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LTE-A Virtual Drive Testing for Vehicular Environments

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Presentation by Di Kong on 'LTE-A Virtual Drive Testing for Vehicular Environments' at VTC Spring in Sydney in June.

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LTE-A Virtual Drive Testing for Vehicular Environments

  1. 1. Communication Systems & Networks © CSN Group 2017 LTE-A Virtual Drive Testing for Vehicular Environments VTC 2017 Spring Michael Charitos, Di Kong, Jue Cao, Denys Berkovskyy, Angelos A. Goulianos, Tom Mizutani, Fai Tila, Geoffrey Hilton, Angela Doufexi and Andrew Nix Communications Systems & Networks University of Bristol, UK
  2. 2. Communication Systems & Networks © CSN Group 2017 Contents • Introduction • Methodology • Channel modelling and antenna radiation pattern • System setup • Key results • Conclusion
  3. 3. Communication Systems & Networks © CSN Group 2017 Introduction • A Virtual Drive Testing (VDT) methodology for a MIMO LTE Vehicle to Infrastructure (V2I) urban scenario is proposed and compared with actual road drive tests. • This unique and generic radio performance analysis process is based on: • 3D ray traced channel models; • Theoretic or measured antenna patterns; • RF channel emulation and hardware-in-the-loop radio measurements (BS and On Board Unit (OBU)). • VDT is shown to provide a reliable, cost efficient and repeatable alternative to physical drive tests.
  4. 4. Communication Systems & Networks © CSN Group 2017 Methodology • Virtual base stations and vehicles are connected as they drive around a digital 3D map of Bristol. • 3D city-scale ray-tracing channel models are used to generate dynamic V2I channels. • Theoretic and/or measured antenna patterns are incorporated by spatial and polarimetric convolution with the channel data. • The resulting channel are streamed into Keysight PropSim F8 channel emulator, which is programmed to generate the RF channels between an LTE-A dual-BS emulator (a Rohde & Schwarz CMW500) and a Samsung S5 mobile client (representing the vehicular On-Board Unit). Route Selection Channel Generation Data Logging HIL VDT
  5. 5. Communication Systems & Networks © CSN Group 2017 Channel modelling: ray-tracing tool • Databases include 3-D terrain, buildings and foliage; all represented at a spatial resolution of 10m. • Ray information along the drive routes include: amplitude, delay and AoD/AoA in the azimuth and elevation planes for each MPC. • Vehicle motion is modelled by adding the Doppler-shift corresponding to each MPC. • YouTube animation of the radio channel and handover between two BS: https://youtu.be/tD6uyAFLm9U
  6. 6. Communication Systems & Networks © CSN Group 2017 Channel modelling: antenna patterns BS Antennas: • Measured data for an 800MHz panel sector antenna with a gain of 16dBi. • BS uses three antenna panels (120° rotated) with a downtilt of 10°. On Board Unit (OBU) Antennas: • Two antennas are housed in a single shark-fin pod located towards the rear of the vehicular rooftop. • The patterns were supplied by JLR.
  7. 7. Communication Systems & Networks © CSN Group 2017 Channel modelling: convolution • Point-source 3D ray tracing was performed from the BS to each of the vehicular OBU locations along the test route. • The double-directional time-variant channel impulse response h for a link is given by the following equation: ℎ 𝑡, 𝜏, 𝛺 𝐴𝑜𝐷, 𝛺 𝐴𝑜𝐴 = 𝑙=1 𝐿 ℎ𝑙 𝑡, 𝜏, 𝛺 𝐴𝑜𝐷, 𝛺 𝐴𝑜𝐴 = 𝑙=1 𝐿 El 𝑡 𝛿 𝜏 − 𝜏𝑙 𝛿 𝛺 𝐴𝑜𝐷 − 𝛺 𝐴𝑜𝐷,𝑙 𝛿 𝛺 𝐴𝑜𝐴 − 𝛺 𝐴𝑜𝐴,𝑙 where 𝐸𝑙 𝑡 = 𝐸 𝑇𝑥 𝑉 𝐸 𝑇𝑥 𝐻 𝑇 𝑎𝑙 𝑉𝑉 𝑒 𝑗𝜑 𝑙 𝑉𝑉 𝑎𝑙 𝑉𝐻 𝑒 𝑗𝜑 𝑙 𝑉𝐻 𝑎𝑙 𝐻𝑉 𝑒 𝑗𝜑 𝑙 𝐻𝑉 𝑎𝑙 𝐻𝐻 𝑒 𝑗𝜑 𝑙 𝐻𝐻 𝐸 𝑅𝑥 𝑉 𝐸 𝑅𝑥 𝐻 𝑒 𝑗2𝜋𝜐 𝑙 𝑡
  8. 8. Communication Systems & Networks © CSN Group 2017 Emulation system • Channel emulator: Keysight PropSim F8 • BS emulator: Rhode and Schwarz CMW500 • OBU: Samsung Galaxy S5 • 2x2 MIMO with both downlink and uplink
  9. 9. Communication Systems & Networks © CSN Group 2017 Route selection • A representative route connecting two major points of interest in the centre of Bristol. • 1809 ray tracing location points were chosen along the route, with the exact co-ordinates based on the vehicular GPS logs from the real-world drive tests. • A handover scenario was selected as vehicle moves between two BSs. Handover also considered between different sectors. OBU BS 1 Ray-tracing between BS and OBU BS2 BS1 Direction of Movement
  10. 10. Communication Systems & Networks © CSN Group 2017 Test scenario settings Environment Type Urban (Bristol city-centre) Vehicle Route Length 2.7 km Number of ray-tracing points 1809 Frequency of Operation 806 MHz (LTE band 20) Channel Bandwidth 10MHz BS antenna type Panel Antenna (16 dBi gain) Vehicle antennas MIMO1 (6 dBi) MIMO2 (8 dBi) OBU Receive Sensitivity -95 dBm Transmit Power 34 dBm • The assumed BS transmit power was calibrated based on the ray tracing results and the logged data from the real-world vehicular measurement reports. • Channel dependent link quality metrics, such as Reference Signal Received Power (RSRP) and Physical Downlink Shared Channel (PDSCH) throughput were logged from VDT system and physical drive tests.
  11. 11. Communication Systems & Networks © CSN Group 2017 Key results (1) • Good alignment between the prediction and measurement (left: RSRP1; right: RSRP2). • Better alignment for RSRP1 since Transmit power was calibrated for the primary antenna at the OBU. • Handover was triggered based on OBU measured RSRP values, indicating that the handover occurs in the region around user id 1400.
  12. 12. Communication Systems & Networks © CSN Group 2017 Key results (2) • The variability associated with the VDT process is less than that observed in the real world. • The emulation results faithfully follow the measurement trends. • Without prior knowledge, it is not possible to determine which results are real and which are generated from VDT. • Throughput depends strongly on channel conditions, resource allocation and the link adaptation algorithm applied at the BS. •
  13. 13. Communication Systems & Networks © CSN Group 2017 Conclusions • The laboratory based conductive test process developed and reported in this paper was shown to be more reliable and repeatable than real-world drive tests. • Antenna optimisation (type and location on the car) can be performed before physical prototypes of the antenna and/or vehicle have been developed. • VDT is able to provide automotive manufacturers with a powerful and cost effective alternative to on-road testing. • The use of city wide geographic databases allows a wide range of operating environments to be considered, including rural as well as urban routes.

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