Path Loss in an Urban Peer-to-Peer Channel for Six Public-Safety Frequency Bands

We provide path loss data and models for a peer-to-peer wireless channel for an urban environment in six public safety bands, for simultaneous transmission to five spatially separated receiving sites. Results are from measurements in Denver, Colorado. The six frequencies at which we measured are (in MHz) 430, 750, 905, 1834, 2400, and 4860. Both line-of-sight and non-line-of-sight conditions were covered, and we quantify path loss exponents and linear-fit standard deviations as functions of frequency and location. Line-of-sight results agree with prior work, but non-line-of-sight exponents, from 3.6-7.3, are generally larger than in most other references

Large-Scale Site and Frequency Diversity in Urban Peer-to-Peer Channels for Six Public Safety Frequency Bands

We report on peer-to-peer large-scale wireless channel characteristics for an urban environment in six public-safety bands, for five simultaneous receiving sites. Results are based upon measurements taken in Denver in July 2009 with stationary receivers and a pedestrian transmitter. The six frequencies at which we measured are (in MHz) 430, 750, 905, 1834, 2400, and 4860. We quantify both site and frequency diversity, and show that 5-site selection yields minimum average gains of 15 dB in mean received power levels; 5-site selection diversity also reduces received power variation by 17-29 dB, depending on frequency. Frequency diversity yields similar gains. By approximating received powers as lognormal, we describe an analytical method to approximate the cdf of the per-site, or per-frequency (or both) maximum received power. These data and diversity models should be useful for public-safety and ad hoc communication system designers, and for cooperative diversity schemes, wherein multiple users act as a virtual array

Sixth Generation (6G)Wireless Networks: Vision, Research Activities, Challenges and Potential Solutions

The standardization activities of the fifth generation communications are clearly over and deployment has commenced globally. To sustain the competitive edge of wireless networks, industrial and academia synergy have begun to conceptualize the next generation of wireless communication systems (namely, sixth generation, (6G)) aimed at laying the foundation for the stratification of the communication needs of the 2030s. In support of this vision, this study highlights the most promising lines of research from the recent literature in common directions for the 6G project. Its core contribution involves exploring the critical issues and key potential features of 6G communications, including: (i) vision and key features; (ii) challenges and potential solutions; and (iii) research activities. These controversial research topics were profoundly examined in relation to the motivation of their various sub-domains to achieve a precise, concrete, and concise conclusion. Thus, this article will contribute significantly to opening new horizons for future research direction

Propagation and Wireless Channel Modeling Development on Wide-Sense Vehicle-to-X Communications

The need for improving the safety and the efficiency of transportation systems has become of extreme importance. In this regard, the concept of vehicle-to-X (V2X) communication has been introduced with the purpose of providing wireless communication technology in vehicular networks. Not like the traditional views, the wide-sense V2X (WSV2X) communications in this paper are defined by including not only vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications but also train-to-X (T2X) communications constituted of train-to-train (T2T) and train-to-infrastructure (T2I) communications. All the information related to the wide-sense V2X channels, such as the standardization, scenarios, characters, and modeling philosophies, is organized and summarized to form the comprehensive understanding of the development of the WSV2X channels

Investigation of path loss prediction in different multi-floor stairwells at 900MHz and 1800MHz

Wireless communication along the stairwell in a high rise building is important to ensure immediate response to take place via consistent relaying of necessary information or data in emergency situations. Thus, a good understanding of signal wave attenuation along the stairwell is necessary to allow a better wireless network planning. This paper presents empirical path loss prediction model for multi-floor stairwell environment. The proposed model is based on measurement at 4 different stairwells, at 900MHz and 1800 MHz which are near public safety communication bands. The model incorporates the effect of different floor heights and unique path loss-to-distance relation on selected stair flights observed during measurement campaign. The proposed model demonstrates higher accuracy than 3 standard path loss models at 2 other stairwell

Cooperative Content Dissemination on Vehicle Networks

As redes veiculares têm sido alvo de grandes avanços nos últimos anos, sobretudo devido ao crescente interesse por veículos inteligentes e autónomos que motiva investimentos avultados por parte da indústria automóvel. A inexistência de uma forma oportuna e económica de executar atualizações OTA (over-the-air) está a contribuir para o adiar do lançamento de grandes frotas de veículos inteligentes. O custo associado à transmissão de dados através de redes celulares é muito elevado e não se pode garantir que cada veículo tenha acesso a uma estação ou estacionamento com conectividade adequada em tempo útil, onde possa obter os dados esperados. Com base nestas premissas, esta tese apresenta a concepção e implementação de um protocolo cooperativo de disseminação de conteúdos que aproveita as ligações Veículo-a-Veículo (V2V) para assegurar uma distribuição de dados pela rede com custos reduzidos. Além disso, este trabalho é complementado e suportado com uma análise do desempenho do protocolo numa rede de 25 veículos.Vehicular networks have seen great advancements over the last few years, mostly due to the increased eagerness for smart and autonomous vehicles that motivate hefty investments by the automotive industry. The absence of a timely and cost-effective way to perform over-the-air (OTA) updates is contributing to defer the deployment of large fleets of connected vehicles. There is a high cost associated with transmitting data over cellular networks and it cannot be expected that every vehicle has access to a station or depot with adequate connectivity where it can get the awaited data cheaply nor that this solution happens timely enough. With this in mind, this thesis presents the design and implementation of a cooperative content dissemination protocol that takes advantage of Vehicle-to-Vehicle (V2V) communication links to distribute data across a network with reduced costs. Moreover, this work is complemented with a performance analysis of the protocol on a deployed network of 25 vehicles

