A localization system for detecting a location of a mobile device within an environment, the localization system comprising a plurality of wireless reference nodes, wherein each of one, some or all of the wireless reference nodes comprises one or more lamps, wherein: each of the wireless reference nodes comprises a wireless interface arranged to transmit localization beacon signals to be detected by the mobile device, and/or to listen for localization beacon signals from the mobile device; the system comprises one or more lamps co-located with each of one, some or all of the wireless reference nodes arranged to provide or contribute to providing another utility into the environment, other than localization of mobile devices, the another utility comprising illumination for illuminating the environment; the system further comprises one or more controllers (13, 20) arranged to control said one or more lamps, and to use said wireless interface of each of the lamps to transmit and/or listen for control-related signals, other than localization beacon signals, related to controlling the provision of said utility, the location system characterized in that: the one or more of the wireless reference nodes further comprise a light level sensor and/or a presence sensor, the presence sensor arranged to detect the presence of a human in a certain defined region in the environment; the control-related signals being communicated on a same or overlapping frequency band as the localization beacon signals; wherein at least some of the control-related signals comprise sensor data transmitted from at least one of said one or more wireless reference nodes, taken using a respective sensor of the at least one of said one or more wireless reference nodes; wherein the wireless reference nodes are configured to time-multiplex the transmission of and/or listening for the localization beacon signals into different time slots than the transmission of and/or listening for said control-related signals, and the time slots for the localization signals are between the time slots of the control-related signals; wherein the at least one of the wireless reference nodes is further configured to detect one or more sensing events based on activity sensed using the respective sensor, transmit the sensor data in an allocated one of said time slots if one of the sensing events is detected, and transmit one of the localization beacon signals in said allocated time slot if none of the sensing events is detected. each of the wireless reference nodes comprises a wireless interface arranged to transmit localization beacon signals to be detected by the mobile device, and/or to listen for localization beacon signals from the mobile device; the system comprises one or more lamps co-located with each of one, some or all of the wireless reference nodes arranged to provide or contribute to providing another utility into the environment, other than localization of mobile devices, the another utility comprising illumination for illuminating the environment; the system further comprises one or more controllers (13, 20) arranged to control said one or more lamps, and to use said wireless interface of each of the lamps to transmit and/or listen for control-related signals, other than localization beacon signals, related to controlling the provision of said utility, the one or more of the wireless reference nodes further comprise a light level sensor and/or a presence sensor, the presence sensor arranged to detect the presence of a human in a certain defined region in the environment; the control-related signals being communicated on a same or overlapping frequency band as the localization beacon signals; wherein at least some of the control-related signals comprise sensor data transmitted from at least one of said one or more wireless reference nodes, taken using a respective sensor of the at least one of said one or more wireless reference nodes; wherein the wireless reference nodes are configured to time-multiplex the transmission of and/or listening for the localization beacon signals into different time slots than the transmission of and/or listening for said control-related signals, and the time slots for the localization signals are between the time slots of the control-related signals; wherein the at least one of the wireless reference nodes is further configured to detect one or more sensing events based on activity sensed using the respective sensor, transmit the sensor data in an allocated one of said time slots if one of the sensing events is detected, and transmit one of the localization beacon signals in said allocated time slot if none of the sensing events is detected.