Theory on Fixed Wireless Broadbands

Introduction:

Fixed wireless broadband should not be confused with text-only or limited-graphics wireless Internet services aimed at handheld mobile phones and PDAs. After a fixed-base wireless broadband signal reaches your computer, your Internet experience is just as rich in content and about as speedy as wired services such as cable modem and DSL. Essentially, fixed wireless broadband Internet access is a form of cable modem service that substitutes microwave receivers or transceivers for the HFC cabling of the cable modem network. Similar to cable modems, fixed wireless broadband is an always-on service.

Working Principle:

Fixed-base wireless broadband is an offshoot of wireless CATV broadcasting; both use microwave towers to broadcast encrypted signals to receivers within a specified radius (up to 45 miles, but generally 35 miles or less) of the transmitter. Wireless CATV delivers the same cable TV content that conventional CATV operators provide for rural users and others who aren’t served by conventional CATV services. Similarly, fixed-base wireless broadband delivers encrypted Internet content to customers within the radius of the transmitter. If only a single transmitter/receiver site is used, the distance for two-way service can be significantly less than that available for wireless CATV users—as little as 15–20 miles. Because of the directional nature of the receiving antennas used for fixed-base wireless broadband, only some of the users in that radius might qualify for two-way service. Users who live within the radius served by the transmitter but don’t qualify for two-way service might be eligible for one-way (also called telco return) service, which uses wireless signals for downloading only and an analog modem for uploading. Some fixed wireless broadband services offered in larger cities might use multiple transmitters, enabling all users to enjoy two-way service. Wireless signals are similar in their bandwidth use and modulation to CATV cable modem signals; in fact, some wireless broadband routers (which serve the same function as cable modems but are used for wireless networking) can also be used in CATV cable modem service.

Several frequencies are used for fixed wireless broadband Internet, but the most commonly used service

types are

• MMDS. The most common form of fixed wireless broadband Internet has a range of up to 35 miles. It’s used by Iowave’s Hybrid Networks product line (now known as ioQuasar), Spike Broadband  systems, and Vyyo. It uses the 2.5GHz–2.7GHz and 3.4GHz–3.7GHz frequencies. MMDS uses the same modulation techniques (QPSK and QAM) used by cable modems.
• LDMS Lite. Has a range of 3–5 miles and is used by Vyyo. It uses the 10MHz–43MHz frequencies and the QPSK and QAM modulation techniques.

Fixed wireless broadband can also use 3.5GHz, 10.5GHz, UHF, and unlicensed frequencies.

Major fixed wireless broadband equipment and services vendors include

• Iowave (www.iowave.com)
• REMEC (www.remecmagnum.com)
• Vyyo (www.vyyo.com)

Even though these companies have installed a number of service sites around the United States, fixed wireless broadband is more popular outside the United States, partly because of a lack of wired telephone or cable TV infrastructure (and thus a lack of competition from broadband Internet services (based on those technologies).

The Wireless Broadband Router and Other Equipment

The connection between the wireless broadband service and your computer is provided by a wireless broadband router (also referred to as a WBR or wireless cable modem). A WBR resembles an external cable modem, but most models also include either an RS-232 connection to an external analog phone modem or an integrated analog modem, enabling the same WBR to be used in either two-way or oneway (telco return) service, as shown in Figure.

The WBR is connected via the same type of coaxial cable used by CATV cable modems to various types of receivers (for one-way service) or transceivers (for two-way service) that are mounted on a roof or tower. The placement of the transceiver or receiver is critical, especially in systems that use only one transmitter/receiver location. A site survey performed by the provider usually is required to verify that the service is available and to select a location for the transceiver/receiver’s antenna. If a direct line of sight back to the transmission/receiving tower can’t be established, two-way service is impossible. However, one-way service might be available if the signal can be reflected off a nearby tower or building. Devices referred to as benders can be mounted on nearby structures to permit reception of the signal from the wireless broadband provider, but benders can’t be used to return data from the customer back to the provider’s receiver.

Fixed Wireless Security Issues:

All fixed wireless broadband services are encrypted—even the one-way offerings—so casual snooping by others receiving the signal is impossible. However, you should guard against other types of Internet intrusion common to all forms of Internet access.