular Link Level Simulator for the Physical Layer of Beyond 5G Wireless Communication Systems

AbstractThe low THz band is a promising candidate to enable data rates of up to 1 Tbit/s. To develop suitable communications systems, novel simulation approaches are needed that account for the specifics of the evolving technology. This article presents a modular link level simulator for the physical layer of beyond‐5G and 6G wireless communication systems in the THz range. The simulator, that is oriented toward the IEEE Std 802.15.3d‐2017 is contrasted to the state of the art of physical layer simulation tools. Its concept and basic building blocks are presented and the simulator is validated by channel simulations considering an AWGN channel model. Moreover, it is applied to a top‐of‐rack scenario in a wirelessly augmented data center. Different parameter sets are compared showing that a LOS condition and sufficient transmit power are a prerequisite in order to profit from the large bandwidth in the low THz range. The extensive data set of simulation results serves as input for future studies with higher layer simulation tools.

Full Physical Layer Simulation Tool to Design Future 77 GHz JCRS-Applications

Vehicular communication systems get more and more attention with the upcoming fifth and sixth generation. Hereby, the focus lies on the development of the co-design or co-existence of communications and sensing. So called joints communications and radar sensing systems are seen as one key technology of 6G. As joint systems will have shared waveforms and hardware platforms, there is a huge benefit in cost and space which is one essential argument for the automotive industry. However, to design such a system for new applications like platooning or intersection assistance a physical layer has to be set up to represent the real physical layer properly. The proposed system design closes the lack of such a simulation tool and allows for full physical layer simulations, including e.g. the hardware non-idealities and the channel model for 77GHz. The whole signal processing chain of the physical layer is built up and will be integrated in the higher layer state-of-the-art simulation frameworks like Veins or Artery in the next step. The communications design is developed in Simulink, whereas the sensing part is discussed. The proposed communications architecture covers several transmission approaches (serial, parallel), a CDMA based spreading, a radio frequency representation, the channel (simulated in a 3D-Ray-Tracing-tool) and the receiver structure (e.g. the synchronisation or the channel estimation). Several design criteria are discussed, like the serial or parallel design architecture, the maximum ratio combining or the phase and frequency compensation method. The whole system architecture is freely available (<uri>https://doi.org/10.5281/zenodo.6482565</uri>) and in consequence, the different signal blocks and parameters can be enabled or disabled for evaluations according to future design criteria requirements.

Cross-Layer Analysis of Multi-Static RFID Systems Exploiting Capture Diversity

In this paper, we propose a framework for cross-layer analysis of multi-static passive RFID systems. The model takes into account details of the shared wireless channel, including fading and capture effect, whereas, at the medium access control (MAC) layer, the anti-collision mechanism proposed in the EPC Generation 2 standard is taken as a reference. To address the complexity of the system model, we rely on a semi-analytical approach, that combines a moment matching approximation method to abstract the physical layer and Monte-Carlo simulations to describe the MAC dynamics. Furthermore, based on the space diversity feature offered by the multi-static settings, we introduce the concept of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">capture diversity</i> and propose a modification to the standard to fully support this form of diversity. Numerical results show the impact of deployment conditions and the relative positions of interrogator, tags, and detection points on the performance of tags’ identification. We show how the number of detection points impacts the system performance under various channel conditions and MAC parameters’ settings. Finally, we validate the proposed update of the MAC protocol, showing substantial performance improvement with respect to the standard collision resolution policy.

NetSquid, a NETwork Simulator for QUantum Information using Discrete events

In order to bring quantum networks into the real world, we would like to determine the requirements of quantum network protocols including the underlying quantum hardware. Because detailed architecture proposals are generally too complex for mathematical analysis, it is natural to employ numerical simulation. Here we introduce NetSquid, the NETwork Simulator for QUantum Information using Discrete events, a discrete-event based platform for simulating all aspects of quantum networks and modular quantum computing systems, ranging from the physical layer and its control plane up to the application level. We study several use cases to showcase NetSquid’s power, including detailed physical layer simulations of repeater chains based on nitrogen vacancy centres in diamond as well as atomic ensembles. We also study the control plane of a quantum switch beyond its analytically known regime, and showcase NetSquid’s ability to investigate large networks by simulating entanglement distribution over a chain of up to one thousand nodes.

