TEST & MEASUREMENT
The current WLAN standard, 802.11ax, is an evolutionary improvement to 802.11ac. It adds a significantly higher efficiency, capacity, and coverage for a better user experience, especially for dense deployment scenarios in indoor and outdoor environments such as stadiums, airports, and shopping centres. Unlike 802.11ac, 802.11ax operates in 2.4, 5, and 6 GHz bands. It employs technology building blocks like orthogonal frequency division multiple access (OFDMA) for high efficiency, 8x8 multi-user, multiple-input, and multiple- output (MU-MIMO) for high capacity, and uplink scheduling for increased capacity, efficiency, and better user experience. Other technologies, such as 1024 QAM modulation, improve throughput.
What Is New to 802.11be While in the early development stage, 802.11be holds great promises. Many new features will significantly increase throughput and provide support for real- time applications. These features include 320 MHz transmission bandwidth, use of 4096 QAM modulation, and enhancements to MIMO with more spatial streams. Like 802.11ax, 802.11be will also operate in 2.4, 5, and 6 GHz frequency bands. These new features are a vast improvement over the previous generation.
The new wireless local area network (WLAN) devices should be backward compatible and coexist with legacy IEEE 802.11 devices operating in the same band. Table 1 compares key physical layer (PHY) technologies of 802.11n, ac, ax, and be. Table 1. Physical layer (PHY) comparison of 802.11n, 802.11ac, 802.11ax, and 802.11be
802.11be regulatory challenges However, with new features such as backward compatibility, coexistence, and 4096 QAM modulation, there will be signal challenges in meeting the regulatory standard.
Let us take the 4096 QAM modulation as an example. Compared to previous generation 802.11ax, the QAM modulation is 3 dB more stringent than the error vector magnitude (EVM) requirement from -38 dB for 802.11be versus -35 dB for 802.11ax. With a challenging EVM requirement, error contributors such as noise, non-linearity of power amplifier, phase noise, and more will play a major factor. These changes require high-performance signal analysis test software and equipment to meet a lower EVM floor analysis. EVM analysis and measurements are critical key metrics used to evaluate signal quality. Measuring one signal with the right EVM can pose its own difficulties. However, measuring multiple signals simultaneously
Figure 2. Cross-correlated EVM results (frame A) compared with EVM results of the individual receiver (frames B and C).
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The performance of wireless solutions is improving, but meeting regulatory standards is becoming a challenge if not prepared correctly.
to demodulate and evaluate the EVM, along with reducing any error, can pose a significant challenge, especially when pinpointing the error’s location.
analysis. Software options provide an advanced troubleshooting and evaluation toolset designed to handle the challenge of analysing legacy and new wireless signals, covering technologies such as MU-MIMO and OFDMA used in the latest standards. 802.11 standards are among over seventy- five signal and modulation types that a single software can support.
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Software plays a critical role in testing new standards such as Wi-Fi 7. As standards evolve, so do the tools used to measure and test. Software is continuing to make advancements to help improve wireless connectivity.
Signal analysis test software Measurement software for signal analysis, signal generation, and even automation provide a unique solution to enable a specific result. It is important to choose software that enables a future-proof solution. Designers can now gain an advantage over the latest wireless signals with software for 802.11n/ac/ax and 802.11be modulation
The appropriate test software enables users to explore virtually every facet of a signal and optimise even the most advanced designs. The software helps engineers reduce complexity as they assess design trade-offs.
The history of wireless standards has shown there is no slowdown in improvements and performance. Reviewing the regulation standards and choosing software to help solve those issues is important. Let us look at the new 4096 QAM modulation requirement for Wi-Fi 7. Phase noise is often the dominant cause of EVM issues in OFDM systems. Vector signal analysis software enables users to characterise phase noise within the 802.11be demodulation measurement using an OFDM channel called phase noise spectrum trace. This method evaluates signal quality and error vector measurements of transmitted signals. For all wireless standard formats,
MARCH 2024 | ELECTRONICS FOR ENGINEERS 47
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