Systems and methods for detecting nodes or signals of a radio access technology (RAT) by a node of another RAT

• US 10,278,214 B2
• Filed: 07/15/2015
• Issued: 04/30/2019
• Est. Priority Date: 06/12/2015
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Schmidt, Alfred
• Primary Examiner(s): Park, Jung H
• Application Number:
  US14/763,206
• Publication Number:
  US 20170142752A1
• Time in Patent Office: 1,385 Days
• CPC Class Codes: H04J 11/0093 Neighbour cell search
• CPC Class Codes: H04L 25/00 Baseband systems
• CPC Class Codes: H04L 25/03012 operating in the time domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 27/2636 with FFT or DFT modulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] transmitter or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 72/044 based on the type of the allocated resource
• CPC Class Codes: H04W 74/085 collision avoidance
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Embodiments of systems and methods enabling a node of a first Radio Access Technology (RAT) to detect (co-channel) frames and/or Access Points (APs)/nodes of a second RAT using receiver hardware of the first RAT are disclosed. While not being limited thereto, in some embodiments, the first RAT is Long Term Evolution (LTE) and the second RAT is Wi-Fi, and systems and methods are disclosed that enable a LTE node (e.g., an LTE Radio Access Network (RAN) node such as a base station or a low power node operating in an unlicensed frequency band) to detect Wi-Fi preambles and/or Wi-Fi beacons (and thus the number of co-channel Wi-Fi APs).

Claims

1. A method of operation of a radio access node of a first Radio Access Technology, RAT, comprising:

receiving a signal sampled at a sampling rate used for the first RAT;

performing frequency domain matched filtering of the received signal with a Fast Fourier Transform, FFT, of a known, repetitive waveform transmitted by access nodes of a second RAT, where the known, repetitive waveform is sampled at the sampling rate used for the first RAT and a FFT size used for the first RAT; and

detecting transmissions of the known, repetitive waveform by access nodes of the second RAT based on results of the matched filtering.

2. The method of claim 1 wherein the first RAT is Long Term Evolution, LTE, and the second RAT is Wi-Fi.

3. The method of claim 2 wherein the known, repetitive waveform is a Legacy Short Training Field, L-STF, waveform, and detecting transmissions of the known, repetitive waveform comprises detecting Wi-Fi preambles based on detection of the L-STF waveform.

4. A radio access node of a first Radio Access Technology, RAT, comprising:

receiver baseband processing circuitry for the first RAT, the receiver baseband processing circuitry operable to receive and process a received signal according to the first RAT at a sampling rate used for the first RAT;

a matched filter operable to perform frequency domain matched filtering of the received signal with a Fast Fourier Transform, FFT, of a known, repetitive waveform transmitted by access nodes of a second RAT, where the known, repetitive waveform is sampled at the sampling rate used by the receiver baseband processing circuitry for the first RAT and a FFT size used for the first RAT; and

a detector operable to detect transmissions of the known, repetitive waveform by access nodes of the second RAT based on results of the matched filtering.

5. The radio access node of claim 4 wherein the first RAT is Long Term Evolution, LTE, and the second RAT is Wi-Fi.

6. The radio access node of claim 5 wherein the known, repetitive waveform is a Legacy Short Training Field, L-STF, waveform, and detecting transmissions of the known, repetitive waveform comprises detecting Wi-Fi preambles based on detection of the L-STF waveform.

7. A method of operation of a radio access node of a first Radio Access Technology, RAT, comprising:

dividing a beacon interval for a second RAT into N time bins;

detecting, for each of the N time bins for each of M consecutive beacon intervals, transmissions of Wi-Fi preambles by access nodes of the second RAT or received energy; and

determining a number of beacons transmitted by access nodes of the second RAT by;

determining an average number of the detected Wi-Fi preambles for each of the N time bins over the M consecutive beacon intervals; and

determining the number of beacons transmitted by access nodes of the second RAT based on the average number of the detected Wi-Fi preambles for each of the N time bins over the M consecutive beacon intervals.

8. The method of claim 7 wherein the first RAT is Long Term Evolution, LTE, and the second RAT is Wi-Fi.

9. The method of claim 7 wherein detecting the Wi-Fi preambles comprises detecting the Wi-Fi preambles based on detection of a Legacy Short Training Field, L-STF, L-STF waveform.

10. The method of claim 7 wherein detecting, for each of the N time bins for each of the M consecutive beacon intervals, transmissions of the known, repetitive waveform by access nodes of the second RAT or received energy comprises performing matched filtering of a received signal based on a known, repetitive waveform, but sampled at a sampling rate used for the first RAT.

