Smartphones generally operate using one of two mobile network technologies, which determines how the device communicates with its cellular network:

•  GSM: Global System for Mobile Communications
Some Carriers: Verizon, U.S. Cellular and Sprint

•  CDMA: Code Division Multiple Access
Some Carriers: AT&T, T-Mobile, Verizon (unlocked)

Although GSM and CDMA provide similar basic features and services to end users (voice calling, text messaging, and data services), they operate differently at many technical levels, making GSM phones completely incompatible with CDMA networks, and vice versa.

There are several generations of each technology, but for the purposes of smartphone handset forensics, it is primarily important to simply know whether you are working with a CDMA or GSM phone. In the past, it was easy to determine whether a phone was CDMA or GSM based on whether it contained a SIM card because only GSM phones contained SIM cards. Now, however, newer-technology (many) CDMA smartphones can have the capability to work on both CDMA and GSM networks and, therefore, may contain a SIM card or a R-UIM (Removable User Identity Module) card. Therefore, you may have to do some investigation to see whether the phone you are working with is a GSM or CDMA phone.

You can determine what network technology a phone is using by checking that phone by make and model at www.phonescoop.com, or by determining what service provider that phone uses, because the carrier either uses a CDMA or a GSM network. Knowing what general technology, the handset you’re trying to examine is using is an important first step in the examination process.

The get to these settings on and Android and iOS follow the steps below. These steps will also help you with the identifiers on the next slide.
iOS – Settings > General > About
Android – Settings > About phone > Status