Connected and automated driving V2X (Vehicle-to-Everything) services generate aperiodic traffic of variable size that can produce packet collisions in sidelink Cellular V2X or C-V2X communications when vehicles autonomously select their radio resources. A significant portion of these collisions stem from unutilized reservations that occur when a vehicle does not have a packet to be transmitted in a resource it had previously reserved. Unutilized reservations increase transmissions on selected resources (not-reserved), and augment the risk of packet collisions as vehicles cannot reserve resources for their following transmission. This paper addresses this challenge for the first time by introducing V2X Rebroadcasting , a novel and standard-compliant scheme that enables vehicles to rebroadcast packets from other vehicles in detected unutilized reservations. Unlike existing state-of-the-art mechanisms, the proposed scheme can be applied to improve the effectiveness of C-V2X communications for any V2X message and traffic patterns. V2X Rebroadcasting provides two main benefits. First, the vehicle can use the rebroadcasted packets to reserve resources for its next transmission, preventing other vehicles from selecting those resources and reducing packet-collision risk. Second, the proposal improves the reliability of the rebroadcasted packets, as the additional transmission may help overcome propagation losses or collisions experienced by the original packet. We evaluate V2X Rebroadcasting over 5G NR V2X mode 2 under realistic reference scenarios with different vehicle densities and traffic loads. The results indicate that the proposal can yield a more than 2x reduction in the probability of packet collisions and improves the reliability of V2X communications compared to the standard 5G NR V2X mode 2, even under challenging channel-load conditions. In these scenarios, V2X Rebroadcasting can improve the Packet Delivery Ratio (PDR) by up to 20% at short to medium distances, where safety-critical V2X data is particularly relevant, and it can also more than double the range at which high PDR levels are maintained.

Future 6 G networks are envisioned as a “network of networks” (NoN) ecosystem, integrating communication and computing resources across multiple domains. At the deep edge, IoT and end-user devices will form subnetworks for local communication and distributed task processing. These subnetworks will seamlessly integrate into the NoN ecosystem, creating an IoT-edge-cloud continuum. The unified resources across this continuum facilitate dynamic and scalable task offloading, unlocking new possibilities to support emerging services, including critical vertical services with stringent reliability and deterministic service level requirements. In this context, this paper demonstrates that a deterministic approach to task offloading and resource (communication and computing) allocation in the IoT-edge-cloud continuum not only ensures deterministic service levels but also enhances scalability compared to existing task offloading and resource allocation methods. By flexibly managing task completion deadlines while maintaining deterministic (i.e. bounded latency) service levels, deterministic policies achieve a more balanced workload and resource distribution across the continuum, ultimately improving scalability.

Next generation wireless networks must sustain deterministic service levels to support emerging time-sensitive applications. The ability to guarantee bounded latencies depends on the efficient management of radio resources. Several studies propose leveraging the native intelligence of future networks to develop predictive schedulers capable of efficiently managing resources. However, existing proposals focus on semistatic scheduling, where resources are reserved based on traffic predictions, and these reservations are susceptible to inefficiencies due to prediction inaccuracies. This study advances the state of the art with a novel predictive dynamic scheduling scheme that avoids such inefficiencies, and leverages traffic predictions to allocate resources to incoming requests that meet their latency requirements while avoiding resources likely to be needed by future predicted packets. Our results demonstrate that the proposed predictive dynamic scheduling effectively supports deterministic communications in scenarios with mixed traffic flows and varying QoS requirements.

Future cellular networks will sustainably integrate computing, intelligence and services within a “network of networks” ecosystem that includes IoT devices and subnetworks for local communications and distributed processing. This integration creates an IoT-edge-cloud continuum that enables opportunistic task offloading across the continuum, enhancing network performance, reducing response times and allowing a flexible resource allocation that can facilitate the system to scale according to demand. Future networks should also natively support deterministic service levels for critical and time-sensitive vertical applications. In this paper, we propose a deterministic task offloading and resource allocation scheme for the joint management of communication and computing resources in the IoT-edge-cloud continuum. The proposed scheme prioritizes task completion before deadlines over minimizing the latency in the execution of individual tasks. The scheme leverages flexible latencies across tasks to support a higher number of tasks through a more efficient management of computing and communication resources that better adapts to scenarios with constrained resources.

Automated vehicles rely on onboard sensors to perceive their surroundings and navigate autonomously. However, sensor performance may degrade under adverse weather conditions or when line-of-sight is obstructed. Cooperative perception (or collective perception) is expected to mitigate these limitations by enabling Connected and Automated Vehicles (CAVs) to share sensor data and collaboratively enhance situational awareness. Several studies have analyzed the potential of cooperative perception, yet the fusion of V2X data with information from onboard sensors has received limited focus. V2X data may contain errors that affect the quality of the fused data, and hence the effectiveness of cooperative perception. This study analyzes the impact of sensing measurement errors, V2X packet losses, and GNSS inaccuracies on the effectiveness of cooperative perception. The results highlight the potential of cooperative perception to enhance perception levels and range compared to using onboard sensors alone. However, they also identify key challenges related to the generation of ghost vehicles during the fusion process, which must be addressed to prevent V2X data from introducing additional errors when fused with onboard sensor data.

This paper examines the critical role of intent-sharing in enabling effective maneuver coordination for connected and automated vehicles (CAVs). Successful maneuver coordinations require vehicles to accurately know other vehicles' driving intentions. Intent-sharing can be achieved by the remote vehicles directly communicating their plans with the ego vehicle, as opposed to the ego vehicle predicting the trajectory on the remote vehicles’ behalf. In this paper, we investigate the potential of intent-sharing on maneuver coordination effectiveness by quantifying the percentage of successful coordinations. We analyze the potential of intent-sharing by comparing its effectiveness for coordinated lane changes in a highway scenario with the effectiveness of a trajectory prediction method based on current kinematic data. Our analysis demonstrates in two scenarios substantial improvements in maneuver coordination when CAVs have direct access to the nearby vehicles’ driving intentions through intent sharing. These findings highlight the importance of including intent-sharing in the maneuver coordination protocol.

Future wireless networks must enhance their capacity to sustain deterministic service levels and support emerging time-sensitive services in key verticals. The ability to guarantee bounded latencies heavily depends on efficient radio resource management. Configured Grant (CG) scheduling can reduce latency by pre-allocating resources, but its effectiveness and efficiency decrease under variable traffic patterns. This study presents a novel predictive CG scheduling scheme that pre-allocates resources based on traffic predictions while accounting for prediction inaccuracies. By considering these inaccuracies, the scheme significantly improves the ability to meet bounded latency requirements, which are essential for supporting deterministic service levels. Our evaluations show that the proposed scheme significantly enhances the capacity to support deterministic service levels while improving resource utilization, even in scenarios with variable and mixed traffic flows with diverse requirements.

Connected and automated driving introduces a myriad of new V2X services, such as cooperative perception and maneuver coordination, that significantly increase the channel load and require multi-channel V2X operation. Policies for Multi-Channel Operation (MCO) and congestion control are therefore essential for simultaneously supporting multiple V2X services across several channels. In this context, this paper presents the design, implementation, and extensive validation of a Facilities layer V2X congestion control solution for multi-channel operation integrated into an ETSI-compliant Cooperative Intelligent Transportation Systems (C-ITS) protocol stack. Our approach dynamically adapts transmission parameters based on real-time channel conditions and the priorities and requirements of the V2X services operating in a C-ITS station. By employing a Traffic-Class based proportional fairness strategy, the solution allocates available communication resources among multiple V2X services, effectively responding to varying channel loads in real time. Scalable experimental results in a virtualized environment demonstrate that our solution meets ETSI Release 2 requirements while bridging the gap between simulation-based evaluations and real-world testing, accounting for hardware limitations and processing delays. This work lays a robust foundation for scalable and congestion-aware C-ITS testing and validation prior to real world deployments. This paper makes our code publicly available so that other researchers can replicate our study and further explore MCO solutions for V2X communications.

