A method of a network node of a cellular communication system for mobility from a first radio access network, RAN, operating using a first radio access technology, RAT, to a second RAN operating using a second RAT. The first RAT has synchronisation signals with a first frequency allocation and the second RAT has synchronisation signals with a second frequency allocation in relation to a network frequency for the second RAT. The method comprises determining allocation information about the synchronisation signals of the second RAT, and transmitting a radio resource control, RRC, message including the allocation information about the synchronisation signals of the second RAT. A method for the wireless communication device is also disclosed, as well as a network node, a wireless communication device and computer programs for them.