Spectral Efficiency of MIMO Millimeter-Wave Links with Single-Carrier Modulation for 5G Networks

Future wireless networks will extensively rely upon bandwidths centered on carrier frequencies larger than 10GHz. Indeed, recent research has shown that, despite the large path-loss, millimeter wave (mmWave) frequencies can be successfully exploited to transmit very large data-rates over short distances to slowly moving users. Due to hardware complexity and cost constraints, single-carrier modulation schemes, as opposed to the popular multi-carrier schemes, are being considered for use at mmWave frequencies. This paper presents preliminary studies on the achievable spectral efficiency on a wireless MIMO link operating at mmWave in a typical 5G scenario. Two different single-carrier modem schemes are considered, i.e. a traditional modulation scheme with linear equalization at the receiver, and a single-carrier modulation with cyclic prefix, frequency-domain equalization and FFT-based processing at the receiver. Our results show that the former achieves a larger spectral efficiency than the latter. Results also confirm that the spectral efficiency increases with the dimension of the antenna array, as well as that performance gets severely degraded when the link length exceeds 100 meters and the transmit power falls below 0dBW. Nonetheless, mmWave appear to be very suited for providing very large data-rates over short distances.Comment: 8 pages, 8 figures, to appear in Proc. 20th International ITG Workshop on Smart Antennas (WSA2016

Single-Carrier Modulation versus OFDM for Millimeter-Wave Wireless MIMO

This paper presents results on the achievable spectral efficiency and on the energy efficiency for a wireless multiple-input-multiple-output (MIMO) link operating at millimeter wave frequencies (mmWave) in a typical 5G scenario. Two different single-carrier modem schemes are considered, i.e., a traditional modulation scheme with linear equalization at the receiver, and a single-carrier modulation with cyclic prefix, frequency-domain equalization and FFT-based processing at the receiver; these two schemes are compared with a conventional MIMO-OFDM transceiver structure. Our analysis jointly takes into account the peculiar characteristics of MIMO channels at mmWave frequencies, the use of hybrid (analog-digital) pre-coding and post-coding beamformers, the finite cardinality of the modulation structure, and the non-linear behavior of the transmitter power amplifiers. Our results show that the best performance is achieved by single-carrier modulation with time-domain equalization, which exhibits the smallest loss due to the non-linear distortion, and whose performance can be further improved by using advanced equalization schemes. Results also confirm that performance gets severely degraded when the link length exceeds 90-100 meters and the transmit power falls below 0 dBW.Comment: accepted for publication on IEEE Transactions on Communication

Three-dimensional assessment on digital cast of spontaneous upper first molar distorotation after Ni-ti leaf springs expander and rapid maxillary expander: A two-centre randomized controlled trial