A Spectrum-Efficient Cross-Layer RF Distance Bounding Scheme

Distance bounding protocols guarantee a credible distance upper bound between the devices which require the spatial distance as a security parameter to defend Mafia Fraud attacks. However, in RF systems, the realization of distance bounding protocol faces obstacles due to low spectrum efficiency, since the distance bound estimation consumes a significant amount of frequency band in existing schemes. This hinders RF distance bounding from being practically deployed, especially in commonly used ISM bands. In this work, we propose an alternative, spectrum-efficient scheme for RF distance bounding. We build the physical layer as well as a protocol design based on SFCW signal and SFCW ranging. Thus, comparing existing schemes that consume many frequency bands, our scheme frees many spectrum resources. We propose solutions to the unique challenges facing such an SFCW-based scheme design, namely, data communication over unintelligent SFCW signals, and secure synchronization in the SFCW-based challenge-response exchange. We evaluate our scheme via the security analysis and physical layer simulations. The results show (i) its resistance to attacks commonly concerned in distance bounding, (ii) the feasibility of the physical layer design such as accurate ranging and data communication function, and (iii) the communication noise tolerance and the ability of multipath signal discrimination.

PHY Abstraction Techniques for V2X Enabling Technologies: Modeling and Analysis

IEEE 802.11p and LTE-V2X are the current wireless standards of interest to enable connected and autonomous driving. The specification for their follow up generations, i.e., IEEE 802.11bd and NR-V2X are being developed and expected to be completed soon. To evaluate and compare the performance of these technologies, system-level studies are required to be carried out for various channel conditions and reliability requirements. However, these studies are time-intensive and require highly complex computations, if they are performed using link-level simulators. Therefore, the physical layer performance is usually abstracted using a link quality model, also known as Physical layer abstraction (PLA). For this purpose, we present novel PLA techniques to model different fading and interference effects for considered technologies. Further, we compare the performance of PLA techniques in terms of estimation accuracy against physical layer simulations. The results show that the estimated packet error rate (PER) by proposed PLA methods are close to the results obtained through physical layer simulations. Besides, we compare the performance of all considered technologies (i.e., IEEE 802.11p, LTE-V2X, IEEE 802.11bd, and NR-V2X) in terms of data rates, latency, and reliability. The results indicate that NR-V2X is superior in terms of average data rates compared to other technologies. In contrast, IEEE 802.11bd has lower transmission latency and higher reliability compared to other technologies.

Simulative assessment of non-linear interference generation within disaggregated optical line systems

Lightpaths within optical line systems (OLS)s that deploy coherent optical technologies are mainly impaired by two additive Gaussian disturbances: the amplified spontaneous emission (ASE) noise from the optical amplifiers and the non-linear interference (NLI) from fiber propagation, together with some amount of phase noise, typically compensated for by the carrier phase estimator module within the digital signal processing (DSP) unit. The main obstacle in accurately modelling the physical layer of a disaggregated optical network arises from the spatially-coherent and spectrally-aggregated general behavior of the NLI generation. Within this paper, we perform an accurate split-step Fourier method (SSFM) physical layer simulation campaign over a wide range of fiber chromatic dispersion values that range from 2 to 16.7 ps / (nm·km) and channel symbol rates from 32 GBd to 85 GBd. For all the explored scenarios, we first show that the NLI generation in an OLS can be spectrally disaggregated in a practical manner by considering a superposition of self-channel (SC) and cross-channel (XC) NLI components only. Secondly, by considering the span-by-span generalized signal-to-noise ratio (GSNR) deterioration, we show that the XC-NLI accumulation components can also be considered as spatially disaggregated, leaving the SC-NLI as the only spatial coherency contribution. Consequently, by appropriately managing these coherent NLI contributions, we find that it is possible to produce a conservative physical layer model that is both spectrally and spatially disaggregated.

