Systems and methods for detecting passive inter-modulation (pim) interference in cellular networks

A data center in communication with a transmitter and with a receiver of a cellular site, the transmitter being configured to use a first set of digital electrical baseband I and Q samples received from the data center to modulate a first carrier frequency to transmit a radio frequency (RF) signal in a downlink direction, the receiver being configured to receive and demodulate an RF signal sent to the data center in an uplink direction to generate a second set of digital electrical baseband I and Q samples, the data center comprising:

• a first server comprising:
• a first memory that stores the first and second sets of digital electrical baseband I and Q samples captured over multiple adjacent time windows;
• and
• first processing logic configured to execute a comparison algorithm that, for the multiple adjacent time windows:
• converts the first and second sets of digital baseband I and Q samples from a time domain into first and second sets of frequency domain components, respectively;
• computes first and second sets of signal magnitude values from the first and second sets of frequency domain components, respectively;
• performs a cross-correlation algorithm with the first and second sets of signal magnitude values to produce a set of cross-correlation result values;
• compares a maximum of the cross-correlation result values to a first predetermined threshold (TH) value to determine whether or not the maximum of the cross-correlation result values exceeds the first predetermined TH value, and if so, increments a counter;
• and
• determines whether a count of the counter exceeds a second predetermined TH value, and if so, decides that PIM interference has been detected.

A method for detecting passive intermodulation (PIM) interference in a cellular site, the method comprising:

• storing first and second sets of digital baseband in phase (I) and quadrature phase (Q) samples captured over multiple adjacent time windows, wherein the first set of digital baseband I and Q samples is used by a transmitter of the cellular site to transmit an RF signal having a first carrier frequency in a downlink direction from the cellular site to a mobile device, wherein the second set of digital baseband I and Q samples are obtained from an RF signal having a second carrier frequency received by a receiver of the cellular site from a mobile device in an uplink direction, the second carrier frequency being different from the first carrier frequency;
• and
• with processing logic, executing a comparison algorithm that, for the multiple adjacent time windows:
• converts the first and second sets of digital baseband I and Q samples from a time domain into first and second sets of frequency domain components, respectively;
• computes first and second sets of signal magnitude values from the first and second sets of frequency domain components, respectively;
• performs a cross-correlation algorithm with the first and second sets of signal magnitude values to produce a set of cross-correlation result values;
• compares a maximum of the cross-correlation result values to a first predetermined threshold (TH) value to determine whether or not the maximum of the cross-correlation result values exceeds the first predetermined TH value, and if so, increments a counter;
• and
• determines whether a count of the counter exceeds a second predetermined TH value, and if so, decides that PIM interference has been detected.

A computer program comprising computer instructions for execution by one or more processors for detecting passive intermodulation (PIM) interference in a cellular site, the computer program being embodied on a non-transitory computer-readable medium, the computer program comprising:

• a first set of instructions that stores first and second sets of digital baseband in phase (I) and quadrature phase (Q) samples in memory captured over multiple adjacent time windows, wherein the first set of digital baseband I and Q samples is used by a transmitter of the cellular site to transmit a radio frequency (RF) signal having a first carrier frequency in a downlink direction from the cellular site to a mobile device, wherein the second set of digital baseband I and Q samples are obtained from an RF signal having a second carrier frequency received by a receiver of the cellular site from a mobile device in an uplink direction, the second carrier frequency being different from the first carrier frequency;
• a second set of instructions that converts the first and second sets of digital baseband I and Q samples from a time domain into first and second sets of frequency domain components, respectively;
• a third set of instructions that computes first and second sets of signal magnitude values from the first and second sets of frequency domain components, respectively;
• a fourth set of instructions that performs a cross-correlation algorithm with the first and second sets of signal magnitude values to produce a set of cross-correlation result values;
• a fifth set of instructions that compares a maximum of the cross-correlation result values to a first predetermined threshold (TH) value to determine whether or not the maximum of the cross-correlation result values exceeds the first predetermined TH value, and if so, increments a counter;
• and
• a sixth set of instructions that determines whether a count of the counter exceeds a second predetermined TH value, and if so, decides that PIM interference has been detected.