DroneBerlin · Microsoft PowerPoint - DroneBerlin.pptx Author: jwigard Created Date: 10/4/2018 8:49:29 AM

© 2018 Nokia1 © 2018 Nokia1

Enabling BVLOS flights through Cellular Connectivity

Public DroneBerlin 2018

Presenter: Jeroen Wigard

Contributors:István Z. Kovács, Jeroen Wigard, Preben Mogensen

Nokia Bell Labs, Aalborg, Denmark

Rafhael Amorim, Troels Sørensen, Preben Mogensen, Steffen HansenAalborg University, Aalborg, Denmark

DroC2om

This research has received funding from the SESAR Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme, grant agreement No 763601. The research is conducted as part of the DroC2om project.

© 2018 Nokia2

Motivation


• A large variety of commercial UAV types, UAV services and UAV scenarios are rapidly emerging

• Beyond Visual Line of Sight (B-VLOS) radio communications solutions are needed for large scale cost efficient UAV services.

• Mission: Investigate how to enable reliable BVLOS reliable operations through wide area radio connectivity

© 2018 Nokia3

Wide area radio connectivity options

1. Satellite Networks

2. Cellular Networks

3. Hybrid solutions

4. Dedicated Networks

?


DroC2om

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• C2 is expected to become mandatory for BVLOS flights (navigation, dynamic geofencing,support for sense & avoid, …).

• In 3GPP the following assumption on the traffic have been used:

• Packet size: 1250 B• Interarrival time: 100 ms

• Requirements (3GPP)

RequirementsCommand and Control (C2) link

Reliability 99,9%

Latency 50 ms

C2C2


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Cellular networks

Public IEEE SECON 2018 Hong Kong

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How are things different up there?Aerial radio channel measurements


• Radio connectivity and interference for UAV flights at different heights and locations have been investigated in real/live LTE networks

– Rural and urban scenarios (Denmark)

– Real/live commercial LTE networks and frequency bands

– DJI 600 equipped with network scanner and measurement phones

– Heights: 1.5 (ref), 15, 30, 60 and 120 m

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Rural path loss (PL) investigationsAerial radio channel measurements

• Increased heights result in lower signal attenuation (lower PL slope) and fading.

NLOS @1.5m

LOS @ 120m


PL=3,5

PL=2

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measurements in DenmarkIncreased heights lead to more detectable cells

25 km radius

Flight Area

More detectable cells means more potential interference.


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Rural LTE network investigationsAerial performance simulations


• Large scale, DL/UL simulations of the site-specific rural LTE network.

• Standard LTE/A mechanisms and interference mitigation solutions

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Reliability

• UAVs enter Qout when SINR < -8 dB and get active again when SINR > -6dB

• A UAV in outage means we cannot reach it.• UAV experience a larger outage than

terrestrial users• Only at low load and low heights potential

acceptable values can be achieved for the reliability.


© 2018 Nokia11

applications requiring a large uplink throughputWhat about the uplink?


- Lower signal attenuation- More visible cells

What happens in the uplink when we have a camera drone live streaming 4K video?

Test:

- Phone at 100 m height (attached to a drone)

- Uploading as much data as possible

- Test done at night time, i.e. almost no other traffic

- Collect cell stats from the network (15 min resolution)

- Redo the test on ground level

- Tests done in rural area and in urban area

© 2018 Nokia12

Collected from phone software – rural areaUL Throughput statistics


• Tx power close to maximum for both ground UE and airborne UE, while both use almost the full 10 MHz.

• Median throughputs:• Ground UE: 14 Mbps• Airborne UE: 18.5 Mbps (+30%)

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x 106

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PUSCH Throughput

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Airborne Test

PUSCH Throughput (MB/s)

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Collected from cellsInterference over Thermal (IoT)


- IoT values beyond 10 dB (vs empty network).

- Increase over ground level for worst impacted cell beyond 6 dB.

