Wireless Internet Using 2.4 GHz

Your Wi-Fi know-how could make or break your ISPs future. If you're looking for a profitable way to provide high-speed Internet access for your customers, now is the time to amplify your aptitude about wireless systems.

by Michael F. Young President, YDI [February 15, 2001]

First, large companies own the licenses for cellular and PCS radio channels, so it is highly unlikely that your Internet business could afford to gain access to the networks. Second, the throughput on these channels is very slow, less than 10 Kbps. While cellular systems provide ideal transport for WAP Internet applications, it is not useful for offering high-speed Internet access.

This is where using the 2.4 GHz band of spectrum has proven to be an effective and profitable way to offer high-speed wireless Internet services to customers at fixed locations.

There are three main advantages of operating your wireless Internet service in this band. First, it is allocated as experimental spectrum, so your ISP has a license to operate free of fees. Second, The 2.4GHz band supports high data rates needed to provide broadband Internet services. And third, the equipment to set up a fixed wireless broadband network is affordable, so initial start-up costs are minimized.

The primary disadvantage to offering fixed wireless Internet access is clear—your ISP must maintain an unobstructed line-of-sight between your base station and clients antennas.

Unlicensed free spread spectrum
The Federal Communications Commission has set standards under Part 15 of the Rules and Regulations for equipment used in the 2.4 GHz band—the exact spectrum is 2400 to 2483.5 MHz. If the equipment uses spread spectrum techniques, then effective radiated transmit powers of up to 64 watts can be used.

Your Internet service can apply two different types of spread spectrum methods to construct a fixed wireless broadband network—Frequency Hopping Spread Spectrum (FHSS) or Direct Sequence Spread Spectrum (DSSS) technology (See figure 1, below).

The primary advantage shared by both spread spectrum technologies is that many radios are able to operate in this band with a minimum amount of interference—to a certain extent. FHSS systems send data packets first to a random channel in the band, while the next packet is sent—after a pausing for a few milliseconds—to another random channel in the same band. With 80 channels or more available—one channel per MHz, as in 2401, 2402, 2403, and so on—signals from multiple radios basically hop around each other.

DSSS radios operate on a fixed radio channel, in which the signal is spread-out by mixing it with a Pseudo-Noise (PN) code. When the spectrum is extended, the radio signal transporting a data packet occupies a much wider band. The signal also looks like noise to receivers that are not designed to separate the spectrum and interference is avoided.

Why WIPOPs?
A Point of Presence (PoP) is a term commonly used in the Internet industry to denote a facility that has wired access to the Internet through a broadband backbone. In order to offer high-speed wireless Internet access, your ISP needs to set up a base station, often referred to as a Wireless Internet PoP (See figure 2, below).

In a typical WIPOP setup, antennas are placed on a tall building or radio tower so that customer’s antennas have a clear, unobstructed view of the antenna at your base station. Line-of-sight (LOS) is required because trees and buildings will block wireless signals.

Your ISPs client sites typically use a high-gain directional antenna aimed back at the WIPOP. Customers can use an Ethernet station adapter to connect a LAN to your WIPOP through an inexpensive router or a single machine equipped with a wireless LAN (WLAN) card and an antenna. As long as the client antennas have clear LOS and are pointed directly at your ISPs base station antenna, customers can access the Internet like a traditional wired setup. The beauty of a WIPOP is that there are no wires to bury or string across utility poles, and your business is not dependent on a local telephone company to complete a fixed wireless connection.

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