This paper presents a practical evaluation of a distributed $4 \times 2$ MIMO-OFDM downlink transmission in millimeter wave (mmW) spectrum. Focusing on a scenario with a limited number of users and antennas, a comparison between different antennas deployment topologies and precoders implementations is performed. A 5G-NR based physical layer (PHY) allowing distributed downlink MIMO transmissions in the $\mathbf{~ m m W}$ spectrum is proposed. Performance evaluations are conducted experimentally, first by simulations on 3GPP Tap Delay Line (TDL) channels, and second thanks to a channel emulator running different scenarios with mobile user equipments (UEs). Results show that centralized implementation of precoders with distributed antennas offers better performance and are more robust to blockage.

This paper presents a study of a downlink (DL) cell-free MIMO-OFDM transmission under maximal ratio transmission (MRT) and full pilot zero-forcing precoding (FZF) in the presence of carrier frequency offsets (CFO). This hardware impairment causes intercarrier interference (ICI) which degrades the transmission performance. We derive exact closed form expressions of the achievable spectral efficiency considering frequency selective, uncorrelated, Rayleigh fading channels. Numerical results are obtained considering a transmission scenario using 5G RedCap specifications in the millimeter wave band to illustrate our derivations and quantify the performance for different values of the CFO.

Connected and Automated Vehicles (CAV) can leverage both physical sensing and wireless communications to improve road safety and efficiency. While standalone perception is practically limited by the range of on-board sensors and/or by the presence of obstacles that prevent seeing through, collective perception indeed allows vehicles to exchange -and even beyond, to fuse- information related to the obstacles they detect independently. In this paper, by means of system-level simulations, we analyze the performance of Vehicle-to-Network (V2N) connectivity based on the 5th Generation - New Radio (5GNR) as a support to Cooperative, Connected and Automated Mobility (CCAM), in the light of scalability concerns (as a function of the number of connected users). Focusing on a canonical centralized Cooperative Collision Avoidance (CoCA) use case, we assess the link reliability and the End-to-End latency of all the critical messages involved. Simulation results emphasize the potential of 5GNR connectivity to enable cooperative obstacles detection and thus accordingly, to improve vehicle’s/driver’s awareness (regarding distant vehicles, vulnerable road users, etc.).

Low Power Wide Area (LPWA) networking has emerged as a major communication mean for the Internet of Things (IoT) but currently relies only on terrestrial waves. However, for IoT applications in remote areas, Satellite-based IoT services could provide a dependable alternative. This paper evaluates the system performance of Narrowband-IoT (NB-IoT), a 3GPP standard which is one of the major terrestrial IoT technology, for Geostationary (GEO) and Low Earth Orbit (LEO) satellites. Despite lower visibility times and Doppler levels, LEO systems present the best performance in terms of latency of access and density the network can accommodate.

By means of system-level simulations, we analyze in this paper the performance of Vehicle-to-Network (V2N) connectivity based on the 5th Generation - New Radio (5GNR) as a support to Cooperative, Connected and Automated Mobility (CCAM), in light of both network and Multi-access Edge Computing (MEC) deployments. Focusing on a canonical centralized Cooperative Lane Change (CLC) use case that involves three vehicles in a cross-border highway environment, we assess the link reliability and the End-to-End (E2E) latency of all the messages involved in the CLC negotiation phase (from/to interconnected MECs hosting the centralized maneuvering application), while assuming different deployment configurations and the coexistence with a second demanding vehicular service running over the same radio resources. On this occasion, we illustrate possible benefits from Bandwidth Partitioning (BWP) on Uplink (UL) latency, as well as from an hypothetically tight cooperation between Mobile Network Operators (MNOs) on reliability and continuity, leveraging low-latency inter-MEC transactions and seamless cross-border handover capabilities.

