Optimal Power Control for Superimposed Pilots in Uplink Massive MIMO Systems

Abstract

In Massive MIMO, the pilot contamination effect reduces the spectral efficiency (SE) gains and Superimposed pilot (SP) transmission has been proposed to mitigate this effect. SP is based on transmitting pilot and data symbols simultaneously to allow for longer pilots and no pilot overhead. This work studies the optimal power control strategies in the uplink of a Massive MIMO system with SP and detection based on maximum ratio combining. The optimization objectives are maximum product of SINRs and max-min fairness, and these problems are reformulated as geometric programs which allow for efficient implementations. The numerical results indicate that the SE gains from the optimal power control with respect to the heuristic statistical channel inversion power control, are more significant when the interference from pilot symbols is subtracted before data detection.

Massive-MIMO Iterative Channel Estimation and Decoding (MICED) in the Uplink

“…, ENC }. Assuming that the bits at the output of the decoder are independent, then the achievable SE is where the probabilities in (33) are obtained as in (32). Note that the achievable SE in (33) accounts the overhead from coding and using dedicated pilot symbols in the case of RP.…”

“…Note that Δ has been selected to maximize the SE with pilot only channel estimation based on numerical results that are omitted in this paper for brevity. See[33] for more details on power control optimization with SP.…”