The disclosure discloses a method for a joint multi-carrier operation of narrowband Internet-of-Things (NB-IoT) in both licensed and unlicensed frequency spectrum. The object of the disclosure to provide a method that uses the existing technologies of multi-carrier operation, but can also handle and use ISM bands (unlicensed bands) and thereby all regulatory requirements are observed, will be solved by a method for a joint multi-carrier operation of narrowband Internet-of-Things (NB-IoT) in both licensed and unlicensed frequency spectrum by extending the existing NB-IoT regulations standard in licensed spectrum by additional uplink and/or downlink NB-IoT carriers operating in unlicensed spectrum, wherein additional data depending on a scheduled medium access procedure is added to configuration data, which is broadcasted between a base station and a UE for ensuring regulatory compliance during operation on both the UE and base station side.