Gain measurement of distributed antenna system (DAS) segments during active communications employing autocorrelation on a combined test signal and communications signal

• US 9,078,218 B1
• Filed: 03/27/2014
• Issued: 07/07/2015
• Est. Priority Date: 03/27/2014
• Status: Active Grant

• Current Assignee: Corning Optical Communications LLC (Corning Incorporated)
• Original Assignee: Corning Optical Communications Wireless Ltd. (Corning Incorporated)
• Inventors: Harel, Dror
• Primary Examiner(s): Ly, Nghi H
• Application Number:
  US14/227,215
• Time in Patent Office: 467 Days
• Field of Search: 455/424, 455/423, 455/425, 455/422.1, 455/403
• US Class Current: 1/1
• CPC Class Codes: H04B 1/40 Circuits
• CPC Class Codes: H04B 17/0085 using test signal generators
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/18 Monitoring during normal operation
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04B 17/29 Performance testing
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/243 taking into account interferences

Abstract

Gain measurement of distributed antenna system (DAS) segments during active communications employing autocorrelation on a combined test signal and communications signal is disclosed. In one embodiment, a test signal is injected into one or more DAS segments in a DAS. The test signal power is measured at the input and output of the DAS segment(s) for which gain measurement is desired. The difference in power of the test signal between the input and the output of the DAS segment is the gain of the DAS segment. The frequency of the test signal is provided to be within the frequency band of the communications service signals supported by the DAS segment. To allow for gain measurement of a DAS segment during active communication periods when the DAS segment is actively transmitting communications service signals, autocorrelation is employed to separate the test signal from combined test signal and communications service signals.

Claims

1. A distributed antenna system (DAS) segment gain measurement system, comprising:

a signal correlator configured to;

receive a first measurement signal comprising a power-related measurement of a combined test signal and communications service signal at an input node of a DAS segment, the combined test signal of a frequency in a frequency band of the communications service signal;

receive a test replication signal indicative of the test signal;

autocorrelate the first measurement signal with the test replication signal to retrieve a first test measurement signal indicative of the power in the test signal at the input node of the DAS segment;

provide the first test measurement signal at the input node to a controller;

receive a second measurement signal comprising a power-related measurement of the combined test signal at an output node of the DAS segment;

autocorrelate the second measurement signal with the test replication signal to retrieve a second test measurement signal indicative of the power in the test signal at the output node of the DAS segment;

provide the second test measurement signal at the input node to a controller;

a controller configured to;

receive the first test measurement signal;

receive the second test measurement signal; and

subtract the first test measurement signal from the second test measurement signal to determine a measured gain of the DAS segment.

2. The DAS segment gain measurement system of claim 1, wherein the controller is further configured to adjust the gain of the DAS segment based on the measured gain of the DAS segment.

3. The DAS segment gain measurement system of claim 1, wherein the controller comprises the signal correlator.

4. The DAS segment gain measurement system of claim 1, further comprising:

a first power detection circuit comprising a first power detector coupled to the input node of the DAS segment, the first power detector configured to;

detect the power in the combined test signal at the input node of the DAS segment; and

provide the first measurement signal indicative of the detected power in the combined test signal at the input node of the DAS segment; and

a second power detection circuit comprising a second power detector coupled to the output node of the DAS segment, the second power detector configured to;

detect the power in the combined test signal at the output node of the DAS segment; and

provide the second measurement signal indicative of the detected power in the combined test signal at the output node of the DAS segment.

5. The DAS segment gain measurement system of claim 4, further comprising:

a first analog-to-digital converter (ADC) configured to sample the first measurement signal to provide the first measurement signal comprising a digital first measurement signal; and

a second analog-to-digital converter (ADC) configured to sample the second measurement signal to provide the second measurement signal comprising a digital second measurement signal.

6. The DAS segment gain measurement system of claim 1, further comprising a test signal generator configured to:

generate the test signal; and

inject the test signal to the input node of the DAS segment.

7. The DAS segment gain measurement system of claim 1, wherein the signal correlator further comprises:

a first signal correlator configured to;

autocorrelate the first measurement signal with the test replication signal to retrieve a first test measurement signal indicative of the power in the test signal at the input node of the DAS segment; and

provide the first test measurement signal to the controller;

a second signal correlator configured to;

autocorrelate the second measurement signal with the test replication signal to retrieve a second test measurement signal indicative of the power in the test signal at the output node of the DAS segment; and

provide the first test measurement signal to the controller;

a signal switch configured to;

receive the first measurement signal;

receive the second measurement signal;

switch the first measurement signal to be provided to the first signal correlator; and

switch the second measurement signal to be provided to the second signal correlator.

