16 WI-FI CONNECTIVITY www.nordicsemi.com Issue 4 2023 Power Electronics Europe www.power-mag.com Low power Wi-Fi opens doors in smart buildings and industry Adding Wi-Fi 6 enhances current IoT applications while enabling many new ones. By Finn Boetius, Product Marketing Engineer, Nordic Semiconductor According to the Wi-Fi Alliance, the organisation that promotes the use of WiFi, the economic value derived from the technology is $3.5 trillion. (Global Economic Value of Wi-Fi 2021 - 2025.) The alliance says there are 18 billion WiFi devices in use and 4.4 billion annual shipments, of which 2.3 billion meet the latest Wi-Fi 6 standard. That makes Wi-Fi seriously big business, with much of its huge popularity down to Wi-Fi’s internet protocol (IP) interoperability. This allows a Wi-Fi device to connect directly to the cloud using any of the millions of alreadyinstalled access points (AP). Public Wi-Fi access will benefit from the new standard’s high bandwidth and speed, for example allowing large numbers of users in malls or at airports to make quick purchases and stream videos or music. Moreover, the adoption of Wi-Fi 6 has made the technology better suited to the IoT (internet of things), where it complements existing IoT technologies used for low power networks, for example, Bluetooth LE and Thread. Wi-Fi 6 offers higher throughput and longer range than these other protocols, allowing it to enhance existing IoT applications while enabling new ones. Building Wi-Fi 6 for the IoT Wi-Fi 6 introduced many enhancements to the specification but those most useful for IoT solutions are OFDMA (orthogonal frequency division multiple access), beamforming, longer symbol duration, target wake time or TWT, a new power saving mode (PSM) and basic service set (BSS) colouring (a method of differentiating between APs broadcasting on the same channel). TWT and OFDMA make the most significant contribution to power saving and enable energy-constrained devices to use the benefits of Wi-Fi where it might not have previously been possible. Earlier versions of the Wi-Fi standard do include PSM, but these are controlled by the AP and offer limited flexibility to the end device. Generally the end device has to remain awake to receive the AP’s beacon ahead of any data exchange, which effects battery life. By contrast, the TWT PSM included in Wi-Fi 6 enables the end device to individually negotiate a wake-up schedule with the AP. This allows it to sleep for defined periods, helping cut power consumption significantly and allowing data exchange to happen at the agreed wake-up time. A further benefit of TWT is that it enables interference mitigation by letting the AP allocate dedicated time slots for each end device’s data transfer. More sub-carriers allow larger sensor networks The OFDMA employed in Wi-Fi 6 allows for a higher number of sub-carriers within a single Wi-Fi channel. For example, a 20MHz channel can be further divided into 117 sub-carriers each side of the channel’s central frequency. Groups of sub-carriers can then be allocated to a certain end device while other groups can be allocated to different end devices depending on the data traffic requirement. The proliferation of protocols enables many new applications in cities, buildings and vehicles.
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