Scott Muellers Upgrading and Repairing Laptops, Second Edition

With the proliferation of local area networks in offices and homes , along with the ever-increasing popularity of broadband Web access and wireless "hotspots," most laptop users are now addicted to having a fast network connection for much if not all their online work. For laptops, there are basically two ways to make this connection: with a wire and without.

Wired LANs

Network access has become such a standard feature of today's computers that most new systems ”including laptops ”are now shipped with a network interface card of some type. Whether you connect with an office LAN or a home broadband modem (either DSL or cable), a network adapter is required. The only question is which one?

Early laptops did not have an easy time with network access. Users had to carry around small external boxes that connected to the laptop's parallel printer port. Later, when PCMCIA cards became available, network cards made up a large percentage of these cards sold. With the appearance of the mini-PCI bus (a smaller, laptop-oriented version of the PCI expansion bus in desktops), network interfaces began to appear in this format. For several years it was common to have notebooks equipped with a mini-PCI that included both a modem and a network interface. Because network interfaces have dropped in size and cost and have become vital features of a notebook, manufacturers now routinely install network interface circuitry on the laptop's motherboard.

10BASE-T

Not long ago, the most common type of network interface card was the 10BASE-T Ethernet card. The card got its name from the fact that it had a theoretical maximum throughput of 10Mbps, used baseband technology, and was strung together with twisted-pair cable, indicated by the T . The 10BASE-T cards were very popular because of their use of this type of cabling. Compared to coaxial and fiber- optic cables, the twisted-pair cables were very easy to work with and could be connected to interface cards and routers using simple RJ-45 connectors, which were merely larger cousins of the familiar modular phone connectors. As faster 10/100BASE-T interfaces began to get more and more inexpensive, manufacturers discontinued making 10BASE-T cards. However, many of these cards are still in use. Note that the actual throughput of these 10Mbps networks was far lower than the theoretical maximum. Actual speeds depended on the quality of the network cabling and cards. A measured speed of 6Mbps was considered good.

10/100BASE-T

The most common network interface sold today is the 10/100BASE-T card. This card can work with both 10Mbps and 100Mbps networks. In fact, both networks generally use the same cabling and connectors. As with 10BASE-T networks, 100BASE-T networks carry data at rates significantly less than their theoretical maximum.

10/100/1000BASE-T

As might be expected from its name, a 10/100/1000BASE-T network interface will work with Gigabit Ethernet (1000Mbps networks) as well as the older 10Mbps and 100Mbps varieties. As with the other types of network cards, it does suggest the actual operating speed. Currently in the desktop world, 10/100/1000BASE-T cards cost only about $30 more than the older 10/100BASE-T cards. PC Card versions of these cards will soon appear. Already some notebook manufacturers, such as Dell, are shipping notebooks with 10/100/1000BASE-T interfaces integrated onto the motherboards. As prices of these interfaces continue to decline, they will gradually supplant the 10/100BASE-T interfaces on laptops as well as on desktops.

Wireless LANs

Just as they are for desktops, wired LAN connections are enormously useful for laptops. Their only problem is that they eliminate the prime advantage of laptops ”their portability. Fortunately, wireless LANs enable us to enjoy the benefits of high-speed network access without hobbling our mobility.

802.11 Standards

A number of wireless LAN standards have been developed by various subcommittees of the 802.11 standard group of the Institute of Electrical and Electronics Engineers (IEEE).

802.11b

By far the most popular wireless standard is known by the unwieldy name 802.11b . A consortium of manufacturers called the Wi-Fi Alliance has come up with a program to ensure compliance with the 802.11b standard. Many but not all 802.11b products are Wi-Fi certified. Because it is so much easier to pronounce , Wi-Fi is used by many people to refer to 802.11b in general. Technically speaking, however, the name Wi-Fi, which derives from wi reless fi delity, should only refer to products that are certified as such.

The 802.11b standard specifies a maximum theoretical throughput rate of 11Mbps (or 1.375 megabytes per second). The actual speed depends on the environment. Some researchers have reported maximum speeds in ideal conditions at about 6Mbps. The radio frequency used is in the 2.4GHz band , which is unlicensed by the U.S. government. Some manufacturers report ranges of 300 feet for 802.11b equipment. Note, however, that as range increases , effective throughput rates drop. In a typical office environment, an effective range of about 75 feet can usually be expected, but this range can drop depending on the type of materials used in the construction of the office. Thick cement walls reduce range considerably, whereas open space extends the range. It is not uncommon for laptops in window offices looking out onto narrow Manhattan streets to have better connections with the office across the street than with their own office LANs.

Basically two types of equipment are used in 802.11b LANs: a client node, which is usually in the form of a PC Card, like the one shown in Figure 12.4, but is increasingly implemented as a mini-PCI card inside a notebook, and an access point, which bridges a wireless LAN to a traditional wired LAN. An 802.11b wireless LAN (WLAN) can be set up in two ways: either as a peer-to-peer network consisting only of client nodes, or as an "infrastructure" network consisting of both client nodes and access points (APs).

A large number of hotels, airport lounges, and coffee shops have set up small 802.11b wireless LANs as a convenience for their laptop-toting customers. These oases of high-speed wireless network access are usually called "hotspots."

Client nodes use two types of antennas. PC Card adapters have a small nub containing an antenna that extends outside the laptop's PC Card slot. This nub works fairly well, but it can easily break off. Many new notebooks are manufactured with an 802.11b antenna preinstalled around the laptop's display, which is a sturdier design.

