Singapore has 3 telco operators, they are Singtel, Starhub and M1. IMDA has released it’s report of the indoor and outdoor coverage of the three telcos for the months of Jan, Feb and Mar 2018.
For 4G outdoor coverage, the three telcos performed well around 99.xx across the board. Singtel seems to be the better one among the three while M1 and Starhub are doing equally well. You can refer to the report in details here : 4G Outdoor Nationwide coverage: https://www.imda.gov.sg/…/complian…/4g-services/jan-mar-2018
As for indoor 4G coverage, which includes signal in tunnel coverage, M1 is way ahead of the other 2 telcos. You can find the details here : 4G In-building coverage & in-tunnel coverage: https://www.imda.gov.sg/…/4g-measurement-survey-results-for…
