Papers

The work in the DroC2om project has resulted in the following publications/presentations, available for download in pre-print (author) or published versions. According to the H2020 Open Access Policy, publications are, or will be, also available via OpenAire - DroC2om.

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    Validation of Large-scale Propagation Characteristics for UAVs within Urban Environment (VTC Fall 2019)

    IEEE Vehicular Technology Conference (VTC Fall), 22–25 September 2019, Honolulu, Hawaii
    DOI: to become available

    Abstract:

    Cellular networks based on current LTE Advanced or coming 5G technology, constitute an attractive candidate to provide communication links for drones in low level airspace. This paper extends previous findings on path loss exponent and shadow fading variation for an urban environment, by adding new and more extensive empirical evidence. Specifically, by way of the measurements methodology we study also the spatial correlation of the shadow fading, including the lateral spatial  autocorrelation (decorrelation distance) and the cross-correlation in shadowing variability between different heights. Data was obtained with the use of a drone flying at heights up to and above rooftop, using a radio network scanner measuring live LTE signals at 1800 MHz. The path loss analysis confirmed the validity of previously presented modelling frameworks for the behaviour versus height, as well as the characteristics of the increased interference observed when the drone if above rooftop level. As for the spatial correlation of the shadow fading, the results indicate that decorrelation distance does not change appreciably from ground level up to and above rooftop level, and remains in the order of 10m. The shadow fading variability is generally uncorrelated versus height, although with a trend to be correlated below rooftop level, but not above.

    To be presented.

    Pre-print (author) version is available for download © IEEE 2019

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    Shadow Fading Spatial Correlation Analysis for Aerial Vehicles: Ray Tracing vs. Measurements (VTC Fall 2019)

    IEEE Vehicular Technology Conference (VTC Fall), 22–25 September 2019, Honolulu, Hawaii
    DOI: to become available

    Abstract:

    Although the use of cellular networks to serve drones has been investigated in several recent works, the path loss or shadowing variation is still relatively unexplored. The variation and its dynamic behaviour is of importance in characterizing the reliability of the drone communication link, but difficult to assess by experimental means on a large scale. The main goal of this paper is to study the feasibility of ray tracing models to accurately predict shadow fading variations at different heights, so that the shadow fading correlation distances for the UAV channel can be found in both vertical and horizontal directions, without the need of performing extensive field measurement campaigns. For that, predictions obtained through a ray tracing tool are compared to field measurements in an urban scenario. Our results show that with accurate 3D maps, the tool is useful for predicting the dynamics of the UAV propagation channel, and therefore can be used partly as a substitute for field measurements.

    To be presented.

    Pre-print (author) version is available for download © IEEE 2019

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    Forecasting Spectrum Demand for UAVs Served by Dedicated Allocation in Cellular Networks (WCNC 2019)

    IEEE Wireless Communications and Networking Conference (WCNC), 15-19 April 2019, Marrakech, Morocco
    DOI: to become available

    Abstract:

    In this paper, the usage of dedicated portions of cellular spectrum to provide the high-reliable Command and Control (C2) link for Unmanned Aerial Vehicles (UAVs) is evaluated. Simulations are performed using data settings of a real operating Long-Term Evolution (LTE) network in Denmark, in order to assess the reliability of the C2 link. Up to date databases of drone registrations and market projections are used to infer the drone densities and estimate the future traffic demand. Based on these estimations, network capacity results show that, deploying a sparse network with reservation of 1.4 MHz is sufficient for most cases according to current demands. In the next 20 years, the increase in demand can be followed by a continuous deployment of sites and an increase in the bandwidth up to 5 MHz. The paper also presents a discussion about which solutions can be used to further boost network capacity, and help to achieve high reliability even for the most stringent traffic demand cases.

    The paper was presented in the International Workshop on Smart Spectrum (IWSS) in conjunction with IEEE WCNC 2019.

    Pre-print (author) version is available for download © IEEE 2019

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    Drone critical communication (World ATM Congress 2019)

    DroC2om Presentation in the SESAR walking tour 3 at the World ATM Congress in Madrid, March 12, 2019

    Abstract:

    The coordinator presented an overview to the particpants in SESAR walking tour 3 - "Ensuring the safe and secure integration of drones (U-Space R&D)" - on the research activities and concept that is being pursued in the DroC2om project.

    Relying on existing cellular infrastructure, in combination with a satellite network, provides an almost ubiquitously available communication channel for reliable command and control of drones, sharing spectrum and infrastructure, but also cost and  technological evolution with terrestrial services. 

    Presentation is available for download © DroC2om 2019

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    Enabling BVLOS flights through Cellular Connectivity (Drone Berlin 2018)

    Drone Berlin, September 25-26, 2018

    Abstract:

    Partner Nokia Bell Labs presented research conducted in the DroC2om at the Drone Berlin event. The presentation of the project results discussed the differences between communication to drones and ground users, based on measurements and simulation results for Command and Control (C2) data link performance with drones flying in VLL air space. The presentation also highlighted that practical, and relatively low complexity, interference mitigation techniques, such as interference coordination, beamsteering and hybrid access, improves the reliability of the C2 link even in highly loaded cellular networks in urban and rural areas. 

