Broadband

ADSL modems, a more recent development, are not limited to the telephone's "voiceband" audio frequencies. Some ADSL modems use coded orthogonal frequency division modulation (DMT).

Cable modems use a range of frequencies originally intended to carry RF television channels. Multiple cable modems attached to a single cable can use the same frequency band, using a low-level media access protocol to allow them to work together within the same channel. Typically, 'up' and 'down' signals are kept separate using frequency division multiple access.

New types of broadband modems are beginning to appear, such as doubleway satellite and power line modems.

Broadband modems should still be classed as modems, since they use complex waveforms to carry digital data. They are more advanced devices than traditional dial-up modems as they are capable of modulating/demodulating hundreds of channels simultaneously.

Many broadband modems include the functions of a router (with Ethernet and WiFi ports) and other features such as DHCP, NAT and firewall features.

When broadband technology was introduced, networking and routers were unfamiliar to consumers. However, many people knew what a modem was as most internet access was through dial-up. Due to this familiarity, companies started selling broadband modems using the familiar term "modem" rather than vaguer ones like "adapter" or "transceiver".

Many broadband modems must be configured in bridge mode before they can use a router. For more information visit our friends here.

Modern Modems and Routers

Modems which use mobile phone lines (GPRS, UMTS, HSPA, EVDO, WiMax, etc.), are known as Cellular Modems. Cellular modems can be embedded inside a laptop or appliance, or they can be external to it. External cellular modems are datacards and cellular routers. The datacard is a PC card or ExpressCard which slides into a PCMCIA/PC card/ExpressCard slot on a computer. The most famous brand of cellular modem datacards is the AirCard made by Sierra Wireless. (Many people just refer to all makes and models as "AirCards", when in fact this is a trademarked brand name.) Nowadays, there are USB cellular modems as well that use a USB port on the laptop instead of a PC card or ExpressCard slot. A cellular router may or may not have an external datacard ("AirCard") that slides into it. Most cellular routers do allow such datacards or USB modems, except for the WAAV, Inc. CM3 mobile broadband cellular router. 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"), 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 "per Megabyte" or even "per Kilobyte" plans that charge a fixed rate per Megabyte or 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. See : flat rate.

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. For more information visit our friends here.