On the Fundamental Limits of Random Non-orthogonal Multiple Access in Cellular Massive IoT

Machine-to-machine (M2M) constitutes the communication paradigm at the basis of Internet of Things (IoT) vision. M2M solutions allow billions of multi-role devices to communicate with each other or with the underlying data transport infrastructure without, or with minimal, human intervention. Current solutions for wireless transmissions originally designed for human-based applications thus require a substantial shift to cope with the capacity issues in managing a huge amount of M2M devices. In this paper, we consider the multiple access techniques as promising solutions to support a large number of devices in cellular systems with limited radio resources. We focus on non-orthogonal multiple access (NOMA) where, with the aim to increase the channel efficiency, the devices share the same radio resources for their data transmission. This has been shown to provide optimal throughput from an information theoretic point of view.We consider a realistic system model and characterise the system performance in terms of throughput and energy efficiency in a NOMA scenario with a random packet arrival model, where we also derive the stability condition for the system to guarantee the performance.Comment: To appear in IEEE JSAC Special Issue on Non-Orthogonal Multiple Access for 5G System

Beta-Conversion, Efficiently

Type-checking in dependent type theories relies on conversion, i.e. testing given lambda-terms for equality up to beta-evaluation and alpha-renaming. Computer tools based on the lambda-calculus currently implement conversion by means of algorithms whose complexity has not been identified, and in some cases even subject to an exponential time overhead with respect to the natural cost models (number of evaluation steps and size of input lambda-terms). This dissertation shows that in the pure lambda-calculus it is possible to obtain conversion algorithms with bilinear time complexity when evaluation is carried following evaluation strategies that generalize Call-by-Value to the stronger case required by conversion

A low complexity resource allocation algorithm for multicast service delivery in OFDMA networks

Allocating and managing radio resources to multicast transmissions in Orthogonal Frequency-Division Multiple Access (OFDMA) systems is the challenging research issue addressed by this paper. A subgrouping technique, which divides the subscribers into subgroups according to the experienced channel quality, is considered to overcome the throughput limitations of conventional multicast data delivery schemes. A low complexity algorithm, designed to work with different resource allocation strategies, is also proposed to reduce the computational complexity of the subgroup formation problem. Simulation results, carried out by considering the Long Term Evolution (LTE) system based on OFDMA, testify the effectiveness of the proposed solution, which achieves a near-optimal performance with a limited computational load for the system

Analysis of a contention-based approach over 5G NR for Federated Learning in an Industrial Internet of Things scenario

The growing interest in new applications involving co-located heterogeneous requirements, such as the Industrial Internet of Things (IIoT) paradigm, poses unprecedented challenges to the uplink wireless transmissions. Dedicated scheduling has been the fundamental approach used by mobile radio systems for uplink transmissions, where the network assigns contention-free resources to users based on buffer-related information. The usage of contention-based transmissions was discussed by the 3rd Generation Partnership Project (3GPP) as an alternative approach for reducing the uplink latency characterizing dedicated scheduling. Nevertheless, the contention-based approach was not considered for standardization in LTE due to limited performance gains. However, 5G NR introduced a different radio frame which could change the performance achievable with a contention-based framework, although this has not yet been evaluated. This paper aims to fill this gap. We present a contention-based design introduced for uplink transmissions in a 5G NR IIoT scenario. We provide an up-to-date analysis via near-product 3GPP-compliant network simulations of the achievable application-level performance with simultaneous Ultra-Reliable Low Latency Communications (URLLC) and Federated Learning (FL) traffic, where the contention-based scheme is applied to the FL traffic. The investigation also involves two separate mechanisms for handling retransmissions of lost or collided transmissions. Numerical results show that, under some conditions, the proposed contention-based design provides benefits over dedicated scheduling when considering FL upload/download times, and does not significantly degrade the performance of URLLC