    Presentation is available for download © DroC2om 2018

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    C2 for U-Space services via combined cellular and satellite systems (U-Space Coordination Group 2018)

    DroC2om Webinar on WebEx to U-Space Coordination Group, 11:00 to 12:00 CET on October 25, 2018

    Abstract:

    DroC2om partners presented progress on the design of an integrated cellular-satellite Command and Control (C2) data link system to support reliable and safe operation of drones, and how this C2 link could benefit and integrate in the U-Space context. The forum was the U-Space Coordination Group.

    Presentation is available for download © DroC2om 2018

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    LTE Radio Measurements Above Urban Rooftops for Aerial Communications (WCNC 2018)

    IEEE Wireless Communications and Networking Conference (WCNC), 15-18 April 2018, Barcelona, Spain
    DOI: 10.1109/WCNC.2018.8377373

    Abstract:

    This paper focus on the investigation of aerial communications targeting drones flying above rooftops in urban scenarios in a near future. A radio scanner is attached to a construction-lift to measure the radio signal from three different live LTE networks (800, 1800, and 2600MHz) at heights up to 40m in urban senarios. The measurements suggest that the clearance of the radio path cause the number of cells in the detectable range of the equipment to increase. Also, it is found more neighbors within 3dB of the serving cell in the receiver. There are 4 or more neighbors in this range in 2.6%, 4.2% and
    7.4% of the samples in each frequency respectively at 100m, while this number does not exceed 1% at 1.5m. The paper also compares the path losses observed during the measurements with 3GPP reference models and previous studies. At last, heightdependent closed form expressions for the path loss slope and shadowing variation are provided for future investigations under similar scenarios.

    The paper was presented in the PHY and Fundamentals "PHY15 - Channel Modeling III" session at the IEEE WCNC.

    Pre-print (author) version is available for download © IEEE 2018

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    How to Ensure Reliable Connectivity for Aerial Vehicles Over Cellular Networks (IEEE Access 2018)

    IEEE Access, Special Section on Networks of Unmanned Aerial Vehicles, vol. 6, Feb 23, 2018,
    DOI: 10.1109/ACCESS.2018.2808998

    Abstract:

    Widely deployed cellular networks are an attractive solution to provide large scale radio connectivity to unmanned aerial vehicles. One main prerequisite is that co-existence and optimal performance for both aerial and terrestrial users can be provided. Today’s cellular networks are, however, not designed for aerial coverage, and deployments are primarily optimized to provide good service for terrestrial users. These considerations, in combination with the strict regulatory requirements, lead to extensive research and standardization efforts to ensure that the current cellular networks can enable reliable operation of aerial vehicles in various deployment scenarios. In this paper, we investigate the performance of aerial radio connectivity in a typical rural area network deployment using extensive channel measurements and system simulations. First, we highlight that downlink and uplink radio interference play a key role, and yield relatively poor performance for the aerial traffic, when load is high in the network. Second, we analyze two potential terminal side interference mitigation solutions: interference cancellation and antenna beam selection. We show that each of these can improve the overall, aerial and terrestrial, system performance to a certain degree, with up to 30% throughput gain, and an increase in the reliability of the aerial radio connectivity to over 99%. Further, we introduce and evaluate a novel downlink inter-cell interference coordination mechanism applied to the aerial command and control traffic. Our proposed coordination mechanism is shown to provide the required aerial downlink performance at the cost of 10% capacity degradation in the serving and interfering cells.

    Published version is available via the DOI link above © IEEE 2018

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    How cellular networks can enable reliable communications to aerial vehicles (IEEE SECON 2018)

    CPC-UAV workshop, IEEE SECON 2018, 11-13 June 2018, Hong Kong, China

    Abstract:

    Our project partner Nokia Bell Labs presented an overview of the DroC2om studies on radio connectivity options for enabling BVLOS drone flights via a highly reliable Command and Control (C2) link at the CPC-UAV workshop at SECON 2018 in Hong Kong. The invited presentation gave an overview of the radio connectivity options for C2 communication, with specific emphasis on the measurements and performance simulations that have been conducted within DroC2om for using the existing cellular infrastructure for C2 communication. Challenges wrt. interference and radio mobility were discussed and exemplified, as well as some promissing solutions for handling them. Particularly beam selection and hybrid access were mentioned as attractive solutions. Further work in relation to radio mobility was mentioned as one of the future topics, considering specifically hybrid access mechanisms and context awareness for QoS prediction and conditional handover preparation.

    Presentation is available for download © DroC2om 2018

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    Measured Uplink Interference Caused by Aerial Vehicles in LTE Cellular Networks (IEEE WCL 2018)

    IEEE Wireless Communications Letters (early access)
    DOI: 10.1109/LWC.2018.2841386

    Abstract:

    Aerial users, such as unmanned aerial vehicles (UAVs), experience different radio propagation conditions than users on the ground. This is a concern regarding the integration of such users in the cellular networks in the near future. This paper investigates the impact of uplink transmissions from an aerial user equipment. Full buffer transmissions were performed by a device at ground level and also flying attached to a UAV at 100 m height. The field measurements show a higher number of cells affected by the aerial transmission, with an increase of up to 7.7 dB in the interference over thermal noise in cells within 15 km of the test location. This letter also assesses two strategies to reduce the uplink interference caused by aerial users: 1) UAV’s cruise height control and 2) directional transmissions. Results show the directional transmission is a more promising technique and have the advantage of not reducing the uplink received power.

    Published version is available via the DOI link above, or available for download in pre-print (author) version © IEEE 2018

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