Design and Verification of a Virtual Drive Test Methodology for Vehicular LTE-A Applications

In this paper, a virtual drive test (VDT) emulation methodology for vehicle-to-infrastructure long-term evolution-advanced (LTE-A) communications is proposed, evaluated, and compared against a traditional drive test approach. A generic antenna and radio test process is developed based on 3-D ray-traced channel models, theoretic and measured antenna patterns, radio frequency (RF) channel emulation, and hardware-in-the-loop (HIL) radio measurements. The spatial and temporal multipath components of the radio propagation channel between the multiple-input and multiple-output (MIMO)-enabled LTE-A base stations (BS) and the vehicle under test are accurately modeled for a site-specific virtual environment. Measured BS and LTE-A vehicular antenna patterns are incorporated into the system via spatial and polarimetric convolution with the synthetic ray data. The resulting channels are streamed into a wideband channel emulator that connects a multichannel LTE-A BS emulator to a smartphone representing the vehicular on-board-unit (OBU). The laboratory-based LTE-A HIL system is used to study the handover process between two serving LTE-A BSs according to the received RF powers at the vehicular OBU. Emulated RF powers and data throughputs are compared with data from a traditional drive test to verify the legitimacy of the proposed methodology. Our VDT results in terms of reference signal received power and physical downlink shared channel throughput match well the real-world LTE-A measurements for single-input and single-output and MIMO operation. This new process benefits from being repeatable and via the use of ray-tracing scales to support a wide range of urban and rural operating environments.