419 research outputs found
Towards UAV Assisted 5G Public Safety Network
Ensuring ubiquitous mission-critical public safety communications (PSC) to all the first responders in the public safety network is crucial at an emergency site. The first responders heavily rely on mission-critical PSC to save lives, property, and national infrastructure during a natural or human-made emergency. The recent advancements in LTE/LTE-Advanced/5G mobile technologies supported by unmanned aerial vehicles (UAV) have great potential to revolutionize PSC.
However, limited spectrum allocation for LTE-based PSC demands improved channel capacity and spectral efficiency. An additional challenge in designing an LTE-based PSC network is achieving at least 95% coverage of the geographical area and human population with broadband rates. The coverage requirement and efficient spectrum use in the PSC network can be realized through the dense deployment of small cells (both terrestrial and aerial). However, there are several challenges with the dense deployment of small cells in an air-ground heterogeneous network (AG-HetNet). The main challenges which are addressed in this research work are integrating UAVs as both aerial user and aerial base-stations, mitigating inter-cell interference, capacity and coverage enhancements, and optimizing deployment locations of aerial base-stations.
First, LTE signals were investigated using NS-3 simulation and software-defined radio experiment to gain knowledge on the quality of service experienced by the user equipment (UE). Using this understanding, a two-tier LTE-Advanced AG-HetNet with macro base-stations and unmanned aerial base-stations (UABS) is designed, while considering time-domain inter-cell interference coordination techniques. We maximize the capacity of this AG-HetNet in case of a damaged PSC infrastructure by jointly optimizing the inter-cell interference parameters and UABS locations using a meta-heuristic genetic algorithm (GA) and the brute-force technique. Finally, considering the latest specifications in 3GPP, a more realistic three-tier LTE-Advanced AG-HetNet is proposed with macro base-stations, pico base-stations, and ground UEs as terrestrial nodes and UABS and aerial UEs as aerial nodes. Using meta-heuristic techniques such as GA and elitist harmony search algorithm based on the GA, the critical network elements such as energy efficiency, inter-cell interference parameters, and UABS locations are all jointly optimized to maximize the capacity and coverage of the AG-HetNet
Design and Analysis of Conformal Antenna for Future Public Safety Communications: Enabling Future Public Safety Communication Infrastructure
Future 4G wireless communication systems include, in their capabilities portfolio, emergency-specific needs, such as data support, broadband communication, and extremely high reliability. An emergency situation can be addressed with undoubtedly more chances of success if augmented information is enabled within the public safety communication novel capabilities. In this article, for a fully augmented information provision based on broadband transmission, a user-end (UE) communication-capabilities enhancement is addressed by deploying multiple antennas without compromising the portability and light weight of first-responder equipment. With this aim, we propose the design of a 4.9-GHz conformal antenna array at the rescuer side (integrated in a helmet) and evaluate its performance in terms of relative data rate gain. The conformal array design is based on traditional patch antennas that consider the need for deployment over an ellipsoidal surface. The antenna array is simulated and then built, and several parameter characterizations (bandwidth, radiation pattern, reflection coefficient, and MC) and measurements are undertaken to ensure the suitability of the design. Furthermore, an analysis of the specific absorption rate (SAR) is performed to guarantee that the exposure to electromagnetic fields is below the standardized levels.The authors would like to thank Prof. Eva Rajo-Iglesias from Universidad Carlos III de Madrid. This work has been partly funded by the Spanish Government through projects CIES (RTC-2015-4213-7), MIMOTEX (TEC2014-61776-EXP) and TERESAADA (TEC2017-90093-C3-2-R) (MINECO/AEI/FEDER, UE
A survey of measurement-based spectrum occupancy modeling for cognitive radios
Spectrum occupancy models are very useful in cognitive radio designs. They can be used to increase spectrum sensing accuracy for more reliable operation, to remove spectrum sensing for higher resource usage efficiency, or to select channels for better opportunistic access, among other applications. In this survey, various spectrum occupancy models from measurement campaigns taken around the world are investigated. These models extract different statistical properties of the spectrum occupancy from the measured data. In addition to these models, spectrum occupancy prediction is also discussed, where autoregressive and/or moving-average models are used to predict the channel status at future time instants. After comparing these different methods and models, several challenges are also summarized based on this survey
Spectrum Policy and Management
This project provides an examination of the FCC’s policies towards spectrum reallocation. The project examines the National Broadband Plan and how the FCC has approached the goals described within it. The demand for broadband communications has increased dramatically in recent years and has resulted in a predicted spectrum deficit in the near future. In addition to a number of spectrum auctions and their winners the project examines how the redistribution of spectrum impacts the broadband community. The project also provides an examination of spectrum reallocation and policy in other countries, to provide a broader view of spectrum policy. Finally the project examines new spectrum technologies and spectrum usage policies to further examine how the US’s spectrum policies should evolve
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
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