A monitoring system, for a distributed antenna system comprising at least a central transmitter and a plurality of distributed antenna devices (16.1 to 16.n) connected to the central transmitter via a respective physical branch (14.11, 14.12) of a signal transmission network comprising a plurality of branches (14.1, 14.2), each of the distributed antenna devices comprising at least one antenna which is associated with a frequency band having a centre frequency f c and a corresponding wavelength λ c, the monitoring system comprising: - a central monitoring unit which is coupled to the network; - at least one respective monitoring device (28.1) associated with at least one of said distributed antenna devices (16.1) and permanently mounted at a distance d away from the at least one antenna of the distributed antenna device, the distance d being less than 2 times λ c; - the at least one monitoring device (28.1) comprising a local controller, a transceiver, a memory arrangement and an antenna; - the central monitoring unit being configured to transmit a monitoring signal, in a downward direction and along a downward path via the respective physical branch (14.11) of the network and the associated distributed antenna device (16.1), to the respective monitoring device (28.1); and - the local controller being configured upon being polled by the central monitoring unit with the monitoring signal, to cause the transceiver to respond to the monitoring signal by transmitting a response signal in an upward direction and along an upward path to the central monitoring unit via the associated distributed antenna device and the network; - the at least one respective monitoring device (28.1) being associated with a respective unique address which is stored in the memory arrangement and being configured to measure a quality of the monitoring signal and wherein the response signal comprises the measured signal quality; - the central monitoring unit comprising means for measuring the strength of the response signal received from the at least one respective monitoring device; and the central monitoring unit further being configured to utilize the measured signal quality of the monitoring signal and the measured strength of the response signal to monitor the status of asymmetrical up and down paths between the central monitoring unit and the at least one respective monitoring device. - a central monitoring unit which is coupled to the network; - at least one respective monitoring device (28.1) associated with at least one of said distributed antenna devices (16.1) and permanently mounted at a distance d away from the at least one antenna of the distributed antenna device, the distance d being less than 2 times λ c; - the at least one monitoring device (28.1) comprising a local controller, a transceiver, a memory arrangement and an antenna; - the central monitoring unit being configured to transmit a monitoring signal, in a downward direction and along a downward path via the respective physical branch (14.11) of the network and the associated distributed antenna device (16.1), to the respective monitoring device (28.1); and - the local controller being configured upon being polled by the central monitoring unit with the monitoring signal, to cause the transceiver to respond to the monitoring signal by transmitting a response signal in an upward direction and along an upward path to the central monitoring unit via the associated distributed antenna device and the network; - the at least one respective monitoring device (28.1) being associated with a respective unique address which is stored in the memory arrangement and being configured to measure a quality of the monitoring signal and wherein the response signal comprises the measured signal quality; - the central monitoring unit comprising means for measuring the strength of the response signal received from the at least one respective monitoring device; and the central monitoring unit further being configured to utilize the measured signal quality of the monitoring signal and the measured strength of the response signal to monitor the status of asymmetrical up and down paths between the central monitoring unit and the at least one respective monitoring device.