Efficient Pre-Processing of Site-Specific Radio Channels for Virtual Drive Testing in Hardware Emulators

Performance testing under realistic propagation
channel conditions is essential for virtual drive testing (VDT), where
radio channel emulators are typically employed in the laboratory for
such applications. Optimal allocation of tap resources in the channel
emulator is critical in hardware-in-the-loop emulation of radio
channels due to the constraint of real-time operation requirements,
hardware complexity and cost. As a result, replaying arbitrary site specific
e.g. measured or ray tracing (RT) simulated radio channels in channel emulators requires delay alignment and reduction in
the number of multipath components (MPCs) in the channel to
match the available hardware resources. However, such operations
would essentially introduce inaccuracies in the emulated channel.
In this paper, a framework for pre-processing site-specific radio
channels for hardware emulation is proposed. The delay alignment
problem is formulated as a finite impulse response (FIR) filter
design problem whereas the subsequent tap reduction and selection
process is formulated as a sparse approximation problem. This
approach enables maximization of the accuracy of the reproduced
channel frequency response (CFR) and Doppler profile in the
hardware emulator using a limited number of taps. The efficiency
of the proposed framework is demonstrated experimentally with a
dynamic vehicular RT simulated channel which is replayed on a
state-of-the-art radio channel emulator.