Disclosed is a method comprising providing a primary cell capable of serving a terminal device; determining a candidate secondary cell group, comprising one or more cells that have coverage area within the coverage are of the primary cell; determining, from the candidate secondary cell group, a cell that, based on information obtained before or during a connection setup signalling, has the highest probability of being successfully configured as a secondary cell for an inter-site carrier aggregation for the terminal device; and configuring the cell as the secondary cell for the inter-site carrier aggregation.