By Eve Danel

November 30, 2020

LitePoint’s Eve Danel has developed this three-part blog series on Wi-Fi 6E and testing challenges. Throughout this series of blog posts, you’ll learn the basics of operating rules for Wi-Fi 6E in the 6 GHz band, the challenges when validating Wi-Fi 6E designs and what testing solutions LitePoint has available for Wi-Fi 6E.

Building and Testing the Next Generation High Performance Wi-Fi 6E Devices

In my previous blog post, I explored the IEEE 802.11ax rules of operation in the 6 GHz band and how they differ from operation in the 2.4 GHz and 5 GHz bands. In my final post as part of this Wi-Fi 6E series, I want to explore the challenges device makers must consider when building the next generation of Wi-Fi 6E devices and some of the testing solutions that LitePoint offers.

With the FCC’s Report on Order establishing rules for unlicensed devices in Wi-Fi 6E and the IEEE 802.11ax rules of operation, Wi-Fi 6E device makers have a lot to consider. As exciting as this new Wi-Fi spectrum availability is, it is critical that new Wi-Fi 6E devices meet the stringent requirements for performance and interoperability.

Challenges to Building the Next Generation, High Performance Wi-Fi

Building on the analogy of Wi-Fi 6E as a new, large freeway that only allows the fastest cars, how can device makers build the next generation of high-performance Wi-Fi devices that can take advantage of this highway of brand new spectrum? It’s exactly like building a high-performance sports car. There are many challenges to overcome, the below are a few that are particularly demanding.

• 1200 MHz of additional spectrum added to Wi-Fi devices. It is double the frequency range coverage needed in the past for 2.4 GHz and 5 GHz bands. This can be particularly challenging for Wi-Fi 6E design, especially for the RF front end, because there is a need to deliver consistent performance across the entire spectrum from the low channels to high channels. You also need excellent linearity of the power amplifiers. Peak performance typically starts to roll off when you reach the higher frequency, or the edge of the band and devices will need to be tested to the very highest channels to make sure that they can operate at the expected power levels. Calibration of the transmitter power is very important and will be needed for consistent performance.

• 160 MHz channels were already defined in the previous Wi-Fi 5 (802.11ac) generation, but they were not mandatory and were not often supported or deployed. With Wi-Fi 6E however, deployments will make full use of these wider channels because there is now sufficient contiguous spectrum. With wider bandwidth, you can have more distortions of the OFDM subcarriers as they cover a wider frequency range. The important metric to focus on for these wider channels is the spectral flatness to ensure even distribution of power. Also, wider channels mean lower SNR per carrier, therefore it requires excellent transmitter modulation performance.

• OFDMA, the multi-user version of OFDM, is part of Wi-Fi 6 in the 2.4 GHZ and 5 GHz band, but in Wi-Fi 6E it will be even more prevalent because there will be no legacy devices operating in the 6 GHz band. This means all the devices in the 6 GHz band will be able to take advantage of OFDMA. For each transmission in highly congested areas, there will be multiple devices able to share the bandwidth to improve capacity and reduce latency. OFDMA is a very powerful feature, but it’s also one of the most challenging aspects of the IEEE 802.11ax standard because it requires all devices participating in the transmission to be synchronized. One bad actor can ruin the transmission for the others. All of the client stations participating in the transmission must be synchronizing time, they must have their frequency aligned and they must transmit power that is accurate.

• 1024 QAM modulation was introduced in the IEEE 802.11ax standard and carries 10 bits per subcarrier. This improves peak data rates by 25 percent over previous versions, which is how the highest data speed is achieved. Because the high modulation rates can only be used in very good RF conditions, the 6 GHz spectrum will provide a better and cleaner environment with less interference from other devices since it has enough spectrum to avoid adjacent channels or overlapping channel interference. 1024 QAM also requires the highest level of modulation accuracy. This accuracy is usually measured by EVM (error vector magnitude) that measures the deviation of the constellation points compared to their ideal location.

