Monitoring System for a Distributed Antenna System

1. A monitoring system for a distributed antenna system comprising at least a central transmitter and a plurality of distributed antenna devices connected to the transmitter via a respective physical branch of a signal transmission network comprising a plurality of branches, each of the distributed antenna devices comprising at least one antenna which is associated with a frequency band having a centre frequency fc and a corresponding wavelength λc, the monitoring system comprising: a central monitoring unit which is coupled to the network; at least one monitoring device associated with at least one of said distributed antenna devices and permanently mounted a distance d away from the at least one antenna of the distributed antenna device, the distance d being less than 2 times λc (2λc); the at least one monitoring device comprising a local controller, a transceiver and an antenna; the local controller being configured, upon being polled by the central monitoring unit with a monitoring signal via the associated distributed antenna device and the respective branch of the network, to process the monitoring signal to measure the quality of the monitoring signal and to cause the transceiver to respond to the monitoring signal by transmitting a response signal comprising an indication of the measured quality to the central monitoring unit via the associated distributed antenna device and the network.

2. The monitoring system as claimed in claim 1 wherein d is less than λc/2.

3. The monitoring system as claimed in claim 1 wherein the at least one monitoring device comprises a local power supply comprising at least one of a battery and an energy harvesting circuit for collecting energy from the distributed antenna device through the antenna of the monitoring device.

4. The monitoring system as claimed in claim 1 wherein the at least one monitoring device is associated with a respective unique address which is stored in a memory arrangement of the monitoring device.

5. The monitoring system as claimed in claim 4 wherein the central monitoring unit comprises means for measuring the strength of the response signal received from the at least one monitoring device and a database for storing data relating to the unique addresses of the at least one monitoring device and at least one of data relating to the monitored status and data relating to a position of the associated distributed antenna device.

6. The monitoring system as claimed in claim 1 wherein the at least one monitoring device comprises an indicator arrangement for providing a human perceivable indication relating to a monitored status of at least one of the associated distributed antenna device and the branch connected thereto, based on the measured quality of the monitoring signal.

7. The monitoring system as claimed in claim 1 wherein the at least one monitoring device is mounted in or on the associated distributed antenna device.

8. The monitoring system as claimed in claim 7 wherein the at least one monitoring device is encapsulated in a housing which is mountable on an optional radome of the associated distributed antenna device.

9. The monitoring system as claimed in claim 1 wherein the central monitoring unit is coupled to the network by a coupler to inject the monitoring signal into the network.

10. The monitoring system as claimed in claim 1 wherein the monitoring signal and the response signal are at least one of a) at least 10 dB weaker than a main signal transmitted by the central transmitter and b) out of band relative to the main signal.

11. The monitoring system as claimed in claim 1 comprising at least one path diagnostic switching device which is connected in a branch of the network and configured to be switched between a first state wherein it passes along the branch input power received by the switch device and a second state wherein it attenuates or diverts away from the branch at least some of the input power received by the switch device.

12. A distributed antenna system comprising a monitoring system as claimed in claim 1.

13. A system as claimed in claim 1 wherein the quality of the monitoring signal is measured by measuring the strength of the monitoring signal and wherein the indication of the measured quality comprises data relating to the measured strength.

14. A method of monitoring performance of a distributed antenna system comprising at least a central transmitter and a plurality of distributed antenna devices connected to the transmitter via a respective physical branch of a signal transmission network comprising a plurality of branches, each of the distributed antenna devices comprising at least one antenna which is associated with a frequency band having a centre frequency fc and a corresponding wavelength λc, the method comprising: for at least some of the distributed antenna devices, providing a respective associated monitoring device at a distance d<2λc from the at least one antenna; transmitting from a central monitoring unit to at least one targeted monitoring device a monitoring signal via the associated distributed antenna device and the respective branch of the network; at the at least one targeted monitoring device processing the monitoring signal to measure the quality of the monitoring signal and generating a response signal comprising an indication of the measured quality and transmitting the response signal to the central monitoring unit via the associated distributed antenna device and the network.

15. The method as claimed in claim 14 wherein the monitoring signal is addressed to the at least one targeted monitoring device by utilizing a respective unique address of the at least one targeted monitoring device.

16. The method as claimed in claim 14 wherein the monitoring signal is processed by measuring the strength of the monitoring signal at the at least one targeted monitoring device.

17. The method as claimed in claim 16 wherein data relating to the measured strength is sent from the at least one targeted monitoring device via the associated distributed antenna device and the network to the central monitoring unit and wherein the data is identified by the respective unique address.

