Patent Description:
Lock devices and key devices are evolving from the traditional pure mechanical locks. These days, there are wireless interfaces for electronic lock devices, e.g. by interacting with a portable key device. For instance, Radio Frequency Identification (RFID) has been used as the wireless interface. When RFID is used, the user needs to present the portable key device very close to a reader of the lock.

In order to provide a more user-friendly solution, wireless interfaces, such as Bluetooth Low Energy, BLE, with greater range are starting to be used. This allows the interaction between the portable key device and the lock device to occur without user interaction, e.g. with a portable key device being located in a pocket or handbag. However, in such a situation, there is a risk that someone on the inside unlocks the lock device by simply walking by the lock device. In order to prevent this from happening, without introducing user interaction to open the lock device, there needs to be a way to block portable key devices on the inside from unlocking the lock device.

One way to achieve this is to determine where the portable key device is located, i.e. inside or outside a barrier. In this way, automatic access control could be disabled for inside devices, preventing inadvertent unlocking. Prior art lock and key devices are known by <CIT> and <CIT>.

One objective is to improve how it is determined when a portable key device is located on the inside or outside of a barrier.

The objective is solved by a method according to claim <NUM>.

The method may further comprise the step of: determining the portable key device to be located on the inside of the metal door when the portable key device is not determined to be on the outside of the metal door.

The ToF measurements may be obtained using ultra-wideband, UWB, technology.

According to claim <NUM>, it is provided a credential communication device for determining whether a portable key device is located inside or outside a metal door.

The credential communication device may further comprise instructions that, when executed by the processor, cause the credential communication device to determine the portable key device to be located on the inside of the metal door when the portable key device is not determined to be on the outside of the metal door.

According to claim <NUM>, it is provided an access control system comprising: the credential communication device according to claim <NUM>; and a metal door, wherein the metal door is provided between the first antenna and the second antenna of the access communication device.

The metal door may be configured to be connected to ground.

According to claim <NUM>, it is provided a computer program for determining whether a portable key device is located inside or outside a metal door.

According to claim <NUM>, it is provided a computer program product comprising a computer program according to claim <NUM> and a computer readable means on which the computer program is stored.

<FIG> is a schematic diagram showing an environment in which embodiments presented herein can be applied.

Access to a physical space <NUM> is restricted by an openable barrier <NUM> which is selectively unlockable. In this case, the openable barrier is in the form of a metal door. In order to unlock the barrier <NUM>, a credential communication device <NUM> is provided. The credential communication device <NUM> is connected to a physical lock device <NUM>, which is controllable by the credential communication device <NUM> to be set in an unlocked state or locked state. In this embodiment, the credential communication device <NUM> is mounted close to the physical lock device <NUM>.

The credential communication device <NUM> communicates with a portable key device <NUM> over a wireless interface using a plurality of antennas (shown in <FIG>). The portable key device <NUM> is any suitable device portable by a user and which can be used for authentication over the wireless interface. The portable key device <NUM> is typically carried or worn by the user and may be implemented as a mobile phone, a smartphone, a key fob, wearable device, smart phone case, RFID (Radio Frequency Identification) card, etc. Using wireless communication, the authenticity and authority of the portable key device can be checked in an unlock procedure, e.g. using a challenge and response scheme, after which the credential communication device <NUM> grants or denies access. As described in more detail below, the antennas are also used to determine when the portable key device <NUM> is on the inside <NUM> or outside of the metal door <NUM>, based on Time-of-Flight (ToF) measurements.

Providing multiple antennas provides additional benefits. For instance, the antennas can be used for beam forming, multiple input/multiple output (MIMO) transmissions, redundancy between antennas, differential antennas, etc..