Wireless Technologies for IoT in Smart Cities

[EN] As cities continue to grow, numerous initiatives for Smart Cities are being conducted. The concept of Smart City encompasses several concepts being governance, economy, management, infrastructure, technology and people. This means that a Smart City can have different communication needs. Wireless technologies such as WiFi, ZigBee, Bluetooth, WiMax, 4G or LTE (Long Term Evolution) have presented themselves as solutions to the communication needs of Smart City initiatives. However, as most of them employ unlicensed bands, interference and coexistence problems are increasing. In this paper, the wireless technologies available nowadays for IoT (Internet of Things) in Smart Cities are presented. Our contribution is a review of wireless technologies, their comparison and the problems that difficult coexistence among them. In order to do so, the characteristics and adequacy of wireless technologies to each domain are considered. The problems derived of over-crowded unlicensed spectrum and coexistence difficulties among each technology are discussed as well. Finally, power consumption concerns are addressed.García-García, L.; Jimenez, JM.; Abdullah, MTA.; Lloret, J. (2018). Wireless Technologies for IoT in Smart Cities. Network Protocols and Algorithms. 10(1):23-64. doi:10.5296/npa.v10i1.12798S236410

Empirical stairwell propagation models for long term evolution applications

This thesis presents investigation of path loss, PL, and shadowing, Xσ, of signal wave along and about multi floor stairways that have dog-leg stairwell configuration. The objective is to develop frequency-dependent empirical propagation models that could approximate PL and Xσ for two conditions. The first condition is when both transmitter, Tx, and receiver, Rx, are within the stairwell structure. The second condition is when either one of the Tx or Rx is inside adjacent rooms to the stairwells. Attention was also drawn towards the influence of stair flights and floor height to attenuation of signal wave as it propagates within the stairwell. Analysing the impact of the aforementioned structures within the stairwell, signal wave propagating between stairwell and adjacent in-building space as well as developing frequency-dependant empirical propagation model are research areas which have yet to be covered by previous propagation studies pertaining to multi floor stairway. Frequencies of interest, f, ranged from 0.7 GHz up to 2.5 GHz that cover various long term evolution (LTE) and public safety communication bands. Research works involved measurement campaign in four different multi-floor buildings inside Universiti Teknologi Malaysia’s campus. PL’s relations with separation distance between Tx and Rx, d, and f were formulated with auxiliary site-specific terms added to improve two proposed empirical propagation models. It was found that for signal wave propagation where both Tx and Rx were within the stairwell, placing Rx at elevated or lower position than Tx does not influence significantly recorded PL data. However, for propagation between stairwell and adjacent rooms, placing Rx at elevated or lower than Tx may influence significantly recorded PL data. Suitable measurement campaign planning was arranged in the light of this finding. The proposed models were then examined and compared with ITU-R, COST and WINNER II indoor empirical propagation models. From measurement in dedicated testing sites, it was demonstrated that the proposed models have the smallest computed mean, μR, relative to the other standard models. The largest μR was -2.96 dB with a 3.34 dB standard deviation, σR. On the other hand, results from COST, ITU-R and WINNER II models demonstrated lower precision in all inspected settings, with the largest μR being 8.06 dB, 7.71 dB and 15.98 dB respectively and their σR being 3.79 dB, 6.82 dB and 9.40 dB accordingly. The results suggest that the proposed PL models, which considered the impact of building structures within and about the stairwell could provide higher PL prediction’s accuracy for wireless communication planning pertaining to the stairwell environment, particularly for public safety responders

Unmanned Aerial Vehicle (UAV)-Enabled Wireless Communications and Networking

The emerging massive density of human-held and machine-type nodes implies larger traffic deviatiolns in the future than we are facing today. In the future, the network will be characterized by a high degree of flexibility, allowing it to adapt smoothly, autonomously, and efficiently to the quickly changing traffic demands both in time and space. This flexibility cannot be achieved when the network’s infrastructure remains static. To this end, the topic of UAVs (unmanned aerial vehicles) have enabled wireless communications, and networking has received increased attention. As mentioned above, the network must serve a massive density of nodes that can be either human-held (user devices) or machine-type nodes (sensors). If we wish to properly serve these nodes and optimize their data, a proper wireless connection is fundamental. This can be achieved by using UAV-enabled communication and networks. This Special Issue addresses the many existing issues that still exist to allow UAV-enabled wireless communications and networking to be properly rolled out