Within a cell area, an RBS typically provides communication services to UEs. During operation, the UE adjusts its transmission power according to a transmission parameter value such as the E-TFCI. The RBS provides a predetermined number of reference points for E-TFCI that covers the limited range. For any intermediate values not specifically provided, the UE calculates the SIR through interpolation. The RBS predicts a range of transmission power likely to be used by the UE and provides the reference points based on the prediction. The prediction is performed based on operational measurement.