In IEEE 802.11be multi-link operation, transmissions occur simultaneously over multiple links that typically support different rates due to channel impairments and variability. Combining multi-link operation with frame aggregation can lead to suboptimal medium utilization, due to inefficient assignment of frames across the links. In this letter, we thoroughly investigate this matter and introduce a time-balancing technique, implemented through a low-complexity algorithm, that accounts for channel differences and aggregates frames to achieve roughly equal and minimized transmission times across the links. Simulation results show that the proposed technique enhances throughput and delay performance up to 23% and 17%, respectively, particularly under high-load traffic conditions.

IEEE 802.11bd is a modern standard in the Vehicle-to-Everything (V2X) domain, designed to address the evolving demands of vehicular communications. Building on its predecessor IEEE 802.11p and considering today’s stringent communication requirements, IEEE has crafted a robust communication tool introducing the next-generation vehicle-to-everything (NGV) station. This involves significant modifications in the physical (PHY) and the medium access control (MAC) layers. This paper explores the new IEEE 802.11bd standard highlighting its predecessor’s limitations. The major PHY and MAC layer characteristics are elucidated to aid newcomers and facilitate a comprehensive comparison between the two standards. Finally, the paper underscores the impact of IEEE 802.11bd on contemporary V2X use cases and scenarios, offering concise explanations of its role in each case.

The multi-link operation (MLO) feature, introduced in IEEE 802.11be, allows wireless local area networks (WLANs) to reach high transmission rates needed to support the more demanding contemporary and future targeted use cases. However, the implications of MLO on energy consumption and energy efficiency have not been widely studied. This work investigates the energy consumption for IEEE 802.11be networks composed of battery-operated devices employing MLO. Different configurations are considered for the number of links used for transmission, the incoming traffic rates, and the number of served devices. Via extensive simulations, we analyze the average energy consumption per device and how it is split among the various transmission phases, as well as the average energy per bit. Throughput results are also provided for context. The results are compared with those obtained with the legacy single link operation (SLO). Overall, the energy consumed per device increases when using more than one link. However, from an energy per bit consumption point of view, further analysis was necessary. Thus, we investigate how the per device energy consumption is affected by the total network traffic. In particular, we found that when the network is in a saturated condition, MLO is the best choice, providing a lower energy per bit consumption than SLO, especially when employing three links. However, for low traffic conditions and with fewer devices in the network, SLO achieves a slightly better energy per bit, which makes this configuration suitable for specific applications.

In this work, we design a reconfigurable intelligent surface (RIS) through an analytical path-loss (PL) model, which describes its behaviour in both near- and far-field regimes. At first, we reconsider the well established path loss model for intelligent reflecting surfaces, which has been recently presented in the literature, in terms of polarization. In particularly, we introduce a piecewise function for the radiation element pattern, which varies according to the polarization of the incident field. Next, we combine an optimization algorithm and PL simulations for designing a RIS with reduced sidelobe level that is valid for both polarizations. By adding nulls in specific angles of the farfield scattering pattern we demand reduced lobe level over a wide range of angles.

This work introduces a non-orthogonal multiple access (NOMA) scheme suitable for low-rate ultra-reliable low-latency communication (URLLC) and enhanced mobile broadband (eMBB) services multiplexing in downlink communication. Tailored to minimize mutual interference, URLLC information is conveyed via a modified index modulation (IM) scheme on top of quadrature amplitude modulation (QAM) transferring eMBB traffic. Aiming at providing a proof of concept of the proposed scheme, we calculate the bit error rate of both services over Rayleigh fading with diversity, as well as the eMBB service achievable rate with typical multi-input multi-output (MIMO) configuration when the URLLC service utilizes space–time coding or diversity. The proposed scheme achieves a low bit error rate for the URLLC IM signal, at the cost of a lower information rate, while affecting the performance of the eMBB user mainly due to power sharing among the IM and QAM signals. To further investigate the feasibility of the proposed scheme, we calculate the transmission energy required by the base station to support both services over a typical cellular channel model, for various service requirements and user distances, in comparison to an orthogonal multiple access (OMA) puncturing scheme utilizing time-multiplexing of QAM for the eMBB traffic and BPSK for the URLLC traffic. Overall, our results show that the proposed scheme attains better performance compared to the puncturing scheme and offers a robust solution with easy user pairing for low-rate URLLC and typical eMBB downlink service multiplexing for 5G communications and beyond.

