The IEEE 802.11ac amendment (Wi-Fi 5) operating in the 5 GHz ISM band allows a significant increase in data throughput to almost 7 Gbit/s. The key improvements are the increased channel bandwidth thanks to double the number of subcarriers, more spatial streams and higher modulation schemes. Current WLAN devices typically support 160 MHz bandwidth, up to four spatial streams and 256QAM modulation. These advanced features require appropriate test solutions in R&D and production.
WLAN IEEE 802.11ac testing
The unique feature set of 802.11ac
The IEEE 802.11ac PHY is based on the well-known orthogonal frequency division multiplexing (OFDM) modulation used for the legacy standards IEEE 802.11a and 802.11n. It maintains the same modulation, subcarrier spacing, interleaving and coding architecture. In order to largely improve the data throughput, 802.11ac supports 80 MHz channels as multiples of legacy 20 MHz channels and optionally 160 MHz channel bandwidth. In addition to the 64QAM modulation of 802.11n, a higher order 256QAM modulation scheme is supported. The number of possible spatial streams has been doubled so that 8x8 MIMO schemes are supported. As part of the second wave of the 802.11ac rollout, multi-user MIMO (MU-MIMO) on the downlink and beamforming are supported, allowing simultaneous transmission of data to stations at different locations.
IEEE 802.11ac key parameters
| Properties | Mandatory | Optional |
|---|---|---|
| 20 MHz, 40 MHz, 80 MHz channels | x | |
| 1 spatial stream | x | |
| BPSK, QPSK, 16QAM, 64QAM | x | |
| 256QAM | x | |
| 80+80 MHz channels | x | |
| 160 MHz channels | x | |
| 2 to 8 spatial streams | x | |
| Multi-user MIMO (MU-MIMO) | x | |
| 400 ns short guard interval | x | |
| Space time block coding (STBC) | x | |
| Low density parity check (LDPC) | x |
Detailed IEEE 802.11ac signal analysis using the R&S®FSW signal and spectrum analyzer.
Detailed IEEE 802.11ac signal analysis using the R&S®FSW signal and spectrum analyzer.
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Your 802.11ac test challenges
The standard defines various transmitter and receiver tests such as EVM, TX power, spectrum emissions and sensitivity. 256QAM modulation requires signal generation capabilities to transmit reference signals with very low distortion over a bandwidth of up to 160 MHz and spectrum analyzers with the required analysis bandwidth that can perform with a very low residual EVM. Testing of MIMO requires encoding or decoding of composite signals, including multipath channel emulation. This is important in R&D, but needs to be tested and verified in production as well.
Benefits of Rohde & Schwarz 802.11ac test solutions
- Complete set of solutions covering tests for chipsets, modules, stations and access points across all application layers from RF to signaling testing and end-to-end data application testing functionalities.
- Test solutions for every purpose – from R&D to production and certification – developed together with the key players in the ecosystem.
- Best-in-class solutions providing the required bandwidth, accuracy and efficiency.
