BACKGROUND

The present invention relates to operating active radio frequency identification (RFID) systems. More particularly, the present invention relates to reducing response times in active RFID systems.

Recently, active RFID systems have come into use with devices such as smart phones equipped with Bluetooth or other longer distance technologies. While convenient, these methods have limitations. The first is that the long-range capability of these RFID systems (many feet) can cause confusion in applications such as close-spaced access control systems having controlled access barriers such as doors, turnstiles, and the like. Various schemes for operating active RFID systems have been adopted, such as requiring a twisting or turning motion (HID access cards and readers) or a physical tapping of the device (Samsung uses this for activation in its near field communication (NFC) protocol) or pressing a button to start the process or starting the process when the device is at a close distance by measuring the signal strength using, for example, the RSSI (Receive Signal Strength Indicator) function in an IEEE 802.11 system. Using the RSSI method as an example, the current practice is to trigger the process at a predetermined signal level which then starts the authentication process.

All of these mechanisms work but all have certain drawbacks. The principal drawback is the delay time for the credential to be authenticated. In higher security applications, the processing delay can be several seconds. From the user point of view, this is a major issue as there is no way to tell what is going on and why the gate, door, turnstile or other access point is not operating. This causes problems at the access control points because the throughput of the access point, such as, for example a turnstile, is expected to be between about 40-60 accesses per minute. If a three second delay is introduced into the access system by the authentication process, the maximum throughput drops to less than about 20 per minute. This is a significant problem.

FIG. 1is a diagram showing an illustrative prior-art system10for operating a controlled access barrier at an access point separating a public area identified at reference numeral12from a controlled access area identified at reference numeral14. The controlled access area14may take many forms, such as, but not limited to, transit systems, commercial buildings, stadiums and other entertainment venues, government facilities, etc. An access barrier16, such as a wall, a fence, or other barrier separates the public area12from the controlled access area14.FIG. 1shows a plurality of access points18a,18b, and18c, which, for purposes of illustration are depicted as turnstiles. Persons of ordinary skill in the art will readily appreciate that the access points18a,18b, and18ccould be doors, gates, or any other means for accessing the controlled access area. AlthoughFIG. 1arbitrarily depicts a system for controlling three access points, such skilled persons will appreciate that some applications will require but a single access point while other applications will require the use of more than one access point.

A RFID reader20ais positioned proximate to access point18aSimilarly, RFID readers20band20care positioned proximate to access points18band18c, respectively. RFID readers are coupled to a control system22by communication links collectively identified by reference numeral24. Persons of ordinary skill in the art will appreciate that communication links24could be hardwired or wireless communication links although hardwired communication links may provide an enhanced level of security over wireless communication links.

FIG. 1depicts a RFID device26in dashed lines at locations designated a, b, c, and d successively closer to the access point18b. The RFID device26is shown in solid lines at the location e closest to the access point18b. As will be appreciated by persons of ordinary skill in the art, the RFID device may take numerous forms, a cellular telephone being a common such device. The RFID device may be carried by a person or may be, for example, attached to a vehicle.

Across the region including locations a, b, c, and d identified by reference numeral28, the strength of the RFID signal (represented by curved lines one of which is identified by reference numeral30) transmitted by the RFID device26is below a threshold set by the control system22for establishing a communication link between the RFID reader20band the RFID device26(such as by use of an RSSI protocol). Once the RFID device26is located at a position e identified by dashed line32, it is close enough to the RFID reader20b, a communication link is established between the RFID reader20band the RFID device26and data is exchanged between the RFID reader20band the RFID device26. Data identifying the RFID device26is received by the RFID reader20band is communicated to the control system22. The control system22queries an access list32to determine whether the RFID device is authorized to permit entry into the controlled access area14. If the RFID device is authorized to permit entry into the controlled access area14, the control system22sends a control signal to the access point18bto enable entry through the access point18b.

In many such systems, a communication link is not established between the RFID device26and the RFID readers20aand20c, located further away from the RFID device26than RFID reader20b. In some systems, the controller can use the relative signal strengths of the RFID signal sent by RFID device26to determine which one of access points18a18b, and18cshould be activated.

Referring now toFIG. 2, a diagram shows the operation of an illustrative prior-art system for operating a controlled access barrier at an access point, such as the system depicted inFIG. 1. Numerous elements of the system10ofFIG. 1are shown inFIG. 2and will be identified using the same reference numerals used to identify those elements inFIG. 1.

