skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: UAV Positioning for Improving Coverage-Connectivity Tradeoff in Millimeter-Wave Wireless Channels
In this work, we utilizie unmanned aerial vehicles (UAVs) to enhance the connectivity of the backhaul of small-cells (SCs) network and achieve better coverage for those user equipment (UE) in deep fade and not attached to any SCs. Deploying UAVs as a backbone for communication systems has gained an increasing prominence, especially in emergency network breakdown as an efficient and reliable alternative to restore the network connectivity. Moreover, to meet the ever increasing demand on high date rate applications, larger bandwidth is needed which is realizable in mm-wave frequencies range from 20 to 60 GHz. In mm-wave frequencies range, transmitted signals suffer from deleterious path loss mainly due to direct path blockages and significant penetrations losses. We exploit the mobility of UAVs and optimize its position to cope with such impairments. To the best of our knowledge, this work is the first to optimize the UAVs’ locations to jointly increase the connectivity between SCs and improve coverage by overcoming mm-wave harmful pathloss.  more » « less
Award ID(s):
1618692
PAR ID:
10042061
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
The second NSF millimeter wave workshop
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; (, Computing and Communication Workshop and Conference (CCWC))
    null (Ed.)
    Intelligent robot swarms are increasingly being explored as tools for search and rescue missions. Efficient path planning and robust communication networks are critical elements of completing missions. The focus of this research is to give unmanned aerial vehicles (UAVs) the ability to self-organize a mesh network that is optimized for area coverage. The UAVs will be able to read the communication strength between themselves and all the UAVs it is connected to using RSSI. The UAVs should be able to adjust their positioning closer to other UAVs if RSSI is below a threshold, and they should also maintain communication as a group if they move together along a search path. Our approach was to use Genetic Algorithms in a simulated environment to achieve multi-node exploration with emphasis on connectivity and swarm spread. 
    more » « less
  2. ; ; ; (, ITU Journal on Future and Evolving Technologies)
    To integrate unmanned aerial vehicles (UAVs) in future large-scale deployments, a new wireless communication paradigm, namely, the cellular-connected UAV has recently attracted interest. However, the line-of-sight dominant air-to-ground channels along with the antenna pattern of the cellular ground base stations (GBSs) introduce critical interference issues in cellular-connected UAV communications. In particular, the complex antenna pattern and the ground reflection (GR) from the down-tilted antennas create both coverage holes and patchy coverage for the UAVs in the sky, which leads to unreliable connectivity from the underlying cellular network. To overcome these challenges, in this paper, we propose a new cellular architecture that employs an extra set of co-channel antennas oriented towards the sky to support UAVs on top of the existing down-tilted antennas for ground user equipment (GUE). To model the GR stemming from the down-tilted antennas, we propose a path-loss model, which takes both antenna radiation pattern and configuration into account. Next, we formulate an optimization problem to maximize the minimum signal-to-interference ratio (SIR) of the UAVs by tuning the up-tilt (UT) angles of the up-tilted antennas. Since this is an NP-hard problem, we propose a genetic algorithm (GA) based heuristic method to optimize the UT angles of these antennas. After obtaining the optimal UT angles, we integrate the 3GPP Release-10 specified enhanced inter-cell interference coordination (eICIC) to reduce the interference stemming from the down-tilted antennas. Our simulation results based on the hexagonal cell layout show that the proposed interference mitigation method can ensure higher minimum SIRs for the UAVs over baseline methods while creating minimal impact on the SIR of GUEs. 
