  We consider a tandem queue with coupled processors, which is subject to
global breakdowns. When the network is in the operating mode and both queues
are non empty, the total service capacity is shared among the stations
according to fixed proportions. When one of the stations becomes empty, the
total service capacity is given to the non-empty station. Moreover, arrival
rates depend on the state of the network. The system is described by a Markov
modulated random walk in the quarter plane representing the number of jobs in
the two stations and the state of the network. By applying the generating
function approach, we first apply the power series approximation method to
obtain power series expansions of the generating function of the stationary
queue lengths for both network states. Then, we also provide a way to derive
the generating function of the stationary queue lengths for both network states
in terms of the solution of a Riemann-Hilbert boundary value problem. Numerical
results are obtained to show insights in the system performance.
