Low-cost and low-delay intelligent door lock device based on ultra-wideband transceiver

Abstract

The invention relates to the technical field of intelligent door locks, and particularly discloses a low-cost and low-delay intelligent door lock device based on an ultra-wideband transceiver, which comprises the ultra-wideband transceiver connected with two antennas facing the inside and the outside of a door respectively and used for distinguishing whether a paired intelligent key is inside or outside the door, the two antennas are respectively defined as an inner antenna and an outer antenna; the communication module is provided with a Bluetooth transceiver and an ultra-wideband transceiver at the same time, an additional antenna is used for Bluetooth communication, and the inner antenna and the outer antenna are used for ultra-wideband communication; the ultra-wideband transceiver is in a low-power-consumption sleep mode when no user approaches, and is awakened after being in communication handshake with a key through Bluetooth when a user appears or approaches. The double-antenna switching is realized in the same data frame, so that the delay caused by switching different antennas by using a plurality of data frames is avoided, the requirement that the delay from the time when a user reaches an effective range to the time when the unlocking is completed is less than 500ms can be met, and the non-sensitive experience of the user is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of smart door locks, and in particular to a low-cost and low-latency smart door lock device based on an ultra-wideband transceiver. Background Art

[0002] With the rapid development of smart homes, smart door locks, as the core entry point to smart homes, are facing increasingly stringent performance requirements. Security requirements include resistance to physical damage and digital attacks, such as relay attacks and key cracking. Accurate distance measurement is crucial to ensure that the door lock opens only when the key is within a safe distance. A seamless experience requires accurate judgment of user intent, enabling low-latency unlocking and distinguishing between inside and outside the door, eliminating waiting at the door. Ecosystem compatibility requires integration with smart home systems to support multi-scenario automation.

[0003] Currently, key performance indicators for smart door locks include accurate distance measurement, precise distinction between inside and outside the door (error in distinguishing between inside and outside the door is less than 0.3 meters), low-latency unlocking (delay from the user reaching the effective range to unlocking completion is less than 500ms), ultra-low power consumption (battery life must be 12-24 months (triggering 20 times a day)), and good environmental adaptability (adaptability to complex electromagnetic environments such as metal doors, concrete walls, and dense WiFi / Bluetooth signals).

[0004] Ultra-wideband (UWB) technology holds great potential for smart door lock applications due to its large bandwidth, relatively low cost, stable performance, high temporal resolution, and anti-interference properties. UWB systems operate in the 3.1GHz to 10.6GHz frequency range, and their distance measurement is based on the Time of Flight (ToF) method, achieving centimeter-level ranging accuracy. Furthermore, UWB's inherent physical layer characteristics, combined with encryption protocols, effectively prevent replay attacks and location falsification.

[0005] However, existing technologies have numerous shortcomings when determining the key's position inside and outside the door. For example, methods that incorporate multiple Bluetooth or ultra-wideband receiver chips within the door lock, or deploy antenna arrays to distinguish key locations using angle-of-arrival (AoA) detection, not only significantly increase the cost and energy consumption of smart door locks, but also compromise performance in complex electromagnetic environments. Summary of the Invention

[0006] The purpose of the present invention is to provide a low-cost, low-latency smart door lock system based on an ultra-wideband transceiver to solve the problems of existing smart door locks in distinguishing between inside and outside the door, cost control, delay optimization, and environmental adaptability, and to achieve accurate distinction between inside and outside the door, low-cost, low-latency unlocking, and good environmental adaptability.

[0007] The purpose of the present invention can be achieved through the following technical solutions: A low-cost, low-latency smart door lock device based on an ultra-wideband transceiver, characterized by comprising: Ultra-wideband transceiver: Connected to two antennas facing inside and outside the door, defined as the inner antenna and outer antenna, respectively; the inner antenna and outer antenna share the ultra-wideband transceiver in time-division multiplexing; the ultra-wideband transceiver is configured to measure the distance to the paired smart key in ranging mode and compare the strength of the signals received by the inner antenna and the outer antenna to distinguish whether the paired smart key is inside or outside the door; Control module: configured to control the ultra-wideband transceiver to enter the ranging mode from the sleep mode or low-power mode when the presence or approach of a user or user device is detected; wherein the detection of the user or user device is performed by the ultra-wideband transceiver operating in the low-power mode, or when the smart door lock device includes a Bluetooth transceiver or a low-power radar module, it is performed by one of them.