When access is granted, the credential communication device <NUM> sends an unlock signal to the lock device <NUM>, whereby the lock device <NUM> is set in an unlocked state. In this embodiment, this can e.g. imply a signal over a wire-based communication, e.g. using a serial interface (e.g. RS485, RS232), Universal Serial Bus (USB), Ethernet, or even a simple electric connection (e.g. to the lock device <NUM>), or alternatively a wireless interface. When the lock device <NUM> is in an unlocked state, the metal door <NUM> can be opened and when the lock device <NUM> is in a locked state, the metal door <NUM> cannot be opened. In this way, access to a closed space <NUM> is controlled by the credential communication device <NUM>. It is to be noted that the credential communication device <NUM> and/or the lock device <NUM> can be mounted in a fixed structure (e.g. wall, frame, etc.) by the metal door <NUM> (as shown) or in the metal door <NUM> (not shown).

<FIG> are schematic top views of the environment of <FIG>, where also antennas are visible according to two embodiments. Specifically, there is a first antenna 5a on the outside <NUM> of the metal door <NUM> and a second antenna 5b on the inside <NUM> of the metal door <NUM>. The antennas 5a-b are connected to the credential communication device <NUM>.

First, the embodiment of <FIG> will be described. Here, the two antennas 5a, 5b are provided attached to the metal door <NUM>, on either side.

When a portable key device <NUM> is in the vicinity, the credential communication device <NUM> will determine whether the device is on the inside or outside of the metal door. This determination is based on Time-of-Flight (ToF). ToF, known in the art per se, uses timing of radio signals to determine distance between two devices. One technology where ToF is used for positioning is Ultra-Wideband (UWB), which can be employed in embodiments presented herein. In ToF, it is determined the time a signal takes to travel between two points. This time is converted to distance using the speed of light.

In this way, a first distance 19a being the distance between the first antenna 5a and the portable key device <NUM> can be determined using ToF. Additionally, a second distance 19b can be determined using ToF.

The components between the antennas 5a-b comprises an RF barrier that delays, fades, blocks or otherwise negatively affects radio signals. The RF barrier is in the form of a metal section of the metal door. In other words, since, the barrier <NUM> is a metal door, the metal section is integral to the barrier. The presence of metal skews ToF measurements and makes measurements such as angle-of-arrival practically impossible since these depend on very exact time difference measurements. Hence, in the prior art, metal materials are avoided as much as possible when positioning using ToF. Optionally, the RF barrier also comprises RF absorbing material other than metal.

In contrast to the prior art, in the embodiments presented herein, the presence of the metal in the metal door is instead used to improve positioning. Specifically, the time to transfer signals between the portable key device <NUM> and the second antenna 5b is increased in the scenario of <FIG>, e.g. due to the radio signal having to take a different path, such as via the openings between the metal door <NUM> and the surrounding structure <NUM>. In this way, the determined distance based on ToF between the second antenna 5b and the portable key device <NUM> is greater than the actual distance, the second distance 19b. This is exploited to determine which side (inside <NUM> or outside <NUM>) of the metal door <NUM> that the portable key device <NUM> is located.

When a ToF measurement between the first antenna 5a (on the outside) and the portable key device <NUM> is less than a ToF measurement between the second antenna 5b (on the inside) and the portable key device <NUM> by an amount which is greater than a ToF corresponding to a physical distance 19c between the antennas 5a-b, the portable key device <NUM> is determined to be on the outside. In other words, the ToF measurement from the first antenna 5a needs to be less than the ToF measurement from the second antenna 5b. Moreover, the difference between the ToF measurements needs to be greater than a threshold value. According to the invention, the threshold value is greater than a ToF corresponding to the actual distance 19c between the two antennas 5a, 5b. This is the case if the portable key device indeed is on the outside, since the RF barrier in the metal door <NUM> increases the time for the radio signals to travel between the second antenna 5b and the portable key device. Hence, the RF barrier in the metal door <NUM> increases the difference between the ToF measurements from the two antennas 5a-b, which thus provides a more reliable determination of when the portable key device <NUM> is on the outside <NUM>. The threshold value can be increased depending on the ToF delay resulting from the RF barrier. The greater the threshold value, the less the risk is to incorrectly determine the portable key device to be on the outside. In other words, a more effective RF barrier generating a greater ToF delay allows a greater threshold value to be determined, which increases accuracy in determination of inside and, in particular, outside, of the portable key device <NUM>.

