This article appeared in Microwaves & RF and has been published here with permission.
What you’ll learn:
- Wi-Fi was borne of several wireless innovations dating back to the 1970s.
- Wi-Fi 6 brings technical advantages to IoT deployments.
- The technology is poised to become the foundation of future smart homes.
Wi-Fi has a complex history. That’s perhaps not surprising since the radio technology represents a melding of many innovations, four of which stand out. The first was the development of a pioneering packet-radio network in Hawaii during the 1970s. ALOHAnet connected seven campuses on four islands across the archipelago, ensuring that they could all communicate with each other through a central computer on Oahu.
Second, in 1985, the U.S. Federal Communication Commission (FCC) formalized the use of the 2.4-GHz spectrum (among other allocations) for unlicensed industrial, scientific, and medical (ISM) use. The move encouraged commercial organizations to consider how they could make use of this new radio resource.
Then, in the 1990s, radioastronomy scientists at Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) worked out a way to overcome the multipath problems that afflicted indoor, high-throughput radio communications. The invention formed the basis of wireless local-area networks (WLANs) and paved the way for widespread Wi-Fi deployment.
Finally, an Institute of Electrical and Electronic Engineers (IEEE) standards committee was formed and tasked with defining the physical-layer (PHY) and media-access-control (MAC) specification for a WLAN protocol dubbed IEEE 802.11. The target application was “wireless Ethernet,” using RF technology to link computers together in the fashion pioneered by wired networking.
The committee’s work resulted in the first version of the Wi-Fi specification, IEEE 802.11-1997, which was published in June 1997. Then a 1999 amendment to the standard introduced the technology upon which today’s versions of Wi-Fi are largely based. The Wi-Fi Alliance was formed to commercialize the technology.
Power and Deployment Challenges
Now there’s a fifth key event influencing Wi-Fi’s evolution—the Internet of Things. It’s a phrase that was still two years away from being coined—the term was dreamt up in 1999 by Kevin Ashton, an executive working to promote RFID—when the first version of Wi-Fi was officially adopted. Today, connecting billions of devices (or "things") to the established internet is largely being achieved by wireless technology.
For short-range IoT networks, Bluetooth Low Energy (BLE), Thread, Zigbee, and other protocols are shouldering the load. For the IoT’s wide-area networks (WANs), LTE-M/NB-IoT (cellular IoT) and LoRaWAN are proving good options. But what of Wi-Fi? At first glance, it would appear to be the perfect option for wireless networks needing greater range than that provided by the short-range, low-power protocols, but not the kilometer-plus range of the WAN technologies. However, closer inspection reveals Wi-Fi has some considerable drawbacks for IoT applications.
The first problem is power consumption. Wi-Fi was primarily designed for good throughput, which costs battery power. In contrast, IoT wireless technologies typically try to limit on-air time to extend battery life and hence minimize maintenance. The tradeoff is lower throughput, but this is hardly an issue for sensors and actuators that only infrequently send small amounts of data.
Second, Wi-Fi struggles in dense deployment scenarios. Many of us are familiar with patchy service when accessing public hotspots in busy malls and libraries. It’s annoying, but consumers can typically afford to be tolerant. Industrial networks comprising hundreds of sensors are a different matter.
Built for the IoT
Now a version of Wi-Fi, technically named IEEE 802.11ax and marketed as Wi-Fi 6, promises to address the deficiencies that have hampered the technology’s widespread adoption for the IoT. Approved by the Wi-Fi Alliance earlier this year, Wi-Fi 6 was specifically designed to meet the requirements of dense deployments, both public and industrial. The new version offers several enhancements, but the headline features are improvements to throughput and spectral efficiency, which allow for more network connections while still maintaining good service.
For example, with the new orthogonal frequency-division, multiple-access (OFDMA) feature, devices can use less than one channel bandwidth, sharing the bandwidth with other devices on the network to increase capacity. Moreover, these technical advances also enable faster response to and from connected units. Where previous versions of Wi-Fi struggled to cope with more than a few sensors, Wi-Fi 6 can comfortably manage large sensor networks comprising hundreds of devices.
Wi-Fi 6 also brings a key technical enhancement for smart-home and -industry applications. Called "target wake time" (TWT), the advance is a significant evolution over the power-saving efforts of prior generations of Wi-Fi.
When using the TWT technology, client devices negotiate wake-up times with access points (APs). Therefore, the clients needn't stay awake to maintain the wireless connection. As a result, an AP can aggregate large groups of client requests into fewer triggered transmit opportunities. The benefits are more efficient, contention-free channel access and significant client-device power savings—up to 80% in like-for-like applications. That makes IoT devices with long battery lifetimes more practical.
Wi-Fi 6 also brings improved security using Wi-Fi Protected Access (WPA) 3 (although this was rolled out separately to Wi-Fi 6). WPA3 uses the Simultaneous Authentication of Equals (SAE) protocol in place of the Pre-Shared Key (PSK) protocol common to older WPA2 protection. SAE prevents some brute-force attacks that could be used against routers employing PSK.
Another key advantage of Wi-Fi 6 is that it offers IoT sensors direct connection to the cloud through routers without having to pay additional data subscriptions. Furthermore, the technology’s higher throughput compared to other short-range wireless solutions enables new use cases like wireless security cameras and high-quality video doorbells. The additional throughput also can be used to complement Bluetooth during the transfer of large amounts of data, such as music streaming in wearables.
Wi-Fi for the Smart Home
The Connectivity Standards Alliance—an organization aiming to ease the challenges of connecting devices using different wireless protocols—is backing Wi-Fi 6 as a foundation technology of the smart home. Matter, the alliance’s unified IP-based connectivity protocol, is designed to run over Wi-Fi 6 (and older versions) in addition to Ethernet and Thread (and for ease of commissioning, BLE).
The CSA initiative will see the widespread introduction of "border routers." Such devices aren’t a new concept. However, until now, vendors were forced to develop their own solutions. The product is a specific type of router that provides connectivity from an IEEE 802.15.4 network to adjacent networks using other physical layers (such as Wi-Fi). Border routers could be routinely embedded into items such as smart speakers and lighting fixtures, making Internet Protocol (IP)-based connectivity more convenient for both vendors and consumers.
Industrial Wi-Fi 6 products are only just starting to reach the market. In a few years, though, we’ll see short-range wireless, Wi-Fi 6, and cellular IoT complementing each other to build the large, robust, and low-latency networks needed for the IoT to deliver on its promise. Nordic Semiconductor, a leading developer and manufacturer of all three wireless technologies, hopes to be in the vanguard of that revolution.