Genetic algorithm-based joint Spectral-Energy efficiency optimisation for 5G heterogeneous network

ABSTRACT Carrier Aggregation (CA) technology, introduced in 3GPP release 10, aims at increasing Spectral Efficiency (SE) only, which may lead to huge undesirable circuit power consumption. Hence, not only SE, but also Energy Efficiency (EE), particularly the tradeoff between both the parameters, is crucial in the design of CA systems. In this work, a novel approach, using Genetic Algorithm (GA) is proposed to solve the SE-EE tradeoff problem for a 5 G heterogeneous network with intra-band contiguous Carrier Aggregation (CA). Complete physical layer simulation is performed for generating the CA waveform, with parameters set in accordance with practical deployment scenarios, as specified in 3GPP TS 38.104. Carrier aggregated waveform is generated in 5 G New Radio (NR) frequency band FR1, using frequency bands in India which are currently not allocated for licenced usage. From simulations, it is observed that the proposed technique ensures that neither SE nor EE is seriously degraded for improving the other, for any given value of transmit power. The proposed technique, which performs Multi Objective Optimisation (MOO) using SPEA-2 GA outperforms Single Objective Optimisation (SOO) methods providing a maximum of 37% improvement in SE and 43% improvement in EE.

Throughput Performance Evaluation of LTE-Advanced with Inter-band Carrier Aggregation

The increasing number of mobile smartphone users requires additional spectrum to maintain cellular quality of service. The 800 MHz band is a good candidate to achieve this goal. It can be used as standalone spectrum or aggregated with other licensed bands to increase the available bandwidth. This paper compares through physical layer simulation the downlink throughput versus distance performance of LTE-Advanced in two different bands. We consider a high frequency band at 2.6 GHz and the 800 MHz to model bands 7 and 20 of inter-band carrier aggregation CA_7-20 respectively. The link level simulation is performed for single antenna system at three different urban locations. The channel is modelled using an enhanced 3D ITU-R channel model combined with measured 3D radiation patterns for the base station and user equipment antennas. The BER versus SNR results show that the 800 MHz band enjoys a gain of up to 1 dB as a result of higher Ricean K-factors. Moreover, for the assumed simulation parameters, at distances beyond 400 m the throughput of the 800 MHz band is significantly higher than the 2.6 GHz band. At a distance of 750 m, the throughput for the 800 MHz band is 4.5 times greater than the 2.6 GHz band. These benefits are shown to relate to the lower path loss values observed in the 800 MHz band.

Rendimiento de la técnica de acceso múltiple no ortogonal (NOMA) en un sistema de comunicación móvil Long-Term Evolution (LTE)

La creciente demanda de datos a través de las redes móviles y la búsqueda de servicios más eficientes por parte de los usuarios han inducido a la generación de nuevas técnicas que incrementen la eficiencia espectral. El acceso múltiple no-ortogonal (NOMA) es una de las técnicas que están siendo evaluadas dentro del 3GPP (Third Generation Partnership Project), esta proporciona servicios a múltiples usuarios mediante multiplexación en potencia. Esta investigación evalúa el rendimiento de NOMA en sistemas LTE (Long Term Evolution) mediante simulaciones de capa física, en relación con las tecnologías de acceso múltiple ortogonales convencionales TDM (Time Division Multiplexing) y FDM (Frequency Division Multiplexing). Se compararán, además, las ganancias obtenidas, con las publicadas en la bibliografía de Advanced Television Systems Committee(ATSC) 3.0. Los resultados demuestran que NOMA es mejor que TDM en los casos que se utilice una tasa baja en el receptor móvil y una tasa media en el receptor fijo, demostrando ganancias de 3.35 y 0.25 respectivamente.

