Description
Date depot: 1 janvier 1900
Titre: Self-organizing flying mobile relays for wireless Internet access networks
Directeur de thèse:
David GESBERT (Eurecom)
Domaine scientifique: Sciences et technologies de l'information et de la communication
Thématique CNRS : Non defini
Resumé:
This PhD project proposes to study the use of flying mobile relays as a way to improve coverage, capacity, and flexibility in future mobile internet access networks. (Self-)controllable drones that carry wireless transceiver equipment in order to relay information streams between the infrastructure and user terminals, as well as other type of communication, storage and processing devices, yield the promise of ultra-flexible network deployments, able to provide coverage and capacity when and where it matters the most. Studies of the benefits of such flying relays in mobile networks (5G and beyond) have recently started to arise in the literature [JYM2014, MSB2015, IEY2016, CG2016.]. In the civilan networking area, initiatives include those by prominent Internet content providers Google and initial ones from Facebook where the exploitation of some large aerial platforms (usually from a fairly high altitude) to help relay internet access possibly fom satellite backhaul towards rural or developing areas, has been featured recently in popular media. In October 2016, another effort to leverage UAVs in the context of small cells for urban deployment of 5G and Beyond was announced by Nokia where this time regular-sized drones were used as delivery tool (reminiscent of Amazon‘s initiative with parcels) to carry and drop small cell base stations at suitable locations in the network where they are most needed.
In this project we will consider the use of smaller, low altitude UAVs which offer a much better position control and can form radio beams to spatially discriminate between close-by groups of user terminals on the ground. We will focus in particular on the problem of optimum (autonomous) positioning of such flying relays, in individual or fleet form.
Optimized Deployment of one mobile flying relay
In order to capitalize on the flexibility and fast adaptation capability of aerial networks, the UAV must be enabled with a smart positioning algorithm that solves a challenging multi-purpose optimization. This optimization is a challenging problem which will be at the heart of the PhD thesis. In particular drones must autonomously design a trajectory that simultaneously maintains (i) a good connection to the wireless hubs (base stations) on the backhaul network, and (ii) the best possible service performance to ground users. In doing so, the self-positioning algorithms must intelligently exploit local propagation measurements (for instance to maximize line of sight connections or the Signal to Noise Ratio – SNR ), minimize interference to/from non-served users, and finally smoothly adapt to spatio-temporal patterns of ground traffic demand. Finally, in the scenario of UAV fleet deployment, the UAVs should coordinate between themselves to optimally divide the coverage task among themselves, as addressed in the next section.
The problem of optimizing the position of a single flying relayett45 was addressed in some recent work based on a combination of air-to-ground (ATG) channel modeling and subsequent numerical analysis of the relay channel capacity via the UAV. When it comes to ATG channel modeling, a fine representation of the path loss and the likelihood to meet line of sight was found critical.
Some early works on ATG channel analyzed this LoS probability via statistical analysis and some models were derived [FTN2006a], subsequently a propagation model valid for frequency ranges from 200 MHz to 5 GHz is obtained via combining of LoS probabilities, the accounting of random shadowing and ray tracing techniques [FTN2006b]. The model also accounts for the height and elevation angle of the UAV seen from the ground user.
Other ATG models are defined for standardized simulations such as the one characterized by the ITU-R Rec. P.1410; for instance, [AKJ2014] describes a generic radio model between a low altitude platform and ground nodes using frequencies from 700 MHz to 5.8 GHz based on random virtual city maps and ray tracing.
In the current literature, channel models are exploited to obtain UAV positioning and trajectories based on numerical optimization. An example is [LOC2016], which considers multiple UAVs with the aim to maintain the overall network connectivity in a 3D scenario with several ground nodes. The optimal position of drones acting as relays is found through the particle swarm optimization, following different network performance metrics. In [MSB2015], the optimal three-dimensions placement of multiple UAVs was addressed to optimize downlink coverage in terms of antenna gain and UAVs altitude. Disk packing theory was used to handle the interference of the overlapping coverage areas of the UAVs, while minimizing the transmit power. The novelty introduced by [IEY2016] is summed up by creating a variable that relates the altitude of the drone-cell to the radius of its coverage area. The authors investigated the air-to-ground channel and how it differs from those of terrestri
Doctorant.e: Esrafilian Omid