1,721,015 research outputs found
Coverage analysis for 2D/3D millimeter wave peer-to-peer networks
Full text linkThis paper presents a theoretical analysis for estimating the coverage probability in two-dimensional (2D) and three-dimensional (3D) peer-to-peer (P2P) millimeter-wave (mmWave) wireless networks. The analysis is carried out adopting suitable link state models and realistic propagation conditions, involving path-loss attenuation, angular dispersion, mid- and small-scale fading, which comply with recent channel measurements. The presented framework accounts in detail for the actual shape of the transmitting/receiving antenna patterns and for the spatial statistic that describes the node location, by considering the widely adopted Poisson point process, the uniform distribution, and the random waypoint mobility model. Analytical expressions for the statistic of the received power and simple integral formulas for the coverage probability in the presence of interference and noise are derived. The accuracy of the obtained estimations and of the introduced approximations is checked by independent Monte Carlo validations. As possible applications in the 3D mmWave context, the conceived mathematical theory is used to discuss the impact of the interference model on the reliability of the noise-limited approximation, and to estimate the average link capacity of an interfered P2P communication
Segmented Framed Slotted Aloha (SFSA) with Capture and Interference Cancellation
No full textThis paper investigates the throughput of a Framed Slotted Aloha (FSA) random access scheme, called Segmented FSA (SFSA), in which each packet is encoded and subdivided into segments before the transmission, and where Interference Cancellation (IC) is adopted to improve the success probability in case of collision between segments. The overall system performance is estimated by considering a decoding criterion based on the average information rate that is experienced during each communication. This criterion, which enables to properly consider the capture effect in the presence of interference, noise, and fading, is compared to the classic packet erasure channel model, with the aim of identifying the reliability of the two decoding approaches in different network scenarios. The final purpose of the presented study is to discuss the benefits of the interference diversity mechanism that is triggered by the combination of segmentation and IC in a capture channel
Impact of Header on Coded Slotted Aloha with Capture
No full textAmong the recently proposed non-orthogonal multiple access techniques, the Coded Slotted Aloha (CSA) scheme has been identified as one of the most efficient ones. This scheme relies on the subdivision of a packet into segments and of a slot into slices, in order to enable the transmission of different segments in different slices. With respect to SA, the CSA implementation is more sophisticated, since the header of each segment must contain proper pointers specifying the slices where the other segments of that packet lie. Purpose of this paper is to investigate the impact of these pointers on the CSA throughput by properly considering the capture effect at the receiver. To this aim, a capture analysis accounting for the modulation and the header coding rate in the presence of Rayleigh fading is developed. The numerical results, which also involve a realistic millimeter-wave channel, show that the beneficial interference diversity effect introduced by the segmentation process is not significantly reduced by the overhead due to the pointers, thus confirming the practical usefulness of the CSA scheme
Explicitly Invertible Approximations of the Gaussian Q-Function: A Survey
Full text linkCommunications and information theory use the Gaussian -function, a positive and decreasing function, across the literature. Its approximations were created to simplify mathematical study of the Gaussian -function expressions. This is important since the -function cannot be represented in closed-form terms of elementary functions. In a noise model with the Gaussian distribution function and various digital modulation schemes, closed-form approximations of the Gaussian -function are used to predict a digital communications system's symbol error probability (SEP) or bit error probability (BEP). Another significant scenario pertains to fading channels, whereby it is important to accurately determine, through a closed-form expression, the precise evaluations of complex integrals involved in the computations of SEP or BEP. In addition to the aforementioned scenarios, it is imperative for a communications system designer to ascertain the requisite operational signal-to-noise ratio for the specific application, based on the target SEP (or BEP). In this scenario, the crucial role of the explicit invertibility of the Gaussian -function approximation is of significant importance in achieving this objective. In this paper we propose a survey of the approximations of the Gaussian -function found in the literature, reviewing also the approximations originally given for the 4 classical special functions related to it, restricting the analysis to the explicitly invertible ones, and classifying them on the basis of their accuracy (on the significant range), simplicity, and easiness of inversion, also distinguishing the bounds from approximations. We also list the inverses of some of them, already published or newly found in this research
Energy-constrained design of joint noma-diversity schemes with imperfect interference cancellation
