This disclosure describes methods, apparatus, and systems related to a channel estimation field (CEF) for various standards, for example, the 802.11ay standard, for single carrier (SC) MIMO channel estimation. In one embodiment, the CEF can use Golay complementary sequences. In another embodiment, the Golay complementary sequences can be defined similar to Golay complementary sequences definitions that can be found in various legacy standards, for example, the legacy 802.11ad standard. Various embodiments of the disclosure can allow channel estimation in the time domain and/or frequency domain, having small or negligible inter-stream interference. Various embodiments of the disclosure can enable an extendable structure for various M×N MIMO configurations, where M and N are positive integers.