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- The DEWI high-level architecture: Wireless sensor networks in industrial applicationsPublication . Samano-Robles, Ramiro; Nordstrom, Tomas; Santonja, Salvador; Rom, Werner; Tovar, EduardoThis paper presents the high-level architecture (HLA) of the research project DEWI (dependable embedded wireless infrastructure). The objective of this HLA is to serve as a reference for the development of industrial wireless sensor and actuator networks (WSANs) based on the concept of the DEWI Bubble. The DEWI Bubble is defined here as a high-level abstraction of an industrial WSAN with enhanced interoperability (via standardized interfaces), technology reusability, and cross-domain development. This paper details the design criteria used to define the HLA and the organization of the infrastructure internal and external to the DEWI Bubble. The description includes the different perspectives, models or views of the architecture: the entity model, the layered model, and the functional view model (including an overview of interfaces). The HLA constitutes an extension of the ISO/IEC SNRA (sensor network reference architecture) towards the support of industrial applications. To improve interoperability with existing approaches the DEWI HLA also reuses some features from other standardized technologies and architectures. The HLA will allow networks with different industrial sensor technologies to exchange information between them or with external clients via standard interfaces, thus providing a consolidated access to sensor information of different domains. This is an important aspect for smart city applications, Big Data and internet-of-things (IoT).
- DynaVLC 13 towards dynamic GTS allocation in VLC networksPublication . Kurunathan, John Harrison; Gutiérrez Gaitán, Miguel; Sámano-Robles, Ramiro; Tovar, EduardoEnvisioned to deliver superior Quality of Service (QoS) by offering faster data rates and reduced latency in 6G communication scenarios, pioneering communication protocols like the IEEE 802.15.7 are poised to facilitate emerging application trends (e.g. metaverse). The IEEE 802.15.7 standard that supports visible light communication (VLC) provides determinism for time-critical reliable communication through its guaranteed time-slots mechanism of the contention-free period (CFP) while supporting non-time-critical communication through contention-access period (CAP). Nevertheless, the IEEE 802.15.7 MAC structure is fixed and statically defined at the beginning of the network creation. This rigid definition of the network can be detrimental when the traffic characteristics evolve dynamically, for example, due to environmental or user-driven workload conditions. To this purpose, this paper proposes a resource-aware dynamic architecture for IEEE 802.15.7 networks that efficiently adapts the superframe structure to traffic dynamics. Notably, this technique was shown to reduce the overall delay and throughput by up to 45% and 30%, respectively, when compared to the traditional IEEE 802.15.7 protocol performance under the same network conditions.
- The DEWI High-Level Architecture: Wireless Sensor Networks in Industrial ApplicationsPublication . Samano-Robles, Ramiro; Nordström, Tomas; Kunert, Kristina; Santonja, Salvador; Himanka, Mikko; Liuska, Markus; Karner, Michael; Tovar, EduardoThis paper presents the High-Level Architecture (HLA) of the research project DEWI (Dependable Embedded Wireless Infrastructure). The objective of this HLA is to serve as a reference for the development of industrial Wireless Sensor and Actuator Networks (WSANs) based on the concept of the DEWI Bubble. The DEWI Bubble is a concept that can be used to integrate legacy industrial sensor networks with a modern, interoperable, and flexible IoT (Internet-of-Things) infrastructure. The DEWI Bubble is defined as a high-level abstraction of an industrial WSAN with enhanced interoperability (via standardized interfaces), dependability, technology reusability, and cross-domain development. The DEWI Bubble aims to resolve the issue of how to improve commercial WSAN technology to match the dependability, interoperability and high criticality needs of industrial domains. This paper details the criteria used to design the HLA and the organization of the infrastructure internal and external to the DEWI Bubble. The description includes the different perspectives, models or views of the architecture: the entity model, the layered model, and the functional model (including an overview of interfaces). The HLA constitutes an extension of the ISO/IEC 29182 SNRA (Sensor Network Reference Architecture) towards the support of wireless industrial applications in different domains: aeronautics, automotive, railway and building. To improve interoperability with existing approaches, the DEWI HLA also reuses some features from other standardized technologies and architectures. The DEWI HLA and the concept of Bubble allow networks with different industrial sensor technologies to exchange information between them or with external clients via standard interfaces, thus providing a consolidated access to sensor information of different industrial domains. This is an important aspect for smart city applications, Big Data, Industry 4.0, and the Internet-of-Things (IoT). The paper includes a non-exhaustive review of the state of the art of the different interfaces, protocols and standards of this architecture. The HLA has also been proposed as the basis of the European project SCOTT (Secure Connected Trustable Things) for security and privacy in the IoT.