The RFID device26is shown at the top ofFIG. 2approaching the access point18bat position a located at a distance from the access point18bidentified at reference numeral34. At this distance34from the access point18bat a time indicated on an elapsed time scale36at reference numeral38, no communication is established between the RFID device and the RFID sensor20b.

At a time indicated at reference numeral40at a desired trigger distance from the access point18bidentified at reference numeral32, the RFID device26is shown at the approaching the access point18bat position e and an RFID link is established between the RFID device26and the RFID sensor20b. The authentication procedure that is performed in the control system22ofFIG. 1begins at this time and is completed at a time indicated at reference numeral42. At a time indicated at reference numeral44, the control system22ofFIG. 1then sends the control signal to the access point18bto enable entry through the access point18b.

Persons of ordinary skill in the art will appreciate that the time scale36is shown for purposes of illustration only and is not linear in that the actual times40,42, and44will depend on system sensitivity, latency, and processing throughput.FIG. 2illustrates that a time delay identified at reference numeral46will exist at the access point18bbetween the time that the RFID device26is located at position e and comes into range of the RFID sensor20b.

As previously stated, this time delay46at the access point18bis the necessary delay time for the credential to be authenticated. In higher security applications, this processing delay can be several seconds, and can be a major issue as there is no way for the user to determine why the gate, door, turnstile or other access point is not operating. This time delay46reduces the throughput of the access point. Where the access point18ais, for example a turnstile, an average throughput is expected to be between about 40-60 accesses per minute as was previously noted. If the time delay at the access point18aintroduced into the access system by the authentication process is three seconds, the maximum throughput at the access point18adrops to less than about 20 per minute. This is a significant problem.

Persons of ordinary skill in the art will appreciate that there are places other than access points where users would use an RFID link for authentication. One non-limiting example is for elevator dispatching and control (floor choice is an example). An elevator dispatch system or other system may employ a kiosk in a hall to direct people to the proper elevator or other location. On upper floors, the access control system can be employed to limit which direction a particular person could go. For instance, a person may be allowed access to floor21, but may not be permitted to request an up elevator from that floor. Such controls could be located either in the foyer of a building, at the main bank of elevators, or on an individual floor. These are all versions of access control systems.

Increasing the speed of the authentication process for an existing access system may not be an option due to limitations of the computing portion of the security system chosen.

There exists a need for a system and method for operating an RFID system such as a controlled access system that addresses the limitations of the prior art.

BRIEF DESCRIPTION

In accordance with one aspect of the present invention, a method is described which gives an easily implemented apparent reduction in the response time of RFID access systems.

According to one aspect of the present invention a method for operating a controlled access barrier at an access point includes exchanging data with an RFID device associated with a user in response to a first trigger event, determining from data received from the RFID device whether to authenticate the user, and exchanging data with the RFID device in response to a second trigger event occurring after the first trigger event, and only if the user has been authenticated, operating the controlled access barrier to grant access to the user at the access point after exchanging data with the RFID device in response to the second trigger event.

The method may include releasing a latch mechanism in the controlled access barrier. The controlled access barrier may take many forms. A non-exhaustive list of these forms includes a latch mechanism of a turnstile, a latch mechanism of a gate or door.

According to one aspect of the invention, the first trigger event is exchanging data with the RFID device at a first received signal strength threshold from the RFID device, and the second trigger event is exchanging data with an RFID device at a second received signal strength threshold from the RFID device greater than the first received signal strength threshold.

In some embodiments of the invention, the device is worn by or carried by the user. In such embodiments the first trigger event is sensing the presence of the user at a first distance from the access point, and the second trigger event is sensing the presence of the user at a second distance from the access point closer to the access point than the first distance. Sensing the presence of the user may include one of sensing at least one user action, interruption of a light beam, sensing pressure on a pressure pad on which the user has made contact, and sensing the presence of the user by one of transmission and reflection of energy from the user.

In accordance with another aspect of the invention, a method for operating one of a plurality of controlled access barriers at an access point includes exchanging data with an RFID device associated with a user in response to a first trigger event, determining from the detected RFID signal whether to authenticate the user, and exchanging data with the RFID device near at least one of the controlled access barriers in response to a second trigger event occurring after the first trigger event. Only if the user has been authenticated, the one of the at least one controlled access barriers from which a detected RFID signal from the device is the strongest is operated to grant access to the user at the access point in response to the second trigger event.

