Development and enhancement of CFR estimate in WLAN and testing in Vector Signal Transceiver

Use of Wireless Local Area Networks (WLAN) has dominantly supported the field the wireless communication in achieving high data rates and security. Instead of sending a single copy of data from transmitter to receiver, it is preferable to send copies of the same data to maintain the integrity of the information. This includes preamble or pilot symbols prior to data. Modern OFDM receivers complying to 802.11n / ac / ax WLAN standards use legacy equalizer training sequence (L-LTF) to equalize SIG symbols, which carry details pertaining to the Data being transmitted. However, Data itself is equalized using HT / VHT / HE- LTFs. The aim of this project is to leverage the legacy CFR, in conjunction with the actual one, to compute a better response to equalize Data. This helps in characterizing the transmitter more accurately to provide the best possible Error Vector Magnitude (EVM) result to the customer. A novel Channel Frequency Response (CFR) combining technique for equalizer training of data is presented in this paper. The results include a comparison of EVM values for both with and without equalizer training in LabView.It also includes the test results of the same in NI PXIe Vector Signal Transceiver (VST) hardware.