Wide-area wireless networks connect users to the Internet over a geographically dispersed territory. These networks typically operate over the licensed spectrum-that is, they use portions of the wireless spectrum that are regulated by the government.

In contrast, Bluetooth and Wi-Fi operate over the unlicensed spectrum and are therefore more prone to interference and security problems. In general, wide-area wireless network technologies fall into two categories: cellular radio and wireless broadband.

Cellular Radio

Cellular telephones (cell phones) provide two-way radio communications over a cellular network of base stations with seamless handoffs. Cellular telephones differ from cordless telephones, which offer telephone service only within a limited range through a single base station attached to a fixed landline, for example, within a home or an office.

The cell phone communicates with radio antennas, or towers, placed within adjacent geographic areas called cells. A telephone message is transmitted to the local cell-that is, the antenna-by the cell phone and then is passed from cell to cell until it reaches the cell of its destination. At this final cell, the message either is transmitted to the receiving cell phone or it is transferred to the public switched telephone system to be transmitted to a wireline telephone.

Cellular technology is quickly evolving, moving toward higher transmission speeds and richer features. The technology has progressed through several stages:

• First generation (1G) cellular used analog signals and had low bandwidth (capacity).

• Second generation (2G) uses digital signals primarily for voice communication; it provides data communication up to 10 Kbps.

• 2.5G uses digital signals and provides voice and data communication up to 144 Kbps.

• Third generation (3G) uses digital signals and can transmit voice and data up to 384 Kbps when the device is moving at a walking pace, 128 Kbps when it is moving in a car, and up to 2 Mbps when it is in a fixed location. 3G supports video, Web browsing, and instant messaging. 3G does have disadvantages. Perhaps the most fundamental problem is that cellular companies in North America use two separate technologies: Verizon and Sprint use Code Division Multiple Access (CDMA), while Cingular and others use Global System for Mobile Communications (GSM). CDMA companies are currently using Evolution-Data Optimized (EV-DO) technology, which is a wireless broadband cellular radio standard. In addition, 3G is relatively expensive. In fact, most carriers limit how much information you can download and what you can use the service for. For instance, some carriers prohibit downloading or streaming audio or video. If you exceed the carriers’ limits, they reserve the right to cut off your service.

• Fourth generation (4G) is still under development, and it is not one defined technology or standard. The International Telecommunications Union has specified speed requirements for 4G: 100 Mbps (million bits per second) for high-mobility communications such as cars and trains, and 1 Gbps (billion bits per second) for low-mobility communications such as pedestrians. A 4G system is expected to provide a secure all-IP (Internet Protocol)-based mobile broadband system to all types of mobile devices. Many of the current “4G” offerings do not meet the ITU specified speeds, but they call their service 4G nonetheless. See “IT’s Personal” for more information.

Wireless Broadband or WiMAX

Worldwide Interoperability for Microwave Access, popularly known as WiMAX, is the name for IEEE Standard 802.16. WiMAX has a wireless access range of up to 31 miles, compared to 300 feet for Wi-Fi. WiMAX also has a data-transfer rate of up to 75 Mbps. It is a secure system, and it offers features such as voice and video.

WiMAX antennas can transmit broadband Internet connections to antennas on homes and businesses located miles away. For this reason WiMAX can provide long-distance broadband wireless access to rural areas and other locations that are not currently being served.