Article

802.11 by the numbers

In the first of his occasional columns, Craig Keefner, kiosk guru and founder of kiosks.org, explains all about the five digits that are going to change the kiosk industry.

March 31, 2002 by Craig Keefner — manager, Olea

Craig Keefner founded kiosks.org in 1993. The Houston native resides in Minnesota, though he spends much of his time in Kentucky and traveling to kiosk events around the world. He is a sought-after speaker at a variety of kiosk events worldwide.

Kiosks.org founder Craig Keefner

Seems like every other e-mail, Web page or press release I see these days has that magic word in it: "wireless." We are going to take a look at where wireless has come from and where it's going, since more and more kiosks will be going wireless.

We'll do it in a few parts:

1. Introduction
2. Products that are available
3. Applications
4. Integration Issues
5. End-to-end solutions

What's wireless?

Wireless networks are just like traditional wired networks such as the Ethernet used in your office, except that they don't use wires. Look at any wireless computer and you'll see it still has a network card, called a Network Interface Card (NIC), but where the network cable usually plugs in, you'll see an antenna. Broadcasting data over a radio frequency has a bunch of advantages to the kiosk user:

• You get an infrastructure without having to wire up the whole place
• You're freed from wires; your location choices go way up

On the downside, security can be a problem, which I'll get into later.

Just remember that somewhere along the way a wireless network still has to connect to a wired network. That's the job of the base station, a radio receiver with a couple of antennas and a network plug in the back. Base stations, also called access points, are usually mounted high up on a wall where reception is clearer and nosy people can't get to them. They take the signals from all the wireless computers in range and feed them into the wired network.

Not just any wireless device can connect to your network, though. Wireless computers, whether they are kiosks, handhelds, or some other type of computer, are usually configured with ids and passwords to tell the network they're allowed in. Otherwise, anyone with a wireless NIC and some ingenuity can hack in.

How'd we get here?

Most computer specifications are known by their numbers. Tell any computer geek "802.11" and he or she knows you mean the specs for wireless networking. 802.11 was created by the IEEE Wireless Local Area Networks (WLAN) Standards Working Group. IEEE (pronounced I-triple-E to those in the know) stands for the Institute of Electrical and Electronics Engineers, a fact you can now forget.

The IEEE WLAN Standards Working Group was formed in 1990 to design a radio-frequency-based networking standard in the 2.4 gigahertz (GHz) band. Since a gigahertz is a billion cycles per second, 2.4 GHz a very high frequency band of 2.4 billion cycles per second.

Speed counts

The group came up with 802.11a, which turned out to be a mixed blessing. The ink was barely dry on that spec when Lucent Technologies announced enhancements that greatly increased data rates from 1-2 megabits per second, or Mbps, to 11 Mbps. That's 11 million bits per second, a bit being the smallest piece of data a computer can send, one binary digit.

In contrast, typical Ethernet speeds are 10 and 100 Mbps, and the fastest telephone line modems download data much more slowly at 56 kilobits per second (Kbps), or 56,000 bits per second.

In 1999 the group unveiled 802.11b, a "High Rate" standard. IEEE 802.11 is now the technical designation of a high-speed (up to 11 Mbps, 802.11b) wireless networking standard that allows devices to communicate with each other. It is comparable to Ethernet (or 802.3 to geeks).

This latest 802.11b standard is based on a technology called Direct Sequence Spread Spectrum (DSSS). DSSS spreads the networked data between several channels in the radio frequency band. This method reduces interference and quickens the speed.

Don't interfere

Since wireless networks are vulnerable to all the problems that affect radio waves such as interference and shielding in walls, the 802.11b standard is designed to slow down when there are traffic problems. These "fallback rates" automatically reduce connection speeds to 5.5 Mbps, 2 Mbps, and 1 Mbps.

Interference can be caused by anything giving off signals in the 2.4 GHz range, such as machinery, other nearby wireless networks, and even microwave ovens. Mall crowds absorb radio waves, also causing interference. That's another reason to mount base stations up high.

Legacy support

One important consideration when 802.11a turned into 802.11b was support for legacy systems. It uses the same bandwidth as the 2 Mbps DSSS standard and thus interoperates with your older IEEE DSSS systems, if you have one. Faster rates allow more nodes to effectively connect to a WLAN via a single channel.

We are currently spec-wise up to 802.11g (almost). C and d came and then e (security enhancements). Rumor has it that g will be friendly to b devices and that its speed may be in the 40 Mbps range. That's pretty quick!

Anyway back to reality (11 Mbps)...

How far can I roam?

There are still the usual attenuation factors that create "dead zones" but here are some general guidelines for transmission rates (courtesy of Compaq Computers).

Distance from Data Transmission up to 100 feet up to 150 feet up to 300 feet

Access Point Speed up to 11.0 Mbps up to 5.5 Mbps up to 2.0 Mbps

What about Interoperability?

Interoperability means that 802.11b devices such as base stations and wireless NICs purchased from different vendors should work together. Most of the major companies are working together to make sure that their devices can be interchanged and still function. One group is the Wireless Ethernet Compatibility Alliance (WECA) that certifies interoperability of 802.11b equipment. WECA also promotes Wi-Fi as the global wireless LAN standard. By the way, 802.11 is also known as Wired-Fidelity (Wi-Fi).

About 40 companies support this group, including Compaq, IBM, Apple, Dell, Symbol and Cisco.

What About Security?

When you set up a kiosk network, it's important to agree ahead of time on security policies. The problem is that many companies won't have a good answer when your technical person asks about security. Wireless security, spec-wise, was ratified at 40-bit, a form of encryption that uses a secret key of 40 binary digits to scramble and then decode transmissions.

The encryption standard, called WEP for Wired Equivalency Privacy has since increased to 64-bit strength and will soon be 128-bit (comparable to secure browsers in the United States).

An online white paper, "Your 802.11 Wireless Network has No Clothes," analyzes the shortcomings of the current protocol. Read it. You'll learn about the two modes that 802.11 operates in: ad-hoc (also called peer-to-peer), where one machine connects to another without using a base station, and infrastructure, where machines connect to a base station.

You'll also learn how clients are authenticated and "associated" with the network in those modes. Issues with "shared key authentication" exist where configuration is somewhat left to the vendors, which can be a recipe for security holes.

Suffice to say there are still concerns and personally I am not yet ready to begin transmitting my credit card number over wireless.

Next Time...

We are going to focus on some products that are available and supported now that can be used in providing wireless communications to self-service terminals. Until then, catch you in the ether...