Estudio y optimización de los procedimientos de adaptación al enlace en HSDPA

[ES] La tecnología HSDPA (High Speed Downlink Packet Access) es una evolución de UMTS creada con el objetivo de aumentar la capacidad de transmisión en el enlace descendente. Su mejora se basa en la utilización de un canal compartido de comunicación gestionado de forma eficiente desde la estación base (por medio de un packet scheduler), la utilización de mecanismos de retransmisión y combinación de información avanzados (hybrid ARQ) y la posibilidad de emplear modulaciones de alto orden (16QAM y 64QAM). Las dos últimas características nombradas serían inútiles sin unos buenos procedimientos de adaptación al enlace (link adaptation) que ajustaran los parámetros de transmisión a la calidad del enlace radio. La presente tesina aborda el estudio y optimización de los mecanismos de link adaptation en HSDPA. Para tratar el problema se siguen dos estrategias. Por un lado, se estudia un link adaptation genérico con el fin de obtener conclusiones fácilmente trasladables a sistemas particulares como HSDPA. Por otro lado, se aportan soluciones a problemas específicos de HSDPA como los fallos del link adaptation con baja carga.[EN] HSDPA (High Speed Downlink Packet Access) technology is an evolved version of UMTS focused on the improvement of the downlink capacity. HSDPA enhancement is based on the efficient management of a shared channel done by the Node-B (employing a packet scheduler), the using of advanced retransmission and combination mechanisms (hybrid ARQ) and the availability of high order modulations (16QAM and 64QAM). The later characteristics would be worthless without good link adaptation procedures that adjust transmission parameters according to the radiolink quality. This thesis deals with the study and optimization of link adaptation mechanisms in HSDPA. Two strategies are followed herein. First, a generic link adaptation is studied with the aim of reaching some general conclusions and applying them to real systems as HSDPA. Besides, a more detailed study is done for HSDPA finding solutions for some specific problems as link adaptation failures with low loadMartín-Sacristán Gandía, D. (2007). Estudio y optimización de los procedimientos de adaptación al enlace en HSDPA. http://hdl.handle.net/10251/12494Archivo delegad

On the Integration of Grassmannian Constellations into LTE Networks: a Link-level Performance Study

This paper presents Grassmannian signaling as a transmission scheme that can be integrated in Long Term Evolution (LTE) to support higher user speeds and to increase the throughput achievable in the high Signal to Noise Ratio (SNR) regime. This signaling is compared, under realistic channel assumptions, with the diversity transmission modes standardized in LTE, in particular, Space-Frequency Block Coding and Frequency-Switched Transmit Diversity for two and four transmit antennas, respectively. In high-speed scenarios, and even with high antenna correlation, Grassmannian signaling outperforms the LTE diversity transmission modes starting from four transmit antennas. Furthermore, in the high SNR regime, Grassmannian signaling can increase the link data rate up to 10% and 15% for two and four antennas, respectively

Link abstraction models based on mutual information for LTE downlink

Postprint (author’s final draft

Assessing 3GPP LTE-Advanced as IMT-Advanced Technology: The WINNER+ Evaluation Group Approach

[EN] This article describes the WINNER+ approach to performance evaluation of the 3GPP LTE-Advanced proposal as an IMT-Advanced technology candidate. The official registered WINNER+ Independent Evaluation Group evaluated this proposal against ITU-R requirements. The first part of the article gives an overview of the ITU-R evaluation process, criteria, and scenarios. The second part is focused on the working method of the evaluation group, emphasizing the simulator calibration approach. Finally, the article contains exemplary evaluation results based on analytical and simulation approaches. The obtained results allow WINNER+ to confirm that the 3GPP LTE Release 10 & Beyond (LTE-Advanced) proposal satisfies all the IMT-Advanced requirements, and thus qualifies as an IMT-advanced system.This work has been performed in the framework of the CELTIC project CP5-026 WINNER+. The authors would like to acknowledge the contributions of their colleagues in the WINNER+ consortium. The authors wish to thank colleagues from Ericsson, Per Skillermark and Johnan Nystrom, for their effort in leading the simulations part of the WINNER+ evaluation group. The work of David Martin-Sacristan was supported by an FPU grant of the Spanish Ministry of Education.Safjan, K.; D'amico, V.; Bültmann, D.; Martín-Sacristán, D.; Saadani, A.; Schöneich, H. (2011). Assessing 3GPP LTE-Advanced as IMT-Advanced Technology: The WINNER+ Evaluation Group Approach. IEEE Communications Magazine. 49(2):92-100. doi:10.1109/MCOM.2011.5706316S9210049