18. The method as claimed in claim 17 wherein the strength of the response signal is measured at the central monitoring unit and wherein results of the measurements are utilized to monitor the status of asymmetrical up and down paths between the central monitoring unit and the at least one targeted monitoring unit.

19. The method as claimed in claim 14 wherein distributed switches in the network are utilized selectively to attenuate or divert power propagating to at least some of the distributed antenna devices, thereby to switch the at least some of the distributed devices out of the distributed antenna system and wherein the switches are controlled by command signals from at least the central monitoring unit.

20. The method as claimed in claim 19 wherein the monitoring signal, the response signal and the command signals are at a signal level to ensure communication and sensing between central monitoring unit, the monitoring devices and the switches devices, but below the level of a main signal transmitted by the central transmitter.

21. An antenna monitoring system comprising: a first monitor device configured to be adhered to a radome of a first antenna connected to a wired signal transmission network, the first monitor device configured to transmit a first antenna monitor signal, the first antenna monitor signal including first monitor data associated with the first monitor device; a second monitor device configured to be adhered to a radome of a second antenna connected to the wired signal transmission network, the second monitor device configured to transmit a second antenna monitor signal, the second antenna monitor signal including second monitor data associated with the second monitor device, the second monitor data being different from the first monitor data; a coupler configured to be connected to the wired signal transmission network; and a monitoring unit configured to be connected to the wired signal transmission network through the coupler, the monitoring unit further configured to receive the first antenna monitor signal, receive the second antenna monitor signal, generate a first antenna status indicating a status of the first antenna, and generate a second antenna status indicating a status of the second antenna; wherein, within a predetermined time period, the first monitor device transmits the first antenna monitor signal, and within a same predetermined time period, the second monitor device transmits the second antenna monitor signal; wherein, responsive to receiving the first antenna monitor signal, the monitoring unit generates the first antenna status indicating an operational status of the first antenna; wherein, responsive to failing to receive the second antenna monitor signal, the monitoring unit generates the second antenna status indicating a defective status of the second antenna; wherein the monitoring unit is configured to transmit a first signal to the first monitor device and transmit a second signal to the second monitor device; wherein the coupler is configured to inject the first signal and the second signal into the wired signal transmission network; wherein the first monitor device is configured to transmit the first antenna monitor signal responsive to receiving the first signal via the wired signal transmission network; and wherein the second monitor device is configured to transmit the second antenna monitor signal responsive to receiving the second signal via the wired signal transmission network.

22. The antenna monitoring system of claim 21, wherein the first monitor data includes a first monitor device identifier identifying the first monitor device, and wherein the second monitor data includes a second monitor device identifier identifying the second monitor device.

23. The antenna monitoring system of claim 22, further comprising an antenna status database, wherein the monitoring unit stores a database entry representing the first antenna status in the antenna status database and stores a database entry representing the second antenna status in the antenna status database.

24. The antenna monitoring system of claim 23, wherein: the first monitor device periodically and once within each of successive predetermined periods of time transmits the first antenna monitor signal; the second monitor device periodically and once within each of successive predetermined periods of time transmits the second antenna monitor signal; responsive to receiving the first antenna monitor signal, the monitoring unit generates the first antenna status indicating the operational status of the first antenna and stores the database entry representing the operational status of the first antenna; responsive to receiving the second antenna monitor signal, the monitoring unit generates the second antenna status indicating an operational status of the second antenna and stores the database entry representing the operational status of the second antenna; responsive to failing to receive the first antenna monitor signal, the monitoring unit generates the first antenna status indicating a defective status of the first antenna and stores a database entry representing the defective status of the first antenna; responsive to failing to receive the second antenna monitor signal, the monitoring unit generates the second antenna status indicating the defective status of the second antenna and stores a database entry representing the defective status of the second antenna.

25. The antenna monitoring system of claim 24, wherein: the first monitor device is configured to transmit the first antenna monitor signal via the first antenna; the second monitor device is configured to transmit the second antenna monitor signal via the second antenna; and the monitoring unit receives the first antenna monitor signal from a communication path that includes the first antenna and receives the second antenna monitor signal from a communication path that includes the second antenna.

26. The antenna monitoring system of claim 25, wherein the first monitor device is powered by a first battery and the second monitor device is powered by a second battery.

27. The antenna monitoring system of claim 26, wherein the first monitor data includes data representative of a current status of power of the first battery, and wherein the second monitor data includes data representative of a current status of power of the second battery.