[0008] When the smart door lock device does not include an additional communication or radar module, the ultra-wideband transceiver can be configured in radar detection mode in low-power mode to detect the presence or approach of a user. Another implementation method is to configure the ultra-wideband transceiver in narrowband operation mode in low-power mode to detect the presence or approach of a smart key. Narrowband operation mode is a mode in which the ultra-wideband transceiver operates with a narrower bandwidth (less than the bandwidth in ranging mode). Due to the narrower operating bandwidth, the required power consumption is also lower than that in ranging mode. This narrowband operation mode can refer to the narrowband assistance technology introduced in IEEE802.15.4ab, which aims to use narrowband signals to complete some preparatory work before the start of ultra-wideband ranging.

[0009] As a further solution of the present invention: the low-cost and low-latency smart door lock device based on the ultra-wideband transceiver also includes: A Bluetooth transceiver connected to an additional antenna, distinct from the internal and external antennas; Control module: Configure the Bluetooth transceiver and ultra-wideband transceiver at the same time. The ultra-wideband transceiver is configured in sleep mode by default; the Bluetooth transceiver is configured in working mode by default; after the Bluetooth communication handshake with the smart key, the ultra-wideband transceiver is controlled to enter the ranging mode from sleep mode.

[0010] A low-cost, low-latency smart door lock device based on an ultra-wideband transceiver. The ultra-wideband transceiver is connected to two antennas, one facing inside the door and the other facing outside the door, for distinguishing whether the paired smart key is inside the door or outside the door. The two antennas are defined as the inner antenna and the outer antenna respectively. Control module: configured with both Bluetooth and ultra-wideband transceivers, where Bluetooth communication uses an additional antenna and ultra-wideband communication uses the internal antenna and external antenna; the ultra-wideband transceiver is in a low-power sleep mode when no user is approaching, and is awakened after a Bluetooth handshake with the key communication when a user appears or approaches.

[0011] As a further aspect of the present invention, the angle between the beam axes or the visual axes of the inner and outer antennas is greater than 90 degrees. In a preferred embodiment, the angle between the beam axes or the visual axes of the inner and outer antennas is 180 degrees.

[0012] As a further solution of the present invention: when receiving a UWB data frame, the ultra-wideband transceiver operates in the following manner: Switch antennas within the same data frame. Specifically, use the outer antenna to receive the synchronization field of the data frame, switch to the inner antenna before the scrambling timestamp sequence (i.e., the STS field) begins, and use the inner antenna to receive the STS field. Compare the received signal strengths of the synchronization field and the STS field to determine whether the key is closer to the outer antenna or the inner antenna, and thus determine whether the key is outside or inside the door; The signals received using different antennas are respectively subjected to ranging and security verification operations. Ranging is performed through the synchronization field, and security verification is performed through the STS field to determine whether it is a paired key and whether the key is within the safe distance.

[0013] As a further solution of the present invention: when receiving different UWB data frames, the ultra-wideband transceiver repeatedly switches the antenna within the same data frame, and determines the user's movement speed by comparing the changes in the measured distance between different frames, and transmits the speed information to the door lock central control center to assist the central control center in setting the unlocking delay.

[0014] The safe distance for unlocking is generally set at 2 meters or less. To avoid accidental unlocking caused by excessive sensing distance, the safe distance can be reduced to about 1 meter. In this way, the lock will only be unlocked when the paired smart key is within 1 meter of the door lock.

[0015] As a further solution of the present invention: the door lock central control center sets the unlocking delay according to the user's moving speed in the following manner: When the user enters the safe distance at a higher speed, the unlocking delay is appropriately reduced; when the user enters the safe distance at a lower speed, the unlocking delay is appropriately increased.