5G is a fundamental technology for the digitalization of smart manufacturing. Smart manufacturing relies on the use of digital models to optimize industrial processes before implementation on the manufacturing plants. These models should account for the impact of 5G communications to adequately dimension and optimize 5G-based industrial processes. This paper presents the first integration of industrial digital models with a 5G digital model, implemented as an Asset Administration Shell (AAS) of a 5G system. The two models are interconnected using an OPC UA-based interface. We evaluate the impact of the integrated model using a use case where Automated Guided Vehicles (AGVs) transport material from a warehouse to production lines. The AGVs periodically exchange their positions over 5G to avoid potential collisions. If the communications fail, the AGVs stop for safety reasons until a reliable 5G connection can be guaranteed. We demonstrate that, by integrating 5G and industrial digital models, it is possible to account for, and quantify, the impact of 5G communications on the operation and productivity of industrial processes. This result highlights the importance and necessity of integrating 5G into industrial digital models for their joint design and optimization.

5G is a fundamental technology for the full digitalization of smart manufacturing. The use of Asset Administration Shells (AAS) can facilitate the integration of 5G with Industry 4.0 systems and applications while minimizing the complexities associated with the 5G network management. This study presents the design and implementation of the first full 5G system AAS that is openly released to the community [1]. It includes a 5G UE (User Equipment) AAS and a 5G NW (network) AAS that have been designed following the 5G-ACIA guidelines as well as the Plattform Industrie 4.0 and 3GPP standards. The AASs have been defined to provide and expose the data and capabilities of 5G necessary to facilitate the integration of 5G with Industry 4.0 systems and applications.

Teleoperated driving (ToD) enables the remote driving or control of vehicles. For this purpose, vehicles must transmit video feeds to the ToD control center so that the remote operator is fully aware of the driving conditions and can safely control the vehicle. 5G (and beyond) networks are fundamental for the deployment of ToD as they can provide the low latency, reliable and broadband connection necessary to connect the vehicle and ToD control center. However, it is unclear whether common 5G network architectures and configurations are well-suited to support the simultaneous teleoperation of multiple vehicles with demanding uplink bandwidth, as current networks are mainly configured to support mobile broadband services. This paper demonstrates that MEC or edge-based 5G networks are better suited to support and scale the ToD service than centralized networks, and quantifies the bandwidth required to simultaneously teleoperate multiple vehicles under various 5G network architectures and configurations, including different duplexing modes and TDD frame structures. Finally, the study shows that the configuration of the control channels can help mitigate the impact that the processing time of the video feeds has on the capacity to support and scale the ToD service.

The 5G New Radio (NR) Vehicle-to-Everything (V2X) Sidelink (SL) standard defines multiple DeModulation Reference Signal (DMRS) patterns to support direct vehicular communications in high mobility scenarios. The DMRS pattern is a pre-defined sequence of signals that can be adapted for the transmission of each Transport Block (TB), and is used to estimate the channel response and mitigate the impact of the Doppler shifts experienced by the received signal in high relative speed conditions. The standard defines multiple DMRS patterns, but it does not provide any recommendations to indicate when each pattern should be used. To this end, this study presents an exhaustive analysis of the impact that the DMRS patterns have on the link level performance of NR V2X SL communications, deriving the first set of NR V2X SL recommendations on the DMRS pattern selection. The recommendations identify the maximum Modulation and Coding Scheme (MCS) that can be supported by each DMRS pattern to ensure high reliability levels, and cover different relative speeds, propagation scenarios, and number of subchannels. We also openly release the link level results generated and analysed in this study to derive the recommendations. To the authors’ knowledge, the obtained results represent the largest NR V2X SL link level dataset openly available.

Connected and automated vehicles can leverage V2X communications to coordinate their maneuvers. Maneuver coordination is expected to improve traffic efficiency and safety, but the design of maneuver coordination is a challenging task in complex traffic scenarios, as maneuvers affect not only the involved vehicles but also nearby traffic. This study introduces a reference state machine for the design of maneuver coordination. Furthermore, we identify and analyze the challenges that maneuver coordination may encounter. We quantify the relevance of each challenge and propose a set of countermeasures to enhance the robustness and effectiveness of maneuver coordination.

Connected Automated Vehicles (CAVs) will use multiple V2X services to support connected and automated driving functions. The bandwidth required to support such services will augment as CAVs are gradually deployed. It is therefore important to accurately estimate the spectrum requirements to anticipate possible scalability challenges ahead. Current estimations consider a simplified modeling of the transmitter as well as context factors such as the number of vehicles in the communication range. Moreover, they do not accurately model if the Quality of Service (QoS) of the considered V2X services is satisfied or not. This study progresses the state of the art with a novel analytical model that quantifies the bandwidth required to support multiple V2X services. The model considers the impact of the vehicular context, the transmission parameters and the communication requirements to take into account the QoS at the receiver. This is important since adapting the transmission parameters can reduce the channel load but also impacts the probability to correctly receive each packet and therefore the bandwidth required to guarantee a target QoS at the receiver. The proposed model can be adapted to different wireless technologies and messages, but is applied in this study to quantify the bandwidth required by LTE-V2X to support the transmission of CAMs, CPMs and MCMs. The study demonstrates the scalability challenges ahead to support multiple V2X services.

The Internet of Vehicles (IoV) will interconnect vehicles, vulnerable road users, and infrastructure nodes for a safer, more efficient, and digitalized mobility. In the IoV vision, traditional network-based communications will be complemented with direct Sidelink (SL) Vehicle-to-Everything (V2X) communications. To this aim, 3GPP introduced in Release 16 the New Radio (NR) V2X SL technology. The NR V2X SL standard includes important Physical (PHY) layer novelties with respect to LTE V2X SL and NR Uplink/Downlink, and is characterized by a large set of configurable parameters. However, existing NR V2X SL link level studies focus on a confined set of configurations. This limits a thorough understanding of the NR V2X SL link level performance and impacts the accuracy of system level evaluations, which typically leverage link level models to accurately represent the PHY layer performance. These models are based on Look-Up Tables (LUTs) that map the link level performance, e.g., BLock Error Rate (BLER), as a function of the link quality, e.g., Signal-to-Noise Ratio (SNR). This study presents an exhaustive NR V2X SL link level evaluation that analyzes the impact of relevant PHY layer aspects, e.g., modulation and coding scheme, channel model, and transmitter-receiver relative speed, considering the wide set of configurations recommended by 3GPP and ETSI. The obtained standard-compliant LUTs are openly released, representing the largest NR V2X SL link level dataset available. The released dataset represents a valuable asset for the community, as it allows exhaustive NR V2X SL system level investigations under a broad range of settings and configurations.

Teleoperated driving (ToD) can support autonomous driving under complex or unexpected traffic scenarios that an autonomous vehicle may not understand or be able to handle. In ToD, autonomous vehicles transmit video feeds and perception data to the remote control center. The operator uses this data to understand the driving environment and remotely control the vehicle that can take over the control once the scenario is resolved. ToD requires reliable and low latency communications between the vehicle and the ToD control center. This study analyzes the feasibility to support ToD with 5G networks. The study demonstrates that the feasibility strongly depends on the bandwidth and the Time Division Duplexing (TDD) frame structure that conditions how the bandwidth is distributed between uplink and downlink transmissions. The study also shows that scaling the number of 5G-supported ToD vehicles requires the vehicles to reduce the video bitrates. The study also shows that traditional centralized 5G network deployments may be challenged by some of the most stringent ToD latency requirements due to the latency introduced by the Internet connection to the ToD control center.