- Highest interfered cell is 8 km away!

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Interference mitigation needed in both up and downlink

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0,1

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Reference IC (3 interferersremoved)

ICIC, 20 cells Beamsteering, 2beams

Beamsteering, 6beams

Out

age

Prob

abil

ity (%

)

DL Interference Mitigation


• The reference case at high load leads to 23% outage.

• Most promising interference mitigation:– Beam steering with 6 beams,

– ICIC with 20 cells

Rural area, real LTE deployment, 65% PRB load, UAV at 120 m

Target

23%

© 2018 Nokia16

UL Interference mitigation


• UE Beam selection– Using 2 to 6 fixed beams and select the

best one for DL & UL connectivity.

– Improves both terrestrial and UAV throughputs.

• Uplink Power Control– Lower transmit power for UAVs, limits their

generated interference in the uplink

– Solves the uplink interference at the cost of a lower throughput for the UAVs

UAV at 120m height, medium network traffic load conditions

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Reference Power ControldeltaP0 = - 3 dB

Power ControldeltaP0 = - 6 dB

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Mbp

s)

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Reference Power ControldeltaP0 = - 3 dB

Power ControldeltaP0 = - 6 dB

2 Beams 4 Beams 6 beams

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(M

bps)

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Summary interference mitigation


Comparison of the interference mitigation techniques for drones

Technique Gain Potential Complexity drone Complexity network

Grid of fixed beams● ◑ ○

Interference Cancellation ◔ ◑ ○Power Control

◑ ○ ◔Interference Coordination

● ○ ◑

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Dedicated networks

© 2018 Nokia19

Dedicated Networks


• 100% dedicated to drones.• Full separation on sites, spectrum and even

technology or just a subset of these.• Here we focus on using a separate carrier for

C2 related traffic, which is installed in x% of the sites for terrestrial traffic.

• Parameters, like tilt can be fully optimized for drones in dedicated networks.

What is it?

© 2018 Nokia20

Dedicated Carrier – required spectrum to provide reliable BVLOS C2

Nokia internal use, V2X Concept Forum, September 2018

Case study for the 800 MHz band using urban Aalborg area

• 2028 forecast*: A 5 MHz dedicated/ reserved carrier is needed to provide reliable C2 services in in Aalborg.

• The deployment density can be lower than for MBB* Assumptions: 3 missions/take-offs per workweek, 60 minutes per mission

Example LTE network in urban Aalborg area (100 sites)

Aalborg 2028

© 2018 Nokia21

Hybrid Access

© 2018 Nokia22

Hybrid Access


© 2018 Nokia23

Aalborg DenmarkHybrid Access urban test


• 40 meters height• Route of about 4,5 km• Two test phones connected

to the drone.• Active mode with traffic

– 1250 B every 100 ms.

– Uplink and downlink

• KPI’s collected:– RSRQ

– RSRP

– Delay per packet

LTE cells in Network 1

Flight pathRadio hand-over events

© 2018 Nokia24

HA Access test Aalborg, 40 mMeasurement results


Average = -71 dBm

Average = -92 dBm

Average = -14 dB

Average = -11 dB

• Large difference in RSRP, blue network being 21 dB better.

• mean RSRQ difference smaller: red network 3 dB better than the blue network.

• More importantly the amount of time with RSRQ < -20 dB and delay > 50 ms is considerably larger for the blue network.

© 2018 Nokia25

Hybrid Access performance example summary


Hybrid Access benefits from the fact that events often are uncorrelated between different network layers.

11.5%

1.5%

0.015%

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Key take aways


• Cellular networks are attractive for serving drones (C2 link) enabling BVLOS.

• Interference may be an issue.• Several Interference Mitigation techniques

solve this issue.– Grid of fixed beams and Interference coordination

being the most attractive.

• Hybrid access shows a lot of potential to provide the required reliability.

• Dedicated networks are another attractive solution.