This paper investigates decoder diversity architectures for short low-density parity-check (LDPC) codes, based on recurrent neural network (RNN) models of the belief-propagation (BP) algorithm. We propose a new approach to achieve decoder diversity in the waterfall region, by specializing BP-RNN decoders to specific classes of errors, with absorbing set support. We further combine our approach with an ordered statistics decoding (OSD) post-processing step, which effectively leverages the bit-error rate optimization deriving from the use of the binary cross-entropy loss function. We show that a single specialized BP-RNN decoder combines better than BP with the OSD post-processing step. Moreover, combining OSD post-processing with the diversity brought by the use of multiple BP-RNN decoders, provides an efficient way to bridge the gap to maximum likelihood decoding.

In Low Power Wide Area (LPWA) networks, radio localization based on Time Difference of Arrival measurements has major benefits: energy consumption of the node and spectrum usage are contained. Temporal resolution and hence positioning accuracy is however limited by the bandwidth of the LPWA narrowband signals. Multi-channel ranging, that relies on multiple narrowband signals that are sequentially transmitted on different and discontinuous channels, has recently been proposed to improve precision. However, the concept has not been adapted yet to differential uplink localization techniques. This paper studies and proposes adaptations to multi-channel ranging called Multi-Frequency Phase Difference of Arrival (MF-PDoA) for this purpose. It analyzes the impact of imperfect synchronization on its performance and concludes that MF-PDoA is robust and well adapted to the LPWA scenario.

Terrestrial Internet of Things (IoT) communication systems cannot provide worldwide coverage as effectively as satellite systems. Narrowband IoT (NB-IoT) is currently one of the major terrestrial IoT technology. This article provides an evaluation of the NB-IoT physical layer performance in the context of two satellite scenarios: Geostationary (GEO) and Low Earth Orbit (LEO). GEO scenarios suffer from large distances between transmitter and receiver, while LEO systems exhibit very large levels of Doppler. New algorithms are proposed to reliably adapt NB-IoT in these contexts and performance in terms of maximum throughput is evaluated and compared. Finally, NB-IoT main limitations in satellite communication links are identified.

Connected vehicles are equipped with sensors that can detect surrounding objects. However, vehicles perception is limited by sensors range or by the presence of other obstacles. Collective perception can improve vehicles perception by allowing them to exchange information about detected obstacles. In this context, vehicles rely on on-board sensors in order to generate Collective Perception Messages (CPM) that are exchanged by means of LTE-V2X connectivity. In order to reveal hidden obstacles and obtain a coherent visualization about the environment, CPM fusion is then crucial. In this work, we propose a novel low complexity fusion algorithm for CPM. Moreover, we evaluate the impact of LTE-V2X connectivity performance, specially in terms of packets loss, on the fusion. Simulation results in a smart junction demonstrate the relevance and efficiency of our algorithm in terms of obstacles detection capabilities.

Cooperative Intelligent Transport Systems (C-ITS) are expected to fulfill the needs of various emerging road safety applications. In this work, we focus on improving C-ITS vulnerable road users safety by considering a Cooperative Collision Avoidance (CoCA) system. In this system, vehicles rely on on-board sensors in order to generate local occupancy maps that are transmitted by means of LTE-V2X connectivity to a fusion center. The latter executes the fusion of successfully received local maps, in order to generate a global occupancy map, which can reveal obstacles that could not be perceived based uniquely on standalone vehicle's perception means. The resulting map is broadcast to all connected vehicles in transmission range (i.e., even those who have not contributed to the global map) in order to announce a risk of collision. The main objective of this work is to evaluate the impact of LTE-V2X connectivity performance on the fusion result and to define the best compromises between the communication configuration, the definition of occupancy maps and obstacle detection capabilities.