Abstract Objective: The aim of this randomized controlled trial (RCT) was to evaluate the spontaneous distorotation of upper first permanent molars and the transverse dentoalveolar changes on digital casts in growing patients following maxillary expansion treatment using either the Leaf Expander® or the rapid maxillary expander (RME), both anchored to the deciduous second molar. Trial Design and Setting: This study was a two-arm,parallel-assignment, RCT with a dual-centre design conducted at two teaching hospitals in Italy. Participants: Inclusion criteria included maxillary transverse deficiency, prepubertal development stage (cervical vertebra maturation stage [CVMS] 1–2) and early mixed dentition with fully erupted upper first permanent molars. Exclusion criteria were systemic diseases or syndromes, CVMS 3–6, agenesis of upper second premolars, unavailability of the second deciduous molar for anchorage and Class III malocclusion. Randomization: Patients were randomly assigned to the Leaf Expander® or RME group using a computer-generated randomization list created by a central randomization centre. Randomization was conducted immediately before the start of treatment. Intervention: The intervention involved treatment with either the Leaf Expander® or the RME. Both devices were anchored to the second deciduous molars. Following randomization, patients were further categorized based on the presence of no crossbite, unilateral crossbite or bilateral crossbite. Main Outcome Measure: The primary outcome measure was the distorotation of the upper first molar (U6). Secondary outcomes included measurements of interdental linear dimensions, specifically upper inter-canine width (53–63), upper inter-molar width (MV16–MV26) and upper inter-deciduous second molar width (55–65). Blinding: The examiner analysing the digital casts was blinded to the treatment groups to prevent detection bias and ensure objective assessment. However, due to the nature of the intervention, blinding was not feasible for the patients and clinicians involved in administering the treatment. Results: A total of 150 patients were enrolled and randomly assigned to two groups: 75 to the Leaf Expander® group and 75 to the RME group. Recruitment started in November 2021 and was completed in November 2022. At the time of analysis, the trial was complete with no ongoing follow-ups. ANOVA tests revealed no significant differences between the three subgroups (no-cross, unilateral-cross and bilateral-cross) within both the Leaf Expander® and RME groups at T0. The Leaf Expander® demonstrated significantly greater distorotation in the unilateral crossbite subgroup compared to the RME (p = .014). In terms of total molar distorotation, the Leaf Expander® appliance showed a significantly greater effect (12.66°) compared with conventional RME (7.83°). Linear regression analysis demonstrated a significant correlation between the extent of expansion and the degree of molar rotation. Conclusions: Maxillary expansion resulted in significant spontaneous molar distorotation when the appliance was bonded to the second deciduous molars. The Leaf Expander® exhibited significantly greater molar distorotation compared with conventional RME. The degree of molar distorotation was correlated with the extent of expansion obtained on the second deciduous molar. Trial Registration: The trial was registered at ClinicalTrials.gov (ID: NCT05135962)

On the use of multiple satellites to improve the spectral efficiency of broadcast transmissions

We consider the use of multiple co-located satellites to improve the spectral efficiency of broadcast transmissions. In particular, we assume that two satellites transmit on overlapping geographical coverage areas, with overlapping frequencies. We first describe the theoretical framework based on network information theory and, in particular, on the theory for multiple access channels. The application to different scenarios will be then considered, including the bandlimited additive white Gaussian noise channel with average power constraint and different models for the nonlinear satellite channel. The comparison with the adoption of frequency division multiplexing (FDM) is also provided. The main conclusion is that a strategy based on overlapped signals is convenient with respect to FDM, although it requires the adoption of a multiuser detection strategy at the receiver

Cone-Beam Computed Tomography (CBCT) Analysis of Mandibular Condyles’ Diameters in Patient with Juvenile Idiopathic Arthritis and Temporomandibular Joint Affection: A Cross-Sectional Investigation

The aim of this study was to evaluate through analysis using CBCT the transverse and axial diameters of the mandibular condyles in subjects affected by juvenile idiopathic arthritis (JIA) and compare them with those of healthy subjects. Methods: The study was conducted on CBCT scans from the digital archive of the Department of Biomedical Surgical and Dental Sciences, University of Milan, including patients with JIA and using healthy subjects as controls. Inclusion criteria: aged between 7 and 25 years old at the time of the CBCT examination; Caucasian ethnicity; diagnosis of JIA according to the International League of Associations for Rheumatology (ILAR) criteria documented in patients’ records; TMJ involvement; good quality CBCTs covering our region of interest (ROI), from the glabella to the mandibular inferior border; no previous orthodontic/ orthopedic treatment; no history of craniofacial trauma or congenital birth defects involving the craniofacial area. Each CBCT scan underwent examination using 3Diagnosys® software. Since data were normally distributed, parametric tests were used for analysis. The sample was divided into three groups: (1) bilateral JIA subjects, (2) unilateral JIA subjects, and (3) healthy controls. Results: We found a statistically significant reduction (p < 0.0001) in the transverse diameter (TR-Diam) of the affected condyles by an average of 1.7 mm, while the axial diameter (AX-Diam) again showed a slight reduction, on average by 0.1 mm, with a non-statistically significant value. Another comparison was made between the unaffected condyles of patients with unilateral JIA and the healthy condyles of the control group. The unilateral unaffected condyles were found to be slightly smaller than those of healthy patients, but without statistically significant differences. We found that in both JIA males and females, the condylar growth tends to stop earlier than the healthy ones. Conclusions: The transverse diameter was found to be more affected than the axial one, causing typical bone resorption and condylar shape. Moreover, we showed that the pathology, in the case of unilateral JIA, does not compromise only the affected condyles; the corresponding condyle that seems to be healthy is actually partially compromised. In addition, we observed that the growth of affected condyles of JIA subjects tends to stop earlier than the condyles of the healthy controls

