A method of allowing a group of field devices in a process control system for an industrial process to communicate with a process control device while meeting a communication restriction requirement, the method being performed in a network supervisor device of the process control system, said process control system further comprising a first wireless communication network having a first communication structure with a superframe comprising time slots, a second wireless communication network having a second communication structure (SF') with a superframe comprising time slots, and a first group of wireless field devices (16, 18, 20, 22, 24, 26) interfacing the industrial process, being associated with the first wireless communication network and communicating with a first control application being carried out by the process control device, the method comprising the steps of: investigating if the field devices of the first group are able to communicate with the process control device via the first wireless communication network in the same superframe in separate consecutive time slots with data having the same time stamp while meeting the communication restriction requirement (ΔT), where the communication restriction requirement is that all transmissions for the first application of the same superframe fit in a time interval defined by the process control device, and in case the communication restriction requirement is not met, redirecting communication between some of the field devices in the first group and the process control device to the second wireless communication network so that the communication restriction requirement is met for a first part (16, 18, 20) of the field devices in the first group using the first wireless communication network and for a second part (22, 24, 26) of the field devices of the first group using the second wireless communication network, through requesting scheduling of communication of the field devices in the second part of the first group in consecutive time slots of the second communication structure that are close to the time slots assigned to field devices in the first part of the first group remaining in the first wireless communication network so that all time slots of the first communication structure used by the first part of the field devices in the first group and of the second communication structure used by the second part of the field devices in the first group are transmitted within the time interval. investigating if the field devices of the first group are able to communicate with the process control device via the first wireless communication network in the same superframe in separate consecutive time slots with data having the same time stamp while meeting the communication restriction requirement (ΔT), where the communication restriction requirement is that all transmissions for the first application of the same superframe fit in a time interval defined by the process control device, and in case the communication restriction requirement is not met, redirecting communication between some of the field devices in the first group and the process control device to the second wireless communication network so that the communication restriction requirement is met for a first part (16, 18, 20) of the field devices in the first group using the first wireless communication network and for a second part (22, 24, 26) of the field devices of the first group using the second wireless communication network, through requesting scheduling of communication of the field devices in the second part of the first group in consecutive time slots of the second communication structure that are close to the time slots assigned to field devices in the first part of the first group remaining in the first wireless communication network so that all time slots of the first communication structure used by the first part of the field devices in the first group and of the second communication structure used by the second part of the field devices in the first group are transmitted within the time interval.