[0016] When the user moves within a safe distance at a speed greater than or equal to the preset speed, the unlocking delay is reduced; When the user moves within the safe distance at a speed slower than the preset speed, the unlocking delay is increased.

[0017] The average human walking speed is approximately 1.3-1.4 meters per second, which translates to approximately 4.7-5 kilometers per hour. The preset speed can be equal to or slightly lower than the average walking speed, such as approximately 1 meter per second. When a user is detected entering the safety zone at a speed greater than or equal to the preset speed, the unlocking delay can be appropriately reduced to minimize waiting time at the door and improve the user experience.

[0018] As a further solution of the present invention: the ultra-wideband transceiver processes UWB data frames according to IEEE 802.15.4a and IEEE802.15.4z standards, and the data frames include a synchronization field, a start frame delimiter, a physical layer header, a PHY payload, and a scrambling timestamp sequence field.

[0019] As a further solution of the present invention: the inner antenna and the outer antenna share the ultra-wideband transceiver in time division multiplexing, and dual-antenna switching is completed in the same data frame.

[0020] The beneficial effects of the present invention are as follows: by configuring only one UWB transceiver, the two internal and external antennas share the same transceiver through time-division multiplexing, avoiding the cost increase caused by using multiple receiver transceivers and reducing the hardware cost of the smart door lock; the dual-antenna switching is realized in the same data frame, avoiding the delay caused by using multiple data frames to switch different antennas, and can meet the requirement of a delay of less than 500ms from the user reaching the effective range to the completion of unlocking, thereby improving the user's non-sensing experience; the difference in the received signal strength (RSSI) of the two antennas is used to distinguish the key position. Compared with the existing technology, it can more accurately determine whether the key is inside or outside the door, and the error in distinguishing between inside and outside the door is smaller, effectively avoiding the occurrence of accidental unlocking; the anti-interference ability of UWB technology itself enables this smart door lock system to still work stably in complex electromagnetic environments such as metal doors, concrete walls, and dense WiFi / Bluetooth signals, ensuring the accuracy of ranging and position judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of the component structure of the smart door lock in the present invention; Figure 2 It is a structural diagram of the intelligent door lock communication module of the present invention; Figure 3 It is a schematic diagram of the frame structure of the ultra-wideband UWB in the present invention; Figure 4 This is a diagram of the configuration of the physical layer converged protocol data unit single carrier time domain symbol STS data packet structure in the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] Ultra-wideband (UWB) systems typically operate in the 3.1 GHz to 10.6 GHz frequency range. Due to their large bandwidth, relatively low cost, and robust performance, UWB radios are used in a variety of applications, including positioning, communications, and radar sensing. UWB technology's high temporal resolution and interference immunity give it significant advantages in ranging and positioning applications.

[0025] Distance measurement in UWB systems is generally based on the time-of-flight (ToF) method. Two UWB radios exchange a series of ultrashort pulses, and the ToF is measured by calculating the time difference between the transmitted and received pulses. The distance between the two UWB radios can then be calculated using the following formula: Distance = (speed of light x flight time) / 2; Thanks to its large bandwidth, UWB ranging technology can often achieve centimeter-level ranging accuracy.

[0026] Furthermore, UWB offers exceptional security for applications such as car keys and smart door locks. First, the physical layer characteristics of UWB inherently provide a degree of security. The pulse signals it uses are extremely short, making them difficult to intercept or tamper with. Furthermore, combined with encryption protocols, such as the use of dynamic keys for each communication, replay attacks can be prevented. Furthermore, timestamp encryption during ranging ensures that attackers cannot falsify location information. Furthermore, UWB's use of broadband technology provides robust interference resistance, preventing interference from nearby wireless devices (such as Wi-Fi or Bluetooth) from affecting ranging results. Therefore, implementing car or door keys using UWB offers numerous unique advantages.

[0027] As the core entry point of smart homes, smart door locks have been continuously evolving in terms of security, convenience, and intelligence in recent years. Their core requirements can be summarized into the following three points: 1. Security: Resist physical damage and digital attacks (such as relay attacks and key cracking), accurately measure distance, and unlock the door only when the key is within a safe distance; 2. Touchless experience: Accurately judge user intent (distinguishing between inside and outside the door) and unlock with low latency; 3. Ecological compatibility: Linked with smart home systems to support multi-scenario automation.