• Devices operating in the 6 GHz band must coexist with incumbent devices. Therefore, Wi-Fi 6E access points and clients must comply to regulatory defined emissions limits in order to avoid interference with other devices within the band or in adjacent bands. Spectral masks define the limits of the distribution of power across the channel and into the adjacent channels. It’s important to check that the spectral mask can be met for all the channels and especially to identify the worst case scenarios at the channels that output the highest power.

LitePoint Wi-Fi 6E Test Solutions

When developing Wi-Fi 6E devices, compliance verification and performance validation will be imperative to ensure these devices can really take advantage of this new spectrum. LitePoint has innovative, high performance testing solutions that can help device makers validate and accelerate Wi-Fi 6E device development.

IQxel-MW 7G™

LitePoint’s IQxel-MW 7G™ is the first fully integrated tester for Wi-Fi 6 and Wi-Fi 6E. This test solution supports a continuous frequency range from 400 MHz to 7.3 GHz and features native support for per-port 160 MHz and 80+80 MHz signal combination. The IQxel-MW 7G has the best in class, residual EVM performancethat’s needed for 1024 QAM testing and supports packet detection and timing requirements needed for Wi-Fi 6E advanced testing of features like multi-user OFDMA.

IQxel-MW 7G supports legacy Wi-Fi standards, thereby ensuring coverage for Wi-Fi 802.11 a/b/g/n/ac and 802.11ax testing in the 2.4 GHz, 5 GHz and 6 GHz bands. In addition to Wi-Fi, the test system delivers high performance verification for the most popular wireless connectivity standards including WLAN legacy, all Bluetooth device standards (1.x, 2.x, 3.0, 4.x, 5.x), including cellular TDD and FDD non-signaling test modes for 2G/3G/4G and 5G cellular technologies.

The test platform is well suited for use in design verification and manufacturing testing.

IQfact+™ Software

IQfact+™ software is a test automation solution that combines device under test (DUT) and tester control. This software provides turnkey testing and calibration for leading Wi-Fi chipsets, enabling thorough design verification and rapid volume manufacturing with minimal customer engineering effort.

Each IQfact+ software is tailored to provide the best test efficiency for a specific chipset and is designed specifically for the LitePoint tester architecture, resulting in drastically reduced test time and engineering effort. IQfact+ encompasses a growing library of over 350 chipsets and supports all key wireless connectivity technologies.

With IQfact+ turnkey solutions developed for Wi-Fi 6 and 6E chipsets, the IQxel-MW 7G tester provides an out-of-the-box calibration and verification solution that can help device makers accelerate time to market.

Success with LitePoint

LitePoint has helped manufacturers deliver over 10 billion Wi-Fi-enabled products to market. Please visit our Wi-Fi 6E page to learn more about LitePoint’s Wi-Fi 6E solutions, and I invite you to view the full replay of my webinar on this topic. Look for more blog posts on Wi-Fi 6E, UWB and other topics from myself and the LitePoint team in the weeks to come.

By Eve Danel

November 11, 2020

LitePoint’s Eve Danel has developed this three-part blog series on Wi-Fi 6E and testing challenges. Throughout this series of blog posts, you’ll learn the basics of operating rules for Wi-Fi 6E in the 6 GHz band, the challenges when validating Wi-Fi 6E designs and what testing solutions LitePoint has available for Wi-Fi 6E.

Wi-Fi 6E Standard and Channels – 802.11ax Operation in the 6 GHz Band

In my previous blog post, I explored the FCC’s decision to open the 6 GHz band for Wi-Fi 6E standard operation, as well as the rules the FCC put in place to protect incumbent users in that space. Today I want to explore the IEEE 802.11ax rules of operation in the 6 GHz band and how they differ from operation in the 2.4 GHz and 5 GHz bands.

