Wi-Fi 7 adoption is forecast to expand rapidly, with raw speed taking a back seat to network reliability and low latency. At the same time, the latest generation of Wi-Fi requires a more sophisticated radio architecture to enable applications such as online gaming, video conferencing and over-the-top (OTT) media that streams internet content without cable or satellite connections.

Consumers may take the enhanced performance of Wi-Fi 7 for granted, but behind the scenes we know that these advances come at the expense of additional radio complexity. Put simply, the more features we add to the physical layer, the more intricate the RF design becomes to consistently deliver the expected performance across diverse deployment scenarios.

A good example is preamble puncturing, a technique that improves spectral efficiency by allowing the system to transmit data on clean portions of a wide channel while avoiding interfered subcarriers or Resource Units (RUs). It’s important to note that preamble puncturing involves specific puncturing patterns, and these different patterns can lead to different spectral mask requirements that the transmitter must meet. This adds a layer of complexity to testing.

Separately, multi-link operation (MLO) allows devices to transmit and receive across multiple frequency bands simultaneously, for instance, using both 2.4 GHz and 6 GHz to achieve higher throughput or redundancy. The interplay of these features, particularly the various band combinations of MLO and the pattern-dependent spectral characteristics of preamble puncturing, necessitates rigorous analysis and validation of how RF performance impacts overall system performance.

The following use cases illustrate the need for an optimized test and measurement regimen for quick and cost-effective Wi-Fi 7 deployment.

Use Case I: Wi-Fi Device Performance Relies on RF Parametric Performance

For the end customer, there are three things that matter most: range, speed and reliability. These features hinge on the RF parametric, which is the backbone of superior Wi-Fi performance and includes Error Vector Magnitude (EVM) and the Modulation and Coding Scheme (MCS) index.

Even a minor change in the RF parametric can significantly affect performance. Imagine that a Wi-Fi device is operating at the maximum MCS index of 13, which translates to a modulation scheme of 4096 QAM at 320MHz. Let’s say we have two spatial streams that theoretically will yield throughput of approximately 5Gb/s – 6Gb/s. Poor EVM performance could force the device to move to the next-lower MCS scheme, which is MCS 11 (1024 QAM). The penalty of carrying fewer bits per symbol could result in a 20 percent drop in throughput, which would compromise real-world device performance.

Another RF parametric, uplink OFDMA, enables multiple devices to simultaneously transmit traffic to the access point, which reduces latency by enhancing spectrum usage and network performance. That requires tight pre-coordination and pre-correction of three essential physical layer features – power, timing and frequency – between the access point and end devices that include smartphones, tablets and laptops.

When several devices, or stations, connect to an access point, each at a separate distance, the station closest to the access point must balance its power or risk weakening the signals coming from the other stations. From a timing perspective, once a trigger frame is received by the station or client devices, they initiate an uplink OFDMA transmission. These transmissions must be sent within 400 nanoseconds of each other to ensure seamless operation. The third feature, frequency, requires each station to pre-compensate or correct for the carrier frequency-offset of the signal that they receive from the access point. If any residual CFO error after compensation is greater than 350 Hz, it will likely result in inter-carrier interference degrading the quality and success of UL-OFDMA transmission.

Poor performance among any of these physical layer parametrics could lead to a network collision and reduced efficiency. And aside from uplink OFDMA, Wi-Fi does not have a specific scheduling algorithm, which makes it crucial for high-density and multi-user environments to work in harmony.

Use Case II: Device Rate Vs. Range

Rate adaptation, or adaptive modulation, is a device behavior that changes according to signal strength and the range between the station and the access point. A device close to an access point transmits at the highest MCS rate of 13. If conditions change due to noise, or if the device moves away from the access point, then it will try to retransmit or step down to the lower MCS modulation scheme and attempt multiple packet retransmissions. Without rate adaptation, the resulting signal congestion can degrade system throughput, performance and reliability and needlessly drain the device battery.

