  Shadowing is believed to degrade the quality of service (QoS) in wireless
cellular networks. Assuming log-normal shadowing, and studying mobile's
path-loss with respect to the serving base station (BS) and the corresponding
interference factor (the ratio of the sum of the path-gains form interfering
BS's to the path-gain from the serving BS), which are two key ingredients of
the analysis and design of the cellular networks, we discovered a more subtle
reality. We observe, as commonly expected, that a strong variance of the
shadowing increases the mean path-loss with respect to the serving BS, which in
consequence, may compromise QoS. However, in some cases, an increase of the
variance of the shadowing can significantly reduce the mean interference factor
and, in consequence, improve some QoS metrics in interference limited systems,
provided the handover policy selects the BS with the smallest path loss as the
serving one. We exemplify this phenomenon, similar to stochastic resonance and
related to the "single big jump principle" of the heavy-tailed log-nornal
distribution, studying the blocking probability in regular, hexagonal networks
in a semi-analytic manner, using a spatial version of the Erlang's loss formula
combined with Kaufman-Roberts algorithm. More detailed probabilistic analysis
explains that increasing variance of the log-normal shadowing amplifies the
ratio between the strongest signal and all other signals thus reducing the
interference. The above observations might shed new light, in particular on the
design of indoor communication scenarios.