5G and beyond networks can facilitate the digital transformation of manufacturing and support more flexible and reconfigurable factories with ubiquitous mobile connectivity. This requires integrating 5G networks with industrial networks that increasingly rely on TSN (Time Sensitive Networking) to support deterministic communications with bounded latencies. Deterministic communications are critical for many industrial applications, but 5G does not natively support deterministic communications. To address this limitation, this study proposes the coordination of the 5G and TSN schedulers and presents a novel 5G configured grant scheduling scheme to support TSN traffic. The scheme uses information about the characteristics of the TSN traffic (packet size, periodicity, and arrival time) to coordinate its scheduling decisions with the TSN scheduler. The study demonstrates that the proposed scheme outperforms the state-of-the-art in the capacity to support multiple TSN traffic flows with different periodicities.

Cooperative perception (a.k.a. Collective perception or cooperative sensing) will allow Connected and Automated Vehicles (CAVs) to share information about detected objects. Cooperative perception improves the sensing accuracy, confidence and range of CAVs, and extends their perception of the driving environment. First message generation rules based on the mobility and dynamics of detected objects have been proposed to decide when a cooperative perception message should be generated and what information it should include. Studies have shown that this type of generation rules can compromise the scalability of cooperative perception and vehicular networks, as they tend to transmit significant amounts of redundant information and generate small and frequent cooperative perception messages that increase the communications overhead. To combat these inefficiencies, this paper proposes and evaluates three techniques that combine, for the first time, baseline mobility-based generation rules for cooperative perception messages with mechanisms to control the redundancy and organize the information about detected objects in order to avoid the frequent transmission of small messages. This study demonstrates that the proposed techniques improve the perception of CAVs and reduce the information age. In addition, the techniques reduce the channel load and improve the scalability of cooperative perception services and vehicular networks. The study demonstrates that the most effective technique is based on: (1) first applying the generation rules to decide whether a cooperative perception message should be generated, (2) then applying redundancy control, and finally (3) organizing the information about all detected objects to avoid small and frequent messages.

Industry 4.0 and 5.0 applications will contribute towards safer, zero-defect and customized production environments. Such applications (e.g. digital twins, collaborative robotics and extended reality) require communication networks capable to satisfy stringent latency, bandwidth, and reliability requirements. Such requirements can be sustained with 5G networks and their evolution that offer unprecedented communications performance and flexibility thanks to the softwarization of networks and the use of network slicing. Network slicing creates different logical partitions or slices of the common network infrastructure and configures each slice to the requirements of the applications it will support. RAN (Radio Access Network) slicing is a fundamental part of network slicing in 5G as the radio channel is prone to errors and this impacts the capacity to support stringent reliability requirements. To date, RAN slices have been created considering the number of radio resources that must be reserved to guarantee the transmission rate or bandwidth demanded by the applications they will serve. This study demonstrates that this design approach cannot guarantee satisfying the reliability requirements of industrial applications and proposes a novel RAN slice descriptor that takes into account both the reliability and transmission rate requirements of the applications.

5G NR V2X complements LTE V2X to support advanced V2X services for connected and automated driving. 5G NR V2X introduces novel features at the MAC layer that are designed to cope with potential packet collisions, and that could help address the LTE V2X MAC inefficiencies observed under aperiodic traffic of variable size. This is the case of the re-evaluation mechanism that is a mandatory MAC feature of 5G NR V2X, and that seeks to avoid possible packet collisions detected before a vehicle transmits in selected resources. Evaluations conducted to date of 5G NR V2X do not consider the re-evaluation mechanism, and have focused on traffic patterns that do not fully account for the traffic variability of advanced V2X services. This paper extends the current state of the art with the first evaluation of a fully standard compliant 5G NR V2X implementation under the traffic patterns recommended by 3GPP for advanced V2X services. Our study shows that 5G NR V2X mode 2 still faces MAC challenges when using semi-persistent scheduling (SPS) to efficiently support aperiodic traffic of variable size.

Cellular networks usually support non-safety-critical V2X services using Vehicle-to-Network (V2N) connections. However, the flexibility and capabilities of 5G have triggered interest in analyzing whether 5G could also support advanced V2X services using Vehicle-to-Network-to-Vehicle (V2N2V) connections instead of direct Vehicle-to-Vehicle (V2V) connections. V2N2V requires the integration of the 5G network with computing platforms for processing the V2X packets. The flexibility introduced by 5G facilitates the integration with multiple computing platforms such as Multi-access Edge Computing (MEC), edge cloud, shared data center or central cloud. This results in alternative 5G network deployments with the computing platform installed at different locations between the base station and the Internet. These deployments can have important technical implications for supporting V2X services. In this study, we analyze the impact of different 5G and computing platform deployments on the end-to-end (E2E) latency of V2N2V communications under multi-MNO (Mobile Network Operator) scenarios since vehicles may be served by different operators. We also identify which deployment strategies are more suitable to meet the latency requirements of V2X services for connected and automated driving.

5G and multi-access edge computing (MEC) are being considered to support V2X services demanding low latency and highly reliable communications using V2N2V (Vehicle-to-Network-to-Vehicles) communications instead of direct or sidelink V2V (Vehicle-to-Vehicle). Guaranteeing V2X service continuity using V2N2V is a challenging task in multi-Mobile Network Operator (MNO) deployments where vehicles are supported by different MNOs. MEC federations have been proposed to address some of these challenges. A MEC federation is a federated model of MEC systems enabling shared usage of MEC services and applications. Through MEC federations, vehicles can seamlessly access V2X applications independently of whether they are hosted on their MNO’s MEC, or on the MEC of a different (but federated) MNO. This paper presents the first study that analyses the impact of MEC federation on the end-to-end (E2E) latency when supporting V2X services using 5G V2N2V in multi-MNO scenarios. The paper also evaluates the feasibility to support the latency requirements of advanced V2X services in these scenarios, and the benefits introduced by MEC federation. This study considers the V2Xbased cooperative lane merge service as a case study.

5G NR V2X introduces novel MAC features to support advanced V2X services for connected and automated driving. One of these features is the re-evaluation mechanism designed to detect and avoid packet collisions. The re-evaluation mechanism checks before every transmission if the selected resources are still available. If another vehicle has selected the same resources, the re-evaluation mechanism triggers a reselection of resources. The 3GPP standard defines different strategies for vehicles to decide when to perform a re-evaluation check, and how many times a re-evaluation check should be executed before the transmission of a packet. This study evaluates for the first time the impact of two standard strategies on the operation and performance of NR V2X mode 2. The evaluation demonstrates that the two strategies offer a balance between transmission latency and computational cost. We then propose an alternative re-evaluation check strategy that can simultaneously reduce the transmission latency and computational cost without actually degrading the reliability of NR V2X mode 2 transmissions.

Connected Automated Vehicles (CAVs) can utilize V2X communications to exchange their driving intentions and coordinate maneuvers. Previous studies have shown that maneuver coordination can improve traffic efficiency and safety. However, these studies focus on specific scenarios with a limited number of vehicles. Large-scale evaluations with complex interactions among vehicles are necessary to fully recognize the impact of maneuver coordination and to understand how to effectively design and conFigure maneuver coordination. This study progresses the state-of-the-art with a large-scale evaluation of lane change maneuver coordination in a highway scenario. We show how maneuver coordination impacts the traffic distribution and improves traffic fairness. Our study also highlights the need to consider safety when designing maneuver coordination and demonstrates that the coordination triggering conditions impact the execution of the coordination and their spatiotemporal distribution.

