NSA is an acronym for Non-Standalone architecture. 5G NSA is one of two architectures to deploy 5G technology, with the other being the 5G Standalone architecture (SA).
The Non-Standalone architecture, as the name suggests, does not leverage any standalone 5G infrastructure, but taps into the already existing 4G infrastructure instead to deliver better speeds and reliable connectivity.
In Singapore, as mandated by IMDA, 5G NSA is being rolled out by mobile service providers as a market trial and this market trial may be discontinued no later than 31 December 2021. Eventually, all mobile service providers in Singapore are expected to deliver their 5G services over the 5G SA network.