400 Gb/s Silicon Photonic Transmitter and Routing WDM Technologies for Glueless 8-Socket Chip-to-Chip Interconnects

Arrayed Waveguide Grating Router (AWGR)-based interconnections for Multi-Socket Server Boards (MSBs) have been identified as a promising solution to replace the electrical interconnects in glueless MSBs towards boosting processing performance. In this article, we present an 8-socket glueless optical flat-topology Wavelength Division Multiplexing (WDM)-based point-to-point (P2P) interconnect pursued within the H2020 ICT project ICT-STREAMS and we report on our latest achievements in the deployment of the constituent silicon (Si)-photonic transmitter and routing building blocks, exploiting experimentally obtained performance metrics for analyzing the 8-socket chip-to-chip (C2C) connectivity in terms of throughput and energy efficiency. We demonstrate an 8-channel WDM Si-photonic microring-based transmitter (Tx) capable of providing 400 (8 × 50) Gb/s non-return-to-zero (NRZ) Tx capacity and an 8 × 8 Coarse-WDM (CWDM) Si-AWGR with verified cyclic data routing capability in O-band. Following an overview of our recently demonstrated crosstalk (XT)-aware wavelength allocation scheme, that enables fully-loaded AWGR-based interconnects even for typical sub-optimal XT values of silicon integrated CWDM AWGRs, we validate the performance of a full-scale 8-socket interconnect architecture through physical layer simulations exploiting experimentally-verified simulation models for the underlying Si-photonic Tx and routing circuits. This analysis reveals a total aggregate capacity of 1.4 Tb/s for an 8-socket interconnect when operating with 25 Gb/s line-rates, which can scale to 2.8 Tb/s at an energy efficiency of just 5.02 pJ/bit by exploiting the experimentally verified building block performance at 50 Gb/s line. This highlights the perspectives for up to 69% energy savings compared to the standard QuickPath Interconnect (QPI) typically employed in electronic glueless MSB interconnects, while scaling the single-hop flat connectivity from 4- to 8-socket interconnection systems.

Neuromorphic Photonics With Coherent Linear Neurons Using Dual-IQ Modulation Cells

Neuromorphic photonics aims to transfer the high-bandwidth and low-energy credentials of optics into neuromorphic computing architectures. In this effort, photonic neurons are trying to combine the optical interconnect segments with optics that can realize all critical constituent neuromorphic functions, including the linear neuron stage and the activation function. However, aligning this new platform with well-established neural network training models in order to allow for the synergy of the photonic hardware with the best-in-class training algorithms, the following requirements should apply: i) the linear photonic neuron has to be able to handle both positive and negative weight values, ii) the activation function has to closely follow the widely used mathematical activation functions that have already shown an enormous performance in demonstrated neural networks so far. Herein, we demonstrate a coherent linear neuron architecture that relies on a dual-IQ modulation cell as its basic neuron element, introducing distinct optical elements for weight amplitude and weight sign representation and exploiting binary optical carrier phase-encoding for positive/negative number representation. We present experimental results of a typical IQ modulator performing as an elementary two-input linear neuron cell and successfully implementing all-optical linear algebraic operations with 104-ps long optical pulses. We also provide the theoretical proof and formulation of how to extend a dual-IQ modulation cell into a complete $N$ -input coherent linear neuron stage that requires only a single-wavelength optical input and avoids the resource-consuming Wavelength Division Multiplexing (WDM) weighting schemes. An 8-input coherent linear neuron is then combined with an experimentally validated optical sigmoid activation function into a physical layer simulation environment, with respective training and physical layer simulation results for the MNIST dataset revealing an average accuracy of 97.24% and 94.37%, respectively.

Protograph LDPC Code Design for Asynchronous Random Access

This work addresses the physical layer channel code design for an uncoordinated, frame- and slot-asynchronous random access protocol. Starting from the observation that collisions between two users yield very specific interference patterns, we define a surrogate channel model and propose different protograph low-density parity-check code designs. The proposed codes are both tested in a setup where the physical layer is abstracted, as well as on a more realistic channel model, where finite-length physical layer simulations of the entire asynchronous random access scheme, including decoding, are carried out. We find that the abstracted physical layer model overestimates the performance when short blocks are considered. Additionally, the optimized codes show gains in supported channel traffic, a measure of the number of terminals that can be concurrently accommodated on the channel, of around 17% at a packet loss rate of 10 − 2 w.r.t. off-the-shelf codes.