Automated driving is now possible in diverse road and traffic conditions. However, there are still situations that automated vehicles cannot handle safely and efficiently. In this case, a Transition of Control (ToC) is necessary so that the driver takes control of the driving. Executing a ToC requires the driver to get full situation awareness of the driving environment. If the driver fails to get back the control in a limited time, a Minimum Risk Maneuver (MRM) is executed to bring the vehicle into a safe state (e.g., decelerating to full stop). The execution of ToCs requires some time and can cause traffic disruption and safety risks that increase if several vehicles execute ToCs/MRMs at similar times and in the same area. This study proposes to use novel C-ITS traffic management measures where the infrastructure exploits V2X communications to assist Connected and Automated Vehicles (CAVs) in the execution of ToCs. The infrastructure can suggest a spatial distribution of ToCs, and inform vehicles of the locations where they could execute a safe stop in case of MRM. This paper reports the first field operational tests that validate the feasibility and quantify the benefits of the proposed infrastructure-assisted ToC and MRM management. The paper also presents the CAV and roadside infrastructure prototypes implemented and used in the trials. The conducted field trials demonstrate that infrastructure-assisted traffic management solutions can reduce safety risks and traffic disruptions.

Connected and automated vehicles (CAVs) are expected to make use of Vehicle-to-Everything (V2X) communication to exchange sensor and trajectory data. Using this data, CAVs can coordinate their maneuvers for safer and more efficient driving. ETSI and SAE are currently working to define standards for maneuver coordination and cooperative driving. The current approach at ETSI is based on a distributed solution where vehicles use Vehicle-to-Vehicle (V2V) communication to exchange their planned and desired trajectories. This study evaluates the potential benefits of the ETSI Maneuver Coordination Service to improve the traffic speed using a unique simulation tool. To do so, we first evaluate the impact of maneuver coordination on the vehicles involved in a coordination process. We also evaluate the effects of maneuver coordination on the overall traffic compared to scenarios without coordination. Our study shows that maneuver coordination can yield significant benefits to traffic mobility, however these improvements are intimately linked to the surrounding traffic environment and the specifications of the coordinated maneuver. This highlights the need for more detailed studies on the design of maneuver coordination protocols that should consider the vehicular context when executing and configuring the coordination process.

5G offers high flexibility at the radio, transport and core networks to support various services of critical verticals such as connected and automated driving. At the Radio Access Network (RAN), 5G defines a New Radio (NR). 5G NR utilizes different subcarrier spacing, slot durations, modulations and channel coding schemes. This flexibility offers the possibility to support automotive services with different and demanding requirements, such as Advanced Driver-Assistance System (ADAS), cooperative driving, and remote driving. Previous studies showed that 5G NR can be configured to achieve latencies below 2 ms. However, existing studies are generally restricted to scenarios with a limited number of users and unlimited bandwidth. Therefore, it is important to analyze whether 5G NR can effectively support these services as the network scales under limited spectrum allocations. This study advances the current state of the art to demonstrate that the capability of 5G NR RAN to support advanced V2X services depends on the RAN configuration (subcarrier spacing, slot duration and error protection) and network load.

Factories are evolving into fully digitalized and networked structures for more adaptive and agile production ecosystems in the context of the Industry 4.0. Wireless communications will be a technical pillar of this evolution as it improves the reconfigurability of factories and the integration of mobile robots and objects. The integration of industrial wireless networks into the Industry 4.0 requires solutions capable to support highly reliable and deterministic low latency communications. This is particularly challenging for mobile industrial applications with constantly changing link quality conditions. This article experimentally evaluates for the first time the capacity of diversity and redundancy to improve the reliability and latency of wireless networks for mobile industrial applications. To this aim, a prototype is built in a collaborative robotics experimental facility. The prototype wirelessly connects a dual-arm robot and a mobile robot that collects and supplies components to the dual-arm robot. The prototype implements redundancy and diversity (using multipath TCP) for the wireless connections between both robots. The conducted trials show that both techniques improve the reliability of mobile industrial wireless communications even under the presence of interference. However, redundancy achieves lower latency levels and represents then the most attractive solution to support mobile industrial applications.

Connected and automated vehicles will enable advanced traffic safety and efficiency applications thanks to the dynamic exchange of information between vehicles, and between vehicles and infrastructure nodes. Connected vehicles can utilize IEEE 802.11p for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. However, a widespread deployment of connected vehicles and the introduction of connected automated driving applications will notably increase the bandwidth and scalability requirements of vehicular networks. This paper proposes to address these challenges through the adoption of heterogeneous V2V communications in multi-link and multi-RAT vehicular networks. In particular, the paper proposes the first distributed (and decentralized) context-aware heterogeneous V2V communications algorithm that is technology and application agnostic, and that allows each vehicle to autonomously and dynamically select its communications technology taking into account its application requirements and the communication context conditions. This study demonstrates the potential of heterogeneous V2V communications, and the capability of the proposed algorithm to satisfy the vehicles' application requirements while approaching the estimated upper bound network capacity.

Time Sensitive Networking (TSN) is becoming the standard Ethernet-based technology for converged networks of Industry 4.0 due to its capacity to support deterministic latency requirements. However, it cannot provide the required flexibility to support mobile industrial applications required for the factories of the future. This could be enabled through the integration of wireless technologies in factories, and in particular of 5G and Beyond networks since they have been designed to support ultra-reliable and low-latency communications. This has triggered significant interest to integrate 5G and TSN networks, and first frameworks for such integration have been defined. However, the work is at early stages and the solutions to effectively integrate the two networks so that 5G can support TSN QoS levels are yet to be designed. This paper discusses current research and standardization work on 5G-TSN integration, and quantifies for a closed loop control application the 5GS bridge delay. The paper uses an example based on 5G-ACIA [1] to discuss open technical and research challenges to effectively integrate 5G and TSN.

Vehicular networks are based on the wireless exchange of information between vehicles and between vehicles and road side units. To avoid overloading the radio channel, different distributed congestion control mechanisms have been proposed in the literature. A widely adopted mechanism to control congestion is packet rate control. It controls the number of packets that each vehicle transmits to the radio channel through packet dropping. Packet dropping has been shown to effectively improve the radio communications performance thanks to the reduction of the channel load and packet collisions. However, from the application perspective, packets dropped by congestion control mechanisms are not transmitted and are therefore lost. This paper demonstrates for the first time that, while packet dropping can improve the performance at the radio level, it degrades the performance at the application level. This raises the question on whether current congestion control protocols based on packet dropping are actually suitable for vehicular networks.

Cooperative perception (or cooperative sensing or collective perception) enables connected and automated vehicles to exchange sensor data in order to improve their perception of the driving environment. ETSI is currently developing a standard for collective perception. The standard defines the message format and generation rules. These rules identify when a message should be transmitted and what information it should include. This study shows first that the current ETSI solution generates many redundant collective perception messages that increase the channel load and can compromise the networks' scalability. Unnecessary redundancy can reduce the reliability of V2X (Vehicle to Everything) communications and ultimately decrease the effectiveness of collective perception. This study proposes a modification of the current ETSI solution to control redundancy and avoid the transmission of unnecessary CPM data or messages. The evaluation shows that our proposal significantly reduces the redundancy and channel load and improves the reliability of V2X communications compared to current ETSI solution for collective perception. This is achieved while maintaining the perception achieved by ETSI for the safety-critical short and medium distances.

