Demystifying Wireless Standards

In the past few years, the marketplace for WLAN products has grown at an incredible rate, with organizations introducing new standards and improving existing ones. This hasn’t made wireless networking any less confusing for the average consumer. The Wi-Fi Alliance adopted the term Wi-Fi because it is less confusing than the series of numbers used to define the various wireless protocols. Still, it’s necessary to under- stand the principal wireless protocols to avoid confusion and costly mistakes.

For wireless devices to operate on the same network, they must use compatible standards and operate on the same frequency. For example, even though 802.11b and 802.11a are both Wi–Fi standards, they can’t communicate or interoperate because these standards don’t use the same frequency band or technology.

Note 

Wi-Fi devices operate only with compatible devices that use the same frequency band (such as 2.4 GHz or 5 GHz), but there are certified dual-band products that can operate using both frequencies. These dual-band devices contain both 802.11a and 802.11b transceivers and can communicate with devices using either standard.

Introducing 802.11: At the base of it all

First introduced in 1997, 802.11 consists of the family of wireless standards developed by the IEEE. Currently three primary physical layer standards exist within 802.11. Physical layer standards describe the network medium and the mode of transmission; in the case of Wi-Fi the physical standards describe the frequency band, and the transmission technology used to access and communicate on the network operating in that band.

The physical layer standards are 802.11a, 802.11b, and 802.11g. When you’re shopping for Wi-Fi gear, these are the standards that you’ll encounter. Other standards, like 802.11i, describe different aspects of wireless networking, and you don’t really need to know them unless you’re an IT professional.

Explaining 802.11b

802.11b was the first 802.11x protocol introduced, actually appearing prior to 802.11a (the IEEE didn’t release the standards in alphabetical order). Wi-Fi has risen to dominate the home wireless market, and because 802.11b has been around the longest, there is an abundance of 802.11b gear available. This means that 802.11b equipment is inexpensive compared to 802.11a and Wireless-G devices.

802.11b devices operate in the 2.4GHz radio band, with a maximum capacity of 11Mbps. Heavy traffic on the same channel can significantly reduce throughput, and speed can decrease the farther you get from an access point. 802.11b divides the 2.4GHz network into 11 channels, although devices in a network usually utilize three in order to limit the chance of access points interfering with one another.

Other consumer electronic devices, including cordless phones and microwave ovens, also use the 2.4GHz band. When operating, these devices may interfere with 802.11b WLAN functions. If you already own other 2.4GHz devices, you may want to consider this before deciding which wireless standard to use.

Cross-Reference 

I discuss ways of dealing with radio frequency interference (RFI) in Chapter 8.

Comparing 802.11a

802.11a operates in the 5GHz band and has a maximum capacity of 54 Mbps, almost five times faster than the maximum capacity of 802.11b. Realistically, 802.11a must be close to an access point to achieve maximum throughput. Compared to 802.11b and Wireless-G, the range of an 802.11a access point is significantly shorter. Because of this, 802.11a isn’t the best choice for providing Wi-Fi access to a wide area, unless you are willing to invest in multiple access points so that the signal reaches all clients.

802.11a devices aren’t compatible with 802.11b devices, because they operate on different frequencies and use different technologies. If you have an existing 802.11b network, you’ll have to purchase new equipment for every network client.

Speeding up with 802.11g

802.11g, or Wireless-G, is the newest 802.11x physical layer standard. 802.11g has the same maximum throughput as 802.11a, but operates in the 2.4GHz band along with 802.11b. Wireless-G is backward compatible with 802.11b, and devices for both standards can interoperate on the same wireless network. An 802.11g access point can communicate with 802.11b cards, so you can upgrade your clients incrementally; but to take advantage of full Wireless-G throughput, all of your clients and access points must be Wireless-G devices.

Note 

Although Wireless-G is backward compatible with 802.11b, you’ll notice slower WLAN throughput on a network with mixed clients and access points (Wireless-G and 802.11b) than in a homogeneous network built only with Wireless-G gear.

Better security with 802.11i

Wired Equivalent Privacy (WEP) is the original Wi-Fi encryption algorithm used to secure communication on 802.11x networks. Experts defeated WEP, making it useless (well almost, but not entirely). In response, the IEEE began to develop 802.11i, the next Wi-Fi security standard. 802.11i addresses security concerns in Wi-Fi and improves encryption, user authentication, key management, and distribution.

Meanwhile, the Wi-Fi Alliance has developed and introduced Wi-Fi Protected Access (WPA) as a replacement for WEP. The Wi-Fi Alliance based WPA on a subset of the 802.11i standard, and WPA provides better security than WEP. If possible, you should upgrade your gear to use WPA.

Note 

Although WPA is a great improvement over WEP, it isn’t perfect. There are ways that an intruder can defeat WPA, but these are more the result of poor password and passphrase selection by users and not flaws in WPA itself. Refer to Chapter 10 for WPA best practices.

Wireless-G versus 802.11a

Because it offers throughput comparable to 802.11a and is backward compatible with 802.11b, Wireless-G can be a good alternative to 802.11a. Wireless-G has price and performance advantages over 802.11a, especially in a small home or office network; but when system capacity is important, 802.11a has the advantage. 802.11a has more channels available and can support more traffic, which is why it’s a good choice in many enterprise environments. For mission-critical applications, 802.11a is a better choice.

Speeding toward the future with 802.11n

IEEE has recognized the 802.11n working group, which has begun developing the next 802.11x physical layer standard. The IEEE should introduce 802.11n by 2006 and expects it to provide up to 100 Mbps of actual throughput, not just 100 Mbps data rate. For example, the data rate for Wireless-G is up to 54 Mbps, but the actual throughput is often less than half of that.

Expanding with Bluetooth and 802.15.1

Bluetooth is a wireless personal area network (WPAN) technology developed by the Bluetooth Special Interest Group, an industry organization founded by Nokia, Ericsson, IBM, Intel, and Toshiba. Developers named Bluetooth after a twelfth- century king, Harald Blatand (Bluetooth), who unified Denmark and Norway. The goal of Bluetooth technology is to enable users to connect many different devices simply and easily without cables.

Although Bluetooth operates in the 2.4 GHz band, it doesn’t compete directly with Wi-Fi because it is too slow (1 Mbps) and its signal range is too short for a WLAN. Bluetooth devices coexist peacefully and occasionally interoperate with Wi-Fi networks.

Bluetooth connects devices and peripherals without annoying cables. You can already purchase keyboards, mice, printers, digital cameras, and PDAs that employ Bluetooth technology. Bluetooth has even found its way into some automobiles as a way to connect digital music players to the car’s stereo system.

Bluetooth devices can connect and create small ad hoc networks called piconets. In each piconet, the device that first initiates the connection becomes the master device. Each master device in a piconet can manage up to seven slave devices. Figure 1-8 illustrates a master and six slaves, leaving room for one additional device.

Figure 1-8: A Bluetooth piconet

A device can be a member of multiple piconets at one time, but can only be a master in one. Scatternets are piconets connected by one or more devices (see Figure 1-9). A scatternet may contain 10 fully loaded piconets at any one time.

Figure 1-9: A Bluetooth scatternet

Bluetooth is a useful and complementary technology to Wi-Fi, and you will begin to see it integrated into more devices every year. You can upgrade your printers and some other peripherals to use Bluetooth by installing small Bluetooth adapters. These adapters are inexpensive, with some costing less than $20.