Detection of proximity of client device to base station

1. A method in a first base station to detect proximity of a client device, the method comprising:

receiving a signal transmitted by the client device;

analyzing a property of the received signal to determine that the client device is within a communication range of the first base station, wherein analyzing the property of the received signal comprises detecting an envelope of the signal, in response to a communication between the client device and a second base station, to determine whether the envelope of the signal includes a buzz-type waveform; and

in response to the determination that the client device is within the communication range, converting a current operation mode of the first base station to a particular operation mode that enables the first base station to support communication with the client device, wherein a first coverage range of the first base station is smaller than and within a second coverage range of the second base station.

2. The method of claim 1 , wherein converting the current operation mode of the first base station to the particular operation mode comprises converting a long term evolution (LTE) low duty mode or dormant state of the first base station to the particular operation mode.

3. The method of claim 1 , wherein converting the current operation mode of the first base station to the particular operation mode comprises converting a global system for mobile communications (GSM) dormant state of the first base station to the particular operation mode.

4. The method of claim 1 , further comprising decoding uplink control information from the signal.

5. A method in a first base station to detect proximity of a client device, the method comprising:

receiving a signal transmitted by the client device;

analyzing a property of the received signal to determine that the client device is within a communication range of the first base station, wherein analyzing the property of the received signal comprises detecting an envelope of the signal, in response to a communication between the client device and a second base station, to determine whether the envelope of the signal includes a buzz-type waveform, and wherein the buzz-type waveform is a waveform that is included in the signal while the client device transmits the signal to the second base station but is not actively engaged in communication with the first base station; and

in response to the determination that the client device is within the communication range, converting a current operation mode of the first base station to a particular operation mode that enables the first base station to support communication with the client device, wherein a first coverage range of the first base station is smaller than and within a second coverage range of the second base station.

6. The method of claim 5 , wherein the signal is an uplink control signal with a low frequency envelope that is transmitted to the second base station.

7. A method in a first base station to detect proximity of a client device, the method comprising:

receiving a signal transmitted by the client device;

analyzing a property of the received signal to determine that the client device is within a communication range of the first base station, wherein analyzing the property of the received signal comprises:

detecting an envelope of the signal, in response to a communication between the client device and a second base station, to determine whether the envelope of the signal includes a buzz-type waveform, and

determining, whether the detected envelope of the signal matches the buzz-type waveform within a proximity detection threshold; and

in response to the determination that the client device is within the communication range, converting a current operation mode of the first base station to a particular operation mode that enables the first base station to support communication with the client device, wherein a first coverage range of the first base station is smaller than and within a second coverage range of the second base station.

8. The method of claim 7 , further comprising adjusting the proximity detection threshold based on a power strength of the signal.

9. A base station configured to detect proximity of a client device, the base station comprising:

a receiver configured to receive a signal transmitted by the client device;

a proximity detector coupled to the receiver and configured to analyze a property of the received signal to determine whether the client device is within a communication range of the base station, wherein the analysis of the property of the received signal comprises detection of an envelope of the signal, in response to a communication between the client device and a different base station, to determine whether the envelope of the signal includes a buzz-type waveform; and

an operation mode controller coupled to the proximity detector and configured to convert, in response to the determination that the client device is within the communication range of the base station, a current operation mode of the base station to a particular operation mode that enables the base station to support communication with the client device, wherein a first coverage range of the base station is smaller than and within a second coverage range of the different base station.

10. The base station of claim 9 , wherein the buzz-type waveform is a waveform that is included in the signal while the client device transmits the signal to the different base station but is not actively engaged in communication with the base station.

11. The base station of claim 10 , wherein the signal is an uplink control signal with a low frequency envelope.

12. The base station of claim 9 , wherein the proximity detector is further configured to determine whether the detected envelope of the signal matches the buzz-type waveform within a proximity detection threshold.

13. The base station of claim 12 , wherein the proximity detector is further configured to adjust the proximity detection threshold based on a power strength of the signal.

14. The base station of claim 9 , wherein the proximity detector comprises an envelope detector configured to detect the envelope of the signal, and wherein the envelope detector includes:

a rectifier configured to convert an alternating current of the signal to a direct current; and

a low-pass filter coupled to the rectifier and configured to pass low-frequency components of the direct current as the envelope of the signal.

15. The base station of claim 9 , wherein, to convert the current operation mode to the particular operation mode, the operation mode controller is configured to convert a long term evolution (LTE) low duty mode or dormant state of the base station to the particular operation mode.

16. The base station of claim 9 , wherein, to convert the current operation mode to the particular operation mode, the operation mode controller is configured to convert a global system for mobile communications (GSM) dormant state of the base station to the particular operation mode.

17. The base station of claim 9 , wherein the operation mode controller is further configured to decode uplink control information from the signal.

18. The base station of claim 9 , wherein the communication range of the base station includes a communication range of a small-cell network.

19. The base station of claim 18 , wherein the small-cell network includes at least one of a microcell, a femtocell, a picocell, a relay, and a hotspot.

20. The base station of claim 9 , wherein the signal includes a physical uplink control channel (PUCCH) signal or a physical uplink shared channel (PUSCH) signal.