Deployment of Reference Nodes to Guarantee a LoS Condition for Accurate Indoor Positioning

Accurate and precise positioning is required to guarantee the massive adoption of a wide range of 5G indoor applications, such as logistics and smart manufacturing. Native support for New Radio (NR) positioning services was included in 3GPP Rel-16, where angles-of-arrival/departure and time- (difference-)of-arrival measurements were specified in uplink and downlink. However, all these positioning techniques assume Lineof-Sight (LoS) propagation, suffering from systematic bias errors when such a condition cannot be guaranteed. To improve the accuracy and precision of indoor positioning systems that rely on proximity, triangulation, or trilateration principles, this paper considers the deployment of reference nodes to ensure LoS to one, two, or three nodes, respectively. For this purpose, the indoor service area is modeled with a graph whose nodes represent the polygons that partition the floor plan. Then, the graph is partitioned into the minimum number of cliques, which specify the minimum number of reference nodes and their placement to guarantee a LoS condition regardless the user terminal position. The desired accuracy for positioning is guaranteed by setting a minimum distance and a minimum angle between the reference nodes as two configuration parameters of the derived algorithms.Comment: 13 pages, 18 figures, journa

Indoor Planning of Optical Wireless Networks for LoS Condition in Access and Backhauling

Optical wireless technology has the potential to complement the wireless access services provided so far over RF. Apart from the abundant unlicensed bandwidth available for ultra-dense deployments over optical wireless bands, optical wireless also has the potential to offer inexpensive, private, secure, and environmentally friendly communications. However, the main challenge of this technology is the inability to pass through obstacles, requiring a Line-of-Sight~(LoS) condition between transmitter and receiver. In addition, when LEDs are used to provide simultaneously wireless access and illumination, the range of the optical wireless links is notably limited. Since the typical size of Visible Light Communications~(VLC) cells is in the order of few meters, it is challenging to plan the detailed deployment of Access Points~(APs) to prevent coverage holes. This paper proposes a graph modeling approach for identifying the minimum number of APs (and their locations) for the given indoor floor plan. A connectivity tree is considered to ensure that each VLC AP can communicate with (an)other AP(s) through a LoS infrared wireless link for backhauling. The presented deployment procedure can also control the co-channel interference that is generated throughout the entire indoor environment, enhancing the data rate and illumination performance of VLC networks simultaneously.Comment: 13 pages, 17 figures, 5 table

A Method to Shorten Signals in SM-OFDM

Spatial modulation (SM) added to traditional OFDM communications has been intensively studied as a candidate transmission method to convey high-speed, low-delay, powerefficient and high-mobility 5G communications in a reliable basis. This approach implies the use of multiple antennas at the transmitter. Then, the fundamental aspect revised in this work takes into account that in a single-carrier SM system, the selection of the active transmit antenna according to (part of) the information bits makes it possible to use a single power amplifier (PA) that is switched among the available antennas. On the other hand, in a conventional SM-OFDM system, every antenna needs to be continuously active as the index information is typically different for each subcarrier. Consequently, we propose a transmission scheme that precodes the information symbols in frequency domain, such that the global symbol period is split into partitions that enable a sequential operation of antennas which can be fed by a single PA. In addition, it is possible to establish that the proposed approach tends to be more robust against disturbances observed in high mobility environments.Sociedad Argentina de Informática e Investigación Operativa (SADIO

A Method to Shorten Signals in SM-OFDM

Spatial modulation (SM) added to traditional OFDM communications has been intensively studied as a candidate transmission method to convey high-speed, low-delay, powerefficient and high-mobility 5G communications in a reliable basis. This approach implies the use of multiple antennas at the transmitter. Then, the fundamental aspect revised in this work takes into account that in a single-carrier SM system, the selection of the active transmit antenna according to (part of) the information bits makes it possible to use a single power amplifier (PA) that is switched among the available antennas. On the other hand, in a conventional SM-OFDM system, every antenna needs to be continuously active as the index information is typically different for each subcarrier. Consequently, we propose a transmission scheme that precodes the information symbols in frequency domain, such that the global symbol period is split into partitions that enable a sequential operation of antennas which can be fed by a single PA. In addition, it is possible to establish that the proposed approach tends to be more robust against disturbances observed in high mobility environments.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Robust Cooperative Multicarrier Transmission Scheme for Optical Wireless Cellular Networks

