This blog post is the seventh and final in a series of articles about Wi-Fi 6 (and 6E) – the current and future top-of-the-line Wi-Fi standards championed by the Wi-Fi Alliance. We've discussed the history of the evolving standard of Wi-Fi, new features introduced in Wi-Fi 6 and 6E, applications beyond the commonly known consumer use cases, and much more. Additionally, we’ll be releasing a companion series of video interviews with Ezurio (formerly Laird Connectivity) experts, which you can find here.

Design Changes for Wi-Fi 6 –
More Options for OEMs

In this, our seventh and final post in our Wi-Fi 6 and 6E series, we’re finally addressing an important question: With all the changes that have arisen in the Wi-Fi 6 specification, what are the hardware, software, and other form-related characteristics of embedded Wi-Fi 6 devices?

As with all hardware, the available form factors, physical and logical interfaces, and more are driven by broad industry trends as well as the specific needs of the functionality the hardware supports. Old standards give way to new standards, new interfaces achieve ubiquity by supporting more data transfer or easier integration, and manufacturers follow suit. Sometimes driven by the chipset support, and sometimes driven by the connectors and requirements common in host devices, it’s a consistent process – out with the old, in with the new. The emergence of Wi-Fi 6 and its hardware is no different.

To put a fine point on it: OEMs can no longer rely on a certain set of expectations for the availability of particular hardware interfaces, logical interfaces, and more. Wi-Fi 6 brings with it some new and unique characteristics in its available hardware, some of which will make previous options unavailable, add new support for previously niche features, and ultimately require designers to be aware of the new landscape to design in new Wi-Fi offerings.

We’ll be looking specifically at changes necessitated to embedded Wi-Fi radio design by the Wi-Fi 6 specification, not just in terms of what’s no longer available, but what’s new and exciting in terms of new options, features, and more. We’ll also be looking at how these are likely to roll out and change over time, as the 6E specification achieves global acceptance with all its associated 6 GHz frequencies.

Modernizing Interfaces – PCIE v4 and SDIO v3

For years, there have been essentially three interfaces commonly used for Wi-Fi communication between the host device and the Wi-Fi module: PCIe, SDIO, and USB. Each have continued to evolve as wired standards, in milestone versions that have increased the speed possible over the interface. For example, PCI Express (PCIe) has grown since its release in 2003, when it supported 250 MB/s per lane, up to the absolute bleeding edge PCIe v6 that is expected to support 128 GB/s in each direction across 16 lanes.

While USB has long been available for Wi-Fi, it’s no longer supported far and wide for Wi-Fi 6. This is largely down to what is being made available at the chipset level, and for some reasons that we can mostly only speculate on. However, in general for data interfaces within embedded systems, PCIe has largely taken a hold of applications that USB might have served in the past. In many ways, USB as an interface has become more tightly associated with USB as a hardware peripheral, and other internal interfaces like PCIe are growing in usage. For Wi-Fi 6 applications, this is definitely the case.

Rather, the two interface types that will be common to Wi-Fi 6 are PCIE v4 and SDIO v3. In particular, for Wi-Fi 6 on mobile, the PCIe v4 interface will be critical because of what it offers in terms of high speeds with power saving options. PCIe v4 comes with the high speeds found in PCIe v3, but with crucial power save modes that are new to PCIe v4. Taken in the grand scheme of what Wi-Fi 6 represents for efficiency, this fits perfectly into what is expected of mobile devices in the Wi-Fi 6 network.

Wi-Fi over SDIO is also being supported by many chipsets, which is more to the support of truly low-power, lightweight devices. SDIO offers fewer lines of communication, operates on lower power, and can be seen as a more minimal and straightforward interface for these kinds of applications.

Antenna Options

An exciting aspect of Wi-Fi 6 is the application of Bi-Directional MU-MIMO in small embedded devices. As previously discussed, MU-MIMO allows simultaneous streams, and allows the AP and the client to establish where they are relative to each other and optimize their link accordingly. Using MU-MIMO and beamforming, the AP and the client can enjoy power savings by targeting their RF in the physical direction of each other.

This means MIMO has become much more beneficial for embedded Wi-Fi devices in a wider variety of applications. Those which are power sensitive, cost sensitive, or size sensitive are able to take advantage of MU-MIMO without sacrificing on those considerations.

The available configurations will be 1x1 and 2x2 options, with 1x1 being the most common. A single antenna on the client will be sufficient to establish a 1x1 MU-MIMO connection with the AP, and already opens the door to some of the power optimization inherent in Wi-Fi 6. However, 2x2 MU-MIMO will also be open to embedded devices, the most advanced client configuration possible which supports all of the new features of Wi-Fi 6 with a reasonable compromise between power consumption and performance.

Industrial Temperature Range (Operational)

One of the trends within Wi-Fi 6 chip offerings is an increased support for wider operational temperature ranges, those that fall within what we call “Industrial Operating Temperature.” There are many definitions of operational temperature ranges for consumer applications and industrial applications, as well as defined ranges for specific industries like military or automotive applications. However, the industrial temperature range is typically defined as between -40° to +85° C.

Where these wider operating ranges were a specialty feature on previous generations of Wi-Fi chipsets, it’s becoming the standard for Wi-Fi 6. Many new Wi-Fi designs won’t need to support this great a range of temperatures on spec, so for those designs this is an unrequired bonus. However, for the many devices which need extended temperature support to perform, this is no longer a special feature with its own associated increase in cost.  

OS Support: Linux/Android/RTOS

To support Wi-Fi 6 in embedded systems, manufacturers are largely providing support for Linux, Android, and (increasingly) embedded RTOS as the software platforms for these devices. These make up the vast majority of embedded use cases, and not only are they supported, but they are supported for newer OS versions with an eye on the future.