There are many physical layer parametrics that can cause such behavior, including poor EVM and signal-to-noise ratio (SNR) performance. This requires evaluation and measurement at the physical layer to determine EVM performance for each transmission, transmission power, the correct MCS scheme and the distance and transmission timing intervals between the access point and the stations.

Analyzing Bluetooth Coexistence with LitePoint IQsniffer

It’s important to measure and analyze coexistence performance given that Wi-Fi and Bluetooth® share the 2.4GHz spectrum. Any interference caused by transmit-power leakage, co-channel or adjacent channel noise, or unpredictable frequency hopping patterns can result in packet collisions and data loss.

This speaks to the need for a visual tool that identifies power transmission levels, EVM and what type of Bluetooth packet is in use, whether it’s classic Bluetooth, Bluetooth Low Energy or a proprietary Bluetooth protocol that’s impacting Wi-Fi device performance.

The solution is a radio traffic sniffer that can capture and analyze the physical layer and the MAC layer. The sniffer captures the real-world signal exchanges between devices and physical layer parametrics like power, EVM, frequency error and the MCS index to distinguish with nanosecond-level accuracy which device is transmitting the right information. This is especially useful for analyzing and validating uplink OFDMA to determine if the frame gap and timing are correct.

Until they reach economies of scale, every new generation of technology starts out with higher costs. This is especially true for consumer wireless device manufacturers and chipset suppliers that have already made heavy capital expenditures in Wi-Fi deployments. Tools like the LitePoint IQsniffer provide an accessible, scalable and cost-effective means for analyzing both Wi-Fi and Bluetooth packets and capturing the communication between devices to better managing Wi-Fi performance, cost and complexity.

My presentation, “Translating RF Performance to Real-World Results in Wi-Fi 7” is available on-demand, as part of a Wi-Fi Forum hosted by RCR Wireless News.

Wireless connectivity defines the user experience for much of the technology we rely on every day, whether we’re logging into work from a home office, sharing content from our favorite streaming platform or swiping our phones at the grocery checkout line. The healthcare industry is no different and each year spends billions on wireless medical devices that perform essential clinical functions such as patient monitoring, infusion and diagnosis.

The medical field is conservative by nature. Nevertheless, it has excelled at designing wireless solutions to meet a range of use cases, from neonatal vital signs monitoring to a growing geriatric population in need of wearable and implantable devices. The outcomes are remarkable in their ability to improve the quality of patient care. However, embedding Bluetooth® or Wi-Fi components to accurately track glucose levels or securely transmit real-time patient health data to a nursing station is a complex task that requires core wireless engineering expertise that device makers may not possess.

This lack of know-how can create a blind spot in which med-tech companies may inadvertently neglect to adequately test their wireless devices as they graduate from a concept in the lab to the volume production line. The oversight can lead to device under-performance in which patients may experience poor connections and delays in clinical notifications. In the worst cases, devices may fail, which for manufacturers can trigger product recalls, compliance violations and an erosion of customer trust.

With adoption rates rising, the wireless technology landscape is increasingly complicated to manage as it moves from discrete and comparatively simplistic electronic components to highly integrated modules housing multiple wireless protocols such as 5G cellular, Wi-Fi and Bluetooth® Low Energy.

Khushboo Kalyani is a LitePoint Product Manager responsible for wireless connectivity and cellular test systems. She addressed a series of questions that medical device manufacturers should be asking as they prepare test beds for their wireless products.

Which wireless technology is best suited to my product?

Khushboo: The choice depends on how much data needs to be transferred, how swiftly and over what distance. Medical devices carrying large data volumes that require reliable, always-on connections may be better suited to Wi-Fi. These include insulin pumps and devices for monitoring blood pressure and heart rate. Others, like blood glucose monitors and pulse oximeters, transmit small amounts of data just a few times a day and may be better candidates for Bluetooth.

Cost is another important consideration, with Bluetooth modules generally adding less to bill of materials budgets than Wi-Fi or cellular modules. Designers should also familiarize themselves with compliance and regulatory requirements that may influence their connectivity decisions.