5G networks can support the development of the Industry 4.0. To this aim, 5G must be able to guarantee the deterministic latency requirements that characterize many industrial applications. This objective can be achieved using network slicing, a novel 5G paradigm that exploits the softwarization of networks to create different logical instances of the network over a common network infrastructure. Each instance is configured to support specific applications. Slicing can be applied at the Core Network or at the Radio Access Network (RAN). This study focuses on RAN slicing since the RAN typical accounts for a large part of the end-to-end delay. RAN slicing splits (and configures) resources at the RAN level between the slices in order to adequately serve nodes with a particular profile. This includes identifying the necessary radio resources per slice. To date, most proposals define slices in terms of the number of required radio resources. While this descriptor can account for bandwidth or rate requirements, it does not adequately reflect the latency requirements characteristic of many Industry 4.0 applications. This paper proposes a novel latency-based RAN slice descriptor and demonstrates that the new descriptor improves the capacity of RAN slicing to meet the latency requirements of Industry 4.0 applications with deterministic periodic traffic.

Connected and automated vehicles can exploit V2X communications to coordinate their maneuvers and improve the traffic safety and efficiency. To support such coordination, ETSI is currently defining the Maneuver Coordination Service (MCS). The current approach is based on a distributed solution where vehicles coordinate their maneuvers using V2V (Vehicle-to-Vehicle) communications. This paper proposes to extend this concept by adding the possibility for the infrastructure to support cooperative maneuvers using V2I (Vehicle-to-Infrastructure) communications. To this aim, we propose a Maneuver Coordination Message (MCM) that can be used in cooperative maneuvers with or without road infrastructure support. First results show the gains that cooperative maneuvers can achieve thanks to the infrastructure support. This paper also analyses and discusses the need to define MCM generation rules that decide when MCM messages should be exchanged. These rules have an impact on the effectiveness of cooperative maneuvers and on the operation and scalability of the V2X network.

Collective Perception (CP) or cooperative sensing enables vehicles and infrastructure nodes to exchange sensor information to improve their perception of the driving environment. CP enables vehicles to detect objects (e.g. non-connected vehicles, pedestrians, obstacles, etc.) beyond their local sensing capabilities. ETSI is currently developing the European standards for collective perception or cooperative sensing. This includes defining which information should be exchanged about the detected objects, and how often it should be exchanged. To this aim, different CP generation rules for collective perception are currently under analysis, and this paper presents an in-depth analysis of their performance and efficiency. The conducted analysis highlights the existing tradeoffs between performance (capacity to detect surrounding objects) and efficiency (redundant detection and transmission of the same detected objects). It also demonstrates the need to design advanced policies that dynamically control the redundancy on the wireless channel while ensuring the capacity to reliably detect the driving environment.

Industry 4.0 will interconnect and digitalize traditional industries to enable smart and adaptable factories that efficiently utilize resources and integrate systems. A key enabler of this paradigm is the communications infrastructure that will support the ubiquitous connectivity of cyber-physical production systems. The integration of wireless networks will facilitate the dynamic reconfiguration of the factories of the future, and the collection and management of large amounts of data. This vision requires reliable and low latency wireless links with the necessary bandwidth to support data intensive applications and spatio-temporal variations of data resulting from the reconfiguration of Industrial IoT (Internet of Things) systems. To this aim, this paper proposes a load balancing scheme that dynamically manages the wireless links based on their quality and the amount of data to be transmitted by each node. The proposed scheme avoids the saturation of channels, and significantly augments the reliability of industrial wireless networks in comparison with existing solutions.

Industrial wireless communications will be an important technology enabler for the Industry 4.0 paradigm. However, the pervasive introduction of wireless communications in factories requires improving their reliability and capacity to support low latency communications. An approach to do so is through the introduction of redundancy. Several studies have analytically and through simulations demonstrated the benefits of exploiting redundancy in industrial wireless communications. This paper progresses the current state of the art by experimentally analyzing for the first time the benefits that redundancy in industrial wireless communications can provide to support mobile industrial applications. The analysis has been conducted in a collaborative robotics experimental facility under the framework of the H2020 AUTOW ARE project.

The 3GPP has released the C-V2X standard to support V2X (Vehicle-to-Everything) communications using the LTE sidelink PC5 interface. This standard includes two modes of operation, and this study focuses on the Mode 4. This mode does not require the support of the cellular infrastructure, and vehicles can autonomously select their sub-channels for their V2V transmissions. The adequate operation of C-V2X Mode 4 requires a careful configuration of its main parameters. This study analyzes the optimum configuration of the parameters that mostly influence the operation and performance of C-V2X or LTE-V Mode 4. This analysis is conducted for different channel loads and traffic conditions. The conclusions obtained are compared with existing studies taking into account the importance of using accurate models for adequately configuring the C-V2X Mode 4 interface.

V2X deployments using IEEE 802.11p have already been announced, and the 3GPP has published the first Cellular V2X standard based on LTE-V. The limitations of IEEE 802.11p and LTE-V, and the increasing requirements of enhanced V2X applications, raise the question of whether existing V2X standards can provide the reliability levels required to support large scale deployments and the introduction of connected automated driving. Redundancy (two or more V2X links) can increase the reliability, but the gains can be limited if the various links are correlated. IEEE 802.11p and LTE-V utilize sensing-based scheduling schemes, and their MAC errors can hence be correlated since they both suffer packet collisions due to the hidden terminal problem. To address this limitation, this paper proposes the design of multi-link V2X communications where the operation of a link is adjusted with the information received through the other link. This approach is applied in this paper to design an IEEE 802.11p-assisted LTE-V scheduling scheme for multi-link and multi-RAT V2X communications. The proposed scheme is designed to increase the reliability of V2V communications in intersections under NLOS conditions.

Device-to-Device (D2D) communications can increase the spectral efficiency of future cellular networks when sharing part of the cellular spectrum. Radio resource allocation mechanisms are then necessary to control the interference that D2D and cellular transmissions can generate to each other. Most of the existing allocation schemes rely on the knowledge of the channel gain of all possible links between cellular and D2D nodes. This paper proposes to reduce the complexity cost and signalling overhead of the allocation process by using location information available at the network level. Using this information, the base station assigns radio resources to new D2D transmissions with the objective to control and limit the interference to the primary cellular users and existing D2D transmissions. The proposed radio resource allocation scheme continuously monitors that the user QoS requirements are satisfied. If it is not the case, it dynamically modifies the resource allocation to the interfering D2D transmissions. The proposed scheme achieves performance levels similar to that obtained with an optimized centralized allocation scheme, but with a significantly lower complexity cost and signaling overhead.

The 3GPP has recently published the first version of the Release 14 standard that includes support for V2V communications using LTE sidelink communications (referred to as LTE-V, LTE-V2X, LTE-V2V or Cellular V2X). The standard includes a mode (mode 4) where vehicles autonomously select and manage the radio resources without any cellular infrastructure support. This is highly relevant since V2V safety applications cannot depend on the availability of infrastructure-based cellular coverage, and transforms LTE-V into a possible (or complimentary) alternative to 802.11p. The performance of LTE-V in mode 4 is highly dependent on its distributed scheduling protocol (sensing-based Semi-Persistent Scheduling) that is used by vehicles to reserve resources for their transmissions. This paper presents the first evaluation of the performance and operation of this protocol under realistic traffic conditions in urban scenarios. The evaluation demonstrates that further enhancements should be investigated to reduce packet collisions.

The IEEE 802.11p standard has been created for vehicle to vehicle and vehicle to infrastructure communications. Vehicular networks require vehicles to periodically broadcast beacons in order to detect nearby vehicles or road infrastructure nodes and exchange critical information. The IEEE 802.11p standard defines different data rates that can be used for such transmissions, but 6 Mbps has been generally assumed as the default data rate. Limited efforts have been conducted to date to demonstrate whether 6 Mbps is the optimum data rate or not. This study addresses this issue, and demonstrates by means of simulations and field experiments that 6 Mbps is not (always) the optimum data rate for beaconing in vehicular networks. The conclusions are validated in both urban and highway environments.

