RAT

RAT (Radio Access Technology) is the radio standard a device uses to connect to a mobile network — for example GSM, UMTS, LTE or 5G NR. Most devices support several RATs and move between them depending on coverage, network configuration and their own settings, so knowing which RAT was in use is essential to interpreting any result.

Common RATs

Generation	RAT	Typical use
2G	GSM / GPRS / EDGE	Legacy voice, SMS and low-rate data; being switched off in many countries
3G	UMTS / HSPA	Already retired in many markets
4G	LTE (E-UTRA)	Mainstream data, and voice via VoLTE
4G IoT	LTE-M, NB-IoT	Low-power IoT devices
5G	NR, in NSA or SA mode	High-speed data, low latency, VoNR, network slicing

How the RAT is decided

• Network side: operators choose which RATs and bands to deploy, which RATs each subscription may use, and which RATs roaming partners may use. A roaming agreement can cover LTE but not LTE-M, for example.
• SIM side: the PLMN selector lists on the SIM pair each preferred network with access technologies.
• Device side: modems can be restricted to particular RATs — say, LTE-M only — or left to choose automatically. The standard AT+COPS command from 3GPP TS 27.007 reports the access technology in use and can request a specific one.

Why RAT changes results

Signal metrics, throughput, latency and even which services work all depend on the RAT. A data test on LTE and the same test on NB-IoT are not comparable. Voice may run as VoLTE on LTE, VoNR on 5G SA, or circuit-switched on 2G and 3G. Reject behavior differs too: a network can accept a device on LTE but reject it on LTE-M if the subscription or roaming agreement does not include LTE-M.

Why it matters for testing

Testing on whatever RAT the device happens to pick hides problems. Forcing each RAT the product depends on reveals coverage gaps, missing roaming permissions and fallback behavior. SimCheck.ai tests can force the RAT — 5G SA, 5G NSA, LTE, LTE-M, NB-IoT, 3G or 2G — and report the RAT and band actually used — see quick tests.