  We consider a cell-free massive multiple-input multiple-output (CFmMIMO)
network operating in dynamic time division duplex (DTDD). The switching point
between the uplink (UL) and downlink (DL) data transmission phases can be
adapted dynamically to the instantaneous quality-of-service (QoS) requirements
in order to improve energy efficiency (EE). To this end, we formulate a problem
of optimizing the DTDD switching point jointly with the UL and DL power control
coefficients, and the large-scale fading decoding (LSFD) weights for EE
maximization. Then, we propose an iterative algorithm to solve the formulated
challenging problem using successive convex approximation with an approximate
stationary solution. Simulation results show that optimizing switching points
remarkably improves EE compared with baseline schemes that adjust switching
points heuristically.
