In wireless communications for a 20 megahertz (MHz) channel bandwidth, a first device may determine a high efficiency long training field (HE-LTF) mode. The first device may generate an HE-LTF symbol by using a portion or an entirety of an HE-LTF sequence corresponding to the channel bandwidth and HE-LTF mode. The first device may transmit, in the channel bandwidth, a high efficiency physical layer protocol data unit (HE PPDU) that includes the HE-LTF symbol. A second device may receive, in the 20 MHz channel bandwidth, a downlink HE PPDU that includes an HE-LTF symbol. The second device may obtain, from the HE-LTF symbol, a portion or an entirety of an HE-LTF sequence corresponding to the channel bandwidth and an HE-LTF mode of the HE-LTF symbol. The downlink HE PPDU may be the HE PPDU from the first device. Other methods, apparatus, and computer-readable media are also disclosed.