Wireless communication device, network node, methods and computer programs for aiding finding of synchronisation signals

1. A method, performed by a wireless communication device of a cellular communication system, for obtaining mobility measurements of a second radio access network (RAN) operating using a second radio access technology (RAT) when the wireless communication device has established communication with a first RAN operating using a first RAT, wherein 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 comprising:

receiving a radio resource control (RRC) message including allocation information about the synchronisation signals of the second RAT; and

performing synchronisation signal detection based on the allocation information.

2. The method of claim 1 , wherein the allocation information comprises specific frequency information for the synchronisation signals.

3. The method of claim 1 , wherein the allocation information comprises a frequency offset for the synchronisation signal frequency in relation to the network frequency.

4. The method of claim 1 , wherein the performing synchronisation signal detection comprises:

changing receiver frequency based on the frequency allocation of the synchronisation signals such that synchronisation signals are comprised in a received bandwidth;

monitoring within the received bandwidth for synchronisation signals; and

decoding, upon found synchronisation signals, the synchronisation signals.

5. The method of claim 1 , comprising, after performing synchronisation signal detection, tuning a receiver frequency to the determined network frequency.

6. The method of claim 1 , comprising:

determining, upon successful synchronization with the second RAT, allocation information about the synchronisation signals of the second RAT; and

transmitting, to a network node or to neighbouring network nodes of the network node, information about the second RAT on which the successful synchronisation has been performed including the allocation information about the synchronisation signals of the second RAT.

7. A wireless communication device arranged to operate in a cellular communication system and to obtain mobility measurements of a second radio access network (RAN) operating using a second radio access technology (RAT) when the wireless communication device has established communication with a first RAN operating using a first RAT, wherein the first RAT has synchronisation signals with a first allocation and the second RAT has synchronisation signals with a second frequency allocation in relation to a network frequency for the second RAT, the wireless communication device comprising:

a transceiver; and

a controller,

wherein the transceiver is arranged to receive a radio resource control (RRC) message including allocation information about the synchronisation signals of the second RAT; and

the controller is arranged to cause the transceiver to perform synchronisation signal detection based on the allocation information.

8. The wireless communication device of claim 7 , wherein the allocation information comprises specific frequency information for the synchronisation signals.

9. The wireless communication device of claim 7 , wherein the allocation information comprises a frequency offset for the synchronisation signal frequency in relation to the network frequency.

10. The wireless communication device of claim 7 , arranged to perform the synchronisation signal detection by being arranged to:

change receiver frequency of the transceiver based on the frequency allocation of the synchronisation signals such that synchronisation signals are comprised in a received bandwidth;

monitor within the received bandwidth for synchronisation signals; and

decode, upon found synchronisation signals, remaining synchronisation signals of a system network access signalling transmission.

11. The wireless communication device of claim 7 , arranged to, after performing synchronisation signal detection, tune a receiver frequency of the transceiver to the determined network frequency.

12. The wireless communication device of claim 7 , being arranged to:

determine, upon successful synchronisation with the second RAT, allocation information about the synchronisation signals of the second RAT, wherein the allocation information comprises a frequency offset for the synchronisation signal frequency in relation to the network frequency for the second RAT; and

transmit, to a network node or to neighbouring network nodes of the network node, information about the second RAT including the allocation information about the synchronisation signals of the second RAT.

13. The wireless communication device of claim 7 , wherein:

the wireless communication device is a User Equipment (UE); and

at least one of the first and second RATs is 3rd Generation Partnership Project (3GPP) New Radio (NR) access technology.

14. A nontransitory computer readable storage medium comprising computer program instructions which, when executed on a processor of a wireless communication device of a cellular communication system, causes the wireless communication device to perform a method for obtaining mobility measurements of a second radio access network (RAN) operating using a second radio access technology RAT when the wireless communication device has established communication with a first RAN operating using a first RAT, wherein 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 comprising:

receiving a radio resource control (RRC) message including allocation information about the synchronisation signals of the second RAT; and

performing synchronisation signal detection based on the allocation information.