Figure 9From: Radio environment map-based cognitive Doppler spread compensation algorithms for high-speed rail broadband mobile communicationsBlock diagram of REM-based dynamic channel emulator employed in the simulation ( τ n , α n , Δ f n , and G n are the time delay, channel coefficient, Doppler frequency shift, antenna gain for the n th path, respectively; and σ2 is the white Gaussian noise level).Back to article page