11. The method of claim 10 wherein performing matched filtering of the received signal comprises performing time domain matched filtering of the received signal with a filter impulse response that matches the known, repetitive waveform but sampled at the sampling rate used for the first RAT.

12. The method of claim 10 wherein performing matched filtering comprises performing frequency domain matched filtering of the received signal.

13. The method of claim 12 wherein performing frequency domain matched filtering of the received signal comprises performing frequency domain matched filtering of the received signal with a Fast Fourier Transform, FFT, of the known, repetitive waveform but with the sampling rate used for the first RAT and a FFT size used for the first RAT.

14. The method of claim 7 wherein detecting the transmissions of the Wi-Fi preambles by the access nodes of the second RAT or received energy comprises detecting received energy for each of the N time bins for each of the M consecutive beacon intervals.

15. The method of claim 14 wherein determining the number of beacons transmitted by access nodes of the second RAT comprises:

accumulating energy for each of the N time bins over the M consecutive beacon intervals; and

determining the number of detected beacons transmitted by access nodes of the second RAT based on the accumulated energy for each of the N time bins over the M consecutive beacon intervals.

16. The method of claim 7 wherein detecting the transmissions of the Wi-Fi preambles by the access nodes of the second RAT or received energy comprises detecting a maximum energy at an output of a matched filter for each of the N time bins for each of the M consecutive beacon intervals, the matched filter performing matched filtering of a received signal based on the Wi-Fi preambles, but sampled at a sampling rate used for the first RAT.

17. The method of claim 16 wherein determining the number of beacons transmitted by the access nodes of the second RAT comprises:

accumulating the detected maximum energy for each of the N time bins over the M consecutive beacon intervals; and

determining the number of detected beacons transmitted by the access nodes of the second RAT based on the accumulated detected maximum energy for each of the N time bins over the M consecutive beacon intervals.

18. The method of claim 7 wherein determining the number of beacons transmitted by the access nodes of the second RAT based on the results of the detecting comprises:

for each time bin of the N time bins, setting the number of preambles detected for the time bin to a number of preambles detected for the time bin that are correlated across the M consecutive beacon intervals to at least a predefined correlation threshold level.

19. The method of claim 18 wherein the number of preambles detected for the time bin that are correlated across the M consecutive beacon intervals to at least the predefined correlation threshold level is the number of preambles detected for the time bin that are correlated across the M consecutive beacon intervals to at least to the predefined threshold correlation level with respect to at least one of a group consisting of:

start time, duration, and received signal strength.

20. A radio access node of a first Radio Access Technology, RAT, comprising:

a matched filter or energy detector operable to detect, for each of N time bins for each of M consecutive beacon intervals, transmissions of Wi-Fi preambles by access nodes of a second RAT or received energy; and

a detector operable to determine a number of beacons transmitted by access nodes of the second RAT by being operable to;

determine an average number of detected Wi-Fi preambles for each of the N time bins over the M consecutive beacon intervals; and

determine the number of beacons transmitted by the access nodes of the second RAT based on the average number of detected Wi-Fi preambles for each of the N time bins over the M consecutive beacon intervals.

21. The radio access node of claim 20 wherein the first RAT is Long Term Evolution, LTE, and the second RAT is Wi-Fi.

22. The radio access node of claim 20 wherein detecting the Wi-Fi preambles comprises detecting the Wi-Fi preambles based on detection of a Legacy Short Training Field, L-STF, L-STF waveform.

23. The radio access node of claim 20 wherein detecting, for each of the N time bins for each of the M consecutive beacon intervals, transmissions of a known, repetitive waveform by the access nodes of the second RAT or received energy comprises performing matched filtering of a received signal based on the known, repetitive waveform, but sampled at a sampling rate used for the first RAT.

24. The radio access node of claim 23 wherein performing matched filtering of the received signal comprises performing time domain matched filtering of the received signal with a filter impulse response that matches the known, repetitive waveform but sampled at the sampling rate used for the first RAT.

25. The radio access node of claim 23 wherein performing matched filtering comprises performing frequency domain matched filtering of the received signal.

26. The radio access node of claim 25 wherein performing frequency domain matched filtering of the received signal comprises performing frequency domain matched filtering of the received signal with a Fast Fourier Transform, FFT, of the known, repetitive waveform but with the sampling rate used for the first RAT and a FFT size used for the first RAT.