On the Pilot-Data Power Trade Off in Single Input Multiple Output Systems

Abstract:
We consider a single cell single input multiple output (SIMO) system employing orthogonal frequency division multiplexing (OFDM). In such systems, setting the pilot-to-data power ratio (PDPR) has a large impact on the spectral and energy efficiency. In this paper we provide a closed form solution for the mean square error (MSE) of the received data as a function of the PDPR assuming Gaussian channels and minimum mean square error (MMSE) equalization. In numerical experiments we find that the MSE is a convex function of the PDPR and study the PDPR that minimizes the MSE as the number of antennas at the base station (BS) grows large. We find that the MSE-minimizing PDPR heavily depends on the number of antennas and the path loss between the mobile station and the BS. Specifically, as the number of antennas grows large, a larger portion of the total power budget needs to be allocated for pilot signals, especially for low path loss users.