- Orthogonal Space-Time Block Coding for V2V LOS Links with Ground ReflectionsPublication . Gaitán, Miguel Gutiérrez; Samano-Robles, RamiroThis work presents a capacity analysis of Space-Time Block Codes (STBC) for Vehicle-to-Vehicle (V2V) communication in Line-of-Sight (LOS). The aim is to assess how this type of coding performs when the V2V LOS channel is influenced by ground reflections. STBCs of various coding rates are evaluated using antenna elements distributed over the surface of two contiguous vehicles. A multi-ray tracing tool is used to model the multiple constructive/destructive interference patterns of the transmitted/received signals by all pairs of Tx-Rx antenna links. Simulation results show that STBCs are capable of counteracting fades produced by the destructive self-interference components across a range of inter-vehicle distances. Notably, the effectiveness in deep fades is shown to outperform schemes with exclusive receive diversity. Higher-order STBCs with rate losses are also evaluated, showing interesting gains even for low coding rate performance, particularly, when accompanied by a multiple antenna receiver. Overall, these results can shed light on how to exploit transmit diversity in slow fading vehicular channels.
- Outage Probability of V2V Multiple-Antenna Rice Fading Links with Explicit Ground ReflectionPublication . Gutiérrez Gaitán, Miguel; Samano-Robles, Ramiro; Rodriguez, JonathanThis paper investigates the improvement in terms of outage probability of a vehicle-to-vehicle (V2V) communication link with respect to the density of antennas used at each vehicle end. The objective is to find a trade-off between system complexity and communication performance considering that the deterministic component of the link is affected explicitly by multiple ground reflections (self-interference). The antennas are assumed to be located at regularly distributed positions across the surface of contiguous vehicles. Part of the work assumes symbol repetition at the transmitter side, and different signal combining mechanisms at the receiver side, namely, maximum-ratio and equal-gain combining (MRC and EGC, respectively). The objective is to minimize outage probability of the link with deterministic and stochastic channel components (Rice-distributed), where the line-of-sight (LOS) is affected by multi-ray ground reflections as an extension of the well-known two-ray model. This scenario is considered more realistic for V2V scenarios due to the potential proximity of ground to the antenna elements. The outage probability is calculated over a range of inter-vehicle distances with respect to the free-space loss solution. The results show that performance is improved even for a relatively small number of antennas and that a critical point is reached beyond which improvement is only differential. This suggests that an optimum trade-off can be obtained to ensure a value of outage probability with a complexity constraint over a range of inter-vehicle distances.
- On the central Chi-square distribution with even degrees of freedom and correlated multivariate complex componentsPublication . Samano-Robles, RamiroThis paper presents the derivation new expressions for the statistics of a Chi-square distribution with $n$ degrees of freedom and where n is an even number. The complex Gaussian components of the chi-square distribution are modelled with a linear correlated model using different statistics (multi-rate) for each component. We focus on the specific expressions for the probability density function (PDF) and complementary cumulative density function (CCDF). Unlike previous approaches, we use a frequency domain interpretation that allows us to derive a closed form expression for the characteristic function (CF) as an inverse polynomial equation. Using the roots of this polynomial equation, it is possible to decompose the CF as a partial fraction expansion (PFE). This allows us to obtain a simple expression for both the PDF and CCDF by simply using the inverse Fourier transform of PFE decomposition of the CF. The statistics derived here have a much lower complexity than the expressions obtained from conventional non-frequency domain methods at the expense of the complexity of the polynomial root solution scheme. In scenarios where the average statistics of the components do not change over some periods of time, the proposed expressions provide the lowest possible complexity, as the polynomial rooting process needs to be conducted only once and potentially offline.
