Mobile modems and routers
See also: Mobile broadband and Connect card
Modems which use a mobile telephone system (GPRS, UMTS, HSPA, EVDO, WiMax, etc.), are known as cellular modems. Cellular modems can be embedded inside a laptop or appliance or external to it. External cellular modems are connect cards, usb modems for mobile broadband and cellular routers. A connect card is a PC card or ExpressCard which slides into a PCMCIA/PC card/ExpressCard slot on a computer. The best known brand of cellular modem datacards is the AirCard made by Sierra Wireless.[citation needed] (Many people just refer to all makes and models as AirCards, when in fact this is a trademarked brand name.)[citation needed] USB cellular modems use a USB port on the laptop instead of a PC card or ExpressCard slot. A cellular router may have an external datacard (AirCard) that slides into it. Most cellular routers do allow such datacards or USB modems. Cellular Routers may not be modems per se, but they contain modems or allow modems to be slid into them. The difference between a cellular router and a cellular modem is that a cellular router normally allows multiple people to connect to it (since it can route, or support multipoint to multipoint connections), while the modem is made for one connection.
Most of the GSM cellular modems come with an integrated SIM cardholder (i.e., Huawei E220, Sierra 881, etc.) The CDMA (EVDO) versions do not use SIM cards, but use Electronic Serial Number (ESN) instead.
The cost of using a cellular modem varies from country to country. Some carriers implement flat rate plans for unlimited data transfers. Some have caps (or maximum limits) on the amount of data that can be transferred per month. Other countries have plans that charge a fixed rate per data transferred—per megabyte or even kilobyte of data downloaded; this tends to add up quickly in today's content-filled world, which is why many people are pushing for flat data rates.
The faster data rates of the newest cellular modem technologies (UMTS, HSPA, EVDO, WiMax) are also considered to be broadband cellular modems and compete with other broadband modems below.
Reference data and images: http://en.wikipedia.org/wiki/Modem
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