Pilot-to-Data Power Ratio in RIS-Assisted Multiantenna Communication

The optimization of the pilot-to-data power ratio (PDPR) is a recourse that helps wireless systems to acquire channel state information while minimizing the pilot overhead. While the optimization of the PDPR in cellular networks has been studied extensively, the effect of the PDPR in reconfigurable intelligence surface (RIS)-assisted networks has hardly been examined. This letter tackles this optimization when the communication is assisted by a RIS whose phase shifts are adjusted on the basis of the statistics of the channels. For a setting representative of a macrocellular deployment, the benefits of optimizing the PDPR are seen to be significant over a broad range of operating conditions. These benefits, demonstrated through the ergodic minimum mean squared error, for which a closed-form solution is derived, become more pronounced as the number of RIS elements and/or the channel coherence grow large.