Remote diagnosis and cancellation of passive intermodulation

• US 10,039,022 B2
• Filed: 06/09/2015
• Issued: 07/31/2018
• Est. Priority Date: 06/09/2015
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property I LP (AT&T, Inc.), AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property I LP (AT&T, Inc.), AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: Tsui, Ernest, Wong, Peter Richard, Maxwell, Paul, Suh, Young
• Primary Examiner(s): Jiang, Charles C
• Assistant Examiner(s): Defauw, Thad
• Application Number:
  US14/734,766
• Publication Number:
  US 20160366605A1
• Time in Patent Office: 1,148 Days
• CPC Class Codes: H04B 17/0085 using test signal generators
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04B 17/3912 Simulation models, e.g. distribution of spectral power density or received signal strength indicator [RSSI] for a given geographic region
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic

Abstract

A passive intermodulation detection system is provided to remotely identify passive intermodulation at a base station site and diagnose the type of intermodulation and location of the non-linearity that is the source of the passive intermodulation. The passive intermodulation detection system can generate a test signal in a first band that is transmitted by an antenna. Another antenna can receive a signal in another band, and the passive intermodulation detection system can analysis the received signal to determine whether an intermodulation product due to a non-linearity is present. Based on the type of intermodulation product, period, order, frequency, and etc., the type and location of the non-linearity can be identified.

Claims

1. A system, comprising:

a processor; and

a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations, comprising;

cycling a test signal at a defined period, wherein the test signal is in a first band and is transmitted by a transmitter;

receiving a transmission in a second band by a receiver; and

determining that an intermodulation product from the test signal is present in the transmission based on matching a period of a cyclical noise measurement of the transmission to the defined period and based on a noise amplitude harmonic identified at a defined frequency gap from the second band.

2. The system of claim 1, wherein the operations further comprise:

determining a type of a source of non-linearity based on an amplitude and associated frequency period of the intermodulation product.

3. The system of claim 1, wherein the operations further comprise:

determining an intermodulation model based on the intermodulation product; and

modifying the transmission to reduce the intermodulation product based on the intermodulation model.

4. The system of claim 1, wherein the operations further comprise:

cycling the test signal to each sector of a group of sectors.

5. The system of claim 1, wherein the operations further comprise:

determining a source of a non-linearity based on a sector to which the intermodulation product corresponds.

6. The system of claim 1, wherein the test signal simulates a cellular transmission from a base station device to a mobile device.

7. The system of claim 2, wherein the operations further comprise:

determining a location of the source of non-linearity based on a phase difference between the intermodulation product and the test signal.

8. The system of claim 6, wherein the modifying the transmission to reduce the intermodulation product based on the intermodulation model further comprises convolving the transmission with an interference minimizing filter.

9. The system of claim 6, wherein the determining the intermodulation model based on the intermodulation product further comprises:

applying a first adaptive nonlinear filter that models first multipath characteristics of the test signal before a non-linearity;

applying a second adaptive nonlinear filter to the test signal;

applying a third adaptive nonlinear filter that models second multipath characteristics of the test signal after the non-linearity;

determining an interference based on combining results of the applying the first, second, and third adaptive nonlinear filters; and

subtracting the interference from the transmission plus the interference.

10. The system of claim 7, wherein the determining the location of the source of the non-linearity further comprises:

determining radial locations of the source of the non-linearity from a group of receivers; and

determining an intersection location of the radial locations.

11. A method, comprising:

transmitting, by a device comprising a processor, a signal simulating a first transmission to a mobile device, wherein the signal is cycled at a predetermined periodicity, wherein the signal is in a first band;

receiving, by the device, a second transmission in a second band by a receiver; and

determining, by the device, that an intermodulation product from the signal is present in the second transmission based on matching a period of the noise pattern of the second transmission to the predetermined period of the signal and based on identifying a noise pattern amplitude harmonic at a predefined frequency gap from the second band.

12. The method of claim 11, further comprising:

determining, by the device, a type of a source of a non-linearity that led to the intermodulation product based on an amplitude and a frequency period of the intermodulation product.

13. The method of claim 11, further comprising:

determining, by the device, an intermodulation model based on the intermodulation product; and

modifying, by the device, the second transmission to reduce the intermodulation product based on the intermodulation model.

14. The method of claim 11, further comprising:

cycling, by the device, the signal to each sector of sectors; and

determining a source of a non-linearity based on a sector of the sectors to which the intermodulation product corresponds.

15. The method of claim 12, further comprising:

determining, by the device, a location of the source of non-linearity based on a time delay between the intermodulation product and the signal.

16. The method of claim 13, wherein the determining the intermodulation model based on the intermodulation product further comprises:

applying, by the device, a first adaptive nonlinear filter modeling multipath characteristics of the signal before a non-linearity;

applying, by the device, a second adaptive nonlinear filter to the signal;

applying, by the device, a third adaptive nonlinear filter modeling the multipath characteristics of the signal after the non-linearity; and

combining, by the device, results of the applying the first, second, and third adaptive nonlinear filters.

17. A computer-readable storage device storing executable instructions that, in response to execution, cause a device comprising a processor to perform operations, comprising:

transmitting a test signal simulating a first transmission to a mobile device, wherein the test signal is cycled according to a time period, and wherein the test signal is in a first band and is transmitted via a transmitter;

receiving a second transmission in a second band by a receiver; and

determining that an intermodulation product from the test signal is present in the second transmission based on a match being determined between a period of a noise pattern of the second transmission and the time period and based on a noise pattern amplitude harmonic identified at a defined frequency gap from the second band.

18. The computer-readable storage device of claim 17, wherein the time period is a first time period, and wherein the operations further comprise:

determining a type of a source of a non-linearity that led to the intermodulation product based on an amplitude and a second time period of the intermodulation product.

19. The computer-readable storage device of claim 17, wherein the intermodulation product is a first intermodulation product, and wherein the operations further comprise:

applying a series of adaptive non-linear filters to the test signal and a first received signal to determine an error signal associated with the first intermodulation product; and

subtracting the error signal from a second received signal to reduce a second intermodulation product in the second received signal.

20. The computer-readable storage device of claim 17, wherein the operations further comprise:

cycling the test signal to each sector of a group of sectors.