Nordic Mobile Telephone (NMT) and the Advanced Mobile Phone System (AMPS) were among the first standards for analog mobile phone systems. Both are first-generation, or 1G, technology standards.
GSM, named for the group that developed it (Groupe Speciale Mobile), is another wireless standard for mobile communication. Originally developed as a common digital wireless standard for Europe, GSM is second-generation, or 2G, technology. The GSM standard is based on Time Division Multiple Access (TDMA), which divides a radio frequency into time slots and then allocates each slot to a user.
Whereas TDMA has been the standard used in Europe, Code Division Multiple Access (CDMA) is the standard used in the United States. CDMA uses a digital encoding system to spread the signal for a call across a range of frequencies. This technique allows more users to share the network simultaneously.
The General Packet Radio Service (GPRS) uses GSM to handle data transmission. This standard is known as 2.5G technology. GPRS is a packet-switching technology, which means that users are always connected.
The 2.5G technology is currently the most widely used standard for mobile communications. Mobile devices using this standard can provide voice and data transmission, along with Web browsing capabilities. These types of phones can also transmit e-mail. Networks using the 2.5G standard have been implemented worldwide.
WiFi, short for Wireless Fidelity, is more commonly known as the 802.11b standard for wireless communication. WiFi provides short-range wireless connectivity (approximately 150 feet) between devices, primarily for computer networks. So-called "WiFi zones" may be located in airports, hotels, and even warehouses in order to facilitate wireless communications.