A basestation in a cellular communications network is operable to send a message to a Mobility Management Entity, relating to a suspension or resumption of a connection of a UE, wherein the message contains key renewal information. The Mobility Management Entity receives the message, and determines whether a key renewal condition is met. If the key renewal condition is met, the MME forwards a new NH, NCC pair to the base station. If a message received from the MME includes a NH, NCC pair, the basestation derives keying information using the NH, NCC pair for future use in deriving keys.