[0028] It can be seen that the key indicators affecting the performance of smart door locks are: Accurate distance measurement; Determine whether the key is inside or outside the door (for example, the error in distinguishing between inside and outside the door is less than 0.3 meters); Low-latency unlocking (e.g., the delay from the user reaching the effective range to unlocking completion is less than 500ms, avoiding the awkwardness of "walking to the door and waiting"); Ultra-low power consumption (e.g. battery life of 12-24 months (triggering 20 times per day) to avoid frequent battery replacement); Environmental adaptability (for example, adapting to complex electromagnetic environments such as metal doors, concrete walls, and dense WiFi / Bluetooth signals).

[0029] To determine whether a key is inside or outside the door, existing technologies often install multiple Bluetooth or ultra-wideband receiver chips within the door lock. Discrimination is achieved by comparing the distance between the key and the different receiver chips. Other approaches employ antenna arrays within the door lock to detect the angle of arrival (AoA) to distinguish key locations. However, these methods significantly increase the cost and energy consumption of smart door locks. Furthermore, performance can be affected in complex electromagnetic environments.

[0030] See also Figures 1-4 As shown, the present invention is a low-cost, low-latency smart door lock device based on an ultra-wideband transceiver. It mainly includes an ultra-wideband transceiver connected to two antennas, one facing the inside of the door and the other facing the outside. The control module is equipped with both Bluetooth and ultra-wideband transceivers. Bluetooth communication requires a separate antenna, while ultra-wideband communication / ranging relies on two antennas facing the inside and outside of the door. The specific steps for use are as follows: Configure the ultra-wideband transceiver to switch antennas within the same data frame when receiving UWB data frames; Configure the UWB receiver to use the external antenna to receive the synchronization field of the data frame; and use the internal antenna to receive the STS field of the data frame; The UWB receiver is configured to compare the received signal strengths of the synchronization field and the STS field to determine whether the key is closer to the outer antenna or the inner antenna, thereby determining whether the key is outside or inside the door.

[0031] The configured UWB receiver will use the signals received by different antennas to perform ranging and security verification operations respectively, such as ranging through the synchronization field and security verification through the STS field, so as to further determine whether it is a paired key and whether the key is within the safe distance.

[0032] The ultra-wideband transceiver is configured to repeatedly switch antennas within the same data frame when receiving different UWB data frames, and to determine the user's movement speed by comparing the changes in the measured distance between different frames.

[0033] An ultra-wideband transceiver is configured to transmit speed information to the door lock central control center to assist the central control center in adaptively setting the unlocking delay. For example, when the user enters the safe distance at a higher speed, the unlocking delay is appropriately reduced. When the user enters the safe distance at a lower speed, the unlocking delay is appropriately increased.

[0034] like Figure 1 As shown in the figure, the UWB module is equipped with two antennas, one facing inside and one facing outside the door. By comparing the difference in signal strength between the two antennas, it can distinguish whether the key is inside or outside the door. In other words, the key's location is determined by comparing the relative strength of the signals received by the inner and outer antennas. When the inner antenna receives a stronger signal, it indicates that the user is inside the door, and unlocking is not triggered. Conversely, when the outer antenna receives a stronger signal, it indicates that the user is outside the door, and unlocking is triggered when the user enters the effective range. This allows accurate distinction between inside and outside key positions, preventing accidental unlocking.

[0035] In another preferred embodiment of the present invention, Figure 2 As shown, the communication module is equipped with both Bluetooth and UWB transceivers. When no user is near, the UWB transceiver is in a low-power sleep mode. When a user appears or approaches, a handshake is established with the key via Bluetooth communication, waking up the UWB chip for further precise ranging and user authentication. Because Bluetooth and UWB operate in different frequency bands, Bluetooth communication requires one antenna, while UWB requires two antennas, one facing inside and one facing outside the door.