What are the different stages of wireless test and how do they differ?

Khushboo: During R&D and design verification testing, the focus typically is on validating fundamental RF parameters. These include power output, receive sensitivity and Error Vector Magnitude across different frequency bands of operation.

During quality and assurance testing, the focus shifts to the user experience. This includes validating performance across real-world use cases and conducting co-existence and over-the-air (OTA) interference testing to determine if the product will perform well in the field. It’s important to test full parametric performance and not just rely on go/no go tests that only indicate if the device is functional.

Production testing requires an optimum balance of quality and cost economics. That means checking the device’s bare minimum functional performance and then testing multiple devices simultaneously to reduce the cost of test and expedite time to market.

There are two common denominators that cut across these different test stages. The first is hardware test equipment that is capable of scaling from lab to manufacturing. The second is a user-friendly yet advanced automated software tool that reduces RF testing overhead to minimize test-suite development and design and execution times.

What is the best way to comprehensively test wireless performance?

Khushboo: As you progress through the product development cycle, what you test and the way you test will vary. When designing a product from scratch, for example, it’s important to measure the performance of the RF transceiver in isolation to ensure it meets design specifications. Once the device is validated, it must be tested in its entirety. Real-world scenario testing entails attaching the device antenna and casing to ensure the final hardware and software are not impacting wireless performance.

Can testing help ensure patient data accuracy?

Khushboo: Hospitals and home environments can be crowded RF spaces, with multiple devices operating at similar frequencies. Interference can lead to dropped signals, corrupt data or incomplete transmissions. Even a small percentage of lost or distorted data can undermine the reliability of clinical decisions.

Interference testing that measures device sensitivity, Packet Error Rate (PER) and Bit Error Rate (BER) can indicate how often transmissions are corrupted under different conditions. Some throughput tests can also identify design flaws by measuring data transfer rates between devices on a wireless network.

Should I use an off-the-shelf RF module or design-in a chipset technology?

Khushboo: When you buy off the shelf, you typically don’t have access to the wireless chipset and controls for testing. That means you need to use the command provided by the module vendor, write your own software or rely on a test vendor like LitePoint, which has a test methodology set-up to quickly validate performance.

The choice is contingent on two factors:

• Time to market: Off-the-shelf modules can be expensive but often reduce development time, as they come pre-certified and pre-calibrated. Generally, that eliminates time spent working with regulatory labs for compliance testing. On the other hand, commissioning a chipset design means working extensively with the chipset supplier to ensure seamless integration into your product. This can be a complicated, time-consuming process that adds overhead to the design process.

• Form factor: Chipset-based designs offer better control over the end-device form factor by accommodating smaller, compact designs compared to off-the-shelf modules.

Whether you design your chipset or buy an off-the-shelf module, LitePoint provides automation software through the IQfact+ tool that supports the gamut of chipset-specific test packages and can be used out of the box.

Are there additional test considerations when I move into high-volume device production?

Khushboo: Many medical devices sell in the hundreds of thousands or even millions of units, so the ability to scale testing is an important step for accurately determining device yield. Just as importantly, designers want to make sure they aren’t incorrectly failing good units and/or passing bad units. An inaccurate test is as harmful as no test at all.

How can device makers better manage test costs?

Khushboo: If manufacturing volumes are high and test costs are rising, you should consider a cost-of-test analysis, which includes single-test and multi-test options. This can help manufacturers reduce costs and expedite time to market by determining how much time it takes to test one device as a percentage of overall capital equipment costs compared to how long it takes to test multiple devices in parallel.

What would you like medical device manufacturers to remember on their development journey?

Khushboo: It’s clear that the healthcare community is committed to discovering and delivering wireless device technology to improve patient outcomes. LitePoint has helped hundreds of customers successfully launch wireless products over more than 25 years by adapting a combination of hardware and software test automation tools to a range of applications. If there is one word of advice I can share, it’s that accurate, repeatable, scalable testing is a key step in achieving that highest level of care.