Device-centric wireless networks, including Device-to-Device communications and Multi-hop Cellular Networks, are expected to be a relevant component of future 5G wireless networks. Traditionally, opportunistic networking has been proposed for disconnected networks that cannot always reliably ensure real-time end-to-end connections. However, previous studies have demonstrated that opportunistic schemes can also be utilized in connected networks to improve their efficiency by intelligently exploiting context- and content-awareness. In this context, this paper proposes and evaluates a mechanism to select the adequate configuration of opportunistic cellular communications in single-hop and multi-hop cellular networks. To this aim, the mechanism probabilistically identifies for each communications mode the adequate times for cellular transmissions to take place in order to reduce the cellular channel occupancy and improve its capacity. The obtained results show that the proposed scheme reduces the channel occupancy of cellular transmissions for delay-tolerant information by up to 70% compared to conventional single-hop cellular communications.

Device-centric wireless networks, and in particular Multi-hop Cellular Networks (MCN), can improve the capacity and efficiency of wireless networks, and will hence represent a significant element of the 5G ecosystem. Additional gains can be achieved for mobile delay tolerant services when integrating opportunistic networking in device-centric wireless networks. This paper proposes a solution for such integration that is evaluated for the case of 2-hop uplink opportunistic MCN communications. The proposed solution takes into to account the fact that mobile relays might not always be available at the optimum location and time instant, and the fact that sufficient cellular radio resources might not be available when mobile relays want to start forwarding the information towards the base station. The conducted study shows that the proposed scheme can reduce the energy consumption by more than 80% compared to traditional single-hop cellular communications.

Relaying technologies can help address the capacity and energy-efficiency challenges faced by cellular networks as a result of the rapid increase in mobile data consumption. A non-negligible portion of such consumption corresponds to delay tolerant services. This delay tolerance offers the possibility for opportunistic networking to exploit contact opportunities between mobile devices in order to reduce the impact of data traffic on the cellular capacity and energy-efficiency without sacrificing the end-user quality of service. In this context, this paper investigates the use of opportunistic forwarding in MCN-MR (Multi-hop Cellular Networks with Mobile Relays) to reduce energy consumption in the case of delay tolerant services. The study proposes to exploit context information provided at a low cost by the cellular infrastructure to efficiently select the forwarding node in a two-hop MCN-MR scenario. The proposed solution results in significant energy savings compared to traditional single-hop cellular communications and other forwarding solutions reported in the literature.

Multi-hop Cellular Networks using Mobile Relays (MCN-MRs) are being investigated to help address certain limitations of traditional single-hop cellular communications. The MCN-MR benefits depend on the probability to find adequate mobile relays, and on the design of mode selection schemes capable to identify the optimum connection mode. The probability to find adequate mobile relays can be significantly enhanced for delay tolerant services through the adoption of mobile opportunistic networking that exploits the store, carry and forward paradigm. In this context, this paper proposes and evaluates the first mode selection scheme that integrates opportunistic networking into MCN-MR. The obtained results demonstrate that the proposed scheme helps achieve the expected QoS and energy benefits that opportunistic networking can bring to multi-hop cellular networks.

Wireless industrial communications are expected to represent an essential component of the Factories of the Future. Current industrial wireless standards have been designed for networks with fixed devices, while future systems might require the mobility of certain devices within a factory. The neighbour discovery mechanism is an important feature of wireless standards for facilitating the mobility of devices. WirelessHART includes a contention-based neighbour discovery mechanism that is not particularly suited for efficiently discovering mobile devices. In this context, this paper proposes a new protocol, called Listen Advertise Network Neighbour Discovery (LAN-ND) that improves the neighbours' detection probability of WirelessHART, and reduces the average time needed to detect new neighbour devices.

Wireless communications will play a key role in the development of the Factories of the Future. Most applications are initially foreseen to manage and control industrial processes and equipment. However, wireless industrial communications can also have a major impact in improving the workers' health and safety conditions. To demonstrate such impact, this paper presents an heterogeneous wireless industrial testbed and the implementation of two safety use cases (collision avoidance and working at height). The use cases have been tested in a factory where the potential of wireless industrial communications to improve health and safety has been demonstrated.

Cooperative ITS systems are expected to highly improve the efficiency of road mobility. Wireless communications are used by these systems to disseminate centralized real-time traffic information to radio-equipped vehicles. Current proposals for traffic information dissemination either exploit dedicated cellular transmissions to interested vehicles, or cooperatively relay the information through vehicular ad-hoc networks. However, dedicated cellular transmissions may pose energy cost and traffic scalability issues to network operators. On the contrary, purely ad-hoc solutions may suffer from network disconnections and not always ensure adequate service reliability. To overcome these limitations, this paper introduces RoAHD, a hybrid approach in which a few messages injected through the cellular system are followed by a cooperative multi-hop dissemination in the vehicular network. RoAHD exploits multi-hop road connectivity information obtained at a low channel cost. Thanks to this knowledge, it is capable to operate smart injection decisions to ensure good levels of message delivery.

The study and design of Joint Radio Resource Management (JRRM) techniques is a key and challenging aspect in future heterogeneous wireless systems where different Radio Access Technologies (RAT) will physically coexist. In these systems, the total available radio resources need to be used in a coordinated way to guarantee adequate satisfaction levels to all users, and maximize the system revenues. In addition to carry out an efficient use of the available radio resources, JRRM algorithms need to exhibit good computational performance to guarantee their future implementation viability. In this context, this paper proposes novel JRRM techniques based on linear programming techniques, and investigates their computational cost when implemented in DSP platforms commonly used in mobile-based stations. The obtained results demonstrate the feasibility to implement the proposed JRRM algorithms in future heterogeneous wireless systems.

Wireless communication technologies will represent an essential technological component of the Factories of the Future in order to facilitate the real-time monitoring of the industrial processes, as well as the working conditions and the workers' health and safety. To this aim, wireless sensor networking technologies are being evolved to overcome the industrial challenging propagation environments and guarantee the strict QoS requirements characterizing industrial applications. However, a major future demand for wireless industrial systems could be the capability to support mobility. In this context, this paper analyzes the impact of mobility on the performance of industrial wireless communication systems based on a centralized management like the WirelessHART standard.

Many ICT-based future industrial applications will require the localization of machines, devices or even workers. This work presents the experimental implementation, evaluation and optimization of an RSSI-based localization solution using IEEE 802.15.4 wireless sensor networks. The localization accuracy is analysed under different densities of deployed reference nodes. The paper also proposes a simple optimization process that helps improving the localization accuracy.

Improving the workers' health and safety should be a key priority in the design and development of the Factory of the Future concept. To this aim, ICT and wireless communication technologies in particular, can represent very valuable tools to implement distributed and mobile sensing applications capable to continuously sense the working environment and the workers' health and safety conditions. However, the harsh propagation conditions that can characterise industrial environments can complicate the efficient and reliable deployment of wireless solutions in factories. In this context, this paper evaluates the reliability and connectivity of heterogeneous wireless technologies that can be used for implementing fixed and mobile sensing applications.

