Wireless modems transmit modulated data using electromagnetic waves. They connect to a wireless network instead of to a telephone line. Unlike traditional analog modems and some types of network modems, these wireless devices provide very fast, always-on network connections. Typically, users can access the Internet at speeds up to 100 times faster than with analog modems.

Unlike radio modems, wireless modems support non-serial communications such as Ethernet, GSM, and GPRS. Ethernet, a popular protocol for local area networks (LANs), is similar to Global System for Mobile Communications (GSM) and General Packet Radio Service (GPRS) in that all three technologies transmit data in network packets. Each packet contains information such as the sender's Internet Protocol (IP) address and the intended receiver's IP address.

Wireless modems are often used with laptop computers. They allow users to move their portable PCs to different locations and still access network resources. Industrial-quality products can provide high-speed connectivity over EVDO or HSPA networks, and offer Internet access. Communications from an Evolution Data Optimized (EVDO) or High-Speed Package Access (HSDPA) network can be transmitted ATMs, POS terminals, or wireless cameras.

Some wireless modems are bundled with wireless routers, devices which forward network packets. The router sends signals to transmit the information, and the modem receives it before sending the signals to the user's computer. The data packets, which are sometimes called frames, blocks, cells, or segments (depending on the network type) are sent via the most efficient route and can be redirected if necessary.

Radio Links and Techniques

Wireless modems use several different frequency bands and radio techniques.

• 900 MHz is an unlicensed industrial, scientific and medical (ISM) band that does not require FCC registration. The range is 902 to 928 MHz, and the maximum transmission power is 1 W.
• 2.4 GHz is another unlicensed ISM band that does not require FCC registration. The range is 2.40000 to 2.4835 GHz, and the maximum transmission is 1 W. Select wireless modems in this band for 802.11b and 802.11g applications.
• 5 GHz ranges between 5.2 and 5.8 GHz in North America. Select modems in this band if your application is 802.11a.

Wireless modems that operate in the 23 GHz, ultra high frequency (UHF), and very high frequency (VHF) bands are also available.

Specifications

When selecting wireless modems, industrial buyers need to specify the form factor (internal or external), the network type, and the bus or interface type. Engineering360 provides information about products with four network types: dial-up, Ethernet, GSM, and GPRS. It also offers information about products with these network types: Type II Card, CardBus, ISA, PCI, RJ-45, ISDN BRI S/T Interface, serial ports (RS232, RS422, RS485), ST, and USB.

Resources

How a Wireless Modem Works

Image credits:

Banner Engineering Corp. | Solnet.com