8. The DAS segment gain measurement system of claim 1, wherein:

the power-related measurement of the combined test signal and communications service signal at the input node of the DAS segment comprises a voltage measurement of the combined test signal and communications service signal at the input node of the DAS segment; and

the power-related measurement of the combined test signal and communications service signal at the output node of the DAS segment comprises a voltage measurement of the combined test signal and the communications service signal at the output node of the DAS segment.

9. The DAS segment gain measurement system of claim 8, wherein the controller is further configured to:

convert the voltage measurement of the first test measurement signal to a first power test measurement signal; and

convert the voltage measurement of the second test measurement signal to a second power test measurement signal;

the controller configured to;

subtract the first power test measurement signal from the second power test measurement signal to determine a measured power gain of the DAS segment; and

adjust the gain of the DAS segment based on the measured power gain of the DAS segment.

10. The DAS segment gain measurement system of claim 9, further comprising:

a database comprising pre-calibrated correlated voltage measurement to power measurement data pairs;

wherein the controller is configured to;

convert the voltage measurement of the first test measurement signal to the first power test measurement signal by selecting the power measurement in a voltage measurement to power measurement data pair in the database corresponding to the voltage measurement of the first test measurement signal; and

convert the voltage measurement of the second test measurement signal to the second power test measurement signal by selecting the power measurement in a voltage measurement to power measurement data pair in the database corresponding to the voltage measurement of the second test measurement signal.

11. The DAS segment gain measurement system of claim 9, further comprising:

wherein the controller is configured to;

convert the voltage measurement of the first test measurement signal to the first power test measurement signal by calculating power according to P=Vi²/Zi, where Vi is equal to the voltage measurement of the first test measurement signal, and Zi is the impedance at the input node of the DAS segment; and

convert the voltage measurement of the second test measurement signal to the second power test measurement signal by calculating power according to P=Vo²/Zo, where Vo is equal to the voltage measurement of the second test measurement signal, and Zo is the impedance at the output node of the DAS segment.

12. The DAS segment gain measurement system of claim 1, wherein the DAS segment includes at least one of a remote antenna unit and a radio interface unit.

13. The DAS segment gain measurement system of claim 1, wherein the DAS segment includes an optical interface module.

14. A method of measuring gain in a distributed antenna system (DAS) segment, comprising:

receiving a first measurement signal comprising a power-related measurement of a combined test signal and communications service signal at an input node of a DAS segment, the combined test signal of a frequency in a frequency band of the communications service signal;

receiving a test replication signal indicative of the test signal;

autocorrelating the first measurement signal with the test replication signal to retrieve a first test measurement signal indicative of the power in the test signal at the input node of the DAS segment;

receiving a second measurement signal comprising a power-related measurement of the combined test signal at an output node of the DAS segment;

autocorrelating the second measurement signal with the test replication signal to retrieve a second test measurement signal indicative of the power in the test signal at the output node of the DAS segment; and

subtracting the first test measurement signal from the second test measurement signal to determine a measured gain of the DAS segment.

15. The method of claim 14, further comprising adjusting the gain of the DAS segment based on the measured gain of the DAS segment.

16. The method of claim 14, further comprising:

detecting the power in the combined test signal at the input node of the DAS segment;

providing the first measurement signal indicative of the detected power in the combined test signal at the input node of the DAS segment;

detecting the power in the combined test signal at the output node of the DAS segment; and

providing the second measurement signal indicative of the detected power in the combined test signal at the output node of the DAS segment.

17. The method of claim 14, further comprising:

sampling the first measurement signal to provide a first digital measurement signal; and

sampling the second measurement signal to provide second digital measurement signal; and

comprising;

autocorrelating the first digital measurement signal with the test replication signal to retrieve a first digital test measurement signal indicative of the power in the test signal at the input node of the DAS segment;

autocorrelating the second digital measurement signal with the test replication signal to retrieve a second digital test measurement signal indicative of the power in the test signal at the output node of the DAS segment;

subtracting the first digital test measurement signal from the second digital test measurement signal to determine a measured gain of the DAS segment; and

adjusting the gain of the DAS segment based on the measured gain of the DAS segment.