Cooperative vehicular systems have been identified as a promising solution to overcome the current and future needs for increasing traffic safety and efficiency, while providing infotainment and added-value services on the move. To achieve their objectives, cooperative vehicular systems will be based on wireless communications between vehicles and with other infrastructure nodes, and will have to deal with highly dynamic nodes, challenging propagation conditions, and stringent application requirements. By looking at cooperative applications and their data traffic, as well as the current and foreseen spectrum allocations for cooperative vehicular systems, there is a risk that the corresponding radio channels could easily be saturated if no control algorithms are used. The saturation of the radio channels would result in unstable vehicular communications, and thus in an inefficient operation of cooperative systems. As a prime example of upcoming ubiquitous networks contributing to the vision of “a thousand radios per person,” cooperative vehicular systems need to be designed to scale to high densities of radios without centralized coordination, while at the same time guaranteeing the requirements of the implemented applications and services, for example the stringent needs of active traffic safety applications. In this paper, we survey and classify various decentralized methods to control the load on the radio channels and to ensure each vehicle's capacity to detect and communicate with the relevant neighboring vehicles, with a particular focus on approaches based on transmit power and rate control. Finally, we discuss the open research challenges that are imposed by different application requirements and potential existing contradictions.

Heterogeneous wireless systems are envisaged as the integration and joint cooperative management of diverse radio access networks and technologies through which network providers can satisfy the wide variety of user/service demands in a more efficient manner by exploiting their varying characteristics and properties. To achieve this objective, a key tool is common radio resource management technique designed to jointly manage the radio resources from different radio access technologies. In this context, this work proposes and optimizes new common radio resource management techniques designed to efficiently distribute traffic among the available radio access technologies while providing adequate quality of service levels under heterogeneous traffic scenarios. The obtained results demonstrate the ability of the proposed solutions to provide high user/service satisfaction levels while adequately exploiting the overall system resources.

The wide scale deployment of cooperative vehicular ad-hoc networks will require the design of efficient congestion control policies that guarantee stable and reliable communications between vehicles and with infrastructure nodes. These policies should reduce the load on the communications channel, while satisfying the strict application's reliability requirements. To this aim, this letter proposes and evaluates a contextual cooperative congestion control policy that exploits the traffic context information of each vehicle to reduce the channel load, while satisfying the vehicular applications requirements.

Cooperative vehicular systems are being developed to improve traffic safety and management. Reducing road traffic congestion can be achieved through effective management strategies. In this sense, mechanisms for its rapid and accurate detection that allow evaluating the road network performance are crucial. Current Intelligent Transportation Systems (ITS) require the deployment of infrastructure sensors to monitor traffic conditions. Their installation is often expensive and their capability to provide accurate traffic information is limited. In this context, this paper proposes CoTEC (COperative Traffic congestion detECtion), a novel cooperative technique based on Vehicle-to-Vehicle (V2V) communications and fuzzy logic to detect road traffic congestion without the need to deploy infrastructure sensors. The proposed technique is also capable to accurately detect the traffic congestion intensity and length.

Multi-hop Cellular Networks have recently emerged as a promising technology to overcome the current limitations of cellular systems through the integration of cellular and ad-hoc networking technologies. Several studies have addressed the challenges of Multi-hop Cellular Networks based on Mobile Relays, and demonstrated their performance and potential to improve the user-perceived Quality of Service. However, most of these studies are based on analytical and simulation techniques, and there is yet the need for field tests that confirm their performance. In this context, this paper introduces a novel testbed to investigate Multi-hop Cellular Networks using Mobile Relays through field testing. In addition, this paper also presents the first field test results that demonstrate the performance improvements that can be achieved with Multi-Hop Cellular Networks over traditional cellular systems.

MCN-MR (Multi-hop Cellular Network - Mobile Relay) has been proposed as a promising technology for future Beyond 3G and 4G systems due to its foreseen capacity to increase transmission rates and provide homogeneous quality of service levels in the service area. To this aim, mobile nodes are required to cooperate in the relaying of information of other nodes. As a result, selfish nodes refusing to relay packets can have damaging effects on the overall multi-hop connectivity of MCN-MR networks. Different reputation protocols have been already proposed to cope with selfishness in mobile ad-hoc networks, but they tend to overestimate the selfish behavior of nodes, due to the effects of radio errors or packet collisions that can be mistaken for intentional packet drops. Thus, the availability of valid multi-hop routes usable by nodes is reduced. In this context, this paper proposes and evaluates two techniques that improve the operation and ability to accurately detect selfish nodes of the watchdog detection mechanism that is generally employed in reputation based selfishness prevention protocols.

The European Union (EU) Framework Program 7 (FP7) funded project, iTETRIS [1] (An Integrated Wireless and Traffic Platform for Real-Time Road Traffic Management Solutions) targets to extend state of art in simulation of wireless vehicular cooperative systems for evaluation of road traffic management services and applications. In particular, iTETRIS addresses four important and distinct challenges: (a) road traffic and wireless integrated open-source simulation platform, (b) large scale trials, (c) realistic Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communication simulation and (d) dynamic, distributed and self-autonomous Intelligent Transport Systems (ITS) [2] applications based on cooperative systems. iTETRIS will provide a standard compliant, open-source integrated communication and traffic platform suited for large scale scenario simulation. This Paper addresses extension of traffic simulator being used in iTETRIS, scalability studies of networking simulator, which have been achieved as project results. Further the paper presents the adaptation of the Intelligent Communications for Transport Systems (ICTS) [2] reference architecture functionalities being developed by the European Telecommunication Standard Institute (ETSI) at its Technical Committee (TC) on ITS.

Multi-hop wireless mesh networks, including multi-hop cellular networks, base their operation on the establishment of multi-hop paths to route the information from source to destination. To this aim, it is crucial to define adequate neighbor selection techniques that choose the most appropriate nodes over which to route the information. In this context, this paper proposes a set of neighbor selection techniques that exploit spatial diversity to improve the performance and operation of multi-hop wireless mesh networks.

Multi-hop Cellular Networks using mobile relays require efficient multi-hop networking protocols that provide a high end-to-end performance and reduce the terminal's energy consumption. In this context, this paper proposes a set of novel multi-hop routing protocols that exploit the location of the destination node to reduce their network signalling and overall energy consumption. These two aspects are crucial factors to progress towards the future implementation of Multi-hop Cellular Networks based on mobile relays.

The design of efficient Common Radio Resources Management (CRRM) techniques is a crucial aspect to enable the foreseen coexistence and cooperation of heterogeneous Radio Access Technologies in Beyond 3G wireless networks. In this context, this paper proposes a set of CRRM strategies designed to satisfy multimedia users with diverse QoS requirements while efficiently using the radio resources.

Wireless vehicular communication systems require the design and implementation of robust and efficient communication policies to provide the strict quality of service needed by traffic safety applications while guaranteeing the system's scalability. To efficiently guarantee such requirements, the authors have developed an opportunistic-driven adaptive radio resource management mechanism that adapts the transmission parameters based on the operating conditions and traffic safety requirements. Since the performance of adaptive communication techniques can be importantly influenced by channel correlation, this work proposes several compensation policies that allow the proposed opportunistic mechanism to efficiently meet the traffic safety quality of service requirements even under correlated radio channels.

Beyond 3G wireless systems will be composed of a variety of radio access technologies (RATs) with different, but also complementary, performance and technical characteristics. To exploit such diversity while guaranteeing the interoperability and efficient management of the different RATs, common radio resource management (CRRM) techniques need to be defined. This work proposes and evaluates a CRRM policy that simultaneously assigns to each user an adequate combination of RAT and number of radio resources within such RAT to guarantee its QoS requirements. The proposed CRRM technique is based on linear objective functions and programming tools.

Vehicle-to-vehicle and vehicle-to-infrastructure wireless communications are currently under development to improve traffic efficiency and safety. Routing protocols enabling multi-hop communications represent a major technology for information dissemination within vehicular ad-hoc networks. The high node's mobility and propagation conditions experienced by vehicle-to-vehicle communications require a careful routing protocol design to ensure its successful operation and performance under realistic environments. To this aim, this paper analyses the impact and importance of adequately considering physical layer effects to correctly quantify a routing protocol's performance, and understand its networking operation.