In this paper, we explore the potential, as well as a few limitations, of Cellular - Vehicle-to-Everything (C-V2X) sidelink connectivity (a.k.a., PC5-Mode4) for Cooperative Lane Merging (CLM) services in a specific cross-border highway context. Based on a dedicated simulation flow, we assess both the successful completion of the CLM negotiation procedure from the standpoint of messages delivery (service availability) and the accuracy of position awareness, as perceived by the manoeuvre management application out of collected status messages (service reliability). These indicators are evaluated as a function of road traffic, overall system latency and infrastructure deployment. Simulation results suggest that both Vehicle-to-Infrastructure and Vehicle-to-Vehicle communications based on C-V2X PC5-Mode4, which benefit respectively from information redundancy and short-range links, could advantageously complement Vehicle-to-Network connectivity to locally guarantee the seamless continuity of latency-critical services in challenging environments.

The interest for communications between vehicles and the infrastructure or other vehicles (V2X) has recently increased towards connected vehicle applications, and particularly cooperative collision avoidance (CoCA). In this paper, we evaluate the performance of LTE-V2X networks in the context of Intelligent Transportation Systems for traffic collision avoidance applications based on sharing occupancy maps between the infrastructure and the vehicles. We compare by simulation different LTE-V2X configurations under realistic conditions in an intersection scenario. Then, we evaluate every type of communication link (V2I and V2V) as a function of the density of vehicles. The results show the potential of the concept for V2X and the trade-offs in terms of reliability, capacity and latency.

Two technologies are currently competing for providing Vehicle-to-Everything (V2X) communication services in Europe and in the 5.9 GHz ITS band. The oldest one is known as ITS-G5 and specified by ETSI, and the new comer is standardized in 3GPP and derived from LTE technology. It is now conjectured that both technologies will coexist in the deployment phase, at least during a transition period. Several coexistence scenarios are currently under study. Some of them are even considering the option to share a 10 MHz radio channel in the 5.9 GHz band among both technologies under the same geographical area. This approach is called co-channel coexistence. New mechanisms are currently explored and assume some modifications of the standards aimed at minimizing the performance losses. This co-channel coexistence scenario requires a careful assessment, and this article proposes the first performance evaluation in this particular context of coexistence between ITS-G5 and LTE-V2X standards. It presents a simulation work that has been carried out with the purpose of assessing performance of mixed deployments, and also assessing the efficiency of one possible coexistence mechanism. It is based on system level simulation which is itself relying on physical layer performance assessment pertaining to both technologies. The simulation methodology is presented and evaluation results are provided and commented.

Vehicular communications, known under the name of V2X (Vehicle to Everything) are expected to grow fast in the next years, bringing for example safer driving conditions, optimized traffic management, energy reduction, etc.. Currently two short range-based technologies (ITS-G5, standardized in Europe by ETSI and derived from WiFi communications IEEE standards and LTE based Vehicle to Everything or LTE-V2X developed by 3GPP and derived from LTE) consider the use of 5.9 GHz ITS band for their deployment. While different countries are more or less advanced in terms of regulation definition for Intelligent Transport System (ITS), it seems clear that the same solution will not be necessarily worldwide deployed. This study compares performances of both technologies by means of system level simulation, in particular considering the European ITS-G5 protocol stack specification. In order to analyze system level performance, physical layer simulation is used to provide Packet Delivery Rate (PDR) versus Signal to Noise plus Interference Ratio (SINR). Then PDR curves are exploited to feed system level simulation aimed at providing statistics about Cooperative Awareness Message (CAM) transmission reliability, in typical urban scenario. The paper provides a brief description of the systems together with the definition of the assumptions and the key results related to the physical layer analysis; it follows with the description of the NS-3 simulator models used for system level simulation (with particular emphasis on PC5 Mode 4) and the discussion about the results which provide insight about the expected and the simulated behavior of both technologies, in particular comparative statistics with regards to CAM success ratio versus maximum communication distance are provided in order to compare the performance.