Distribution of Road Hazard Warning Messages to Distant Vehicles in Intelligent Transport Systems

© 2018 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] The efficient distribution of intelligent transport system (ITS) messages is fundamental for the deployment and acceptance of ITS applications by mobile network operators and the automotive industry. In particular, the distribution of road hazard warning (RHW) messages to distant vehicles requires special mechanisms. In this case, the combination of direct communication between vehicles and the wide area coverage provided by cellular networks might be crucial not only for reducing the data transmission costs but also for improving the timeliness of ITS information. Moreover, the application of clustering and cluster head selection mechanisms among vehicles can increase the efficiency of hybrid vehicular and cellular communication networks. This paper introduces a novel cluster head selection technique for the distribution of RHW messages, and proposes an implementation of another legacy technique that was originally intended for mobile ad-hoc networks (MANETs). This paper evaluates the performance of these techniques by the means of computer simulations in two scenarios with distinct congestion and propagation conditions. The simulation results show the potential benefit of hybrid networks compared with pure cellular transmissions, especially, if the novel cluster head selection technique is used.Calabuig Soler, D.; Martín-Sacristán, D.; Monserrat Del Río, JF.; Botsov, M.; Gozálvez Serrano, D. (2018). Distribution of Road Hazard Warning Messages to Distant Vehicles in Intelligent Transport Systems. IEEE Transactions on Intelligent Transportation Systems. 19(4):1152-1165. https://doi.org/10.1109/TITS.2017.2718103S1152116519

Comparison of Optimization Methods for Aerial Base Station Placement with Users Mobility

Aerial base stations have been recently considered in the deployment of wireless networks. Finding the optimal position for one or multiple aerial base stations is a complex problem tackled by several works. However, just a few works consider the mobility of the users which makes necessary an online optimization to follow the changes in the scenario where the optimization is performed. This paper deals with the online optimization of an aerial base station placement considering different types of users mobility and three algorithms: a Q-learning technique, a Gradient-based solution and a Greedy-search solution. Our objective is to minimize in an urban environment the path loss of the user at street level with the highest path loss. Simulation results show that the performance of the three methods is similar when a high number of users move randomly and uniformly around the scenario under test. Nevertheless, in some situations when the number of users is reduced or when the users move together in a similar direction, both Gradient and Greedy algorithms present a significantly better performance than the Q-learning method.The work of Danaisy Prado was supported by the H2020 Marie Curie Program, with Project Grant No. 766231 WAVECOMBE - ITN - 2017Prado-Alvarez, D.; Inca-Sanchez, SA.; Martín-Sacristán, D.; Monserrat Del Río, JF. (2019). Comparison of Optimization Methods for Aerial Base Station Placement with Users Mobility. IEEE. 485-489. https://doi.org/10.1109/EuCNC.2019.8802053S48548

D1.1 Refined scenarios and requirements, consolidated use cases, and qualitative techno-economic feasibility assessment

This document describes scenarios, consolidated use cases and associated requirements for wireless access networks in the 2020-2030 timeframe. These are based on METIS project and also taking into account work done in other 5G projects and forums such as ITU-R and NGMN. The document introduces spectrum authorization modes and describes spectrum usages scenarios, spectrum bands and spectrum demand for 5G services. Finally, this document provides qualitative techno-economic feasibility assessment by analyzing main players involved in service delivery, from the radio access network point of view, and describing their mutual positions and relationships.Monserrat Del Río, JF.; Martín-Sacristán Gandía, D. (2016). D1.1 Refined scenarios and requirements, consolidated use cases, and qualitative techno-economic feasibility assessment. https://doi.org/10.13140/RG.2.2.32091.7760

Millimeter-wave Human Blockage Model Enhancements for Directional Antennas and Multiple Blockers

