17 research outputs found
How URLLC can Benefit from NOMA-based Retransmissions
Among the new types of connectivity unleashed by the emerging 5G wireless
systems, Ultra-Reliable Low Latency Communication (URLLC) is perhaps the most
innovative, yet challenging one. Ultra-reliability requires high levels of
diversity, however, the reactive approach based on packet retransmission in
HARQ protocols should be applied carefully to conform to the stringent latency
constraints. The main premise of this paper is that the NOMA principle can be
used to achieve highly efficient retransmissions by allowing concurrent use of
wireless resources in the uplink. We introduce a comprehensive solution that
accommodates multiple intermittently active users, each with its own HARQ
process. The performance is investigated under two different assumptions about
the Channel State Information (CSI) availability: statistical and
instantaneous. The results show that NOMA can indeed lead to highly efficient
system operation compared to the case in which all HARQ processes are run
orthogonally
5G 3GPP-like Channel Models for Outdoor Urban Microcellular and Macrocellular Environments
For the development of new 5G systems to operate in bands up to 100 GHz,
there is a need for accurate radio propagation models at these bands that
currently are not addressed by existing channel models developed for bands
below 6 GHz. This document presents a preliminary overview of 5G channel models
for bands up to 100 GHz. These have been derived based on extensive measurement
and ray tracing results across a multitude of frequencies from 6 GHz to 100
GHz, and this document describes an initial 3D channel model which includes: 1)
typical deployment scenarios for urban microcells (UMi) and urban macrocells
(UMa), and 2) a baseline model for incorporating path loss, shadow fading, line
of sight probability, penetration and blockage models for the typical
scenarios. Various processing methodologies such as clustering and antenna
decoupling algorithms are also presented.Comment: To be published in 2016 IEEE 83rd Vehicular Technology Conference
Spring (VTC 2016-Spring), Nanjing, China, May 201
On the accuracy of asymptotic solutions for TM waves diffracting on an impedance wedge
The contribution focuses on the accuracy of two asymptotic solutions aimed at representing the electromagnetic field scattered by penetrable
wedges. One is a heuristic manipulation of the solution for the perfect electrical conductor, and the other one is a more rigorous coefficient based on approximate boundary conditions. The results presented here extend those proposed by other authors by illustrating the accuracy of such solutions at the edge of validity of the uniform theory of diffraction. In particular, they show that the heuristic formulation can be freely applied in similar conditions, while the other might not always lead to accurate predictions
Interference-Aware OFDM Receiver for Channels with Sparse Common Supports
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