Iu signalling connection management

The purpose of the Initial UE Message procedure is to establish an Iu signalling connection between a CN domain and the RNC. The procedure uses connection oriented signalling. When the RNC has received from radio interface a NAS message to be forwarded to a CN domain to which no Iu signalling connection for the UE exists, the RNC shall initiate the Initial UE Message procedure and send the INITIAL UE MESSAGE message to the CN.