Method for dimensioning a policy and charging rules function (PCRF) module of a communication system, the method comprising: determining a number ( I(t)) of processing nodes ( 205 i) of the PCRF module at a time instant (t); determining a first transaction parameter (TPS(t)) indicative of a number of transactions per second exchanged by the processing nodes ( 205 i) at the time instant ( t); determining a load parameter ( CPU Load (t)) indicative of a processing load of the processing nodes ( 205 i) at the time instant ( t); characterized by the method further comprising: based on said first transaction parameter (TPS(t)), on said load parameter ( CPU Load (t)), on said number ( I(t)) of processing nodes ( 205 i), and on an allowable processing load at which the processing nodes ( 205 i) are set for allowing a safe operation thereof, determining (325,330) a second transaction parameter ( ETPS L (t)) indicative of a number of transactions per second that are expected to be exchanged at the time instant ( t) by the processing nodes ( 205 i) set at the allowable processing load; forecasting the first transaction parameter for a following time instant ( t + 1) following the time instant ( t) thereby obtaining a forecasted first transaction parameter ( TPS(t + 1)); forecasting the second transaction parameter for said following time instant ( t + 1) thereby obtaining a forecasted second transaction parameter ( ETPS L (t + 1)); determining a number ( I(t + 1)) of processing nodes ( 205 i) required at said following time instant ( t +1) according to said forecasted first transaction parameter ( TPS ( t + 1)) and to said forecasted second transaction parameter ( ETPS L ( t + 1)). determining a number ( I(t)) of processing nodes ( 205 i) of the PCRF module at a time instant (t); determining a first transaction parameter (TPS(t)) indicative of a number of transactions per second exchanged by the processing nodes ( 205 i) at the time instant ( t); determining a load parameter ( CPU Load (t)) indicative of a processing load of the processing nodes ( 205 i) at the time instant ( t); characterized by the method further comprising: based on said first transaction parameter (TPS(t)), on said load parameter ( CPU Load (t)), on said number ( I(t)) of processing nodes ( 205 i), and on an allowable processing load at which the processing nodes ( 205 i) are set for allowing a safe operation thereof, determining (325,330) a second transaction parameter ( ETPS L (t)) indicative of a number of transactions per second that are expected to be exchanged at the time instant ( t) by the processing nodes ( 205 i) set at the allowable processing load; forecasting the first transaction parameter for a following time instant ( t + 1) following the time instant ( t) thereby obtaining a forecasted first transaction parameter ( TPS(t + 1)); forecasting the second transaction parameter for said following time instant ( t + 1) thereby obtaining a forecasted second transaction parameter ( ETPS L (t + 1)); determining a number ( I(t + 1)) of processing nodes ( 205 i) required at said following time instant ( t +1) according to said forecasted first transaction parameter ( TPS ( t + 1)) and to said forecasted second transaction parameter ( ETPS L ( t + 1)). based on said first transaction parameter (TPS(t)), on said load parameter ( CPU Load (t)), on said number ( I(t)) of processing nodes ( 205 i), and on an allowable processing load at which the processing nodes ( 205 i) are set for allowing a safe operation thereof, determining (325,330) a second transaction parameter ( ETPS L (t)) indicative of a number of transactions per second that are expected to be exchanged at the time instant ( t) by the processing nodes ( 205 i) set at the allowable processing load; forecasting the first transaction parameter for a following time instant ( t + 1) following the time instant ( t) thereby obtaining a forecasted first transaction parameter ( TPS(t + 1)); forecasting the second transaction parameter for said following time instant ( t + 1) thereby obtaining a forecasted second transaction parameter ( ETPS L (t + 1)); determining a number ( I(t + 1)) of processing nodes ( 205 i) required at said following time instant ( t +1) according to said forecasted first transaction parameter ( TPS ( t + 1)) and to said forecasted second transaction parameter ( ETPS L ( t + 1)).