This paper investigates sum-rate maximization for reconfigurable intelligent surface (RIS)-assisted device-to-device (D2D) networks, while ensuring that the energy constraints of the wireless nodes are satisfied. The formulated problem involves the joint optimization of the phase-shifts of the RIS reflecting elements (passive beamforming) and the transmit power control for each transmitter. Given the highly non-convex nature of this optimization problem, obtaining its global optimal solution is non-trivial. To this end, we propose a new algorithm that leverages fractional programming and penalty dual decomposition techniques to obtain a high-quality sub-optimal solution. Our numerical results highlight the superiority of the proposed algorithm, as it consistently achieves substantially higher sumrates in comparison to the benchmark schemes.

With the massive deployment of Internet of Things (IoT) devices in sixth-generation networks, several critical challenges have emerged, such as large communication overhead, coverage limitations, and limited battery lifespan due to high energy consumption. Federated learning (FL), wireless power transfer (WPT), multi-antenna access point (AP), and reconfigurable intelligent surfaces (RIS) can mitigate these challenges by reducing the need for large data transmissions, enabling sustainable energy harvesting, and optimizing the propagation environment. Compared to conventional RIS, simultaneously transmitting and reflecting (STAR)-RIS not only extends coverage from half-space to full-space but also improves energy saving through appropriate mode selection. Motivated by the need for sustainable, low-latency, and energy-efficient communication in large-scale IoT networks, this paper investigates the efficient STAR-RIS mode in the uplink and downlink phases of a WPT-FL multi-antenna AP network with non-orthogonal multiple access to minimize energy consumption, a joint optimization that remains largely unexplored in existing works on RIS or STAR-RIS. We formulate a non-convex energy minimization problem for different STAR-RIS modes, i.e., energy splitting (ES) and time switching (TS), in both uplink and downlink transmission phases, where STAR-RIS phase shift vectors, beamforming matrices, time and power for harvesting, uplink transmission, and downlink transmission, local processing time, and computation frequency for each user are jointly optimized. To tackle the non-convexity, the problem is decoupled into two subproblems: the first subproblem optimizes STAR-RIS phase shift vectors and beamforming matrices across all WPT-FL phases using block coordinate descent over either semi-definite programming or Rayleigh quotient problems, while the second one allocates time, power, and computation frequency via the one-dimensional search algorithms or the bisection algorithm. Simulation results demonstrate that TS STAR-RIS in both uplink and downlink transmissions achieves the lowest energy consumption, outperforming ES and conventional RIS schemes due to its flexible phase shift adaptation and lower interference levels.

WiFi-enabled Internet-of- Things (IoT) devices are evolving from mere communication devices to sensing instru-ments, leveraging Channel State Information (CSI) extraction capabilities. Nevertheless, resource-constrained IoT devices and the intricacies of deep neural networks necessitate transmitting CSI to cloud servers for sensing. Although feasible, this leads to considerable communication overhead. In this context, this paper develops a novel Real-time Sensing and Compression Network (RSCNet) which enables sensing with compressed CSI; thereby reducing the communication overheads. RSCNet facilitates op-timization across CSI windows composed of a few CSI frames. Once transmitted to cloud servers, it employs Long Short-Term Memory (LSTM) units to harness data from prior windows, thus bolstering both the sensing accuracy and CSI reconstruction. RSCNet adeptly balances the trade-off between CSI compression and sensing precision, thus streamlining real-time cloud-based WiFi sensing with reduced communication costs. Numerical findings demonstrate the gains of RSCNet over the existing benchmarks like SenseFi, showcasing a sensing accuracy of 97.4 % with minimal CSI reconstruction error. Numerical results also show a computational analysis of the proposed RSCNet as a function of the number of CSI frames.

Traditional human-designed medium access control (MAC) protocols cannot tackle the heterogeneous requirements of the future 6G wireless networks. Reinforcement learning (RL) algorithms have been proposed, in which base stations (BSs) and user equipment's (UEs) act as agents to automatically learn the MAC protocols to satisfy the stringent quality of service (QoS) requirements of 6G networks. However, existing RL techniques result in a generalization issue where agents fail to identify and explore useful information in a sparse wireless environment. To tackle this challenge, we propose a cooperative multi-agent exploration (CMAE) framework in which the network state space is projected into a low-dimensional space instead of learning a policy in a high-dimensional space. Consequently, the agents start exploring from low-dimensional state space to high-dimensional space to learn the abstracted information from the wireless environment. In the proposed framework, the nodes and BSs collaborate to explore the under-explored wireless network states to jointly learn the channel access and signalling policy. Simulation results show that the proposed CMAE framework outperforms traditional baseline schemes in terms of good put and collision rate and has better generalization capabilities.

