  Effective capacity (EC) determines the maximum communication rate subject to
a particular delay constraint. In this work, we analyze the EC of ultra
reliable Machine Type Communication (MTC) networks operating in the finite
blocklength (FB) regime. First, we present a closed form approximation for EC
in quasi-static Rayleigh fading channels. Our analysis determines the upper
bounds for EC and delay constraint when varying transmission power. Finally, we
characterize the power-delay trade-off for fixed EC and propose an optimum
power allocation scheme which exploits the asymptotic behavior of EC in the
high SNR regime. The results illustrate that the proposed scheme provides
significant power saving with a negligible loss in EC.
