Past exam of the mathematics course of the University of Cambridge 2010 iii Paper 30 3 c Solution Created 2026-10-03 Updated 2026-10-14
The alternative routing term feeds additional traffic back into the link. We can prove the existence of three solutions rather than relying on an iteration that happens to find different answers. Choose , , and define the continuous residualBy the proportional scaling limit of the Erlang loss formula, at each fixed ,At , the multiplier is , so . At it is , givingAlso and for every , since a finite-capacity Erlang loss formula gives a blocking probability strictly between zero and one. For all sufficiently large , the signs at therefore alternate. Applying the intermediate value theorem in the three disjoint intervening intervals proves at least three distinct fixed points. This supplies a fluid scaling proof of multiple Erlang fixed points.
This multiplicity concerns the Erlang fixed point approximation. It does not imply several equilibrium laws for an exact finite irreducible Markov chain, which has a unique stationary distribution.