- Ultra-Reliable Low Latency based on Retransmission and Spatial Diversity in slowly fading channels with co-channel interferencePublication . Samano-Robles, RamiroThis paper presents the analysis of the statistics of latency and information theoretic capacity of an adaptive link with retransmission-spatial diversity in a scenario with co-channel interference. The paper focuses specifically on the delay of the wireless transmission component, measured from the instant a packet at the head of the queue is first transmitted until it is correctly received by the destination (considering retransmissions). The objective is to evaluate the ability of temporal and spatial diversity tools to achieve ultra-low values of latency as desired in future 5G and machine-to-machine (M2M) networks with real-time requirements. It is assumed that the source transmits information towards the destination in a Rayleigh fading spatially correlated channel. In case the instantaneous signal-to-interference-plus-noise (SINR) ratio has not surpassed a predetermined reception threshold, then the source engages in a persistent retransmission protocol. All the copies of the original transmission and subsequent retransmissions are stored in memory and processed at the destination using maximum ratio combining (MRC) to obtain a more reliable copy of the signal (a scheme also called retransmission diversity). The retransmission scheme stops once the instantaneous post-processing SINR achieves the desired target threshold. This persistent retransmission scheme can also be regarded as a security mechanism against interference jamming attacks. Since retransmissions are assumed to take place in a short time interval in order to achieve very low values of latency, they are modelled with statistical temporal correlation, which is explicitly introduced in the embedded Gaussian channel distribution model. Results suggest that retransmission diversity can provide good latency results in moderate to high values of SINR. However, at low SINR, a combination with other diversity sources will be necessary to achieve the desired target value.
- 5G network as key-enabler for vehicular platooningPublication . Duarte, Paulo; Soyturk, Mujdat; Robles, Ramiro; Araújo, Marco; Yaman, Berkay; Goes, Adriano; Mendes, Bruno; Javanmardi, Gowhar; Gutiérrez Gaitán, MiguelThe future of goods transportation will rely on increased efficiency, lower risks, and diminished delays through the use of vehicle platoons that benefit from vehicular connectivity using V2X (Vehicle to Everything) applications. This article describes a system that offers the aforementioned vehicular connectivity to platoons, based on AI-enhanced 5G for resource allocation in wireless platoon intra-communications under three scenarios (latency emergency braking, platoon wireless resource management in tunnels, V2X communications interference in a traffic congestion). Demos are described for each of the scenarios, targeting different layers, starting by the PHY (physical) layer where propagation models are implemented, then a simulation-based MAC (medium access control) layer that allows the allocation of resources to the connected User Equipments (UE) and finally a management and orchestration layer capable of monitoring and managing the radio network, offering features such as network slicing management using O-RAN (Open Radio Access Network) standards.
- Wireless Channel Prediction Using Artificial Intelligence with Constrained Data SetsPublication . Javanmardi, Gowhar; Samano-Robles, RamiroThis work deals with the study of artificial intelligence (AI) tools for purposes of vehicular wireless channel prediction. The objective is to test the ability of different types of AI and machine learning (ML) algorithms under different types of implementation constraints. We focus particularly in highly changing scenarios where the channel state information changes relatively fast and therefore the relevant measurements or long-term statistical models are therefore scarce. This means that the training of our models can be potentially inaccurate or incomplete and we need to investigate which AI algorithm behaves better in this challenging condition. In future work we aim to investigate also computation complexity constraints, real-time deadlines, and outdated/distorted or noisy data set samples. We also aim to correlate the main properties of the well-known Jakes' channel model with the effectiveness of the type of prediction and the parameters of the different algorithms being tested. The objective of channel prediction in vehicular networks is to reduce allocation and transmission errors, thereby reducing latency and improving message transmission reliability, which is crucial for future applications such as autonomous vehicles. Results show that even in situations with incomplete data sets, AI can provide good approximate predictions on the channel outcome.
- A Multi-Ray Analysis of LOS V2V Links for Multiple Antennas with Ground ReflectionPublication . Farzamiyan, Amir Hossein; Gutiérrez Gaitán, Miguel; Samano-Robles, RamiroThis paper presents a vehicle-to-vehicle (V2V) geometric multi-ray tracing model for an improved line-of-sight (LOS) estimation. The model is especially suited for distributed antenna transceivers in the presence of ground reflections. The multiple antennas are assumed to be spaced regularly in horizontal and vertical directions over contiguous vehicles. The main focus of our study is the ability of the multiple antenna system to counteract or exploit, respectively, the destructive or constructive interference of multiple rays in the LOS channel component. This work is a complement to existing V2V channel models by providing more details on how ground reflections affect the LOS channel. The analysis is initially framed in the context of MIMO (multiple-input multiple-output) systems to investigate general aspects such as capacity limits and singular value distribution. The work then focuses on a scheme with single symbol repetition across the transmit antennas and two different strategies for signal combining at the receiver: maximum-ratio and equal-gain combining (MRC and EGC, respectively). These solutions are compared with a full diversity solution as well as with the information theoretical limits. An adaptive antenna selection mechanism is finally proposed that outperforms all other solutions. The paper shows both vertical and horizontal polarization results with corrected complex Fresnel reflection coefficients for lossy materials. Moreover, it is shown that multiple antenna design in V2V systems can be useful to counteract the destructive interference created by multiple rays on the LOS channel component.