by Dan Kephart, Senior Product Manager of Laird Connectivity
Wi-Fi networks are relied on so heavily for IoT connectivity that the resulting network congestion and RF complexity often leads to degraded performance and reliability. From the early days of the 802.11 standard to today, the 2.4 GHz ISM band has been the home of Wi-Fi-based connectivity. But that band is struggling to support the dueling demands of so many Wi-Fi-based devices today. The solution is for engineers to address these demands with the adoption of dual-band Wi-Fi. Adding the 5 GHz spectrum provides dramatically higher performance and more reliable connections, even in highly congested IoT environments such as industrial facilities, hospitals, and manufacturing plants.
You don’t have to look far for existing examples where dual-band Wi-Fi increases performance and reliability. The nearest family room will do. The use of dual-band Wi-Fi is extensive in residential settings, with its adoption being far faster in this market than in the enterprise, industrial, and medical fields. At one point in time, single-band Wi-Fi on the 2.4 GHz frequency was more than adequate for a household, but as the number of Wi-Fi enabled devices increased and as the demands of those devices on the network intensified, families have experienced the limits of how much traffic single-band Wi-Fi can support. A smart TV streaming Netflix shows, gaming systems running low latency Gears of War, and tablets playing YouTube videos would often lead to arguments about which member of the family was hogging the Wi-Fi and causing the performance issues. Dual-band residential routers have helped alleviate that network congestion, particularly when certain devices are dedicated to each band. A fairly typical approach moves gaming and content streaming, which are sensitive to latency, to the 5 GHz band, while other devices, laptops and tablets on the web, continue to use the 2.4 GHz signal.
Yes, IoT networks in settings like hospitals are very different than the nearest family room, but the same principles for use of dual-band Wi-Fi apply. One of the ways that dual-band allows organizations to relieve congestion and dramatically improve performance is by adding additional networks for devices to connect with. But dual-band also gives organizations the ability to manage traffic and performance by assigning specific devices to specific bands, and prioritizing which of those devices get different levels of connectivity.
Below is an outline of key principles that should steer how you integrate dual-band Wi-Fi into your IoT strategy, as well as a number of best practices and caveats based on the extensive work that my team and I have done with customers on these types of projects.
Design Dual-Band Flexibility into Your IoT Devices
Using dual-band modules and antennas ensures flexibility without impacting the complexity and cost structure of a device in a substantive way. IoT networks are not static, and over time your organization may want flexibility in how wireless devices are utilized and how connectivity is shared by those devices. By integrating a dual-band solution into your platform, you allow maximum flexibility on how and when the connected device is connected to the network.
Assign Bands Based on Criticality of the Devices
Assigning bands to critical/non-critical devices is a rule of thumb to consider in any scenario where some traffic may be more critical than others. One example of this would be inside a hospital. A higher band could be reserved for critical devices that track patient vitals or are directly related to patient care. In this scenario, the 2.4 GHz band becomes the home for less vital devices, such as the personal smart devices of patients and their families.
Take Advantage of Lesser Traffic and Interference with 5 GHz
It is important to note that the 2.4 GHz band is less ideal for mission critical devices not only because of the demands already on that band, but also because of its susceptibility to external interference. In a complex RF environment, the 2.4 GHz band can experience interference from several sources, including the proliferation of device technologies utilizing the frequency, the number of nearby Access Points and gateways broadcasting on that band, and even any nearby microwave ovens. The 5 GHz band is far less susceptible to any of those interferers, underscoring its suitability for supporting critical devices and applications.
Use Channels to Further Improve Performance and Reliability
For engineers who have not worked with dual-band Wi-Fi in the past, one of the key capabilities to be aware of is the number of channels that the 5 GHz band offers. Engineering teams can tune the performance of their devices and networks by assigning 5 GHz devices to specific channels, avoiding co-channel interference within the band. This also enables even more precise control of performance, traffic control, and latency. For this reason, network deployment teams should not only create a strategy for how to segment devices between 2.4 GHz and 5 GHz, but also strategize how to segment devices across the channels in the higher 5GHz band.
You Get What You Pay for with Modules
As with so much other technology in the wireless world, solutions that are inexpensive upfront often cost you much more in the long run than something of higher quality. That rule of thumb holds true when it comes to dual-band Wi-Fi modules. Choosing a low-quality module and technology partner can lead to a much higher TCO in a number of ways. Although integration and deployment of Wi-Fi products has become significantly easier over the last few years, there are many complexities and application demands that are not necessarily supported by all Wi-Fi module suppliers. The most common causes of headaches for developers include missing features, lack of regulatory certification, and minimal integration and deployment support. All of these items can cause significant delays, cost increases and loss of opportunity and customer goodwill. Excellent documentation, readily available technical support, integration guidance for electrical and mechanical application and comprehensive pre-certifications should all be key selection criteria for a high-quality module.
Focus on Future-Proofing Your Module Choice
One of the most important design considerations for projects is to anticipate how long a device may be on the market and in the field. Understanding the module’s lifespan and available strategies for extending its life or providing a replacement needs to be considered. For use cases that will have devices in the field for five, ten, or more years, the engineering team should ensure that the radio and module they have selected will likely still be viable throughout that life cycle based on information available from industry groups and manufacturers.
Antenna Selection and Placement Can Make or Break Your Project
One of the biggest pitfalls for dual-band Wi-Fi design projects is related to antenna selection. Antenna selection is fraught with difficulty no matter what technologies are involved, due to the number of antennas on the market, the confusion created by their marketing-driven data sheets, and the often dramatic difference between reported performance and actual performance. Dual-band Wi-Fi devices require antennas that are well-designed, have successfully optimized performance of both bands, and avoid the detuning that is possible with 5 GHz signal. Engineering teams should not rely on data sheets and RF modeling for antenna selection. That is also true for placement of both internal and external antennas. Testing is critical to ensure that your team has selected the right antenna and has installed it in a manner that optimizes performance. Extensive testing is a wise investment of time up front in the process that will save time and prevent design headaches later on, particularly for IoT deployments in complex RF environments such as those in healthcare, industrial, and manufacturing settings. It is also important to note that working with an antenna provider that is committed to being a partner in the process will give the engineering team invaluable guidance and technical support that lowers the risks involved in this critical decision.
With the recent availability of a new band for Wi-Fi supported by the Wi-Fi 6E solutions, more spectrum continues to open up for the projected device growth over the coming years. With that said, it’s too early for most engineering teams to be factoring 6 GHz Wi-Fi into their product roadmap. For most IoT applications, it will likely be several years before that newest release of the Wi-Fi technology becomes widely adopted.
About the Author:
Dan Kephart is the Senior Product Manager of IoT Platform at Laird Connectivity, which provides a full range of wireless modules and IoT solutions that simplify the process of using wireless technology. In this role at the company he oversees development of solutions utilizing multiple wireless technologies including Wi-Fi. He has 15 years of experience in the engineering and wireless design industry, and he earned his degree in computer engineering from the University of Akron.