Full text linkThis study proposes a set of novel random access protocols combining Packet Repetition (PR) schemes, such as Contention Resolution Diversity Slotted Aloha (CRDSA) and Irregular Repetition SA (IRSA), with Non Orthogonal Multiple Access (NOMA). Differently from previous NOMA/CRDSA and NOMA/IRSA proposals, this work analytically derives the energy levels con-sidering two realistic elements: the residual interference due to imperfect Interference Cancellation (IC), and the presence of requirements on the power spent for the transmission. More precisely, the energy-limited scenario is based on the relationship between the average available energy and the selected code modulation pair, thus being of specific interest for the implementation of the Internet of Things (IoT) technology in forthcoming fifth-generation (5G) systems. Moreover, a theoretical model based on the density evolution method is developed and numerically validated by extensive simulations to evaluate the limiting throughput and to explore the actual performance of different NOMA/PR schemes in energy-constrained scenarios
Coverage and Throughput Analysis for Peer-to-Peer 6G Directional Slotted Aloha Bursty Networks
Full text linkThis paper presents a theoretical framework for investigating the coverage and throughput behavior of sixth generation (6G) peer-to-peer (P2P) directional slotted Aloha (DirSA) networks managing bursty traffic flows. Proper channel models, accounting for interference, noise, path-loss, random node location, power fluctuation, and beam pointing error, are adopted to derive analytical expressions for the statistic of the received power in ground, air, and space propagation contexts. The resulting coverage probability, obtained in simple integral form for different omnidirectional/directional transmission/reception modes, is exploited to derive multidimensional Markov chains for estimating the throughput in the absence and in the presence of a feedback mechanism, considering also the impact of the initial access procedure and of the beam training overhead. The theoretical results, which are validated by exhaustive Monte Carlo simulations, are used to evaluate the influence of the code-modulation scheme, of the operating signal to interference plus noise ratio (SINR), and of the burst length on the performance of 6G terrestrial, aerial, and satellite P2P DirSA subnets
3D Poisson-Based Neighborhood Capacity Analysis for Millimeter Wave Communications
Full text linkThis paper proposes a theoretical model for evaluating the capacity of a millimeter wave (mmWave) source destination link when the nodes are distributed according to a three-dimensional (3D) homogeneous Poisson point process. In the presented analysis, different from the existing approaches, the destination lies in an arbitrary location with respect to the source; thus, the link performance can be evaluated for a neighbor of any order. Moreover, the developed model relies on a realistic propagation environment, characterized by path loss attenuation and shadowing in line of sight (LoS), non-LoS, and outage link state conditions. The derived formulas, which are calculated in closed-form and validated by independent Monte Carlo simulations, are used to investigate the influence of the intensity parameter, of the antenna gain, and of the mmWave frequency band on the link capacity for any possible neighbor in a practical 3D scenario
Exploiting capture and interference cancellation for uplink random multiple access in 5G millimeter-wave networks
Full text linkThe forthcoming 5G technology aims to provide massive device connectivity and ultra-high capacity with reduced latency and costs. These features will be enabled by increasing the density of the base stations, using millimeter-wave (mmWave) bands, massive multiple-input multiple-output systems, and non-orthogonal multiple access techniques. The ability to support a large number of terminals in a small area is in fact a great challenge to guarantee massive access. In this context, this paper proposes a new receiver model for the uplink of 5G mmWave cellular networks. The receiver, called Iterative Decoding and Interference Cancellation (IDIC), is based on the Slotted Aloha (SA) protocol and exploits the capture effect alongside the successive IC process to resolve packet collisions. A 5G propagation scenario, modeled according to recent mmWave channel measurements, is used to compare IDIC with the widely adopted Contention Resolution Diversity SA (CRDSA) scheme to show the performance gain of IDIC, when elements of practical relevance, like imperfect cancellation and receive power diversity, are considered. The impact of packet and power diversity is also investigated to derive the preferable uplink random access strategy that maximizes the system throughput according to the offered channel load
Limiting performance of millimeter-wave communications in the presence of a 3d random waypoint mobility model
Full text linkThis paper proposes a mathematical framework for evaluating the limiting capacity of a millimeter-wave (mmWave) communication involving a mobile user (MU) and a cellular base station. The investigation is realized considering a threedimensional (3D) space in which the random waypoint mobility model is used to probabilistically identify the location of the MUs. Besides, the analysis is developed accounting for path-loss attenuation, directional antenna gains, shadowing, and modulation scheme. Closed-form formulas for the received signal power, the Shannon capacity, and the bit error rate (BER) are obtained for both line-of-sight (LoS) and non-LoS scenarios in the presence of a noise-limited operating regime. The conceived theoretical model is firstly checked by Monte Carlo validations, and then employed to explore the influence of the antenna gain and of the cell radius on the capacity and on the BER of a fifth-generation (5G) link in a 3D environment, taking into account both the 28 and 73 GHz mmWave bands
3D Millimeter-Wave Peer-to-Peer Networks With Boundary Located Destination
Full text linkThis letter presents a theoretical analysis for estimating the coverage probability and the average link capacity of an interfered peer-to-peer millimeter-wave communication, when the destination lies at the boundary of a three-dimensional cell. The proposed model provides closed-form expressions for the statistics of the desired and undesired signal powers, by accounting for the impact of directional antenna gains, path-loss attenuation, mid-scale fading, interference, and noise
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