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Putting Advanced Wi-Fi 7 Features to the Test

December 6, 2023

The latest generation of Wi-Fi, Wi-Fi 7, introduces a range of new capabilities for more sophisticated, higher-throughput/lower-latency wireless communications. Industry leaders anticipate that these features will enable a new generation of applications, from fully automated factories, to mass-scale Internet of Things (IoT) deployments, to immersive augmented reality (AR) gaming, and more. As with all technology advances, however, new Wi-Fi capabilities bring new technical complexity—and new challenges for those tasked with designing and debugging Wi-Fi devices.

Those seeking to exploit Wi-Fi 7 features such as multi-link operation (MLO), enhanced quality of service (QoS), and 4096 quadrature amplitude modulation (4K QAM) will find that legacy testbeds cannot provide the capabilities or visibility that such features require. Indeed, if testers can’t measure coordinated operations across radios, for example, or analyze next-generation modulation schemes, they can’t characterize how new features perform—much less debug devices when something goes wrong.

In our recent paper, Navigating Wi-Fi 7: A Deep Dive into Next-Gen Advancements, we provide an in-depth analysis of the revolutionary changes that Wi-Fi 7 introduces. We discuss the impact that these new features have on testing and the strategies Spirent is advancing to address them. This blog offers a brief overview of some of these innovations.

Measuring multi-link operation

Previous Wi-Fi generations enabled devices to use multiple radios simultaneously, either in the same or across multiple bands. Until now, though, each radio operated independently. Among its most powerful new capabilities, Wi-Fi 7 introduces coordinated multi-link operation (MLO) to improve throughput, increase reliability, or both.

Wi-Fi 7 adds a new Unified Upper MAC (UMAC) layer to coordinate multi-link operations in a multi-link device (MLD) architecture (Figure 1). The UMAC provides the higher-layer protocols with a single MAC address for data transfers in a way that is very familiar to current Wi-Fi radio users. Underneath this, the UMAC contains logic to distribute the data block across the individual radio links, as appropriate, and manage the flow of data at this lower link level. This lower-layer operation is invisible to the higher-layer protocols so that they do not need to care how many radios are being used, or in what way.

Figure 1. MLD architecture

With this additional layer of intelligence, the UMAC can distribute loads across multiple links to improve throughput and latency or transmit redundant packets to improve reliability (Figure 2).

Figure 2. Overview of MLO in action

 

These MLO features can enable significant performance improvements for Wi-Fi users across a variety of scenarios. Validating them, however, requires new testing capabilities. To measure higher-throughput/lower-latency operations, for example, testbeds need additional computing resources to generate and consume traffic at higher rates. Testbeds must also provide visibility into the coordinated radio operations themselves. Effectively, all analysis and debugging capabilities previously performed on a per-radio basis must now extend to multiple radios operating simultaneously in concert.

Spirent’s new multi-link sniffer technology can analyze multiple bands simultaneously and provide consolidated operational data for use in Wireshark or other debugging tools.

Facilitating 4k QAM

As Wi-Fi has evolved over the years, modulation coding schemes (MCS) have evolved alongside it. Each new generation has supported more bits per symbol, increasing throughput by allowing devices to communicate more information per transmission.

However, denser QAM constellations also make devices more sensitive to channel noise—requiring ever-better signal-to-noise ratio (SNR). This issue has presented challenges through previous Wi-Fi evolutions, such as moving to 256 QAM (Wi-Fi 5) or 1024 QAM (Wi-Fi 6). As Figure 3 illustrates, however, the leap to 4096 QAM creates a constellation denser than anything Wi-Fi devices—and testbeds—have contended with before.

Figure 3. Increasing constellation density across Wi-Fi generations

At this density, channel noise that was acceptable in previous Wi-Fi generations can make it impossible to distinguish the position of individual points, introducing modulation errors. To capitalize on 4K QAM the new Wi-Fi 7 devices must be able to support these higher resolutions with finer decision boundaries, and testbeds must be redesigned to minimize as much path loss as possible.

Characterizing QoS enhancements

Latency also continues to improve with each new Wi-Fi generation, especially with the introduction of orthogonal frequency-division multiple access (OFDMA) in Wi-Fi 6, and deterministic latency in Wi-Fi 7. But to support more groundbreaking latency-sensitive applications QoS testing and reporting must also evolve. As part of the Device Metrics Test Plan for Wi-Fi 7, the Wi-Fi Alliance highlighted the need for latency testing that provides not just average one-way delay (OWD), but a detailed statistical spread.

This level of insight is essential for characterizing performance in scenarios where multiple users are contending for the same channel resources, causing latency to fluctuate. For example, consider an AR gaming application where latency exceeding 30 milliseconds will be noticeable (and disruptive) to users. Legacy testing might show that, with OFDMA enabled, a device maintains 30ms average OWD. But knowing that average isn’t particularly helpful if the latency periodically spikes to 100ms, ruining user sessions.

To guarantee consistently good experiences, device makers must know the full range of latency users can experience, how various mechanisms affect delay, and how often OWD exceeds maximum thresholds. Spirent’s OCTOBOX testbeds report not just the average latency but the full statistical distribution. For example, Figure 4 illustrates the change is OWD distribution gained by using OFDMA. This allows testers to fully characterize performance and determine a statistical measure of the probability of achieving any target delay—critical information for guaranteeing QoS in emerging applications.

Figure 4. Characterizing device performance with and without OFDMA

 

The Spirent advantage

As a global leader in wireless testing solutions, Spirent has a long history of continually expanding the in-depth statistics and performance indicators our OCTOBOX testbeds provide to help organizations capitalize on new technologies. In fact, Spirent is typically the first in the industry in enabling in-depth testing and validation for new Wi-Fi advances. Why are we so often ahead of the curve? Because we’re intimately involved in the groups developing and standardizing wireless innovations.

Spirent is extremely active working across the industry to understand the implications of new wireless standards for our customers and what’s needed to test and characterize their performance. That includes working directly with leading wireless equipment and device manufacturers but also participating in industry groups like the Wi-Fi Alliance and IEEE. Spirent engineers currently serve on multiple Wi-Fi Alliance task groups, including leading the group that developed the Wi-Fi 7 Device Metrics Test Plan.

As a result, we don’t have to wait until new standards are finalized to know what will be needed to test them. So, when groundbreaking Wi-Fi advances emerge, we can help our customers start using and benefiting from them right away.

For more details on cutting-edge Wi-Fi 7 features and the latest approaches to characterize their performance, download the new whitepaper Navigating Wi-Fi 7: A Deep Dive into Next-Gen Advancements.