1. A method of simulating a system in a communications network in order to obtain a prediction of a total load of a resource in the system, the method comprising: receiving, at an input of a load prediction apparatus, intensity values {a ij , i=1. .. m,j=1. .. n} for n events occurring in a reference system at m different occasions t i , wherein the occurrence of an event j requires a resource amount x j of the resource in the reference system; receiving, at an input of the load prediction apparatus, values of a total load L i of the resource in the reference system at the m different occasions t i ; receiving, at an input of the load prediction apparatus, intensity values {b pi , p, j=1. .. n} for each of the n events in a scenario p in the system for which the total load of the resource is to be predicted; optimizing, in the load prediction apparatus, an object function S described by: 
 S=Σ n j=1( b pj x j ), subject to the linear inequality constraints described by: y 1 ≤ a 11 ⁢ x 1 + … + a 1 ⁢ j ⁢ x j + … + a 1 ⁢ n ⁢ x n ≤ z 1 y i ≤ a i ⁢ ⁢ 1 ⁢ x 1 + … + a ij ⁢ x j + … + a in ⁢ x n ≤ z i y m ≤ a m ⁢ ⁢ 1 ⁢ x 1 + … + a mj ⁢ x j + … + a mn ⁢ x n ≤ z m wherein y i and z i are functions of the measured total load L i of the resource in the reference system, the optimization resulting in at least one optimized outcome of the object function S; and obtaining a prediction L p of the total load of the resource in the system based on the at least one optimized outcome of the object function S.