[0036] To minimize costs, the present invention advocates for a single UWB module with a single transceiver, allowing both internal and external antennas to share the same transceiver in a time-division multiplexed manner. To further reduce latency, the present invention advocates for dual-antenna switching within the same data frame, enabling simultaneous ranging and security verification within a single data frame, thus avoiding the latency associated with switching between different antennas using multiple data frames.

[0037] In the UWB frame structure, the preamble within a data frame is a key component in communication and positioning systems. It performs several important functions for receiving signals, such as signal detection, time and frequency synchronization between the receiver and transmitter, and channel estimation and equalization. The physical layer specifications for ultra-wideband (UWB) technology are defined by the IEEE 802.15.4a standard, which defines the frame structure, including the synchronization (SYNC) field, the start of frame delimiter (SFD) field, the physical header (PHR) field, and the PHY payload.

[0038] SYNC (Synchronization Field): Contains a predefined pulse pattern, also known as a "preamble," primarily used for synchronization between the transmitter and receiver.

[0039] SFD (Start Frame Delimiter): Marks the beginning of a frame and is used as a timestamp, which is crucial for ranging applications.

[0040] PHR (Physical Layer Header): Provides information about the frame and payload, including fields for data rate, frame length, ranging indicator, and error detection code.

[0041] PHY payload: Contains the actual data to be transmitted, such as user data or other control information.

[0042] STS (Scrambled Timestamp Sequence): An optional field whose location varies by configuration and is used specifically to enhance security and ranging accuracy.

[0043] The SYNC header is constructed using one of the preambles defined in the IEEE 802.15.4a standard. For packets that follow the 802.15.4a standard, the preamble has a length of 31 or 127.

[0044] According to the 802.15.4z standard, there are predefined preambles with lengths of 91 and 127. The preamble is taken from the ternary alphabet {-1, 0, 1}. The IEEE 802.15.4z amendment introduces the Scrambled Timestamp Sequence (STS) field. Figure 3 As shown, it can be placed in three different positions. Due to the limited number of possible preambles, they are repeated multiple times in the SYNC field, which could serve as a starting point for attacks. To prevent these attacks, the STS field was added. It consists of a pseudorandom pulse sequence generated by a deterministic random bit generator using a 28-bit key and a 128-bit random number. Each zero bit generates a pulse with positive polarity, and every other bit generates a pulse with negative polarity. These pulses are broadcast. A receiver can only decode the STS if it knows the key and encryption scheme used to generate it. Furthermore, an STS association is valid only when both the transmitter and receiver initiate it simultaneously.

[0045] It can be seen that according to the standard, the STS sequence immediately following the SFD is a mandatory mode that the UWB system must support.

[0046] The STS consists of a series of pseudo-random pulses generated using a DRBG based on AES-128 in counter mode. These pulse sequences are arranged in blocks of (one to four) active segments, which are enclosed by silent intervals (called "gaps"). The duration of these gaps should be 512 chips (approximately 1 μs). Figure 4 Shows the STS range when it consists of one or two segments.

[0047] UWB ranging is typically performed in the synchronization field or preamble field, while security verification is performed in the STS field. To perform a distance comparison to determine whether the key is inside or outside the door, the present invention proposes that when the UWB chip in the smart door lock receives UWB data frames from the key, it uses different receiving antennas for the synchronization field and the STS field. Initially, the UWB chip uses the outer antenna to receive the synchronization field, then switches to the inner antenna before the STS field begins, receiving the STS field using the inner antenna. During ranging and security verification, the chip also compares the received signal strength (RSSI) of the signals received by the outer and inner antennas to determine whether the key is outside the door. This allows the door lock's central control center to unlock the door only if the key is outside the door, passes security verification, and is within the door lock's effective unlocking range (e.g., within 1 meter).

