g the following formula: LostCells 2 DiscardedCLP0Cells + DiscardedCLP1Cells + EPDCells + PPDCells + DiscardedPolicingCells + DiscardedChecksumErrorCells + DiscardedUTOPIAInterfaceCells + DiscardedCRCErrorCells + DiscardedErroredCells (3.79) A good estimation of the ingress CLR per port would then be LostCells CellLossRate 2 100 (3.80) IngressCells On the egress side similar calculations can be made. Loading Using the formula above and the Ingress PCR of all the ports in the interface unit, we can estimate the average load per unit in ingress using the following formula: IngressCells, AverageLoadPerUnit 2 100 X (3.81) where n = number of used ports per unit T = measurement period Minimising Costs Two ways to minimise costs are minimising the transmission link capacities and transmission media selections. Minimising Transmission Link Capacities The costs of the transmission link capacity can build up from leasing costs of transmission capacity owned by some other company and/or from purchase, installation and maintanance costs of owned transmission capacity. Minimising the transmission link capacities is not a very effective method of improving network profitability if the operator owns the copper, fibre and/or microwave transmission links. Naturally when selecting the media and the bandwidth that will be bought it makes a difference to calculate carefully the foreseen service scenario to the base station level and make decisions about the media and bandwidth based on that calculation. However, when the purchase is done and the transmission links are installed then obviously transmission links should not be minimised but rather maximised within the installed bandwidth to get the most out of it. Minimising the transmission link capacities is, however, quite a fundamental way to minimise the costs if the operator is using a leased transmission capacity. Leased capacity is normally in the form of copper or fibre, but very rarely, if ever, microwave radio links and used. Common granularity of leasing Transmission Netw