A radio base station system includes at least one Radio Equipment Control (REC) that comprises radio functions of a digital baseband domain, and at least one Radio Equipment (RE) that serves as an air interface and comprises analogue radio frequency functions. A Common Public Radio Interface (CPRI) link connects the at least one REC and the at least one RE. CPRI traffic carried by the CPRI link leaves an amount of spare capacity. The CPRI link carries non-CPRI traffic encapsulated within the spare capacity.