The adoption of wireless vehicular communication technologies would strongly depend on the technologies transmission reliability, required by QoS demanding traffic safety applications, and the system's scalability as the technology is gradually introduced. To this aim, this work proposes the use of opportunistic transmission policies that dynamically adapt the transmission parameters based on the operating conditions and potential traffic safety risks. The work analyses different configuration proposals with the aim to meeting the strong traffic safety QoS requirements, while maximizing the technology's robustness and minimising channel congestion, which in turn is crucial to guarantee the future system's scalability.

Wireless Communications Systems are at the centre of a new and passionate era for telecommunications characterised, in industrial terms, by the convergence of systems and technologies, a transition towards all-IP networks, and the development of technologies with a user-centric focus. On the other hand, in terms of Research and Development, researchers are already considering other, more futuristic, aspects beyond those just mentioned, and these days hot topics include things like the Internet of the Future, and all the Post-IP perspectives that come with it. In both grounds, that is the more industrial related one and the one nearer an academic perspective, there is still a long way to go, before many of the ideas being discussed today can see the light of day as a commercial product. In this context, the International Symposium on Wireless Communication Systems (ISWCS) has positioned itself as a dynamic forum for researchers and technologists to present and discuss original ideas and contributions in all fields related to mobile and wireless communication systems. ISWSC'06, the 3rd edition, held in Valencia, Spain, on September 2006, brought together leading and enthusiastic researchers and technologists, willing to identify and discuss the future technical challenges and business opportunities arising in the path towards the realisation of ambient wireless communication networks. Besides this, it was a good forum for Ph.D. students to present their work, and exchange their ideas. The idea of setting up a special issue of a journal with the very best papers of the conference was brought up by the excellent quality of some papers presented at the conference. The objective of a special issue of this kind is always to put together, beyond the conference proceedings, the best papers in an enhanced and revised version, enabling the journal to publish good papers with timely updated information in a very short time. This special issue of Wireless Communications and Mobile Computing contains the very best papers presented at ISWCS'06. An invitation was sent to a restricted number of papers, and an additional review procedure was held, beyond the conference one. At the end, this set of six papers was accepted. The papers in this issue address some of the hot topics being investigated these days, ranging from localisation and frequency sharing to multi carrier-code division multiple access (MC-CDMA) and multiple input multiple output (MIMO). This shows that the physical layer still attracts a lot of attention, and that it still has a lot of topics to be explored. The first two papers address MIMO channels, in modelling or measurement perspectives. Matthias Pätzold and Bjørn Olav Hogstad present a model for a wideband MIMO channel based on the geometric elliptical scattering one, which can be used as a starting point for the derivation of a frequency-selective space–time channel simulator, being also useful for studying MIMO channel capacity under various propagation conditions. Michail Matthaiou et al. bring a paper on dual frequency MIMO measurements around the ISM 2.4 GHz band, in indoor environments, with initial results being promising enough, as the joint spectra seem to be remarkably similar, implying that the underlying propagation mechanisms at the considered bands are also similar. Farrukh Rashid and Athanassios Manikas present one of the papers dealing with MC-CDMA, namely on arrayed reception in space-time diffused multipath vector channels; results show that the use of a diffused channel modelling in arrayed receivers yields better bit error rate (BER) and signal to noise plus interference ratio (SNIR) performance than receivers that ignore the presence of spatial and/or temporal diffusion. The other paper on MC-CDMA, from Nguyen Tran Khoa et al., addresses frequency sharing in hotspot communications for cellular networks; it proposes an overlap in the uplink of an OFDM hotspot system to an MC-CDMA cellular one, in the same frequency band, beam-forming being applied to eliminate inter-system interference. The paper for Barbara Mavì Masini et al. also deals with the coexistence of different systems, in particular on the benefits of diversity schemes for Bluetooth coverage extension in the presence of IEEE 802.11g interference, analysing packet error and coverage probabilities, among other parameters. Finally, Joseph Shmuel Picard and Anthony Joseph Weiss present a paper addressing localisation of networks using various ranging bias models, presenting a set of iterative algorithms that cope successfully with the various bias models and provide Maximum Likelihood position estimates.

In this paper an efficient scheduling mechanism for wireless local area networks (WLAN) is proposed. This innovative scheme, named hybrid HCCA-EDCA centralised scheme (HHE-CS), is based on the hybrid coordination function (HCF) protocol introduced by the IEEE 802.11e standard. The HHE-CS aims at satisfying the user quality of service (QoS) demands for real time (RT) services with variable bit rate while maximising the throughput of best effort users. This paper proves conclusively that an adequate allocation of downlink and uplink traffic between EDCA and HCCA increases system performance as compared with more traditional schemes in which all best effort traffic is exclusively delivered by a distributed mechanism like EDCA.

Vehicle-to-vehicle and vehicle-to-infrastructure wireless systems are currently under development to improve the traffic safety and efficiency while providing Internet connectivity on the move. A widespread adoption of these wireless vehicular communication technologies will require an efficient use of the radio channel resources. To this end, this work proposes and analyses an opportunistic-driven adaptive radio resource management scheme that achieves the target traffic safety performance and efficiently uses the transmission and channel resources.

Multi-channel operation in wireless systems has been proposed to increase user throughput and reduce transmission delays. However, multi-channel operation requires adequate resource allocation policies to guarantee user fairness and avoid channel access stagnation. The definition of such policies is particularly challenging in heterogeneous traffic scenarios where each traffic service has different quality of service requirements. In this context, this work proposes and evaluates various multi-channel radio resource distribution policies designed to operate under heterogeneous traffic environments. In particular, this paper proposes the application of bankruptcy policies to guarantee user fairness, and compares their performance to other schemes. The proposed policies can also be extended to manage radio resources in heterogeneous wireless systems.

This paper evaluates the effect of the channel estimation inaccuracy on the performance of an HSDPA system. This study provides some results from system level simulations that have been conducted over a very complete dynamic simulator which models an HSDPA system full compliant with specifications. This emulator allows performing multi-user transmission and link adaptation with a limited modulation and coding scheme (MCS) selection based on the channel quality indicator (CQI) modes. Many factors such as the user equipment (UE) speed, the employed scheduling algorithm or the traffic load have been considered in the assessment. Moreover the intrinsic constraints of a WCDMA system like HSDPA have been also taken into account, i.e. the maximum number of channelization codes and the maximum transmitted power have been modelled jointly with a complete and dynamic interference characterization.

The use of wireless vehicular communication systems for traffic safety applications imposes a careful and adequate communications dimensioning to ensure the transmission of broadcast safety messages in a timely manner. To date, several studies have proposed an adaptive dimensioning of the inter- vehicle communication protocols based on the particular operating conditions of the transmitting vehicles. This work complements these initial investigations by proposing and demonstrating the need to dimension such communication protocols not only based on the operating conditions but also on the vehicular context. By modifying the communication parameters based on the presence of nearby vehicles, the proposed context-based communications dimensioning reduces the risk of chain collisions.

The paper presents and evaluates a link adaptation algorithm for real-time video transmission within a mobile radio environment. The aim of the algorithm is to improve performance, not only in terms of throughput, but also in terms of delay. The results show that the objectives set by the proposed algorithm are more effectively fulfilled compared to more traditional algorithms aimed at system throughput optimisation.

The General Packet Radio Service (GPRS) is due to be implemented in current mobile networks, introducing a whole new range of mobile data applications and services. Considerable effort has been devoted to test its capabilities and system performance. In this paper, a modular and high-speed GPRS simulator is presented. In order to validate the simulation method, the GPRS link layer performance is assessed. The performance, for a single slot packet data channel, is evaluated in a typical urban environment for a range of mobile velocities. The impact of frequency hopping on link quality measures is also evaluated.