everything RF recently interviewed James Kimery who is the Vice President of Product Management at Spirent Communications. James Kimery leads the product management organization in Spirent Communications' Lifecycle Service Assurance BU encompassing the lab product portfolio, which includes RAN core, network, and channel emulation; Wi-Fi; and mobile-based location testing.
Q. What is Wi-Fi 7 and what are its new features and advantages? What frequency bands does it use?
James Kimery: The best answer to this probably comes from the “industry” itself, in terms of its definition for the marketing requirements for Wi-Fi 7 certification. Since the question is about Wi-Fi 7, looking at the Wi-Fi Alliance (as opposed to the IEEE spec) is the best place to go. So, what is Wi-Fi 7? . The benefits of the Wi-Fi 7 program can be classified into the following categories:
- Higher aggregate throughput (network and link level)
- Improved support for low latency
- Higher efficiency in dense networks
- Increased robustness and reliability
- Reduced power consumption
And it operates in the 6 GHz bands.
Q. What are the key features of Wi-Fi 7?
James Kimery: Here's the list of few technical features:
- Multi-link operation, so the introduction of the whole multi-link device (MLD) framework. There are various modes of operation, but this is the big item. Simultaneous operation in multiple bands.
- A more flexible way of using OFDMA, introduced in WI-Fi 6, with support for multiple resource units per user
- Higher order modulation formats supporting 4K QAM
- Wider channel bandwidth: 320 MHz (twice the current maximum)
- Even better power control that the targeted wake time introduced in Wi-Fi 6, known as restricted Target Wake Time Primarily designed for enhanced QoS management
- Emergency Preparedness Communications Services (EPCS) priority access.
Q. Can you tell us about the new MLO (Multi-Link Operation) feature in Wi-Fi 7?
James Kimery: MLO is, at its core, just a way of saying that the AP and STA will use all available bands simultaneously. So, 2.4 GHz, 5 GHz, and 6 GHz, all at the same time. That’s possible in pre-Wi-Fi 7 operation, but each of these links is a separate link. There are separate protocol stacks all the way up. As long as the radios can operate independently this can be done, but it’s all separate. MLO, on the other hand, says that you literally combine the bands. (Think channel-aggregation in the cellular world.) The MAC is split into a lower MAC (talking to a given band) and an upper MAC which combines all of this together. Above the upper MAC it all looks like one connection. There are 3 expected advantages from MLO:
Example of MLO Operation Between Two Links
1. Higher throughput: 802.11be has a 30 Gbps upper limit.
2. Faster steering/load balancing: These features exist in pre-Wi-Fi 7 (band steering, for example) but you have to go through the whole management process as you move from one band to another. In MLO it’s a straight switch from one band to the other. Connection context is shared, so there is no need for associating, authenticating, etc. In this case, fast transitions should be able to be seen.
3. Lower latency: More access to more bands is supposed to lead to lower latency over SLO (single link operation.)
Q. Can you tell us about the testing processes that Spirent is using for Wi-Fi Testing?
James Kimery: As with all revisions to the standard, Spirent acts at the leading edge of the development, supporting the chipset and equipment vendors through the development process with active participation in the Wi-Fi Alliance plugfests. This is true for Wi-Fi 7 as well. Therefore, Spirent has early access to pre-production Wi-Fi chipsets and devices through our close relationships with those vendors.
This allows us to participate in the early stages of conformance testing (through our work at the Wi-Fi Alliance), as well as to begin performance testing with these early devices. Some of that testing is informed by the vendors themselves who highlight areas in which they believe that Wi-Fi 7 should outperform previous standard generations.
Q. What are some challenges that you have faced when testing Wi-Fi 7 devices?
James Kimery: Here is the list to some of the challenges with Wi-Fi 7:
1. Multi-link operation: Prior to Wi-Fi 6, most Wi-Fi developments focused on throughput between two endpoints. The main challenge for Wi-Fi 6 testing, then, was moving from a point-to-point testing model to a point-to-multi point model (since the major innovations of Wi-Fi 6, OFDMA and Mu-MIMO, have meaning only in the context of multiple, simultaneous, users.) With Wi-Fi 7, this complexity has been extended to the concept of multiple bands. Testbeds must now be able to operate simultaneously across multiple bands, and for TESTING, it’s important to have visibility into those operations.
Wi-Fi 6 vs Wi-Fi 7 Feature ComparisonJust like in Wi-Fi 6 this adds new requirements to testbeds which, until now, have been able to focus their data-gathering on single connections in a single band. Sniffing, for example, which is a very important tool in Wi-Fi testing, will become much more challenging in an MLO environment. Imagine sniffing traffic from multiple devices, simultaneously, while some of those devices are operating on multiple bands.
2. Bandwidth: Until now, the maximum data rate across on RF link was only 10 Gbps, which meant that testbeds with 10 Gbps switches were not in danger of creating bottlenecks in the testbed. This changes with Wi-Fi 7, since the 30 Gbps physical layer rate will translate into throughput's in excess of 10 Gbps. To fully explore those data rates, testbeds need to be enhanced to remove any switching bottlenecks that may exist.
3. Signal to Noise Ratio: 4K QAM requires >40 dB SNR which means that path loss in a test bed must be carefully controlled.
Q. Can you tell us some use cases for Wi-Fi 7 where existing Wi-Fi standards do not suffice?
James Kimery: Here it is useful to look at the MRD which reflects this industry position on this topic:
1. The principal target markets for the program are environments that demand high performance in terms of peak throughput, high network and link efficiency, increased reliability, and low latency in both commercial and consumer market segments …, namely, airports / train stations, stadiums, malls, e-education, hospitals, public transportation, citywide Wi-Fi, apartment buildings, home, and office environments.
2. Concrete examples include support for AR/VR/XR, and low latency applications in, for example, a medical setting. The use cases are similar to those envisioned in a 5G use case discussion – enhanced broadband (although without the focus on mobility that cellular technologies have) and ultra-low latency connections.
Q. When do you expect Wi-Fi 7 to be available to customers?
James Kimery: This depends on your definition. The IEEE specification will not be complete until sometime in 2024. The Wi-Fi Alliance certification will be available before that, probably by the end of 2023. The earliest that “Wi-Fi 7 products” can be available is AFTER that Wi-Fi Alliance certification program is launched. However, as always, companies will release “pre-standard” Wi-Fi 7 products. TP Link has already launched a product based on Wi-Fi 7. Again, it’s not real “Wi-Fi 7”, since that certification doesn’t exist. We should expect wider availability of interoperable products that can be certified by the Wi-Fi Alliance near the end of 2023 or early in 2024.
There is a possibility that the cert date could slip because the workload at each plugfest is enormous and may not be achievable. There is always a debate over keeping the date and dropping features, or keeping the features and slipping the date. Those discussions are already underway.
Spirent Communications is a global leader with deep expertise and decades of experience in testing, assurance, analytics, and security, serving developers, service providers, and enterprise networks. For more information click here to view the Spirent Communications profile on everything RF.