© 2018 Nokia28

References


• R. Amorim, P. Mogensen, T. B. Sørensen, I. Z. Kovács, J. Wigard , “Pathloss Measurements and Modeling for UAVs Connected to Cellular Networks,” IEEE Veh. Tech. Conference Spring 2017.

• R. Amorim, H. Nguyen, P. Mogensen, I. Z. Kovács, J. Wigard and T. B. Sørensen, "Radio Channel Modeling for UAV Communication Over Cellular Networks," in IEEE Wireless Communications Letters, vol. 6, no. 4, pp. 514-517, Aug. 2017.

• I. Z. Kovács, R. Amorim, H. C. Nguyen, J. Wigard, P. Mogensen, “Interference analysis for UAV connectivity over LTE using aerial radio measurements”, Proc. IEEE. Veh. Tech. Conference Fall 2017.

• J. Wigard, R. Amorim, H. C. Nguyen, I. Z. Kovács, P. Mogensen, ”Method for Detection of Airborne UEs Based on LTE Radio Measurements”, Proc. IEEE PIMRC 2017.

• R. Amorim et al, "Measured UL Interference Caused by Aerial Vehicles in LTE Cellular Networks", IEEE Wireless Communication Letters, 2018.

• H. C. Nguyen, R. Amorim, J. Wigard, I. Z. Kovács and P. Mogensen "Using LTE Networks for UAV Command and Control Link: A Rural-Area Coverage Analysis", IEEE Veh. Tech. Conference Spring 2017.

• R. Amorim et al “Machine –Learning Idnetification of Airborne UAV-Ues Based on LTE Radio Measurments", GLOBECOM 2017.

• H. Nguyen et al, "How to ensure reliable connectivity for aerial vehicles over cellular networks", submitted to IEEE Access special issue, February 2018. http://ieeexplore.ieee.org/document/8301389/

• R. Amorim et al, “Enabling 5G reliable communications for aerial vehicles”, submitted to IEEE wireless communication magazine

© 2018 Nokia29

Downlink (network to drone) SINRImpact of height

• SINR gets worse with increasing height.• UAVs more sensitive to increased load.• UAVs have no impact on the terrestrial

users SINR.


© 2018 Nokia30

Increased heights lead to more detectable cells and stronger interference

25 km radius

Flight Area

N=3,5

N=2

stronger signalsMore detectable cells

Nokia internal use, September 2018

© 2018 Nokia31

Issues when sharing spectrum with terrestrial users

Nokia internal use, September 2018

Command & Control (C2), enabling BVLOS flights: Application data (uplink):

C2

HD streaming

© 2018 Nokia32

Interference mitigation at the network


• Interference Coordination– Requires blanking of quite many cells, i.e.

loss of capacity in order to get decent gains

– Complexity is increased by the fact that the cells to be muted may be quite far away, i.e. > 10 km.

• Power Control– Lower power for drones, limiting their

interference in the uplink.

– Solves the uplink interference at the cost of a lower throughput for the drones.

– No downlink gains.

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Reference power control - 3 dBpower control - 12 dB

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dronesground Ues

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Reference ICIC, 5 cells ICIC, 10 cells ICIC, 20 cells

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Downlink (network-to-drone) SINRImpact of UAV height on radio performance


• UAVs can experience a much worse SINR than terrestrial users, as expected, due to the increased LOS conditions

• UAV downlink SINR degrades considerably with increasing height

• UAVs performance is more sensitive to increased network traffic load compared to terrestrial UEs

• UAVs have no impact on the terrestrial UEs downlink SINR

7dB drop

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UE Tx Power & bandwidth used


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High UE Tx power and most of the band used mission accomplished

Airborne user use little bit less power due to their better connection to the serving cell

10 MHz band used almost full band is use din both cases.

Documents

DroneBerlin · Microsoft PowerPoint - DroneBerlin.pptx Author: jwigard Created Date: 10/4/2018 8:49:29 AM