Background on Wi-Fi Standards

Two main groups are responsible for shaping Wi-Fi’s evolution. The IEEE 802.11defines the technical specifications of the wireless LAN standard. The IEEE 802.11ax standard for high efficiency (or HE) covers MAC and PHY layer operation in the 2.4 GHz, 5 GHz and 6 GHz bands. It is scheduled to be finalized by the end of 2020.

The Wi-Fi Alliance focuses on certification of Wi-Fi devices for compliance and interoperability, as well as the marketing of Wi-Fi technology. To improve consumer understanding of the various IEEE 802.11 standard generations, the Wi-Fi Alliance decided to create consumer friendly names. The IEEE 802.11ax standard is now referred to as Wi-Fi 6 or the 6th generation of Wi-Fi and operates the 2.4 GHz and 5 GHz bands.  Wi-Fi 6E operates in the 6 GHz frequency band. Thousands of devices have received Wi-Fi 6 certification since the program started and the Wi-Fi 6E certification is planned to start sometime in early 2021.

IEEE Rules of Operation

Decisions made by the IEEE 802.11ax group and added to the standard will make Wi-Fi 6E even more efficient.

Arguably one of the most important decisions made by the IEEE 802.11ax group is that it disallows older generation Wi-Fi devices in the 6 GHz band, which is important because it means that only high efficiency 802.11ax devices will be able to operate in this band.

Historically, newer Wi-Fi standards have always provided backward compatibility with older generations. This proved to be a great strength to win over consumers, since network equipment doesn’t need to be completely overhauled at each new generation. This has also been a source of congestion, since older slower legacy equipment is sharing available resources (i.e. spectrum) with newer devices.  In the 6 GHz however, only new high efficiency devices will be allowed to operate.

When using the analogy of a freeway to describe Wi-Fi, the 2.4 GHz and 5 GHz band can be compared to congested freeways allowing both fast and slow vehicles, while the 6 GHz band is the equivalent of a new, large freeway that only allows the fastest cars.

With 1200 MHz of spectrum and 59 new 20 MHz channels, a station with a dwell time of 100 ms per channel would require almost 6 seconds to complete a passive scan of the entire band.  The standard implements a new efficient process for clients to discover nearby access points (APs). In Wi-Fi 6E, a process called fast passive scanning is being used to focus on a reduced set of channels called preferred scanning channels (PSC). PSCs are a set of 15 20-MHz channels that are spaced every 80 MHz. The APs will set their primary channel to coincide with the PSC so that it can be easily discovered by a client, and clients will use passive scanning in order to just scan PSCs to look for an AP.

To further improve the efficiency of the 6 GHz operation, the standard is also segregating most of the management traffic to other bands. So, a multi-band AP that has 2.4 GHz and 5 GHz will be discoverable by scanning the lower bands. The client will first go into the lower bands, discover the AP there and then move to the 6 GHz band. This way, no probe request frames will need to be sent in the 6 GHz band. This will reduce the probe requests that are sent by stations just trying to find APs because it will not be allowed unless it is a PSC channel.

Wi-Fi 6E Channelization

The 802.11ax standard also defines channel allocations for the 6 GHz band. This allocation determines the center frequencies for 20 MHz, 40 MHz, 80 MHz and 160 MHz channels.

Channels begin at the start frequency of 5950 MHz, leaving just 25 MHz of guard band between the first 6 GHz channels and the upper range of the U-NII 4 band.

If a U-NII band is not allowed in a specific regulatory domain or operates under different rules, then the regulatory specs take precedence over IEEE and channels that are falling on frequencies or overlapping on frequencies that are not supported, are not allowed.

The FCC is providing this pristine new highway of spectrum and the Wi-Fi 6E standard’s rules of operation are ensuring that we can remove the slowest vehicles on the highway. The question now is how do you build the next generation, high performance device that can really take advantage of this new spectrum? There are many challenges to overcome.

In the next post, we’ll explore what testing solutions LitePoint has available for Wi-Fi 6E. In the meantime, please visit the replay of my webinar on this topic.