Improving determination of when the portable key device <NUM> is on the outside improves security, since a false outside determination can result in inadvertent unlocking, e.g. if a person walks by the metal door <NUM> on the inside <NUM>. In this case, an unauthorised person is able to pass through to the inside <NUM> through the unlocked metal door <NUM>.

Optionally, the metal door is grounded to increase the negative effect on radio signals and thus to increase the difference in the ToF measurements.

Optionally, radiation-absorbent material is provided on a side of the second antenna 5b which does not face the metal door, i.e. towards the inside space. This also increases the difference and quality of the ToF measurements.

The credential communication device <NUM>, the antennas 5a-b and the barrier <NUM> are here collectively called an access control system <NUM>.

In <FIG>, an embodiment is shown which is similar to that of <FIG>, but where the antennas 5a-b are mounted on either side of the surrounding structure <NUM> and either side of the metal door <NUM>. Again, there is material between the two antennas 5a-b which has negative effect on radio signals, exploited in analogy to the description above. The surrounding structure <NUM> can e.g. comprise concrete.

In <FIG>, two antennas 5a-b can be seen. However, there may be more antennas provided as desired as long as there is at least one antenna provided on either side of the metal door <NUM>.

<FIG> is a flow chart illustrating embodiments of methods for determining whether a portable key device is located inside or outside a metal. The methods are performed in the credential communication device.

In an obtain <NUM>st ToF measurement step <NUM>, the credential communication device obtains a first ToF measurement between a first antenna and the portable key device. The first antenna is located on the outside of the metal door.

In an obtain <NUM>nd ToF measurement step <NUM>, the credential communication device obtains a second ToF measurement between a second antenna and the portable key device. The second antenna is located on the inside of the metal door.

As explained above, both ToF measurements can be obtained using UWB technology.

In a conditional <NUM>nd ToF - <NUM>st ToF > threshold step <NUM>, the credential communication device determines when a condition is true that the first ToF measurement is less than the second ToF measurement by an amount which is greater than a threshold amount. The threshold amount is a ToF value corresponding to a physical distance between the first antenna and the second antenna. The ToF measurements can be expressed as times or distances, as long as the comparison is made using the same physical quantity. If this condition is true, the method proceeds to a portable key device inside step <NUM>. Otherwise, the method optionally proceeds to an optional portable key device outside step <NUM> or the method ends.

In the portable key device inside step <NUM>, the credential communication device determines the portable key device to be located on the outside of the metal door.

In the optional portable key device outside step <NUM>, the credential communication device determines the portable key device to be located on the inside of the metal door when the portable key device is not determined to be on the outside of the metal door.

<FIG> is a schematic diagram illustrating components of the credential communication device <NUM> of <FIG>. A processor <NUM> is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions <NUM> stored in a memory <NUM>, which can thus be a computer program product. The processor <NUM> could alternatively be implemented using an application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc. The processor <NUM> can be configured to execute the method described with reference to <FIG> above.

The credential communication device <NUM> further comprises an I/O interface <NUM> for communicating with external and/or internal entities. Optionally, the I/O interface <NUM> also includes a user interface.

Other components of the credential communication device <NUM> are omitted in order not to obscure the concepts presented herein.

Claim 1:
A method for determining whether a portable key device (<NUM>) is located inside or outside a metal door (<NUM>), the method being performed by a credential communication device (<NUM>) and comprising the steps of:
obtaining (<NUM>) a first time-of-flight, ToF, measurement between a first antenna (5a) and the portable key device (<NUM>), wherein the first antenna (5a) is located on the outside of the metal door (<NUM>);
obtaining (<NUM>) a second ToF measurement between a second antenna (5b) and the portable key device (<NUM>), wherein the second antenna (5a) is located on the inside of the metal door (<NUM>); and
determining (<NUM>) the portable key device (<NUM>) to be located on the outside of the metal door (<NUM>) when the first ToF measurement is less than the second ToF measurement by an amount which is greater than a threshold value, characterized in that the threshold is greater than a ToF corresponding to a physical distance between the first antenna and the second antenna.