Abstract
Distributed massive MIMO (DM-MIMO) systems are a key enabler to improve the energy efficiency (EE) in future wireless networks. Thereby, herein this architecture is considered for the estimation of a correlated source vector in wireless sensor networks (WSN), where each sensor node amplifies and forwards its observation through a coherent Multiple Access Channel (MAC) channel. Namely, the fusion centre (FC) consists of a large number of distributed single antenna access points (AP) connected through a backhaul network to a central processing unit (CPU), where a Linear Minimum Mean Square Error (LMMSE) estimation is computed. Within this setting the exact and an approximated MSE, obtained by the LMMSE estimation, are derived. Bearing in mind these results, we address the design of the optimal power allocation, at each sensor node, to minimize the total transmitted power subject to an MSE estimation constraint. The approximation of the MSE paves the way to cast the optimal allocation problem as a Semidefinite Programming Problem (SDP). Finally, the numerical simulations show that our system permits to reduce significantly the total transmitted power compared to related work architectures proposing a massive MIMO system where all the antennas are collocated at the FC.