    more » « less
  3. ; ; (, 2019 IEEE 20th International Symposium on "A World of Wireless, Mobile and Multimedia Networks" (WoWMoM))
    The use of Millimeter-wave (mmWave) spectrum in cellular communications has recently attracted growing interest to support the expected massive increase in traffic demands. However, the high path-loss at mmWave frequencies poses severe challenges. In this paper, we analyze the potential coverage gains of using unmanned aerial vehicles (UAVs), as hovering relays, in integrated access and backhaul (IAB) mmWave cellular scenarios. Specifically, we utilize the WinProp software package, which employs ray tracing methodology, to study the propagation characteristics of outdoor mmWave channels at 30 and 60 GHz frequency bands in a Manhattan-like environment. In doing so, we propose the implementation of amplify-and-forward (AF) and decode-and-forward (DF) relaying mechanisms in the WinProp software. We show how the 3D deployment of UAVs can be defined based on the coverage ray tracing maps at access and backhaul links. Furthermore, we propose an adaptive UAV transmission power for the AF relaying. We demonstrate, with the aid of ray tracing simulations, the performance gains of the proposed relaying modes in terms of downlink coverage, and the received signal to interference and noise ratio (SINR). 
    more » « less
  4. ; ; ; ; (, Geophysical Journal International)
    null (Ed.)
    SUMMARY The method of ScS reverberation migration is based on a ‘common reflection point’ analysis of multiple ScS reflections in the mantle transition zone (MTZ). We examine whether ray-theoretical traveltimes, slownesses and reflection points are sufficiently accurate for estimating the thickness H of the MTZ, defined by the distance between the 410- and 660-km phase transitions. First, we analyse ScS reverberations generated by 35 earthquakes and recorded at hundreds of seismic stations from the combined Arrays in China, Hi-NET in Japan and the Global Seismic Network. This analysis suggests that H varies by about 30 km and therefore that dynamic processes have modified the large-scale structure of the MTZ in eastern Asia and the western Pacific region. Second, we apply the same procedure to spectral-element synthetics for PREM and two 3-D models. One 3-D model incorporates degree-20 topography on the 410 and 660 discontinuities, otherwise preserving the PREM velocity model. The other model incorporates the degree-20 velocity heterogeneity of S20RTS and leaves the 410 and 660 flat. To optimize reflection point coverage, our synthetics were computed assuming a homogeneous grid of stations using 16 events, four of which are fictional. The resolved image using PREM synthetics resembles the PREM structure and indicates that the migration approach is correct. However, ScS reverberations are not as strongly sensitive to H as predicted ray-theoretically because the migration of synthetics for a model with degree-20 topography on the 410 and 660: H varies by less than 5 km in the resolved image but 10 km in the original model. In addition, the relatively strong influence of whole-mantle shear-velocity heterogeneity is evident from the migration of synthetics for the S20RTS velocity model and the broad sensitivity kernels of ScS reverberations at a period of 15 s. A ray-theoretical approach to modelling long-period ScS traveltimes appears inaccurate, at least for continental-scale regions with relatively sparse earthquake coverage. Additional modelling and comparisons with SS precursor and receiver function results should rely on 3-D waveform simulations for a variety of structures and ultimately the implementation of full wave theory. 
    more » « less
  5. ; ; (, International Symposium on Quality Electronic Design (ISQED))
    The emerging unmanned aerial vehicle (UAV) such as a quadcopter offers a reliable, controllable, and flexible way of ferrying information from energy harvesting powered IoT devices in remote areas to the IoT edge servers. Nonetheless, the employment of UAVs faces a major challenge which is the limited fly range due to the necessity for recharging, especially when the charging stations are situated at considerable distances from the monitoring area, resulting in inefficient energy usage. To mitigate these challenges, we proposed to place multiple charging stations in the field and each is equipped with a powerful energy harvester and acting as a cluster head to collect data from the sensor node under its jurisdiction. In this way, the UAV can remain in the field continuously and get the data while charging. However, the intermittent and unpredictable nature of energy harvesting can render stale or even obsolete information stored at cluster heads. To tackle this issue, in this work, we proposed a Deep Reinforcement Learning (DRL) based path planning for UAVs. The DRL agent will gather the global information from the UAV to update its input environmental states for outputting the location of the next stop to optimize the overall age of information of the whole network. The experiments show that the proposed DDQN can significantly reduce the age of information (AoI) by 3.7% reliably compared with baseline techniques. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email