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DroneBerlin · Microsoft PowerPoint - DroneBerlin.pptx Author: jwigard Created Date: 10/4/2018...
Transcript of DroneBerlin · Microsoft PowerPoint - DroneBerlin.pptx Author: jwigard Created Date: 10/4/2018...
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© 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.
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© 2018 Nokia2
Motivation
Public DroneBerlin 2018
• 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
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Wide area radio connectivity options
1. Satellite Networks
2. Cellular Networks
3. Hybrid solutions
4. Dedicated Networks
?
Public DroneBerlin 2018
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
Public DroneBerlin 2018
• 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
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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
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• 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.
Public DroneBerlin 2018
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applications requiring a large uplink throughputWhat about the uplink?
Public DroneBerlin 2018
- 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
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Collected from phone software – rural areaUL Throughput statistics
Public DroneBerlin 2018
• 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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PUSCH Throughput (MB/s)
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Collected from cellsInterference over Thermal (IoT)
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- 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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Reference IC (3 interferersremoved)
ICIC, 20 cells Beamsteering, 2beams
Beamsteering, 6beams
Out
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DL Interference Mitigation
Public DroneBerlin 2018
• 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%
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UL Interference mitigation
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• 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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Power ControldeltaP0 = - 6 dB
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Summary interference mitigation
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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
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Dedicated Networks
Public DroneBerlin 2018
• 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?
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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
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Hybrid Access
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Hybrid Access
Public DroneBerlin 2018
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Aalborg DenmarkHybrid Access urban test
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• 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
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HA Access test Aalborg, 40 mMeasurement results
Public DroneBerlin 2018
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.
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Hybrid Access performance example summary
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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
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• 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.
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Thank you!
Come visit us in the exhibition area (DroC2om)
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References
Public DroneBerlin 2018
• 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
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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.
Public DroneBerlin 2018
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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
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Issues when sharing spectrum with terrestrial users
Nokia internal use, September 2018
Command & Control (C2), enabling BVLOS flights: Application data (uplink):
C2
HD streaming
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Interference mitigation at the network
Public DroneBerlin 2018
• 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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Out
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Downlink (network-to-drone) SINRImpact of UAV height on radio performance
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• 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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14 15 16 17 18 19 20 21 22 230
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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.