A cellular network or mobile network is a wireless network distributed over land areas called cells, each served by at least one fixed-location transceiver, known as a cell site or base station. In a cellular network, each cell uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed bandwidth within each cell. When joined together these cells provide radio coverage over a wide geographic area. This enables a large number of portable transceivers (e.g. mobile phones) to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more than one cell during transmission.
Technology and services
GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile), is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe protocols for second-generation (2G) digital cellular networks used by mobile phones.
2G networks developed as a replacement for first generation (1G) analog cellular networks, and the GSM standard originally described a digital, circuit-switched network optimized for full duplex voice telephony. This expanded over time to include data communications, first by circuit-switched transport, then by packet data transport via GPRS (General Packet Radio Services) and EDGE (Enhanced Data rates for GSM Evolution or EGPRS). Subsequently, the 3GPP developed third-generation (3G) UMTS standards followed by fourth-generation (4G) LTE Advanced standards, which do not form part of the ETSI GSM standard.
2G/3G/4G offers well known services: Voice calls, Short Message Service (SMS), CSD (Circuit Switched Data, data call e.g USSD), Multimedia messaging service(MMS), transmission data over TCP/IP (internet) and other IP based protocols/services(TCP, UDP, FTP, HTTP, SMTP, POP3 etc.).
2G/3G industrial modems
A GSM modem is a wireless modem that works with GSM networks. A GSM modem is a specialized type of modem which accepts a SIM card, and operates over a subscription to a mobile operator, just like a mobile phone. From the mobile operator perspective, a GSM modem looks just like a mobile phone. A wireless modem behaves like a Hayes compatible dial-up modem. The main difference between a standard Hayes modem and a GSM modem is that a hayes modem sends and receives data through a fixed telephone line while a GSM modem sends and receives data through radio waves. GSM modems support an extended set of AT commands. These extended AT commands are defined in the GSM standards. AT commands are instructions used to control a modem through one of the hardware serial protocols.
A GPRS modem is a GSM modem with additional support for GPRS technology for data transmission. GPRS means: 'General Packet Radio Service'. It is based on a packet-switched technology, as an extension to GSM (note that GSM is a circuit-switched). An advantage of GPRS over GSM is that GPRS has a much higher data transmission speed.
Vendors: Gemalto Cinterion, Quectel, Telit, uBlox, Wavecom, Sierra Wireless …
M2M industrial modules (modems) also comes integrated in SOC (systems on chip). They are programmable and can stand alone, because have all you need (uC and peripherals). Well known vendors are Gemalto Cinterion (Java ME) and Sierra Wireless (RTOS, C/C++).