In recent years, advances in immersive multimedia technologies, such as extended reality (XR) technologies, have led to more realistic and user-friendly devices. However, these devices are often bulky and uncomfortable, still requiring tether connectivity for demanding applications. The deployment of the fifth generation of telecommunications technologies (5G) has set the basis for XR offloading solutions with the goal of enabling lighter and fully wearable XR devices. In this paper, we present a traffic dataset for two demanding XR offloading scenarios that substantially extend those available in the current state of the art, captured using a fully developed end-to-end XR offloading solution. We also propose a set of accurate traffic models for the proposed scenarios based on the captured data, accompanied by a simple and consistent method to generate synthetic data from the fitted models. Finally, using an open-source 5G radio access network (RAN) emulator, we validate the models both at the application and resource allocation layers. Overall, this work aims to provide a valuable contribution to the field with data and tools for designing, testing, improving, and extending XR offloading solutions in academia and industry.

We present a consistent approach for a systematic design of an intelligent reflecting surface (IRS), based on a new unit cell with efficient reconfigurability functionalities and a three-step electromagnetic methodology for a rigorous IRS synthesis. First, we design and simulate a reconfigurable unit cell, in which the reconfigurability is accomplished by varactor diodes. Next, we model the IRS as a periodic structure of infinite size, according to Floquet theory. By utilizing the theory of anomalous reflection, we arrive at approximate analytical solutions to calculate the set of necessary varactor diodes' capacitances, which is subsequently fine-tuned by a fast optimization process to achieve enhanced operation. Finally, to arrive at a more realistic design, we properly analyze the IRS as a finite-sized structure. To this end, we employ an efficient finite element method (FEM) analysis, with a properly developed simulation tool, in which the IRS is modeled as an equivalent impedance sheet of zero-thickness. Overall, we extract the far-field scattered pattern of the IRS and evaluate the angular and frequency response of the design for normal and oblique incidence. Our results show that the proposed design exhibits very promising characteristics, both in terms of reconfigurability and frequency response that can be exploited in contemporary and future wireless communication systems.

The upcoming IEEE 802.11be standard aims to provide extremely high bitrates to support next generation use cases. Among the proposed features, multi-link operation (MLO) is probably the one contributing most towards this goal. MLO enables new types of devices, i.e., multi-link devices (MLDs), to transmit simultaneously over multiple frequency bands to achieve massive bitrates (reaching 40 Gbps) and, consequently, lower latency. However, the coexistence of MLDs with legacy devices in existing and future wireless local area network (WLAN) deployments has not yet been explicitly investigated. In this work, we investigate different band management policies over a three-band densely populated WLAN, allowing MLDs to use one or more bands for the access procedure and data transfer. We evaluate, via extensive simulations, the access delay of the devices and the network throughput with respect to the ratio of legacy devices and MLDs. We show that by using different band allocation policies for MLDs, several trade-offs regarding throughput and access delay arise that need careful consideration to avoid performance degradation.

In this chapter, the use of massive open online courses (MOOCs) for the dissemination, training capabilities and learning of telecommunication engineering is described taking as example the successful MOOC ‘Ultra- Dense Networks for 5G and its Evolution’ developed under the European innovative training network (ITN) TeamUp5G. MOOCs are usually understood as a way of teaching or learning for massive potential students. Indeed, this is the main goal of any MOOC. However, we also propose its use for training and dissemination. The ITN TeamUp5G is a training network for 15 PhD students of seven different institutions (universities and companies) where the students make research on different interconnected topics for the common goal of Ultra dense networks for 5G. At the same time they researched, they prepared a MOOC to disseminate their most recent advances and their challenges. For the MOOC, they needed to collect their thoughts, organizse their knowledge and establish a common vision of the whole system. The cooperative work, the cross-related meetings and, the preparation of all the materials for the MOOC were very interesting and useful in their training process. The whole experience of designing and creating the MOOC is described in detail along with the challenges and lessons learned.

