Internet, Networking, & Security Home Networking What Is TDMA and What Does It Do? What you need to know about this 2G cell phone technology By Susan J. Owens Writer Former Lifewire writer Susan J. Owens is a tech writer focused on AI, blockchain, and virtual machines. Her work appears in InformationWeek, Entrepreneur, and Fast Company. our editorial process LinkedIn Susan J. Owens Updated January 21, 2020 EduLeite/Getty Images Home Networking Wi-Fi & Wireless The Wireless Connection Routers & Firewalls Network Hubs ISP Broadband Ethernet Installing & Upgrading Tweet Share Email Time Division Multiple Access (TDMA) is a wireless technology used by cellular providers to connect calls within the 2G network. Cell phone providers in the United States are in the process of phasing out 2G, meaning 2G phones will no longer work in the United States. If you're looking for an inexpensive flip phone or an imported wireless device, you'll need to pay attention to the mobile networks these devices support. Here's what you need to know about cell phone technologies so you can purchase a reliable wireless device that will work in the United States. Why Do Cell Providers Change Technology? Cell phone providers are constantly upgrading their equipment and developing new technologies to improve the quality of their cell services. At the same time, consumer demand for data and cell coverage continues to grow, placing more pressure on cell phone providers to accommodate more users and capacity within their channels. One of the latest technologies is 5G. The "G" in "5G" refers to the generation of wireless technology. 5G is simply one of several upgrades, which began with 1G, before we moved to 2G, 3G, then 4G. Each subsequent generation supports more users more efficiently. TDMA and Your Cell Phone TDMA is one of several methods cell phone providers use to transmit data and is used in 2G, as Global System for Mobile Communications (GSM). AT&T and T-Mobile use GSM, while Sprint & Verizon use Code Division Multiple Access (CDMA) to run their networks. TDMA was originally used by Western Union in 1979 for its Westar 3 communications satellite. The advantage of TDMA is this technology divides signals into different time slots. When calls are made, each call uses a separate time slot, allowing multiple stations to share the same radio frequency while using only a part of its channel capacity. Phones that use GSM have a removable SIM card, which links the phone to a specific mobile carrier and holds the customer's subscription information. You also have the ability to take a SIM card out and put it in another phone that now has the new phone number. Why Would Phone Carriers Drop GSM Service? Major cell phone service providers have a license from the Federal Trade Commission (FTC) which gives them access to blocks of frequencies at different locations across the country. These assignments limit each carrier to a specified spectrum of space they can access for their customers. In an effort to free up space within their limited block of frequencies, carriers are eliminating older technologies, like GSM, to make room for more powerful and robust technologies like 5G. GSM, which utilizes TDMA, is designed exclusively for 2G and doesn't have the capacity for 3G, 4G LTE, or 5G. As a result, phone carriers will be turning off 2G to make room for these newer, more efficient networks. Some have already turned off their 2G service; soon, no 2G GSM phones will work in the United States. What's the Impact of Limited GSM Coverage? Each cell phone carrier has announced their plans for shutting down their 2G network in the United States: AT&T shut down its 2G network in 2017.Sprint will begin shutting down its 2G and 3G network in 2021.Verizon has shut down its 2G network at the end of 2019.T-Mobile has scheduled the shutdown of its 2G shutdown for 2020. Key Takeaways Regarding TDMA Wireless devices that use the 2G network are inexpensive, but typically have slower data speeds, making them ideal for kids, or people trying to save money on cell phone costs by not using their phones for data. These less expensive devices will no longer work within the United States as the 2G network shutdown continues. When shopping for a new cell phone, don't buy a basic flip phone or imported phone made outside of the United States that uses GSM networks, as they won't be supported by U.S. network frequencies. If you already own a 2G device, it's time to upgrade to a newer device that uses 4G or 5G technologies.