Constant Envelope Massive Mimo-Ofdm Precoding: An Improved Formulation And Solution

Constant Envelope (CE) precoding is an efficient technique for systems based on massive antenna arrays since the constant amplitude of the transmit signal facilitates the use of power efficient non-linear transmitter circuitry, such as power amplifiers (PAs). On the other hand, Orthogonal frequency-division multiplexing (OFDM) is a well-known multicarrier transmission scheme which is used to mitigate the effects of multipath propagation, but usually leads to high peak-to-average-power ratio (PAPR). Herein, the problem of CE MIMO-OFDM precoding for transmission over frequency selective channels is tackled. First, a novel efficient formulation is proposed, where the precoding problem is formulated as an unconstrained nonlinear least-squares problem. Next, using the new formulation the problem is solved using the Gauss-Newton algorithm. Numerical results show that the proposed solution is more efficient than the current state of the art techniques both from the aspect of computational complexity and the overall system performance.