LSE Precoder for Load Modulated Arrays With Channel Modulation

In this letter, we consider novel multiuser precoding techniques suited for load modulated arrays (LMAs) on the downlink, wherein a base station employs an LMA to transmit data to multiple users. For implementation simplicity, it is desired that the antenna load impedance values in the LMA are drawn from a discrete set. For such LMAs with discrete-valued load impedances, we propose an iterative precoding algorithm using the least square error (LSE) framework. For the same setting, we also propose a precoding scheme that employs channel modulation (CM) using radio frequency (RF) mirrors in each element of the LMA. This LMA-CM precoding scheme tunes the RF mirrors as well as antenna load modulators such that the instantaneous constraint of constant hypersphere signaling from a discrete set required for LMAs is satisfied. Improved distortion and bit error performance of the proposed schemes are reported.