Overcome smart door lock design challenges using the latest Wi-Fi Standards

February 04, 2025

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Wi-Fi door locks are popular because they offer convenience, security, and are part of smart-home integration. These locks let users control access remotely via a smartphone application, making it easy to lock or unlock doors from at any time. This feature is particularly useful for granting temporary access to guests, service providers, or family members without needing a physical key.

Wi-Fi-enabled door locks also provide enhanced security features like real-time alerts, activity logs, and auto-lock settings. They can integrate with other smart home devices such as security cameras, alarms, and voice assistants, offering a seamless and interconnected home security system. In addition, these locks eliminate the need for traditional keys, reducing the risk of losing or duplicating them.

End users also enjoy the simple setup associated with most Wi-Fi-enabled smart locks. The process is similar to connecting any Wi-Fi device to the home network. There’s no need for an additional bridge/gateway or complex setup.

While convenient for end users, smart door lock design is becoming more complex as longer battery life and increasing network congestion become critical requirements. This use case walks you through the key challenges, how to choose the right Wi-Fi standard to solve these challenges and how designers can overcome them using Infineon smart lock solutions.

Key Challenges

Smart locks require long battery life

Wi-Fi door locks require frequent battery changes or charges to avoid being locked out. This situation is because the smart lock must remain “always on” so it can report on its status, including entry events and lock positions. This feature also allows it to quickly respond to remote lock/unlock commands from the user. Having to charge/change batteries frequently is often cited as the biggest drawback to Wi-Fi-enabled smart lock adoption.

Compatibility issues

End users and designers also may face compatibility issues with existing door hardware or smart home ecosystems, limiting functionality or requiring additional purchases. This scenario typically arises when a proprietary protocol is employed, or when the developer did not maintain strict compliance with the Wi-Fi standard. While Matter, a unifying, IP-based connectivity standard developed by Connectivity Standards Alliance for smart homes, is working to solve this issue. Adoption of a new standard takes time.

How to pick the right standard for your design

Picking the right standard for your smart lock design is critical because you have to think about the current and future needs of end users and IoT market trends. Below is a quick snapshot for Wi-Fi 4-6/6E. While each has its advantages, each has tradeoffs.

Figure 1 Quantifiable and qualitative differences between Wi-Fi versions

Wi-Fi 6: The bedrock to extended range and battery life

Wi-Fi 6 is helping to alleviate the challenge associated with high power consumption in smart door locks, when compared to Wi-Fi 4 and 5 counterparts, though these standards are still useful depending on what your smart lock design are—especially in lowering battery power. One reason the power is significantly lower is due to the specification’s target wake time (TWT) feature, which works end-to-end with a Wi-Fi 6 access point.

TWT allows devices to schedule specific times for communication with the Wi-Fi network. Instead of staying awake and continuously listening for data, devices negotiate a wake time with the access point, reducing the time they need to be active. By coordinating when devices wake up to send or receive data, TWT minimizes power consumption. This situation means that when the smart lock is in an idle state, its Wi-Fi can remain in its low-power sleep mode for longer periods, conserving energy and extending the battery life.

This feature also reduces network congestion by avoiding unnecessary transmissions, improving overall network efficiency. In essence, TWT enables Wi-Fi devices to “sleep” more and only “wake up” when needed, optimizing both energy use and network performance.

One common misconception is that because there are few open/close events during a typical day, the lock needn’t send out signals on a regular basis. However, it’s important to maintain a constant connection to the home’s access point and the cloud, for logging events and to ensure that access is always available. So, even if the lock looks like it’s in standby mode, it’s still active in the background (See the whitepaper Lower Your Power Consumption for Battery-Operated Smart Devices for more information on this topic).

There is a direct correlation between configuring Wi-Fi 6 for the lowest power consumption and the latency that exists when the cloud attempts to access the lock for status updates and remote lock/unlock commands. Thus, a longer TWT sleep time potentially hurts the user’s experience. When the user requests to remotely unlock the door, a delay that’s more than one second will be noticeable and annoying for the user, resulting in a poor experience. Ultimately, it’s up
the developer to decide what is an acceptable responsiveness threshold.

Another challenge that designers face when implementing smart door locks is access to a reliable Wi-Fi signal. Because the lock is attached to an exterior door, the lock might be far from the home’s router/access point. Hence, it is imperative to choose a Wi-Fi solution with excellent RF range and reliability. But, as discussed, that stronger signal shouldn’t come at the expense of low power consumption.