Visible light communication (VLC) is a promising technology to achieve high data rates in heterogeneous scenarios. However, VLC strongly depends on the existence of a line-of-sight (LoS) link between transmitter and receiver to guarantee a good data rate performance, which is often a condition that is difficult to satisfy in practice. In this letter, a novel cooperative multicarrier transmission scheme is proposed, where neighboring attocells smartly cooperate to decrease the probability of blockage in the LoS link. This approach is compared to single-cell transmission schemes, obtaining notable gains in both received signal-to-interference-plus-noise ratio and cell data rate when blockage of the LoS link occurs toward the nearest base station.This work was supported in part by the Catalan Government under Grant 2014SGR1567 and in part by the Spanish Government under the National Project "ELISA" with ID TEC2014-59255-C3-3/1-R. The work of B. Genovés Guzmán was supported in part by the Spanish MECD FPU Fellowship Program

A Method to Shorten Signals in SM-OFDM

Spatial modulation (SM) added to traditional OFDM communications has been intensively studied as a candidate transmission method to convey high-speed, low-delay, powerefficient and high-mobility 5G communications in a reliable basis. This approach implies the use of multiple antennas at the transmitter. Then, the fundamental aspect revised in this work takes into account that in a single-carrier SM system, the selection of the active transmit antenna according to (part of) the information bits makes it possible to use a single power amplifier (PA) that is switched among the available antennas. On the other hand, in a conventional SM-OFDM system, every antenna needs to be continuously active as the index information is typically different for each subcarrier. Consequently, we propose a transmission scheme that precodes the information symbols in frequency domain, such that the global symbol period is split into partitions that enable a sequential operation of antennas which can be fed by a single PA. In addition, it is possible to establish that the proposed approach tends to be more robust against disturbances observed in high mobility environments.Sociedad Argentina de Informática e Investigación Operativa (SADIO

End-to-End Error Control Coding Capability of NB-IoT Transmissions in a GEO Satellite System with Time-Packed Optical Feeder Link

Funding Information: This work has received funding from the Spanish Ministry of Science, Innovation and Universities under project TERESA-TEC2017-90093-C3-1-R (AEI/FEDER, UE) and from the Catalan Government under grants 2017-SGR-891 and 2017-SGR-1479. Publisher Copyright: © 2021, ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.This paper focuses on the return link of a GEO satellite system that collects information from a large number of sparsely distributed IoT devices in a large geographical area. Narrow-Band (NB) IoT transmissions, with suitable Modulation and Coding Scheme (MCS), are Detected-and-Forwarded onboard the satellite, mapping each QAM symbol of the radio access link (uplink) into another PAM symbol that modulates optical feeder link’s intensity (downlink). Given the massive number of IoT devices that is expected to be served by the GEO satellite system, the feeder link (downlink) of the return channel is expected to be the bottleneck. To tackle this limitation, time-packing signaling is used in the waveform that modulates the intensity of the optical feeder link (downlink); this way, the symbol time is reduced, and the number of IoT devices that can be simultaneously served in the radio access link (uplink) can augment without increasing the signal bandwidth in the optical feeder link. The Inter-Symbol Interference (ISI) that the time-packed feeder link generates is partially mitigated in the satellite gateway, using for this purpose an adaptive linear equalizer. After optical-to-electrical conversion, the NB-IoT codewords that are received in the gateway are decoded, correcting simultaneously errors introduced in both radio access and optical feeder links. The aim of this paper is to evaluate the error correction capability that MCS of NB-IoT standard has when used to protect end-to-end the hybrid radio/optical return link that results, particularly when using large overlapping factors in the optical feeder link to increase its achievable data rate.Peer reviewe