Passive intermodulation (PIM) measurements in common public radio interface (CPRI) spectrum analysis
A test device for detecting and measuring distance to passive intermodulation (PIM) is disclosed. The test device may comprise a receiver to receive a signal from a test point of a distributed cell site comprising a remote radio head (RRH) and a baseband unit (BBU) separated and connected via an optical feeder. The test device may also comprise a processor to detect passive intermodulation (PIM) and measure distance to the PIM (internal or external). For example, the processor may replace downlink IQ data in the signal with two-tone waveform IQ data, transmit the two-tone waveform IQ data to the RRH, and to monitor uplink spectrum to detect PIM, where the uplink spectrum may comprise uplink IQ data from the RRH. The processor may also perform uplink spectrum analysis using radio frequency (RF) monitoring, measure a time delay for the two-tone waveform and the detected PIM, and calculate a distance to the PIM based on the time delay.
1. A test device, comprising:
a receiver to receive a signal from a test point of a cell site; and
a processor to detect passive intermodulation (PIM) and measure distance to the PIM, wherein downlink PIM affects uplink PIM, the detection of and measurement of distance to the PIM achieved by:
replacing downlink IQ data in the signal with two-tone waveform IQ data, wherein the two-tone waveform IQ data is acquired from a single antenna or from two single tones from two separate antennas and represents a translation of amplitude and phase data from a polar coordinate system to a Cartesian (x, y) coordinate system;
transmitting the two-tone waveform IQ data to a remote radio head (RRH);
monitoring uplink spectrum to detect PIM, wherein the uplink spectrum comprises uplink IQ data from the RRH;
performing uplink spectrum analysis using radio frequency (RF) monitoring;
measuring a time delay for the two-tone waveform and the detected PIM; and
calculating a distance to the PIM based on the time delay.
2. The test device of claim 1 , wherein the signal is a radio frequency over common public radio interface (RFoCPRI) signal, the signal comprising downlink IQ data.
3. The test device of claim 1 , wherein the cell site is a distributed cell site comprising a remote radio head (RRH) and a baseband unit (BBU) separated and connected via an optical feeder.
4. The test device of claim 3 , wherein the test point is at a front haul of the baseband unit (BBU) or near the BBU of the cell site.
5. The test device of claim 1 , wherein measuring time delay is based on a frequency-modulated continuous-wave (FMCW) technique.
6. The test device of claim 1 , wherein calculating the distance to the PIM is based on time-distance resolution technique, and wherein the PIM comprises at least one of internal PIM and external PIM.
7. The test device of claim 1 , further comprising an output to provide to a user at least one of visual data and audio data, the visual and audio data associated with the detected PIM or the calculated distance to the PIM.
8. A method to detect passive intermodulation (PIM) and measure distance to the PIM at a cell site, the method comprising:
receiving, at a receiver, a signal from a test point of a cell site;
replacing, by a processor, downlink IQ data in the signal with two-tone waveform IQ data, wherein the two-tone waveform IQ data is acquired from a single antenna or from two single tones from two separate antennas and represents a translation of amplitude and phase data from a polar coordinate system to a Cartesian (x, y) coordinate system;
transmitting the two-tone waveform IQ data to a remote radio head (RRH);
monitoring uplink spectrum to detect PIM, wherein the uplink spectrum comprises uplink IQ data from the RRH;
performing uplink spectrum analysis using radio frequency (RF) monitoring;
measuring a time delay for the two-tone waveform and the detected PIM, wherein downlink PIM affects uplink PIM; and
calculating a distance to the PIM based on the time delay.
9. The method of claim 8 , wherein the signal is a radio frequency over common public radio interface (RFoCPRI) signal, the signal comprising downlink IQ data.
10. The method of claim 8 , wherein the cell site is a distributed cell site comprising a remote radio head (RRH) and a baseband unit (BBU) separated and connected via an optical feeder.
11. The method of claim 10 , wherein the test point is at a front haul of the baseband unit (BBU) or near the BBU of the cell site.
12. The method of claim 8 , wherein measuring time delay is based on a frequency-modulated continuous-wave (FMCW) technique.
13. The method of claim 8 , wherein calculating the distance to the PIM is based on time-distance resolution technique, and wherein the PIM comprises at least one of internal PIM and external PIM.
14. The method of claim 8 , further comprising providing to an output at least one of visual data and audio data to a user, the visual data and audio data associated with the detected PIM or the calculated distance to the PIM.
15. A non-transitory computer-readable storage medium having an executable stored thereon, which when executed instructs a processor to perform the method of claim 8 .
16. A method to measure a distance to passive intermodulation (PIM), the method comprising:
monitoring, by a processor of a test device, uplink spectrum to detect PIM, wherein the uplink spectrum comprises uplink IQ data from a remote radio head (RRH), and wherein the PIM comprises at least one of internal PIM and external PIM and wherein downlink PIM affects uplink PIM;
performing uplink spectrum analysis using radio frequency (RF) monitoring;
measuring a time delay for a two-tone waveform IQ data transmitted to the RRH and for the detected PIM, wherein the two-tone waveform IQ data is acquired from a single antenna or from two single tones from two separate antennas and represents a translation of amplitude and phase data from a polar coordinate system to a Cartesian (x, y) coordinate system; and
calculating a distance to the PIM based on the time delay.
17. The method of claim 16 , wherein the test device is used at a cell site that communicates via a radio frequency over common public radio interface (RFoCPRI) signal.
18. The method of claim 16 , wherein measuring time delay is based on a frequency-modulated continuous-wave (FMCW) technique.
19. The method of claim 16 , wherein calculating the distance to the PIM is based on time-distance resolution technique.
20. A non-transitory computer-readable storage medium having an executable stored thereon, which when executed instructs a processor to perform the method of claim 16 .