802.11a

As its name suggests, work on the 802.11a wireless LAN standard was actually initiated before the popular 11b standard. But, because the 11b standard was a relatively minor variation of slower 2.4GHz wireless networking products that were already in existence, manufacturers were able to develop products fairly easily. By contrast, the 11a standard required new and more expensive designs to handle a higher frequency radio band that was hardly used. The 11b standard therefore had a head start and became extremely popular. The people working on the 802.11a standard seem to have put the extra time they had to good use, however. The 802.11a standard has a maximum theoretical throughput of 54Mbps, about five times that of 802.11b. Because the 802.11a standard specifies a higher frequency (5GHz), its signals are less capable of navigating around the walls of an office. Unfortunately, these two WLAN standards are not compatible.

Figure 12.5 shows a typical 802.11a CardBus adapter. In addition to its support of 54Mbps, the card supports a proprietary mode that the company claims can communicate at 72Mbps. It also supports enhanced 152-bit Wired Equivalent Privacy (WEP) and Dynamic Key Exchange to protect data from unauthorized access.

Many corporate IT staffs prefer the new 802.11a standard because of its higher speed and its ability to handle more users. The main reason for this is the number of channels available. On paper, the slower 802.11b standard offers 11 channels, but because of frequency overlap, there are in effect only three channels available for use (1, 6, and 11). By contrast, 802.11a has eight channels available. Most home WLANs and hotspots, however, use the older 802.11b standard. To bridge both types of networks, PCMCIA CardBus cards have appeared that support both types of networks. Recently some combination mini-PCI cards have become available and are being incorporated into notebooks. Note, however, that the two incompatible WLANs use two different types of antennas. To be ready for a combo 11a/11b mini-PCI card, the manufacturer must design in two separate antennas.

802.11g

In many ways, the 802.11g standard is a compromise between 11b and 11a. Its original specification provided twice as much speed as 11b but is still compatible with it. Although not quite as speedy as 11a, this standard has steered clear of its potential compatibility problems.

The 802.11g standard uses the same 2.4GHz frequency as 11b and has about the same range. As I write this, 11g cards are just starting to become available. In view of its compatibility, it will no doubt eventually replace 11b. We will probably soon see combination 11a/11g cards. But even as products are just becoming available, the standard is already evolving into a higher-speed version.

54g

A company called Broadcom, which provides the chipsets for many wireless LAN card manufacturers, announced a high-speed improvement on 802.11g. This new variation, called 54g, provides a maximum theoretical throughput of 54Mbps ”the same as that of 802.11a. Therefore, 54g equipment can provide the speed of the 11a standard and yet still be compatible with 11b hotspots. Note, however, that 54g cards share the same crowded 2.4MHz radio frequency band as that used by multitudes of 11b networks, not to mention wireless phones and microwave ovens. Go to www.54g.com for more information. In early 2003, the 802.11g standard was amended to incorporate the 54Mbps transmission speed of 54g.

You can see a typical 54g notebook adapter in Figure 12.6. Note the metallic band on the left with a row of small protrusions, which is indicative of a high-speed CardBus PCMCIA card. The CardBus connection is required by this high-speed wireless LAN technology. On the right, note the antenna nub, which can extend out the side of the laptop.

Wi-Fi Alliance

As mentioned previously, the Wi-Fi Alliance was set up by certain manufacturers in the wireless LAN industry to certify compliance with the 802.11b standard. All Wi-Fi-certified products are compatible with 802.11b, but not all 802.11b products are Wi-Fi certified. Because Wi-Fi is so much easier to pronounce, it is often used in place of 802.11b, without regard to the certification it was intended to denote.

Wi-Fi5 Alliance

Just as with the Wi-Fi Alliance and the 802.11b standard, a similar compliance certification effort has been set up for the 802.11a standard called Wi-Fi5, the 5 standing for the 5GHz radio frequency used by the 11a standard. Unlike Wi-Fi, however, the term Wi-Fi5 has not caught on as a synonym for 802.11a.

Bluetooth

The primary feature of mobile computers and phones is that they are untethered. They can perform without any cables ”in theory. The fact is, however, that mobile equipment is often hobbled by smaller cables of its own. For example, you might have a cable connected between your cell phone and your laptop, or between your cell phone and a headset.

The Swedish electronics giant Ericsson has sought to get rid of these cables with a short-range or personal wireless networking standard called Bluetooth. The odd name comes from a Danish Viking king who lived 1,000 years ago and obviously had unusual dental characteristics.

Bluetooth has a relatively short range of about 10 feet and an effective data throughput of about 1Mbps. With these specs , of course, it will never compete with any of the 802.11x WLANs, but it is not meant to. Instead, it is designed as a simple, low-cost network for one's own personal devices.

Although the goals behind Bluetooth are admirable, the technology has not caught on. Many compatibility issues arose with the initial v.1.0 release of the spec, causing the industry to issue a v.1.1 version of the spec. Products that conformed to the new spec were indeed more compatible, but not with any of the v.1.0 products. Indeed, compatibility testing was hindered by the fact that there were so few Bluetooth products to test. To date, only a handful of notebook computers have been equipped with Bluetooth transceivers, and if significant numbers of Bluetooth peripherals do not appear soon, this interesting wireless standard will go the way of the Viking longboat.