  We develop an analytical framework for the perfor- mance comparison of small
cell networks operating under static time division duplexing (S-TDD) and
dynamic TDD (D-TDD). While in S-TDD downlink/uplink (DL/UL) cell transmissions
are synchronized, in D-TDD each cell dynamically allocates resources to the
most demanding direction. By leveraging stochastic geom- etry and queuing
theory, we derive closed-form expressions for the UL and DL packet throughput,
also capturing the impact of random traffic arrivals and packet
retransmissions. Through our analysis, which is validated via simulations, we
confirm that D-TDD outperforms S-TDD in DL, with the vice versa occurring in
UL, since asymmetric transmissions reduce DL interference at the expense of an
increased UL interference. We also find that in asymmetric scenarios, where
most of the traffic is in DL, D-TDD provides a DL packet throughput gain by
better controlling the queuing delay, and that such gain vanishes in the
light-traffic regime.
