From the IoT perspective, Wi-Fi developers have recognised that faster is not always the best choice for all Wi-Fi connected devices. In generations prior to Wi-Fi 6, increased raw throughput was the primary objective. Now, the trade-offs between some key performance indexes (KPIs) allow system designers the flexibility to focus on the aspects important in their design. Figure 1 shows key features in the Wi-Fi 6 specification. While the ‘power save’ column shows only one item, features in other columns can also be modified for power saving.
Figure 1. Key features of Wi-Fi 6 include power saving aspects.
Reducing power consumption/increasing IoT device battery life
Wi-Fi 6 includes technologies to optimise efficiency, increase throughput and/or reduce power consumption that include orthogonal frequency-division multiple access (OFDMA), target wake time (TWT), and multi-user, multiple input, multiple output (MU MIMO).
OFDMA divides the 20/40/80 (and even 160 in Wi-Fi 6E) MHz channel into resource units (RUs) that are further divided into subcarriers. Since 80 MHz is achieved at the cost of increased power consumption, the 20 MHz mode in Wi-Fi 6 provides power savings. That saving is important for IoT devices that need to send only a small amount of data very power efficiently. For example, a door lock just needs to transmit that the correct keypad entry occurred. Ideal for this type of signal transmission, the 20 MHz mode is one of the items that differentiates Wi-Fi 6 from Wi-Fi 5 for IoT applications.
With TWT, access points (APs) and station devices negotiate particular times when the station device will be awake and ready to receive traffic from the AP. This feature allows the station to remain in sleep mode much longer than with previous generations of Wi-Fi, thus reducing overall device power consumption.
Previously, IoT devices had to wake up at set intervals dictated by the access point (300 ms in most installations) to see if there was any traffic for them. Consider a window sensor that rarely provides any new data unless there is breakage. With TWT, a sensor can communicate to the network that it only needs to wake up say every three minutes to provide its input. Otherwise, it can sleep, not transmit data and save power. The access point knows that it will not receive information but still recognises that the device is present and will communicate with it at the pre-determined time. This feature allows devices to sleep much longer and save a considerable amount of power so batteries as the power source will last much longer.
The sleep time is usually determined by the system designer to achieve the specified battery life and user experience. Given the wake-up time, the amount of data to be sent, and the frequency it is sent at, the desired sleep time can be calculated quite accurately for a particular battery type. This additional design flexibility provides designers with new options for next generation products and is among the benefits of using the latest Wi-Fi 6 specifications.
Wi-Fi security
Another IoT aspect that is becoming more and more important is security, especially as public breaches occur and IoT devices, like surveillance cameras, get hacked. Wi-Fi 6 incorporates and mandates all the latest security features that have been developed for Wi-Fi. For example, Wi-Fi Protected Access (WPA) has advanced to WPA3 to provide the latest security in Wi-Fi 6 and address vulnerabilities in WPA2. Security is so important that specifications for some of the older technologies, such as Wi-Fi 5, are now making WPA3 mandatory for certification as well.
Security on the Wi-Fi link itself is only the first line of defence for an IoT device. System on chip (SoC) products and standalone Wi-Fi devices offered by Infineon offer a rich set of features crucial to creating a truly secure IoT product. One such feature is validating the authenticity of the firmware (FW) that runs within the Wi-Fi chip itself.
While most CPUs and MCUs today offer a root of trust (RoT) and the ability to authenticate the top-level system image, we at Infineon believe it is equally important to ensure that individual sub-systems in a device provide additional layers of defence. This philosophy is called Defence in Depth and results in a significantly more secure system. Validation of the Wi-Fi chipset firmware involves a hardware root of trust to verify the signature of any image sent to it. Validating the Wi-Fi firmware is important to ensure that the image itself is authentic, even if the host system is compromised. Once authenticity of the firmware is confirmed, the Wi-Fi device will configure itself to allow only enough access over the Secure Digital Input Output (SDIO) interface to perform the data transfer and not modify or tamper with memory or other resources on the chip. Specific hardware on the Wi-Fi device providing restricted access control closes another path for hackers to compromise the security of the chip and the system.
Performance of Wi-Fi 6 and Wi-Fi 6E
MU-MIMO that was initially introduced in Wi-Fi 5 allows Wi-Fi 6 to direct data streams to multiple clients simultaneously, thereby improving network efficiency. With the beamforming technology used in MU-MIMO, the antenna directs the radio signal transmissions to a specific device. This allows increased data rates and reduced interference.
Wi-Fi 6 provides backward compatibility to Wi-Fi 2, 3, 4, and 5. However, the 2,4 and 5 GHz frequency bands used in older versions have become quite crowded. The resulting congestion impacts an IoT device’s ability to transmit its data. The presence of pre- Wi-Fi 6 devices can also hamper achieving the most savings from the power saving capabilities of Wi-Fi 6. Consequently, all the potential benefits of Wi-Fi 6 may not be realised because of supporting the legacy devices that operated in the 5 GHz band.
Wi-Fi 6E adds operation in the 6 GHz band. Since no previous generation Wi-Fi devices will be operating in this band, the ability to access the medium will be much faster. As a result, communicating on the medium is much more efficient vs the 2,4 and 5 GHz bands, resulting in higher overall power efficiency for the IoT device.
All of Infineon’s Wi-Fi 6 solutions for the IoT will support the 6 GHz band because this is the only way that users can fully realise the benefits of Wi-Fi 6. While all three bands are supported in these devices, in the 6 GHz mode, communication only occurs with Wi-Fi 6 for optimum performance. This greenfield 6 GHz band allows Wi-Fi 6E to realise its full potential in network efficiency and power consumption, taking the first step in a journey towards an exciting destination – the future.
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