As is well known, the seamless unlocking function of traditional Bluetooth smart locks typically relies on Received Signal Strength Indicator (RSSI) as the key basis, using path loss calculations to complete the triggering logic.
While this technical solution is simple to implement and cost-effective, in real-world scenarios, it suffers from several vulnerabilities. These include signal fluctuations due to walls, human presence, and metal reflections, insufficient security, and susceptibility to relay attacks.
Consequently, Bluetooth smart locks struggle to accurately determine whether a user is truly close, resulting in an unstable seamless unlocking experience and inadequate security.
RSSI – Received signal strength is inversely proportional to the square of the distance between the transmitter and receiver (Image source: SIG)
The emergence of channel detection functionality has fundamentally changed the role of the BLE protocol in smart locks—it is no longer just a "communication medium" between devices, but can also be a "distance sensor" between devices.
Schematic diagram of a Bluetooth smart door lock solution with channel detection function
As shown in the figure above, by accurately measuring the phase change and round-trip time of the wireless signal, the Bluetooth smart door lock developed based on the channel detection function can directly calculate the physical distance between the device itself and the authorized mobile phone, and its actual accuracy can reach "centimeter level", which greatly improves the distance perception capability of the smart door lock, making home security more reliable and daily entry and exit more worry-free.
Furthermore, from a security perspective, the channel detection function employs a two-way ranging mechanism. The door lock and the authorized mobile phone need to conduct multiple rounds of rigorous round-trip interactions to complete the distance calculation, which physically raises the attack threshold.
Traditional Bluetooth attack methods such as relaying, forwarding, and signal spoofing require simultaneously cracking the key and reproducing the signal phase and timing, resulting in an exponential increase in attack complexity and significantly enhancing the security of Bluetooth smart door locks.
For door lock manufacturers, how to introduce high-precision distance sensing capabilities without significantly increasing development difficulty and system complexity is a practical consideration in the product upgrade process; and a powerful, mature and stable BLE6.0 chip/module is the key foundation for efficiently transforming this cutting-edge channel detection capability into a scalable solution.
For example, the HM-BT2401DA is a channel sounding module independently developed by HOPERF based on a high-performance BLE6.0 chip.
It supports two ranging roles: initiator (which wants to calculate the distance from itself to the target device) and reflector (which responds to the initiator).
It supports dual antenna paths and can quickly realize wireless connection and ranging between the initiator and reflector through AT commands. It has low external MCU resource consumption and simple development process.
terms of wireless performance , the HM-BT2401DA boasts a maximum transmit power of 10dBm and a receive sensitivity of -96.7dBm@1Mbps, ensuring a stable communication link in complex environments.
Furthermore, the HM-BT2401DA supports dual antenna paths, allowing the module to autonomously select the path with the best signal quality (or perform weighted fusion of the two signals).
This effectively mitigates the impact of multipath reflections on ranging accuracy and enhances the reliability of the module's distance sensing capabilities.
From a memory resource perspective , the combination of 1024 KB Flash and 128 KB RAM provides significant system headroom for smart lock solutions.
On one hand, this memory resource allows for the efficient integration of the complete Bluetooth protocol stack, security firmware, upgrade mechanisms, and lock application code within the same SoC; on the other hand, it also reserves ample space for subsequent feature iterations, protocol upgrades, and customized differentiated functions.
From a product design perspective, the HM-BT2401DA also brings greater system flexibility to smart locks.
Because the module's distance judgment is more reliable, manufacturers can more boldly design multi-condition linkage strategies, such as combining time, direction, and usage habits to achieve more intelligent unlocking logic.
At the same time, the precise distance capability provides a solid performance foundation for advanced functions such as anti-tailgating and anti-accidental unlocking, enabling smart locks to evolve from "single-point protection" to "spatial awareness security devices."
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If you are interested in HOPERF's independently developed high-performance BLE 6.0 module HM-BT2401DA or other BLE chips/modules, please scan the QR code above or copy and open the link at the end of the article to apply for samples. We will be happy to serve you!