28. The antenna monitoring system of claim 25, wherein the monitoring unit is configured to measure a signal strength associated with the first antenna monitor signal and to generate an additional first antenna status indicative of the signal strength.

29. An antenna monitoring system comprising: a first monitor device configured to be mounted on or within a housing of a first antenna, the first monitor device comprising a first local antenna, a first transceiver configured to receive and transmit signals, and a first local storage storing first monitor identification data identifying the first monitor device, the first monitor device configured to transmit, responsive to being polled by a monitoring unit, a first antenna monitor signal using the first local antenna and via the first antenna, the first antenna monitor signal including the first monitor identification data; an antenna status database storing one or more antenna status entries indicating a status of the first antenna; and the monitoring unit configured to receive the first antenna monitor signal transmitted by the first monitor device, determine a first antenna status based on receipt or non-receipt of the first antenna monitor signal, and store in the antenna status database a first antenna status entry comprising data indicative of the first antenna status; wherein the first monitor device transmits the first antenna monitor signal; wherein responsive to the monitoring unit failing to receive, after a predetermined number of polls, the first antenna monitor signal, the monitoring unit determines that the first antenna status is defective and stores in the antenna status database the first antenna status entry comprising data indicating that the first antenna is defective; and wherein responsive to the monitoring unit receiving, within the predetermined number of polls, the first antenna monitor signal, the monitoring unit determines that the first antenna status is normal and stores in the antenna status database the first antenna status entry comprising data indicating that the first antenna is operating normally.

30. The antenna monitoring system of claim 29, wherein the monitoring unit is further configured to: upon receiving the first antenna monitor signal, determine a first antenna level status based on a signal strength indicated by the first antenna monitor signal; and responsive to a comparison involving the signal strength indicating degradation, determine that the first antenna level status corresponds to a low level.

31. The antenna monitoring system of claim 30, wherein degradation is indicated when the signal strength indicated by the first antenna monitor signal is lower than a threshold strength.

32. The antenna monitoring system of claim 30, wherein degradation is indicated when a difference between the signal strength and a prior signal strength is greater than a threshold difference.

33. The antenna monitoring system of claim 30, wherein the monitoring unit is further configured to measure the signal strength of the first antenna monitor signal.

34. The antenna monitoring system of claim 30, wherein the first monitor device is further configured to measure signal strength of signals transmitted by the first antenna, and wherein data indicating the measured signal strength is included in the first antenna monitor signal transmitted by the first monitor device.

35. The antenna monitoring system of claim 30, wherein the first antenna status entry further comprises data indicative of the first antenna level status.

36. The antenna monitoring system of claim 29, wherein the first monitor device is powered by a battery.

37. The antenna monitoring system of claim 29, wherein the monitoring unit receives the first antenna monitor signal via the first antenna.

38. The antenna monitoring system of claim 29, wherein the antenna status database is a component of the monitoring unit.

39. The antenna monitoring system of claim 29, wherein the antenna status database is remote to the monitoring unit.

40. The antenna monitoring system of claim 39, wherein the monitoring unit stores data in the antenna status database using wireless communication.

41. The antenna monitoring system of claim 29, wherein the antenna status database stores information indicative of a location of the first antenna.

42. The antenna monitoring system of claim 29, further comprising a second monitor device configured to be mounted on or within a housing of a second antenna, the second monitor device comprising a second local antenna, a second transceiver configured to receive and transmit signals, and a second local storage storing second monitor identification data identifying the second monitor device, the second monitor device configured to transmit, responsive to being polled by a monitoring unit, a second antenna monitor signal using the second local antenna and via the second antenna, the second antenna monitor signal including the second monitor identification data, wherein the one or more antenna status entries indicate a status of at least one of the first antenna or the second antenna; wherein the monitoring unit is further configured to receive the second antenna monitor signal transmitted by the second monitor device, determine a second antenna status based on receipt or non-receipt of the second antenna monitor signal, and store in the antenna status database a second antenna status entry comprising data indicative of the second antenna status; wherein the second monitor device transmits the second antenna monitor signal; wherein responsive to the monitoring unit failing to receive, after the predetermined number of polls, the second antenna monitor signal, the monitoring unit determines that the second antenna status is defective and stores in the antenna status database the second antenna status entry comprising data indicating that the second antenna is defective; and wherein responsive to the monitoring unit receiving, within the predetermined number of polls, the second antenna monitor signal, the monitoring unit determines that the second antenna status is normal and stores in the antenna status database the second antenna status entry comprising data indicating that the second antenna is operating normally.