[0048] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A low-cost, low-latency smart door lock device based on an ultra-wideband transceiver, characterized in that: include: Ultra-wideband transceiver: Connected to two antennas facing inside and outside the door, defined as the inner antenna and outer antenna, respectively; the inner antenna and outer antenna share the ultra-wideband transceiver in time-division multiplexing; the ultra-wideband transceiver is configured to measure the distance to the paired smart key in ranging mode and compare the strength of the signals received by the inner antenna and the outer antenna to distinguish whether the paired smart key is inside or outside the door; Control module: configured to control the ultra-wideband transceiver to enter the ranging mode from the sleep mode or low-power mode when the presence or approach of a user or user device is detected; wherein the detection of the user or user device is performed by the ultra-wideband transceiver operating in the low-power mode, or when the smart door lock device includes a Bluetooth transceiver or a low-power radar module, it is performed by the Bluetooth transceiver or the low-power radar module.

2. A low-cost, low-latency smart door lock device based on an ultra-wideband transceiver according to claim 1, characterized in that: include: A Bluetooth transceiver connected to an additional antenna, distinct from the internal and external antennas; Control module: Configure the Bluetooth transceiver and ultra-wideband transceiver at the same time. The ultra-wideband transceiver is configured in sleep mode by default; the Bluetooth transceiver is configured in working mode by default; after the Bluetooth communication handshake with the smart key, the ultra-wideband transceiver is controlled to enter the ranging mode from sleep mode.

3. The low-cost, low-latency smart door lock device based on an ultra-wideband transceiver according to claim 1, characterized in that: When the ultra-wideband transceiver receives an ultra-wideband data frame in ranging mode, it operates in the following manner: Switching antennas within the same data frame. Specifically, the outer antenna is used to receive the synchronization field of the data frame, and the inner antenna is used to receive the STS field before the start of the scrambled timestamp sequence (STS field). Compare the received signal strengths of the synchronization field and the STS field to determine whether the paired smart key is closer to the outer antenna or the inner antenna, and then determine whether the key is outside or inside the door; The signals received using different antennas are respectively subjected to ranging and security verification operations, i.e. ranging is performed through the synchronization field and security verification is performed through the STS field, thereby confirming whether it is a paired key and whether the key is within the safe distance.

4. A low-cost, low-latency smart door lock device based on an ultra-wideband transceiver according to claim 3, characterized in that: When the STS field cannot be detected in the signal received by the inner antenna or the signal strength is lower than a predetermined threshold, when receiving the next one or more ultra-wideband data frames, only the outer antenna is used for reception without antenna switching.

5. The low-cost, low-latency smart door lock device based on an ultra-wideband transceiver according to claim 4, characterized in that: When the ranging and security verification operations with the matching smart key are completed, the operation of switching antennas within the same data frame is resumed.

6. The low-cost, low-latency smart door lock device based on an ultra-wideband transceiver according to claim 3, characterized in that: When receiving multiple ultra-wideband data frames, the ultra-wideband transceiver repeats the above-mentioned step of switching antennas within the same data frame, and determines the user's movement speed by comparing the changes in the measured distance between different frames, and transmits the speed information to the door lock central control center to assist the central control center in setting the unlocking delay.

7. The low-cost, low-latency smart door lock device based on an ultra-wideband transceiver according to claim 6, characterized in that: The door lock central control center sets the unlocking delay according to the user's movement speed in the following way: When the user moves within a safe distance at a speed greater than or equal to the preset speed, the unlocking delay is reduced; When the user moves within the safe distance at a speed slower than the preset speed, the unlocking delay is increased.

8. The low-cost, low-latency smart door lock device based on an ultra-wideband transceiver according to claim 3, characterized in that: The ultra-wideband transceiver processes UWB data frames according to IEEE 802.15.4a and IEEE 802.15.4z standards. The data frames include a synchronization field, a start frame delimiter, a physical layer header, a PHY payload, and a scrambling timestamp sequence field.

9. The low-cost, low-latency smart door lock device based on an ultra-wideband transceiver according to claim 1, characterized in that: The ultra-wideband transceiver is configured in a radar detection mode in a low power consumption mode to detect the presence or approach of a user, or is configured in a narrowband operation mode to detect the presence or approach of a smart key.

10. The low-cost, low-latency smart door lock device based on ultra-wideband transceiver according to claim 1, characterized in that: The angle between the beam axes or boresights of the inner and outer antennas is greater than 90 degrees.

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