Network call processor must become involved for this one. Expect this to be rare since trees cover large geographic area. Statistical multiplexing suggests that this should be rare. Authors derive the probability of overloading and expected overload period as a function of number of users in total tree and number of users each BS can handle, using binomial distribution to assign users to BS's. Under heavy traffic, its result converges to that of the simple model.
Authors show how the info required by their system fits into the signalling field of the frame.
Trees are a non-optimal routing topology, though authors do derive the expected congestion.