A user apparatus in a multi input multi output (MIMO) mobile communications system using pre-encoding is disclosed. The user apparatus includes a PMI generator which generates, in accordance with a radio propagation condition, a pre-encoding matrix indicator (PMI) which indicates a pre-encoding matrix to be used by a base station; a delay circuit which takes, as an input, the PMI and which outputs the PMI after a predetermined delay period has elapsed; an accumulating unit which takes, as an input, the PMI from the delay circuit and stores the input PMI; and a channel estimator which, on a signal from the base station, performs channel estimation using the PMI stored in the accumulating unit.