To meet demands for higher throughput, the IEEE 802.11 wireless-local-area-networking (WLAN) standard has continually advanced. The recent IEEE 802.11ac standard was specified as an extension of the previous-generation IEEE 802.11n. Although IEEE 802.11ac offers faster data rates and greater bandwidths than previous standards, its increased complexity demands additional test requirements. In the application note "Testing New-Generation WLAN 802.11ac," Keysight Technologies discusses the design and test challenges associated with IEEE 802.11ac.
The application note presents an overview of the key specifications of IEEE 802.11ac. A list of IEEE 802.11n specifications is also provided, allowing readers to see how the two standards compare with one another. The technical differences between IEEE 802.11n and IEEE 802.11ac are explained in further detail. For example, a description of the wider channel bandwidths used in the IEEE 802.11ac standard is presented. Multi-user multiple-input, multiple-output (MU-MIMO), which is new to IEEE 802.11ac, is explained in the document, as well.
The IEEE 802.11ac standard includes a set of transmitter and receiver tests. Error-vector-magnitude (EVM) is an example of a critical test parameter. EVM testing and troubleshooting can be performed by a vector-signal-analysis (VSA) tool, such as Keysight’s 89600 VSA software. Power amplifiers (PAs) for IEEE 802.11ac applications are utilizing digital pre-distortion (DPD) and envelope tracking (ET) to improve linearity and efficiency, respectively. The document describes test solutions for these latest PAs.
Because wider-bandwidth signals are required for IEEE 802.11ac, the application note examines various test instruments that can both generate and analyze these wideband signals. Software solutions are also explained, as they are used in combination with test instrumentation to perform tasks like waveform creation and signal analysis. MIMO and beamforming design verification present another difficult challenge. Techniques to meet these challenges are discussed in greater detail for both receivers and transmitters. The application note concludes with a description of Keysight’s EXM WLAN manufacturing test solution.
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