[EN] The Third Generation Partnership Project (3GPP) has defined a blockage model as an add-on feature to the channel model used in its evaluations of the physical layer in the 0.5-100 GHz frequency range. This letter focuses on the human body blockage losses in the millimeter-wave band proposing: (i) a new criterion to place the diffraction points over the edges of the blockers that considers the precise position of the blocker with regard to the line-of-sight between the transmitter and the receiver, (ii) a specific criterion to determine which potential blockers, from a set of human bodies present in a certain scenario, should be considered effective blockers given the positions of a transmitter, a receiver, and those bodies, and (iii) a modification of the model to provide more accurate estimations in the case in which several blockers are closely located. The validity of our criteria and the accuracy improvement are confirmed by a set of measurements performed at 30 GHz with directional antennas and with multiple human blockers in different positions.The work of Danaisy Prado-Alvarez was supported by the H2020 Marie Curie Program, with Project Grant No. 766231 WAVECOMBE-ITN-2017. Part of this work has been performed in the framework of the H2020 project 5G-SMART co-funded by the EU. This was also supported by the Spanish Ministry of Science, Innovation and University under the project RTI2018-099880-B-C31. The associate editor coordinating the review of this letter and approving it for publication was J. Choi.Prado-Alvarez, D.; Inca-Sánchez, SA.; Martín-Sacristán, D.; Monserrat Del Río, JF. (2021). Millimeter-wave Human Blockage Model Enhancements for Directional Antennas and Multiple Blockers. IEEE Communications Letters. 25(9):2776-2780. https://doi.org/10.1109/LCOMM.2021.3095617S2776278025

Low-Latency Infrastructure-Based Cellular V2V Communications for Multi-Operator Environments With Regional Split

[EN] Mobile network operators are interested in providing Vehicle-to-Vehicle (V2V) communication services using their cellular infrastructure. Regional split of operators is one possible approach to support multi-operator infrastructure-based cellular V2V communication. In this approach, a geographical area is divided into non-overlapping regions, each one served by a unique operator. Its main drawback is the communication interruption motivated by the inter-operator handover in border areas, which prevents the fulfillment of the maximum end-to-end (E2E) latency requirements of fifth generation (5G) V2V services related to autonomous driving. In this work, we enable a fast inter-operator handover based on the pre-registration of the users on multiple operators, which substantially reduces the handover time to guarantee maximum E2E latency values of 100 ms in non-congested scenarios. To further reduce the latency of time-critical services to always less than 70 ms, even with the handover interruption time, while providing a latency around 20 ms in the majority of locations, we propose to complement the former technique with a mobile edge computing approach. Our proposal consists in the localization of application servers and broadcasting entities in all the base stations, to avoid the communication through the core network, together with the use of a new set of nodes in the base stations of cross-border areas called inter-operator relays, to minimize the communication latency between operators. Based on analytic and simulation results, it is demonstrated that the proposed techniques are effective to support low-latency infrastructure-based cellular V2V communications in multi-operator environments with regional split.The work of S. Roger was partially supported by the Spanish Ministry of Science, Innovation and Universities through grant number RYC-2017-22101.Martín-Sacristán, D.; Roger, S.; Garcia-Roger, D.; Monserrat Del Río, JF.; Spapis, P.; Zhou, C.; Kaloxylos, A. (2021). Low-Latency Infrastructure-Based Cellular V2V Communications for Multi-Operator Environments With Regional Split. IEEE Transactions on Intelligent Transportation Systems. 22(2):1052-1067. https://doi.org/10.1109/TITS.2019.29620971052106722

Map-Based Channel Model for Urban Macrocell Propagation Scenarios

The evolution of LTE towards 5G has started and different research projects and institutions are in the process of verifying new technology components through simulations. Coordination between groups is strongly recommended and, in this sense, a common definition of test cases and simulation models is needed. The scope of this paper is to present a realistic channel model for urban macrocell scenarios. This model is map-based and takes into account the layout of buildings situated in the area under study. A detailed description of the model is given together with a comparison with other widely used channel models. The benchmark includes a measurement campaign in which the proposed model is shown to be much closer to the actual behavior of a cellular system. Particular attention is given to the outdoor component of the model, since it is here where the proposed approach is showing main difference with other previous models