18. The method of claim 14, further comprising:

generating the test signal; and

injecting the test signal to the input node of the DAS segment.

19. The method of claim 14, wherein:

the power-related measurement of the combined test signal and the communications service signal at the input node of the DAS segment comprises a voltage measurement of the combined test signal and the communications service signal at the input node of the DAS segment; and

the power-related measurement of the combined test signal and the communications service signal at the output node of the DAS segment comprises a voltage measurement of the combined test signal and the communications service signal at the output node of the DAS segment.

20. The method of claim 19, further comprising:

converting the voltage measurement of the first test measurement signal to a first power test measurement signal; and

converting the voltage measurement of the second test measurement signal to a second power test measurement signal; and

wherein;

subtracting the first test measurement signal from the second test measurement signal to determine a measured gain of the DAS segment comprises subtracting the first power test measurement signal from the second power test measurement signal to determine a measured power gain of the DAS segment; and

adjusting the gain of the DAS segment based on the measured gain of the DAS segment comprises adjusting the gain of the DAS segment based on the measured power gain of the DAS segment.

21. A distributed antenna system (DAS), comprising:

a plurality of DAS segments each configured to distribute communications service signals by being configured to distribute downlink communications service signals towards a plurality of remote antenna units and distribute uplink communications service signals received from client devices towards a central unit;

the plurality of DAS segments each comprising an input node and an output node;

a test signal generator configured to;

generate a test signal of a frequency in a frequency band of the communications service signals; and

inject the test signal to the input node of the plurality of DAS segments;

a plurality of power detection circuits each coupled to an input node or an output node of a DAS segment, each of the plurality of power detection circuits configured to;

detect a power-related measurement of combined test signal and communications service signal; and

provide a measurement signal comprising a power-related measurement of a combined test signal and communications service signal;

a signal switch configured to;

receive a plurality of the measurement signals from each of the plurality of power detection circuits; and

selectively provide a measurement signal from a plurality of the power-related measurements of the combined test signal and communications service signals to a gain measurement system;

the gain measurement system configured to;

receive a first measurement signal at an input node of a DAS segment among the plurality of DAS segments;

autocorrelate the first measurement signal with a test replication signal of the test signal to retrieve a first test measurement signal indicative of the power in the test signal at the input node of the DAS segment;

receive a second measurement signal at an output node of the DAS segment;

autocorrelate the second measurement signal with the test replication signal to retrieve a second test measurement signal indicative of the power in the test signal at the output node of the DAS segment; and

a controller configured to subtract the first test measurement signal from the second test measurement signal to determine a measured gain of the DAS segment.

22. The DAS of claim 21, wherein the controller is further configured to adjust the gain of the DAS segment based on the measured gain of the DAS segment.

23. The DAS of claim 21, wherein the gain measurement system comprises:

a first signal correlator configured to;

autocorrelate the first measurement signal with the test replication signal to retrieve a first test measurement signal indicative of the power in the test signal at the input node of the DAS segment; and

provide the first test measurement signal to the controller;

a second signal correlator configured to;

autocorrelate the second measurement signal with the test replication signal to retrieve a second test measurement signal indicative of the power in the test signal at the output node of the DAS segment; and

provide the second test measurement signal to the controller;

the signal switch configured to;

receive the first measurement signal;

receive the second measurement signal;

selectively provide the first measurement signal to be provided to the first signal correlator; and

selectively provide the second measurement signal to be provided to the second signal correlator.

24. The DAS of claim 21, further comprising an analog-to-digital converter (ADC) configured to sample the measurement signal to provide the measurement signal comprising a first digital measurement signal.

25. The DAS of claim 21, wherein each of the measurement signals from the plurality of power detection circuits comprises a voltage measurement of the combined test signal and the communications service signal at the input node of the DAS segment.

26. The DAS of claim 25, wherein the controller is further configured to:

convert the voltage measurement of the first test measurement signal to a first power test measurement signal; and

convert the voltage measurement of the second test measurement signal to a second power test measurement signal;

the controller configured to;

subtract the first power test measurement signal from the second power test measurement signal to determine a measured power gain of the DAS segment; and

adjust the gain of the DAS segment based on the measured power gain of the DAS segment.