With the increasing development and deployment of new systems for efficient and clean mobility, Electric Vehicles (EVs) are becoming more and more common among people. Those produce large amounts of data streams that need to be collected and analyzed to understand user needs and improve their performance. For this purpose, Artificial Intelligence (AI) techniques are playing a very important role. Within this context, Kafka-ML is a Machine Learning (ML) framework that enables the consumption and processing of data streams and allows the flexible management and deployment of neural networks throughout their entire life cycle. Kafka-ML can work with Distributed Neural Networks (DNN) which reduce latency and response times, perform incremental training over time allowing models to adapt to data on the fly, and carry out Federated Learning (FL) processes for this type of algorithms so a more robust global model can be created while maintaining data privacy and security, but all this separately. This work has considered the joint implementation of FL, for anonymous data sharing, incremental learning for continuous training of the models, and DNN for distribution of the models across different points on the map. All this applied within a Vehicle-to-everything (V2X) domain where EV usage and charge data can be shared to improve the user experience, as well as to better understand the behavior of this type of vehicles and their charging points to achieve savings, and how it affects people daily lives. An evaluation of the system related to this EV use case is presented to demonstrate the viability of the tool.

This paper considers minimizing the age-of-information (AoI) and transmit power consumption in a vehicular network, where a roadside unit (RSU) provides timely updates about a set of physical processes to vehicles. We consider non-orthogonal multi-modal information dissemination, which is based on superposed message transmission from RSU and successive interference cancellation (SIC) at vehicles. The formulated problem is a multi-objective mixed-integer nonlinear programming problem; thus, a Pareto-optimal front is very challenging to obtain. First, we leverage the weighted-sum approach to decompose the multi-objective problem into a set of multiple single-objective sub-problems corresponding to each predefined objective preference weight. Then, we develop a hybrid deep Q-network (DQN)-deep deterministic policy gradient (DDPG) model to solve each optimization sub-problem respective to predefined objective-preference weight. The DQN optimizes the decoding order, while the DDPG solves the continuous power allocation. The model needs to be retrained for each sub-problem. We then present a two-stage meta-multi-objective reinforcement learning solution to estimate the Pareto front with a few fine-tuning update steps without retraining the model for each sub-problem. Simulation results illustrate the efficacy of the proposed solutions compared to the existing benchmarks and that the meta-multi-objective reinforcement learning model estimates a high-quality Pareto frontier with reduced training time.

In this paper, we consider a simultaneous transmitting and reflecting (STAR)-reconfigurable intelligent surface (RIS)-assisted multi mobile-edge-computing (MEC) system, where servers can be placed on both sides of the STAR-RIS and each device offloads a part of its computational tasks to the MEC servers. Specifically, we formulate a weighted-sum computing and communication latency minimization problem to jointly optimize the offloading data volume, edge computing resource of servers, multi-user detection (MUD) matrices, as well as energy splitting coefficients and phase-shifts of the STAR-RIS in the presence of coupling between transmission and reflection phase shifts. Using block coordinate descent (BCD), we decompose the computing and communication problems and solve them in an iterative manner through alternating optimization. We show that the optimal offloading volume can be given by establishing the equivalence of the local computing latency and edge computing latency of servers. Also, we proved that the edge resource allocation problem is jointly convex in both the transmit and reflect MEC resources. Therefore, the optimal MEC resources can be found using KKT conditions and the bisection search method. Numerical results demonstrate the effectiveness of the proposed STAR-RIS-enabled multi-MEC system in terms of obtained latency and convergence compared to the conventional benchmarks.

In this paper, the analysis for the average bit error probability (ABEP) of a dual-hop fixed-gain relay network is conducted. To this end, we consider two different scenarios: 1) the second hop (relay- destination link) is subject to composite multipath/shadowing and the first hop (source-relay link) experiences only multipath fading; 2) the first hop is perturbed by the composite multipath/shadowing and the second hop undergoes only multipath fading. We develop new and exact closed-form expressions of the ABEP for the first scenario in terms of the Meijer-G and Lommel functions. Since the exact closed-form expressions for the second scenario are mathematically intractable, we derive a new approximation and bounds. These approximation and bounds are shown to be tight for medium to high average signal-to-noise ratio (SNR) regime. In addition, we also provide new and relatively simpler asymptotic expressions of the ABEP for both the scenarios. It is shown that some physical insights (e.g., diversity order) of the system can readily be obtained by using these asymptotic expressions. All our analytical results are corroborated by the Monte-Carlo simulations.

Opportunistic relaying is an efficient way of acheiving diversity in wireless cooperative communication systems. In this paper, we analyze the performance of a proactive opportunistic non-regenerative relaying protocol, considering both maximum ratio combining (MRC) and selection combining (SC) schemes at the destination. We derive a closed-form expression for the cummulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) in the presence of Nakagami-m fading and a SC receiver. Utilizing this statistical result, we then derive a new closed-form expression for average symbol error probability (ASEP), valid for many generic modulations, assuming identical integer fading parameters. Furthermore, we also derive a new closed-form expression for the moment generating function (MGF) of the end-to-end SNR considering Nakagami-m fading environment and MRC at the destination. Moreover, using the MGF-based approach, we derive and analyze new closed-form expressions for ASEP when MRC is employed at the destination.