Fixed-Mobile Convergence in the 5G era: From Hybrid Access to Converged Core

The availability of different paths to communicate to a user or device introduces several benefits, from boosting enduser performance to improving network utilization. Hybrid access is a first step in enabling convergence of mobile and fixed networks, however, despite traffic optimization, this approach is limited as fixed and mobile are still two separate core networks inter-connected through an aggregation point. On the road to 5G networks, the design trend is moving towards an aggregated network, where different access technologies share a common anchor point in the core. This enables further network optimization in addition to hybrid access, examples are userspecific policies for aggregation and improved traffic balancing across different accesses according to user, network, and service context. This paper aims to discuss the ongoing work around hybrid access and network convergence by Broadband Forum and 3GPP. We present some testbed results on hybrid access and analyze some primary performance indicators such as achievable data rates, link utilization for aggregated traffic and session setup latency. We finally discuss the future directions for network convergence to enable future scenarios with enhanced configuration capabilities for fixed and mobile convergence.Comment: to appear in IEEE Networ

L'Arabia Sud orientale nell'Età del Ferro. Analisi archeologica dei siti ed organizzazione degli spazi

Proposito della ricerca è stato quello di documentare la maggior parte delle realtà urbanistiche presenti in Arabia Sud orientale, attraverso l’analisi architettonico-planimetrica integrata ai dati archeologici presenti. L’inquadramento del periodo in esame, concerne anche le tappe evolutive di una configurazione cronologica solo apparentemente statica (Età del Ferro I, Età del Ferro II, Età del Ferro III), e la trattazione delle principali fonti epigrafiche. Durante l’Età del Ferro, l’emergere di una nuova cultura regionale, comune a tutta la penisola omanita, è particolarmente evidente rispetto alla precedente Tarda Età del Bronzo, in cui l’occupazione del territorio è scarsamente leggibile. I numerosi insediamenti, distribuiti lungo le principali vie di traffico e nelle oasi pedemontane, costituiscono la manifestazione di una società strutturalmente già formata, organizzata in piccoli villaggi, spesso dotati di mura perimetrali o ubicati in posizioni strategiche, all’interno o presso i quali erano presenti luoghi o edifici di rappresentanza collettiva. I caratteri generali di un’architettura principalmente legata alla dimensione domestica, sono stati integrati dall’analisi dei singoli siti, dalle tavole grafiche delle planimetrie relative, da immagini estratte da Google Earth, allo scopo di illustrare la realtà geomorfologica del territorio di ubicazione

RACH preamble repetition in NB-IoT network

NarrowBand-Internet of Things (NB-IoT) is a radio access technology recently standardized by 3GPP. To provide reliable connections with extended coverage, a repetition transmission scheme is applied in both Random Access CHannel (RACH) procedure and data transmission. In this letter, we model RACH in the NB-IoT network taking into account the repeated preamble transmission and collision using stochastic geometry. We derive the exact expression of RACH success probability under time correlated interference, and validate the analysis with different repetition values via independent simulations. Numerical results have shown that the repetition scheme can efficiently improve the RACH success probability in a light traffic scenario, but only slightly improves that performance with very inefficient channel resource utilization in a heavy traffic scenario

Study of Cardiac Features in Adults with Down Syndrome

Down Syndrome (DS) has a significant impact on the development of many tissues, most notably in the heart and in the brain. According to the clinical need to better investigate these aspects, the main aim of this study was to make an overview on the cardiac features in adult individuals with DS. The following data of 37 individuals with DS (range: 18-60 years) were collected and analysed: age, gender, height, weight, waist to height ratio (WHER), smoking history and cardiac parameters (heart rate and blood pressure), blood glucose level or glycaemia, cholesterol (total, high-density lipoprotein – HDL - and low-density lipoprotein - LDL - cholesterol) and triglycerides. In addition, their gait pattern were quantified with 3D Gait Analysis. BMI, WHER and cholesterol HDL results were above the upper limits of the recommended range in people with DS; on the contrary, blood pressure, heart rate, glycaemia, cholesterol-LDL and triglycerides were within the recommended range. Comparing males and females in the DS group, the females showed statistically different values for cholesterol-total, and triglycerides values, with lower values in comparison to males. In motor performance, people with DS presented abnormal gait patterns. Some significant correlations were found: age with LDL, WHER with weight and BMI, systolic with diastolic blood pressure, total cholesterol with LDL and triglycerides. Our results showed that adults with DS suffer from a high prevalence of physical disorders, including overweight and obesity, and abnormal cholesterol values, together with abnormal gait pattern