For example, emerging is broad support for Linux Kernel versions 5.x. The Linux kernel announced major version 5.0 to be released in October of 2020, making it the latest major revision and a relatively new release. As Wi-Fi 6 chipsets become available they will support this latest Linux architecture, a bit of future-proofing to bring Wi-Fi in alignment with the latest Linux development. The same goes for support of Android versions (which is an extension of Linux support, as Android is fundamentally Linux as well).

What’s emerging as a somewhat new area of broad support for Wi-Fi is RTOS support. Real Time Operating Systems are lightweight, and as their name implies they work in real time performing scheduled tasks, prioritized for predictability within defined time constraints. In practice, RTOS are used to serve automated, hostless applications and tasks in lightweight embedded systems, and have gained a wide degree of acceptance in IoT systems on embedded microcontrollers, often with low power communications protocols like Bluetooth LE, LTE-M, and more.

As Wi-Fi enters an era where truly low power is possible and Wi-Fi enters more confidently into the realm of embedded IoT applications like this, Wi-Fi chipsets are beginning to enjoy wider support for RTOS in Wi-Fi development environments. For example, Infineon has announced plants to support RTOS inclusion in their popular ModusToolbox platform. This is likely to become a broad trend as Wi-Fi has become more and more appealing for these kinds of power-critical applications with the introduction of Wi-Fi 6. 

New FULL Support for Bluetooth 5.1

For many years, Wi-Fi / Bluetooth combination chipsets have mostly been in a partial support state for the full features of the latest Bluetooth specification. It was common for chipset manufacturers to offer 5.x support via addendum, where many but not all Bluetooth features would be supported.  A radio might be a 5.1 radio, but not quite offer the full suite of capabilities that OEMs were looking for.

By virtue of time and development and the cumulative effect of efforts to expand that support, the next generation of Wi-Fi 6 devices are slated to receive full Bluetooth 5.1 support and the full suite of Bluetooth 5.1 features.

Form Factors – M.2 and SiP

Just like some logical interfaces fall in and out of favor, so do physical form factors, and the latest generation of Wi-Fi devices will be experiencing change here as well. For example, right off the top: There are unlikely to be PCIe card form factors, at least generally. While individual niche offerings may make up some of these gaps, the PCIe form factor will largely be unavailable in this generation.

The M.2 and SiP form factors are poised to become the dominant offerings for Wi-Fi 6, for good reasons. M.2 has picked up steam over the last generation, specifically the M.2 2230 and 1218 form factors. The M.2 interface’s popularity and increasing presence is a factor, as growth leads to more growth in these hardware standards. But also, the M.2 form factor is also tightly interlinked with the use of the PCIe interface, making it a natural fit for this generation of Wi-Fi devices.

The SIP form factor is a classic: the solder-down System-in-Package is the complete Wi-Fi chip in a single compact unit. It’s traditionally been a trade-off for OEMs. On one hand, it requires more integration efforts than a PCB module, with the added manufacturing requirement of direct soldering to a board, and with its own integration efforts for a separate antenna. On the other hand, its significantly smaller footprint may be appealing in very compact designs, and doesn’t require a hardware connector (like an M.2 connector) to design in. Wi-Fi 6 SiP offerings are shaping up to have a larger footprint than previous Wi-Fi generations, but otherwise function very similarly to SiP offerings in the past.

One thing that is being phased out, it would appear, is the PCIe card form factor. Instead, M.2 will pick up the baton for PCB modules that support Wi-Fi over the PCI express interface. There are many reasons for this, but as previously mentioned, the slow but sure move towards making M.2 an industry standard has helped push out previous incumbents like the PCIe card. Additionally, growing development with M.2 has helped to tightly interlink the hardware with the logical PCIe interface, creating a well-known, consistent, standards-based offering. This will very likely become the dominant offering for this generation of Wi-Fi 6 devices.

IoT Class of Wi-Fi Devices

Important to note for manufacturers is always the balance between performance and cost. OEMs make their components selections very shrewdly based on considerations like this: a close look at what features and performance are requirements, and setting aside those which are not, often leads to identifying and integrating the most cost-effective wireless offering that ticks all the boxes for a new design.

With that in mind, it’s worth paying attention to a new class of IoT Wi-Fi 6 offerings that are stepping in to fulfill the requirements of ultra-lightweight applications. On some level, every wireless technology has been gradually ramping up and vying to become THE de-facto standard for the connected home, office, factory, and more. Upcoming extremely low power implementations of Wi-Fi 6 will make it much more appealing for use in IoT-type designs where low power, low cost, infrequent communications and a small footprint are highly desirable.

Conclusion – The End of the Road

Wi-Fi 6 is the biggest, most comprehensive overhaul of the Wi-Fi standard in over a decade, and it’s guaranteed to change the game for OEMs, users, and everyone in between. In this series, we’ve looked at the key features of Wi-Fi 6 from the perspective of faster link rates, lower latency, support for an incredible density of devices, incredible power savings, and more than double the spectrum available. And by now it should also be clear that OEMs will need to rethink many assumptions about what Wi-Fi can be, from a design perspective as well as what applications it can serve.

We’re nearer and nearer the end of the road when Wi-Fi 6 and 6E broadly deliver on the promise of the standard, with worldwide support for the new spectrum and channels that makes its full value possible. OEMs can watch this space for further updates as the rollout continues, as well as our wireless offerings that dramatically accelerate YOUR personal road to Wi-Fi 6. Our wireless modules, IoT solutions, and antennas leverage our decades of experience in Wi-Fi into your design, giving you confidence in your route to market.

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