Nowadays is not possible to avoid considering the coexistence and the fusion of different wireless technologies as completely separated entities. The ever-growing number of devices employing multi-RATs (Radio Access Technologies) that require continuous wireless connectivity is posing great challenges. Furthermore, the requirements in terms of both throughput and latency originated by the use cases, are pushing the current technologies to their limits, especially for indoor dense deployments that are usually covered by Wi-Fi. The IEEE 802.11 Working Group is currently tackling such challenges by working on a new amendment of the standard (namely 802.11be), which introduces, among other novelties, the multi-link operation (MLO). Through MLO, the target is to achieve simultaneous transmission over multiple bands to obtain massive bitrate up to 40 Gbps. The introduction of MLO poses challenges on the coexistence with older legacy devices in mixed networks. This contribution explores how the coexistence of legacy IEEE 802.11 devices and new IEEE 802.11be devices realizing the proposed multi-link feature can be improved by using an appropriate static band assignment policy. Another issue is how the overall network behaves when varying the number of devices and the legacy/new nodes ratio. Simulations for three different band allocation cases close to reality are developed. Performance results in terms of aggregated, average throughput and fairness are derived for different conditions.

The increase of the adoption of IoT devices and the contemporary problem of food production have given rise to numerous applications of IoT in agriculture. These applications typically comprise a set of sensors that are installed in open fields and measure metrics, such as temperature or humidity, which are used for irrigation control systems. Though useful, most contemporary systems have high installation and maintenance costs, and they do not offer automated control or, if they do, they are usually not interpretable, and thus cannot be trusted for such critical applications. In this work, we design Vital, a system that incorporates a set of low-cost sensors, a robust data store, and most importantly an explainable AI decision support system. Our system outputs a fuzzy rule-base, which is interpretable and allows fully automating the irrigation of the fields. Upon evaluating Vital in two pilot cases, we conclude that it can be effective for monitoring open-field installations.

This article reports on a research case study about raising the motivation of young boys and girls (14-16 years old) toward science, technology, engineering, and math (STEM) education to increase their prospects of choosing a relevant career. Using the Internet of Things (IoT) at the core of a design-based methodology, multiple implementations of IoT-oriented educational scenarios (ESs) were realized in different educational contexts. More than 150 secondary students and nine teachers, in seven different settings, were involved in an integrated educational framework with hands-on activities and teamwork. Using a concrete evaluation methodology exploiting both quantitative and qualitative data collected before, during, and after the interventions, we analyze the students' and teachers' experience to understand critical parameters and provide directions for successful ESs. Our findings show that the IoTbased ES realizations were successful overall and enhanced STEM career awareness and skills, with boys showing greater appreciation than girls. Different ES timeframes resulted in different conclusions, while proper organization and preparation in all aspects involved in the realization are critical.

This work studies the influence of IoT-driven educational activities and tools (software, hardware and educational material) in STEM education as well as their role as STEM related career enablers to young boys and girls. The study builds on previous related results and applies to over 60 young students that are involved in hands-on learning activities in the context of a summer school. The analysis is based on especially designed close-ended and open-ended questionnaires as well as in-class observations and focuses on age and gender aspects. The results confirm the overall positive stance of the students on the educational activities and show that the provided tools under consideration are well accepted and effectively used. Furthermore, students' choices regarding prospective future careers reveal that their views on STEM fields and related professions have significantly been enriched through their participation in the summer school.

Wi-Fi is the dominant way of connecting indoor mobile devices to the Internet. The main reason behind the huge adoption of this technology is the simplicity of the IEEE 802.11 protocols, which offer low-cost ownership and maintenance combined with the ability to provide high data rates to end users. The increasing demand in traffic volumes leads to the continuous deployment of access points (APs), resulting in densification of the IEEE 802.11 networks. This densification, instead of enhancing the efficiency of wireless local area networks (WLANs), degrades their overall performance due to cochannel interference between overlapped basic services sets (OBSSs). One of the main goals of the IEEE 802.11ax amendment now under development is to address the WLAN densification problem by improving spatial reuse (SR).

In this chapter, a multi-layer ATM architecture is proposed for the interconnection of current and future mobile communications nodes. Consisting of different ATM node types with respect to switching capability, the proposed architecture is adapted to current 2G and evolving 3G systems as well as future 4G wireless systems, as a common and shared backbone transmission network interconnecting core and access nodes between each other and Internet or PLMN/PSTN. Moreover, facing the huge expansion of transmission interconnection network that will support current and future generation mobile communications, a modification of the standard ATM cell structure is introduced in order to efficiently support user mobility functional procedures. The proposed ATM architecture is integrated over a suitable, with respect to region and capacity, physical interface, consisting of SDH or SONET for wide area topologies, wireless links for outdoor areas and LED-POF combination for indoor areas. Being an interesting alternative over copper or traditional fiber, POF characteristics and performance issues are analyzed.

