Does 5G use CDMA or GSM?

In the US, AT&T as well as T-Mobile phones use GSM – and most of the rest of the world uses GSM as well. CDMA in the US is Verizon, Sprint and US Cellular. You need to read up on the subject.

GSM is a second-generation (2G) cellular technology standard and is, therefore, less capable of providing high-speed data as compared to UMTS, which is a third-generation (3G) technology and LTE, which is a fourth-generation (4G) cellular technology.

Comparison table GenerationTechnologySignal quality/coverage area3GW-CDMASmaller cells and lower indoors coverage on 2100 MHz; equivalent coverage indoors and superior range to GSM on 850/900 MHz.4GOFDMASmaller cells and lower coverage on the S band.5GOFDMADense cells on millimeter waves.Comparison of mobile phone standards – Wikipedia en.wikipedia.org › wiki › Comparison_of_mobile_phone_standards