Described is a removable assembly for use on a fixed surface. Messages are exchanges over one or more traffic channels to establish a packet-switched services session between the mobile station and the radio network controller. The whitening filter may be computed based on the covariance matrix of the interference component. Then, a cleaning step is performed to a long cleaning gas injector. The system further includes a sensor for sensing at least one coded data tag and for generating a signal indicative of the sensed coded data tag. Also described is a system and a method in which the mobile station operates.