Spontaneous Mandibular Dentoalveolar Changes after Rapid Maxillary Expansion (RME), Slow Maxillary Expansion (SME), and Leaf Expander—A Systematic Review

Abstract: Background: This systematic review aims to analyze the spontaneous dentoalveolar changes in the mandibular arch after maxillary expansion in growing patients obtained with different expansion protocols: Rapid Maxillary Expansion (RME), Slow Maxillary Expansion (SME), and Leaf Expander. Methods: The study adhered to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Eligibility criteria were established in the PICO format, involving patients who underwent slow, rapid, or leaf maxillary expansion during the mixed or early permanent dentitions. A comprehensive search of electronic databases and manual searches was conducted up to December 2023. The outcome measures included inter-mandibular first permanent molar width, inter-deciduous molar and canine width, arch perimeter, and arch length; both shortand long-term results were considered. The articles that met the inclusion criteria were included in this systematic review and were qualitatively evaluated using a methodological quality scoring system with a 13-point scale. To assess the inter-examiner agreement concerning the article selection and the qualitative assessment of the included studies, Kappa statistics were computed. Results: A total of 1184 articles were identified through electronic and manual searches. After the removal of duplicates and the initial examination of the titles and abstracts, 57 articles were considered for the full text analysis, and according to the eligibility and exclusion criteria, 22 studies were finally selected, composed of 8 randomized controlled trials (RCTs) and 14 retrospective/case-control studies. The qualitative assessment of the included studies showed the following scores: 6 papers have high research quality, 5 have moderate quality, and 11 have low quality. SME demonstrated negligible mandibular changes, with less than 1 mm variation on average (range 0.46–2.00 mm) in the selected parameters and relapses observed in the long term. RME induced more significant increases, particularly in intermolar width greater than 1 mm, which ranged between 0.93 and 3.3 mm, and good stability over the long term. Leaf Expander exhibited promising short-term lower intermolar width increases greater than 1 mm and ranged from 0.5 to 1.69 mm, but long-term stability was not thoroughly evaluated. Conclusions: SME results in negligible short- and long-term effects, while RME, especially with Haas-type appliances, exhibits significant intermolar width increases that remain stable over the years. Leaf Expander shows short-term lower intermolar width increases, requiring further investigation into long-term stability

A highly efficient receiver for satellite-based Automatic Identification System signal detection

An innovative receiver architecture for the satellitebased Automatic Identification System (AIS) has been recently proposed. In this paper, we describe a few modifications that can be introduced on the algorithms for synchronization and detection, that provide an impressive performance improvement with respect to the previous system. The receiver architecture has been designed for an on-board implementation, and for this reason all algorithms have been realized keeping the complexity as low as possible. A prototype for the proposed receiver has been implemented by the University of Parma and CGS S.p.A. Compagnia Generale per 10 Spazio under the ESA project FENICE

Advanced techniques for spectrally efficient DVB-S2X systems

We investigate different techniques to improve the spectral efficiency of systems based on the DVB-S2 standard, when the transmitted signal bandwidth cannot be increased because it has already been optimized to the maximum value allowed by transponder filters. We will investigate and compare several techniques to involve different sections of the transceiver scheme. The techniques that will be considered include the use of advanced detection algorithms, the adoption of time packing, and the optimization of the constellation and shaping pulses. The LDPC codes recently proposed for the evolution of the DVB-S2 standard will be considered, as well as the adoption of iterative detection and decoding. Information theoretical analysis will be followed by the study of practical modulation and coding schemes