Method and apparatus for the detection of distortion or corruption of cellular communication signals
A system for troubleshooting signals in a cellular communications network, and in particular, for determining the cause of distortion or corruption of such signals, includes a robotic or other type of switch. The robotic switch can tap into selected uplink fiber-optic lines and selected downlink fiber-optic lines between radio equipment and radio equipment controllers in a wireless (e.g., cellular) network to extract therefrom the I and Q data. The selected I and Q data, in an optical form, is provided to an optical-to-electrical converter forming part of the system. The system includes an FPGA (Field Programmable Gate Array) or the like, and an analytic computer unit, or web server, and SSD (Solid State Drive) and magnetic disk storage, among other components of the system. The system analyzes the I and Q data provided to it, and determines the cause, or at least narrows the field of possible causes, of impairment to transmitted signals. The system includes a display which provides the troubleshooting information thereon for a user of the system to review, or other form of a report, and may communicate the analytical findings to a remote location over a public or private internet protocol network.
1. A method for use with a system including a radio equipment (RE) and a radio equipment controller (REC) being in communication through a medium having an uplink communication channel supporting uplink data communications from the RE to the REC, and a downlink communication channel supporting downlink data communications from the REC to the RE, the method comprising:
monitoring a transmitted power in the downlink communication channel;
determining a plurality of power levels based on the monitoring of the transmitted power in the downlink communication channel;
recording the plurality of power levels in a memory;
simultaneously with the monitoring of the transmitted power in the downlink communication channel, obtaining a spectrum of a signal in the uplink communication channel;
sorting each piece of the spectrum being obtained in the uplink communication channel into one of a plurality of groups, according to a corresponding simultaneous one of the plurality of power levels being recorded in the memory;
analyzing the spectrum sorted into the plurality of groups according to the plurality of power levels; and
determining, based on the analyzing, whether the signal includes a passive intermodulation distortion (PIM).
2. The method of claim 1 , wherein when the analyzing indicates that a level of an unused piece of the spectrum in the uplink communication channel increases with the transmitted power in the downlink communication channel, the determining determines that the signal includes the PIM.
3. The method of claim 1 further comprising:
displaying the spectrum in the uplink communication channel as a function of the transmitted power in the downlink communication channel.
4. The method of claim 1 further comprising:
simultaneously with the monitoring of the transmitted power in the downlink communication channel, extracting I/Q data from the signal in the uplink communication channel.
5. The method of claim 4 further comprising:
determining a distance to the PIM using the extracted I/Q data from the signal in the uplink communication channel.
6. The method of claim 1 , wherein the analyzing includes comparing the spectrum with a reference spectrum.
7. The method of claim 1 , wherein the analyzing includes obtaining a slope of the spectrum, and the determining includes using the slope of the spectrum.
8. The method of claim 1 further comprising:
detecting the PIM is at a first level on a plurality of antennas of the RE; and
determining that the PIM is caused by an external source based on the detecting.
9. The method of claim 8 further comprising:
determining a polarization angle of the external source; and
using the polarization to confirm that the PIM is caused by the external source.
10. The method of claim 1 further comprising:
detecting the PIM is at only one of a plurality of antennas of the RE; and
determining that the PIM is caused by an internal source based on the detecting.
11. A test device for use with a system including a radio equipment (RE) and a radio equipment controller (REC) being in communication through a medium having an uplink communication channel supporting uplink data communications from the RE to the REC, and a downlink communication channel supporting downlink data communications from the REC to the RE, the test device comprising:
a processor configured to:
monitor a transmitted power in the downlink communication channel;
determine a plurality of power levels based on the monitoring of the transmitted power in the downlink communication channel;
record the plurality of power levels in a memory;
simultaneously with the monitoring of the transmitted power in the downlink communication channel, obtain a spectrum of a signal in the uplink communication channel;
sort each piece of the spectrum being obtained in the uplink communication channel into one of a plurality of groups, according to a corresponding simultaneous one of the plurality of power levels being recorded in the memory;
analyze the spectrum sorted into the plurality of groups according to the plurality of power levels; and
determine, based on the analyzing, whether the signal includes a passive intermodulation distortion (PIM).
12. The test device of claim 11 , wherein when the analyzing indicates that a level of an unused piece of the spectrum in the uplink communication channel increases with the transmitted power in the downlink communication channel, the determining determines that the signal includes the PIM.
13. The test device of claim 11 , wherein the processor is further configured to:
display the spectrum in the uplink communication channel as a function of the transmitted power in the downlink communication channel.
14. The test device of claim 11 , wherein the processor is further configured to:
simultaneously with the monitoring of the transmitted power in the downlink communication channel, extract I/Q data from the signal in the uplink communication channel.
15. The test device of claim 14 , wherein the processor is further configured to:
determine a distance to the PIM using the extracted I/Q data from the signal in the uplink communication channel.
16. The test device of claim 11 , wherein the analyzing includes comparing the spectrum with a reference spectrum.
17. The test device of claim 11 , wherein the analyzing includes obtaining a slope of the spectrum, and the determining includes using the slope of the spectrum.
18. The test device of claim 11 , wherein the processor is further configured to:
detect the PIM is at a first level on a plurality of antennas of the RE; and
determine that the PIM is caused by an external source based on the detecting.
19. The test device of claim 18 , wherein the processor is further configured to:
determine a polarization angle of the external source; and
use the polarization to confirm that the PIM is caused by the external source.
20. The test device of claim 11 , wherein the processor is further configured to:
detect the PIM is at only one of a plurality of antennas of the RE; and
determine that the PIM is caused by an internal source based on the detecting.