Over the last years, advanced wireless connectivity (e.g., 5G, LPWA) has increased its interest for Factory of the Future (FoF). In this work, we evaluate the benefits of LPWA technologies (i.e. LoRa and Turbo-FSK) in the FoF context for massive Machine-Type Communication (mMTC) applications focusing on low power consumption and high reliability. To do so, we evaluate the impact of three factors on Turbo-FSK technology (i.e., FoF propagation models, flexibility of the PHY layer configurations and different base station architectures). Finally, we compare LoRa and Turbo-FSK for equivalent configurations under FoF conditions. The results show the trade-offs in terms of reliability, network capacity, latency and battery lifetime.

Turbo Frequency Shift Keying has been considered as a promising physical layer for low power wide- area network connectivity. Because of its constant envelope amplitude and the efficiency of its iterative receiver performance close to Shannon’s limit can be achieved. However, results published so far in the literature for the waveform have assumed perfect channel estimation or Signal-to- noise (SNR) levels that are higher than the SNR levels considered for these applications. This paper analyzes a channel estimation strategy based on a specifically adapted pilot sequence. Simulations have been performed to evaluate the performance of the proposed approach. Performance loss induced by imperfect channel estimation algorithms is estimated.

Vehicle to vehicle/infrastructure communication systems have a significant role to play in optimizing road traffic and improving road safety. In this context, two standards have emerged, namely ITS-G5 (IEEE 802.11p) and C-V2X (3GPP Release 14). The objective of this article is to compare both standards by evaluating the performance of both physical layers and associated MAC layers. The physical layer performance of a single link is first evaluated and used to derive performance in a loaded network where each user is scheduled by their respective MAC layer. Performance evaluation shows an advantage for the C-V2X for low levels of vehicles density while when the congestion increases the performance gap reduces until ITS-G5 eventually outperforms C-V2X. Finally, latency was also assessed for both communication systems.

In order to meet the contradictory requirements of long range, low power consumption and adaptive throughput, LPWA networks require a decision module based on cognitive functionalities to select the most appropriate RF/PHY configuration and to cover the large variety of LPWA applications. In this paper, we define a new adaptive LPWA network exploiting the flexibility of the Turbo-FSK waveform. The most relevant configurations are selected from the PHY and MAC layers point of view. At the PHY layer, a trade-off between data rate, spectral efficiency, energy consumption and range is considered while the MAC layer deals with the reliability, the latency, the network capacity, the multi-user access (number of users, traffic intensity) to adapt the network. Hence, thanks to this selection, several strategies switching between available selected configurations are defined to adapt the communication to the context and according to the criteria to optimize. The performance for each configuration is evaluated by simulation when all the users select the same configuration. To tackle the three requirements (i.e. range, network capacity and energy consumption), appropriate configurations are identified.

Originally, Low Power Wide Area (LPWA) Networks were predetermined for long range, low power and low data rate transmissions. The existing LPWA technologies trade-off by definition between these parameters and therefore, they can not cover the different scenarios of Machine-to-Machine communications. Moreover, heterogeneity and large-scale are still two main challenges that are not always considered in LPWA studies. In this paper, we evaluate different massive deployment strategies using a flexible radio based on Turbo-FSK: selfish approach where each node selects its own configuration according to its needs and centralized approach where the Base Station selects the best strategies to improve the network performance. Then, we evaluate these deployments with large-scale simulations in terms of reliability, network capacity, battery lifetime and end-to-end latency. The results show the advantages and drawbacks of homogeneous and heterogeneous deployments in different LPWA contexts (e.g., Smart Metering and Agri-systems).

We present an optimized channel coding scheme for OFDM transmitter. Traditional coding methods use regular codes, in the sense that each bit participates in the same way to the channel encoding. Our approach consists in using a priory assumption on the channel available at the transmitter in order to optimize the coding scheme. We have considered the irregular Gallager block codes in our study. Simulations provide evidence of the usefulness of our approach with a gain of 2 dB at a bit error rate equal to 10/sup -5/ for optimized irregular coding scheme compared to regular one.