A method of operation of a base station in a cellular communications network, in which user equipment devices in a cell served by the base station need to be synchronized with the cell on the uplink in order to transmit data, and in which Radio Resource Control, RRC, connected user equipment devices can be kept synchronized with the cell on the uplink or not synchronized. The method comprises making a determination as to whether a specified condition within the cell served by the base station is fulfilled, and, in response to the determination as to whether the specified condition within the cell is fulfilled, determining whether RRC connected user equipment devices should be kept uplink synchronized with the cell, or whether RRC connected user equipment devices should be allowed to become not synchronized on the uplink. Signals are transmitted to user equipment devices to affect whether or not the RRC connected user equipment devices are kept uplink synchronized with the cell, in response to determining whether RRC connected user equipment devices should be kept uplink synchronized with the cell, or whether RRC connected user equipment devices should be allowed to become not synchronized on the uplink.