Doa Estimation In Systems With Nonlinearities For Mmwave Communications

Accurate and efficient methods for Direction of Arrival (DOA) estimation play an important role in mmWave channel estimation methods. This estimation procedure can potentially be affected by the different RF and analog components in the communication system. Such components add an unknown, nonlinear distortion to the received signal. This work looks at addressing this problem of DOA estimation for a general case of a nonlinear distortion of the received signal. Two different scenarios for angle recovery are considered here: with the use of pilot symbols and without the use of pilots. The analysis specifically focuses on the transformation of the signal subspace resulting from the nonlinearity. It is proven that under certain conditions on the nonlinearity, the signal subspace remains conserved. This implies that the angles can be recovered without calibrating or inverting the nonlinearity.