Multi-envelope precoding for massive MIMO systems

Constant envelope (CE) precoding is a recently proposed technique for massive MIMO systems that decreases the hardware complexity of base station circuitry. In this letter, we build on this idea and propose a multi-envelope precoding method, which utilizes more than one (but only a few, e.g., 2 or 3) envelope levels and assigns higher levels on the antenna group(s) requiring more power in order to increase the achievable rates. The results demonstrate substantial gains with respect to the CE approach for both cases of discrete and continuous phase shifters with almost no increase in hardware complexity and a small increase in computational complexity.