In 2011, there were over 1 billion cell phones sold worldwide, and cellular telephones are now the largest providers of access to the Internet. Digital cellular service uses several competing standards. In Europe and much of the rest of the world outside the United States, the standard is Global System for Mobile Communication (GSM). GSM’s strength is its international roaming capability. There are GSM cell phone systems in the United States, including T-Mobile and AT&T Wireless.