Internet of Things and other state-of-the-art technologies like mobile and ubiquitous computing present ample opportunities for developing novel solutions almost in every domain of modern life. The research work presented here aims to leverage on the potential of such technologies in the direction of enhancing learning practices in secondary level education and promoting positive attitudes towards the corresponding scientific and engineering disciplines. The originality of the proposed approach lies on the provision of an educational platform, framed by contemporary pedagogical principles, and with an aim to stimulate collaboration between the relevant stakeholders in the form of operational communities of practice. Such communities are brought together on the basis of participating in on line activities, problem solving, exchanging reflections and experiences in the context of educational scenarios that incorporate modern technologies. The platform development is discussed in terms of the underlined conceptual models, the defined stakeholders’ requirements, the on-line services developed, the software tools integrated and the data management supported. An example educational scenario, the corresponding IoT application developed and preliminary evaluation results of this approach are also reported.

Smart farming era has already begun and its societal and environmental implications are expected to be huge. In this context, the Internet of Things (IoT) technologies have become the major path forward towards novel farming practices. The unprecedented capability of data collection and management offered by IoT is based on several factors of the underlying communication network architecture and technology, one of the most important being the application level protocol that is used among IoT nodes, gateways, and application servers. This work offers an up-to-date survey of research efforts on the IoT application layer protocols, focusing on their basic characteristics, their performance as well as their recent use in agricultural applications. Furthermore, it provides a comparison among them, in terms of well-accepted key performance indicators and comments on their suitability in the framework of smart farming as well as the corresponding challenges that have to be faced towards their efficient implementation.

This paper presents and analyses a set of data that reveal secondary education students’ stance on the educational activities that were realised during a UMI (ubiquitous, mobile computing and the Internet of Things) Summer School. This Summer School deals with an IoT based recycling management application development and is part of UMI-Sci-Ed project that provides a training framework on UMI learning, for students aged between 14–16, with the use of properly designed educational scenarios and communities of practice (CoP) by setting UMI technologies as learning means and learning outcomes, simultaneously. The analysis focuses on the students’ satisfaction and engagement (observed through a set of questionnaires) in relation with students’ potential to follow the activities, the perceived, by the students, easiness, enjoyment and usefulness while setting as parameters the student gender and age. The results clearly show high student acceptability and engagement with the designed IoT-driven activities and reveal certain differentiations with respect to gender and age in these aspects. These findings, together with the observations that high student satisfaction does not translate to equally high engagement and that enjoyment is a critical factor, provide a basis for future adjustment of the educational scenarios and activities scope and design in order to enhance the UMI-Sci-Ed impact on student preference for a future career in the UMI technologies domain.

One of the major challenges that Wireless Local Area Networks (WLANs) are facing is to address dense scenarios, a case that is motivated by the continuous deployment of new Access Points (APs) to cover new areas and, thus, provide higher data rates. To address this challenge, which existing protocols cannot meet, the High-Efficiency WLAN (HEW) group is currently working on a new high throughput amendment named IEEE 802.11ax. In this paper, we introduce an Interference Based Dynamic Channel Access (IB-DCA) algorithm that enhances spatial reuse. We then evaluate our algorithm against the existing channel access algorithm as well as the Dynamic Sensitivity Control (DSC) and Adaptive Transmit Power Control (ATPC) algorithms that are proposed by the HEW group for various density WLAN scenarios.

Recent natural disasters have revealed that emergency networks presently cannot disseminate the necessary disaster information, making it difficult to deploy and coordinate relief operations. These disasters have reinforced the knowledge that telecommunication networks constitute a critical infrastructure of our society, and the urgency in establishing protection mechanisms against disaster-based disruptions. Hence, it is important to have emergency networks able to maintain sustainable communication in disaster areas. Moreover, the network architecture should be designed so that network connectivity is maintained among nodes outside of the impacted area, while ensuring that services for costumers not in the affected area suffer minimal impact. As a first step towards achieving disaster resilience, the RECODIS project was formed, and its Working Group 1 members conducted a comprehensive literature survey on “strategies for communication networks to protect against large-scale natural disasters,” which is summarized in this article.