Ultra-wide band radar for tailgating detection in access control systems

1. A reader device of a physical access control system (PACS), the reader device comprising:

an ultra-wide band (UWB) physical layer; and

processing circuitry operatively coupled to the UWB physical layer and configured to:

receive access credential information from a separate second device;

use two-way ranging to receive ranging information from the second device using the UWB physical layer;

grant access through a physical portal according to the access credential information and ranging information;

use one-way signaling to transmit a UWB signal using the UWB physical layer, wherein the transmitted UWB signal includes a specified pattern of radio frequency (RF) signal pulses;

receive a reflected signal using the UWB physical layer that corresponds to the transmitted UWB signal reflecting off one or more objects;

determine a number of people intending to pass through the physical portal using the reflected signal; and

generate an indication according to the determined number of people.

2. The reader device of claim 1 , including an alarm circuit, wherein the processing circuitry is configured to activate the alarm circuit according to the determined number of people intending to pass through the physical portal.

3. The reader device of claim 1 , including a network interface, wherein the processing circuitry is configured to provide the generated indication of the determined number of people to an access device of the PACS via the network interface.

4. The reader device of claim 1 , including an out of band (OOB) physical layer, wherein the processing circuitry is configured to:

establish an OOB communication layer to receive the access credential information; and

initiate transmitting the UWB signal using the UWB physical layer in response to receiving the access credential information.

5. The reader device of claim 4 , wherein the processing circuitry is configured to initiate transmission of the transmitted UWB signal after granting access.

6. The reader device of claim 4 , wherein the processing circuitry is configured to initiate transmission of the transmitted UWB signal after receiving ranging information from the second device.

7. The reader device of claim 1 , wherein the processing circuitry is configured to:

estimate a channel impulse response (CIR) of the reflected signal using the specified pattern of RF signal pulses included in the reflected signal; and

determine the number of people using the estimated CIR of the reflected signal.

8. The reader device of claim 7 , wherein the processing circuitry is configured to:

include a preamble pattern in a preamble field in the transmitted UWB signal; and

use the preamble pattern in the reflected signal to determine the CIR of the reflected signal.

9. A method of operating a seamless physical access control system, the method comprising:

receiving access credential information at an ultra-wide band (UWB) capable reader device from a credential UWB capable device of a user;

using two-way ranging to receiving ranging information at the UWB capable reader device from the credential UWB capable device;

granting access through a physical portal according to the access credential information and ranging information;

performing one-way UWB signaling to transmit a UWB signal using the UWB capable reader device, wherein the transmitted UWB signal includes a specified pattern of radio frequency (RF) signal pulses;

receiving a reflected UWB signal by the UWB capable reader device that corresponds to a transmitted UWB signal reflecting off one or more objects;

determining, using the UWB capable reader device, a number of people using the received reflected UWB signal; and

generating, using the UWB capable reader device, an indication according to the determined number of people.

10. The method of claim 9 , including:

receiving the access credential information using an out of band (OOB) communication channel established between the UWB capable reader device and the credential UWB capable device; and

transmitting the UWB signal that includes the specified pattern of RF pulses using the UWB capable reader device in response to receiving the access credential information.

11. The method of claim 9 , including:

wherein receiving a reflected RF signal includes estimating a channel impulse response (CIR) of the reflected signal using the specified pattern of RF pulses; and

wherein determining the number of people intending to pass through the physical portal includes determining the number of people according to a change in the estimated CIR of the reflected signal.

12. The method of claim 11 , wherein transmitting an RF signal includes transmitting a preamble field of a transmitted radio packet as the specified pattern of RF pulses.

13. The method of claim 9 , wherein determining the number of people includes the UWB capable reader device determining the number of people after granting access.

14. The method of claim 9 , wherein determining the number of people includes the UWB capable reader device determining the number of people after receiving a request from the credential UWB capable device to open a communication session.

15. The method of claim 9 , wherein generating the indication according to the determined number includes generating an alarm when the determined number is more than one.

16. The method of claim 9 , wherein generating the indication includes sending the determined number of people to an access control device.

17. The method of claim 9 , wherein:

receiving the access credential information includes receiving the access credential information using an out of band (OOB) communication channel established between the UWB capable reader device and the credential UWB capable device; and

receiving ranging information and determining the number of people includes using a UWB communication channel to receive the ranging information and to determine the number of people intending to pass through the physical portal.

18. A non-transitory computer-readable storage medium including instructions that, when executed by processing circuitry of an ultra-wide band (UWB) capable device, cause the UWB capable device to perform acts comprising:

receiving access credential information from a separate second device;

receiving ranging information from the second device using two-way ranging;

granting access through a physical portal according to the access credential information and ranging information;

performing one-way UWB signaling to transmit a UWB signal that includes a specified pattern of UWB signal pulses;

receiving a reflected UWB signal that corresponds to a transmitted UWB signal reflecting off one or more objects;

determining a number of people using the reflected UWB signal; and

generating an indication according to the determined number of people.

19. The non-transitory computer-readable storage medium of claim 18 , including instructions that cause the UWB capable device to perform acts comprising:

determining a channel impulse response (CIR) of the reflected UWB signal, including estimating the CIR of the reflected signal using deconvolution on the received reflected UWB signal according to the specified pattern of UWB signal pulses.