Making the right choices for your design needs

As stated earlier, developers must make tradeoffs between response time and lower power. To combat this compromise and maintain the proper balance, developers can turn to Infineon’s ultra low-power Wi-Fi solutions, which have long been best-in-class leading for low power consumption and extended range.

How the low-power CYW43022 helps increase battery life

The CWY43022 consumes an estimated 86 joules per day for Wi-Fi 5 operations when using the typical smart lock DTIM3 setting or 157 joules with DTIM1 (the DTIM setting is the frequency with which the access point/router out to the smart lock). Even with these specs, the CWY43022 still provides a +18 dBm output power and -98 dBm sensitivity at 1 Mbit/s.

The CYW43022 is part of Infineon’s AIROC™ family of wireless connectivity devices, boasting superior Wi-Fi 4/5 performance in terms of low power consumption for DTIM1 or DTIM3 Wi-Fi sleep modes. Since many access points have not yet been updated to Wi-Fi 6, they generally default to DTIM1 or DTIM3 modes. The ultra-low power single-chip, combo part features 1x1 dual-band 2.4- and 5-GHz Wi-Fi 5 and Bluetooth® 5.4. An embedded Bluetooth® stack and Wi-Fi networking offloads allow the CYW43022 to maintain connectivity even when a host processor goes into its low-power sleep mode. The CYW43022 supports 256- QAM, enabling data rates up to 78 Mbits/s in applications that require such a bandwidth.

How the CYW55512 helps you transition your smart lock design to Wi-fi 6/6E

If you’re ready to take the leap to Wi-Fi 6, the Infineon CWY55512 transceiver consumes an estimated 85 joules per day using Wi-Fi 6 in a typical smart lock with a one-second sleep interval, while still providing +19.5 dBm transmit (Tx)
power and -101.5 dBm receive (Rx) sensitivity at 1 Mbit/s. Such specs come thanks to the Infineon design team’s deep experience with the technology, having shipped over 1 million of Wi-Fi-enabled AIROC™ devices.

The high-performance CYW55512 is a dual-band Wi-Fi 6 and Bluetooth 5.4 single-chip combo that delivers secure, reliable connectivity that goes beyond the written Wi-Fi 6 standard. This includes network offload power save features and WPA2 and WPA3 security. One of the features of Wi-Fi 6 that further suits it for an application like a smart door lock is its reduced TWT, which lets the access point be configured so that connected devices can sleep longer between “check in” periods, which are far longer than with previous versions of the Wi-F- standard.

The CYW55512 serves those products that are making the switch to WI-Wi 6 and its TWT sleep time feature that extends Wi-Fi sleep time beyond DTIM1 or DTIM3, resulting in even lower power consumption. Tests show that the CYW55512 can select this TWT sleep time between 0.5 and 1 second in a smart door lock to achieve the best balance between power consumption and remote access times.

Finally, Infineon has a product that can alloy users’ fears of being locked out of their homes if the batteries drain completely and they aren’t carrying a physical key. Specifically, the NAC1080 is an innovative actuation controller that harvests the NFC energy from a phone, to drive an integrated H-bridge, providing emergency passive lock operation. Based on an Arm® Cortex® M0 MCU core, it integrates an NFC front-end, a sensing unit, a motor driver, and energy harvesting functionality. And, of course, it contains hardware security functions such as a secure area in flash memory, a 128-bit AES accelerator, and a true random number generator.

Summary

With Smart Door Locks, there is no “one size fits all” systems approach for developing your next smart IoT device. Working with suppliers that have a broad portfolio of devices ensures that you can tailor their solutions to your precise needs. To have a successful residential smart lock design that works now, and, in the future, you must have a low-power solution coupled with a reliable Wi-Fi connection. These features can be attained through Infineon’s AIROC™ family of Wi-Fi 4/5 and 6 transceivers. The former provides better responsiveness and maximum compatibility with existing access points, while the latter can provide lower power consumption by selecting a longer TWT sleep time and thus extend the lock’s battery life if your home connectivity infrastructure supports the latest Wi-Fi 6 features. Whatever your needs Infineon’s AIROC™ family has got you covered!

Contact Infineon today for more information.