In this embodiment, the lights 71 and 62 to 69 buffer and forward received command messages to other devices. In an alternative embodiment, the mobile device 81 and the sensor devices 23 and 27 first receive the schedule from light 71 and only transmit a command message to one of the lights 71 and 62 to 69 when it is able to receive messages according to the schedule. In another alternative embodiment, the mobile device 81 and the sensor devices 23 and 27 are not aware of the schedule, but are able to determine whether a command message has been successfully delivered to its destination, e.g. to one or more of lights 71 and 62 to 69, and retransmit the command messages one or more times until it has been successfully delivered to its destination.

An embodiment of the light 71 is shown in more detail in FIG. 7. In this embodiment, the light 71 comprises a transceiver 73 and a processor 75. The processor 75 is configured to determine a group of service-providing devices. The group comprises at least two service-providing devices capable of performing a similar or a same service. The processor 75 is further configured to determine a schedule for the service-providing devices in the group. The schedule indicates for each service-providing device of the group in which time period the service-providing device is able to receive messages such that at least one device of the determined group of service-providing devices is able to receive messages. The processor 75 is also configured to use the transceiver 73 to transmit the schedule to the service-providing devices of the group.