  This paper considers a cell-free massive MIMO (CF-mMIMO) system using
conjugate beamforming (CB) with fractional-exponent normalization. Assuming
independent Rayleigh fading channels, a generalized closed-form expression for
the achievable downlink spectral efficiency is derived, which subsumes, as
special cases, the spectral efficiency expressions previously reported for
plain CB and its variants, i.e. normalized CB and enhanced CB. Downlink power
control is also tackled, and a reduced-complexity power allocation strategy is
proposed, wherein only one coefficient for access point (AP) is optimized based
on the long-term fading realizations. Numerical results unveil the performance
of CF-mMIMO with CB and fractional-exponent normalization, and show that the
proposed power optimization rule incurs a moderate performance loss with
respect to the traditional max-min power control rule, but with lower
complexity and much smaller overall power consumption.
