  We review the characteristics of signalling storms that have been caused by
certain common apps and recently observed in cellular networks, leading to
system outages. We then develop a mathematical model of a mobile user's
signalling behaviour which focuses on the potential of causing such storms, and
represent it by a large Markov chain. The analysis of this model allows us to
determine the key parameters of mobile user device behaviour that can lead to
signalling storms. We then identify the parameter values that will lead to
worst case load for the network itself in the presence of such storms. This
leads to explicit results regarding the manner in which individual mobile
behaviour can cause overload conditions on the network and its signalling
servers, and provides insight into how this may be avoided.
