From Silicon Labs: Using Wi-Fi for Low Power IoT Applications
Wi-Fi may not be the first wireless technology one thinks of when considering low power IoT applications, but it should be. In this Q&A, Silicon Labs’ senior product manager for Wi-Fi products Siddharth Sundar discusses Wi-Fi's advantages and challenges that developers should keep in mind when choosing the right approach to wireless IoT.
What are the advantages to using Wi-Fi in low power IoT applications?
Being a widely deployed protocol with approximately 13 billion deployed devices means that Wi-Fi connectivity is available in most home and commercial/office environments. This avoids the need for a gateway and lets devices be cloud connected without needing new infrastructure. Wi-Fi is also highly interoperable, so you can have confidence that your devices will connect to most Wi-Fi networks out there. The higher data rates and range offered by Wi-Fi also enable a wider range of applications.
How does Wi-Fi compare to other IoT wireless communication protocols?
Wi-Fi has significantly higher data throughput than most other IoT wireless communication protocols – often 10-100x higher, allowing it to tackle higher throughput applications like audio and video. The broad deployment and range of Wi-Fi is also a significant benefit compared to many other protocols.
These benefits do come at a cost. Wi-Fi products typically have higher power consumption and higher implementation costs than IoT specific protocols like BLE and Zigbee, since the range and throughput offered by Wi-Fi demands higher design complexity. However, most of this design complexity can be managed through using pre-certified modules, and the cost and power consumption of Wi-Fi devices is decreasing to a point where it is competitive for many IoT applications.
Why implement 802.11n rather than 802.11ac for IoT platforms?
There are a few key reasons why 802.11n (Wi-Fi 4) may be better suited for most IoT applications than 802.11ac-based products (Wi-Fi 5). First, 802.11ac is based on 5 GHz versus 802.11n which supports both 2.4 GHz and 5 GHz. 2.4 GHz offers more range and better object penetration compared to 5 GHz. This is a key benefit in home environments with multiple walls and barriers.
Also, IoT Wi-Fi devices like Silicon Labs transceivers and modules are designed with enhanced RF selectivity to maintain reliable communication even in the presence of blockers such as nearby APs, 802.15.4 and Bluetooth devices. The below figure illustrates how advanced interference mitigation techniques help overcome the channel limitations related to the 2.4 GHz band. Learn more in Wi-Fi Learning Center.
One final point, the cost and power consumption of 802.11ac based systems is higher due to the higher protocol complexity. While it does provide enhanced throughput, the data rates provided by 802.11n are more than sufficient for most IoT applications including audio and security/IP camera video streaming.
What are some ways to reduce power requirements using Wi-Fi in IoT applications?
There are a number of ways to reduce power consumption using Wi-Fi:
- Minimize the time spent in active TX and RX modes: With Wi-Fi’s high data rates, it may make sense to aggregate data and transmit/receive infrequently. It may also make sense to use higher data rates to transmit data more quickly and reduce the amount of time spent in high power transmit modes.
- Choose the right devices: Not all Wi-Fi chipsets are made the same, so make sure you choose the devices with the lowest possible current consumption for the TX, RX, sleep and DTIM modes you are interested in. Watch out for datasheet tricks and make sure you are comparing apples to apples – this is especially important when looking at “sleep” and “associated” current definitions, as they are defined differently by vendors.
- Think about the system level: The best power optimizations can be found at the system level, by seeing if you can turn off the radio and only power it on infrequently or using techniques like beacon skipping to reduce idle/sleep current if you are OK with tolerating latency.
- Use the low power features available in the Wi-Fi standard: The Wi-Fi standard has a number of power optimizing features like DTIM sleep modes and Power Save that can save you a significant amount of power.
Are Wi-Fi solutions as integrated and compact as something like Bluetooth?
Wi-Fi solutions have traditionally been more complex and larger than solutions for Bluetooth. However, this gap is reducing, and there are increasingly smaller, optimized solutions available for Wi-Fi. This new class of IoT Wi-Fi devices takes advantage of Moore’s law to deliver higher performance, and eliminates size/cost adding features like MIMO. For example, Silicon Labs has a pre-certified Wi-Fi SiP module (including a Wi-Fi Radio, RF, XTAL and antenna) in a 6.5 mm x 6.5 mm package, which allows you to add Wi-Fi to small form factor devices.
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