One or two proprietary products use infrared light to send data. Other than infrared links between laptops and PDAs, you will probably never encounter infrared products outside the specialized environments in which they are used, such as for industrial controllers.

If you have never had to run Ethernet cable, then you can rejoice in your good luck and go skipping into the future free of the emotional (and sometimes physical) scars that many of us carry from years of pulling cable through walls or under houses. If, like me, you suffer from Post Traumatic Ethernet Disorder (PTED), then take heart you have pulled your last Cat5 cable. From this point on your computers are going to be free and untethered.

Wireless networks operate in the unlicensed band of the radio spectrum, typically 2.4 GHz or 5 GHz.

You need three things to set up your first wireless network:

- At least two computers

- A wireless network interface adapter (one for each computer)

- A wireless access point (at least one)

Wireless Network Interface Adapters

Like the Ethernet card on a wired network, the wireless network interface adapter translates between your computer and the network. The network interface adapter is frequently called a network interface card, or NIC. Your computer and the network speak different languages, called protocols, and the NIC acts as an interpreter.

Wireless network interface cards come as PC cards, USB adapters, compact flash cards, or PCI/ISA cards. Each computer on your wireless network needs an adapter.

Wireless Access Points:

A wireless access point (AP) connects wireless devices on your network to each other. Every wireless local area network (WLAN) needs at least one AP. An AP is usually the most expensive piece of hardware in a WLAN (other than the PCs, of course). Prices on wireless products have been coming down, with APs currently ranging in price from $80.00 for a bare-bones AP to over $300.00 for an AP with advanced features.

The main types of adapters are Compact Flash (CF) and Secure Digital (SD). The next section covers these types in more detail but for now you need to know which type of card your PDA accepts to avoid buying the wrong one. The type of card slot your PDA is equipped with is usually listed on the package, in the user manual, and, for some devices, printed on the adapter slot.

Note: You can use CF and SD cards to provide storage or, in the case of wireless adapters, PDA cameras, and even PDA musk players, to add functionality to your PDA. The CF and SD standards describe the physical dimensions of the card and the electrical interface, not the card's function.

There are other types of cards, such as Type H and Type BI PC cards (PCMCIA), but these are not supported by the majority of PDA manufacturers. For a while, CF cards were the dominant adapter, but SD card adapters have caught up and may eventually surpass them in popularity.

Many newer PDAs have Bluetooth functionality built into them and a few even have integrated Wi-Fi, so you won't need to buy a separate adapter. If you choose a Wi-Fi-enabled PDA, pay attention to which standard it supports. An 802.11b or 802.llg PDA will be able to connect at more hotspots than an 802.1 la-enabled PDA will.

There are cellular adapters available for PDAs, too. These are usually CDMA, GSM, or GPRS. If you choose a cellular adapter, you will have the widest coverage and will be able to connect in more places than with Bluetooth or Wi-Fi, but you will also have to subscribe to a cellular carrier that supports the device you have purchased. If cellular is the way you want to go, choose a carrier first and then get the device.

The IEEE produces standards through consensus-based working groups. When the IEEE approves and publishes a standard, industries use it as a blueprint for developing compatible products, processes, or solutions.

Because of IEEE standards, we have the ability to choose between different vendors for WLAN equipment, or even good old Ethernet equipment (IEEE 802.3x standard). The alternative would be multiple incompatible standards and proprietary technologies. In short, because of IEEE standards, you can shop around for great deals, mix and match equipment (to some extent), and be sure that your IEEE 802.1 Ix WLAN will operate.

The Wi-Fi alliance promotes the use of wireless technology worldwide by encouraging manufacturers to comply with the 802.1 lx standards when designing their networking products. The Wi-Fi Alliance also promotes 802.llx technology to home, SOHO, and enterprise consumers, has networking products independently tested to ensure that they are compliant with the 802.llx standard, and tests interoperability between certified products.

If a network component carries the Wi-Fi certified logo, it operates with other Wi-Fi certified products that operate in the same frequency range. This gives consumers a choice when shopping for WLAN products, enabling you to mix components from different manufacturers when building your WLAN.

on the web: For more information about Wi-Fi, visit the Wi-Fi Alliance Web site at
www.wi-fi.org.

Standards address different aspects of wireless networking. Some refer to frequency and encryption while others address quality of service or are extensions of previously existing standards. Standards define each of the three layers of a WLAN network model: infrastructure, Media Access Control, and physical.

Note: I refer to the standard 802.11 protocols as 802.11 x, except where I am speaking about a specific standard (for example, 802.11 b), and I use the term Wi-Fi in reference to the standards 802.11 b, 802.11a, and 802.11g.

Performance and Interoperability:

For WLAN devices to operate on the same network, they must use compatible standards and operate on the same frequency. Even though they are both Wi-Fi standards, 802.11b (2.4 GHz) products do not communicate with 802.11a (5 GHz) devices. They don't broadcast on or listen to the same frequency channel.

When designing your WLAN, be sure to purchase devices that operate on the same frequency and that adhere to the same standard. Some incompatible standards that share the same frequency with 802.llx devices can interfere with data transfer on a Wi-Fi network.

Insider insight: Although 802.11 x devices operate only with compatible devices that use the same frequency band (such as 2.4 GHz), certified products that can operate in both the 2.4 GHz and 5 GHz frequencies have recently reached the market This means that a dual band AP can communicate with an 802.11 b or 802.11a NIC If you have existing WLAN equipment, purchasing a dual band AP would enable you to upgrade to a faster 802.11a (more expensive) network in stages, while still being able to use your older (and much cheaper) 802.11b hardware. In the future, these dual band devices are likely to dominate because of the extended functionality they offer.

Physical Layer Standards

You only need to concern yourself with physical layer standards when deciding on a standard to use for your WLAN; The 802.11 specifications currently describe three physical layer standards for WLANs: 802.11b, 802.11a, and 802.llg. These standards have risen to dominate the market. Adding to the confusion, IEEE did not approve these standards in alphabetical order: 802.11b predates 802.11a.

802.11b:

Also known by the consumer-friendly name "Wi-Fi" (Wi-Fi now also includes 802.11a and 802.11g), 802.11b came on the scene in 1999, competing with the rival standard HomeRF. 802.11b has since risen to dominate the home and SOHO market. The result is an abundance of 802.1 lb-compliant devices available to consumers. This means that the cost of 802.11b equipment is relatively inexpensive.

802.11b devices operate in the unregulated 2.4 GHz radio band, which means that unlike a ham radio, consumers do not need a license to operate the equipment. Although 802.11b allows for operation of 11 channels within the spectrum, devices usually utilize three to limit interference between access points. The maximum link rate is 11 Mbps, but heavy traffic on the same channel can significantly reduce maximum throughput. The data rate also decreases the farther you get from an access point (AP).

Insider insight: Marketing departments often use the terms data rate and throughput changeably when promoting the speed of a networking device, or use data rate as if it were the actual speed when it really represents the capacity. This has led to a lot of confusion, even among IT professionals, so you're in good company if this has left you scratching your head.

Data rate refers to the number of bytes of data transferred in a specified unit of time. For example, an 802.1 lx device operating at 11 Mbps (millions of bits per second), has the capacity to deliver 11 Mbps of data. The data rate is not the true measure of speed on a WLAN, or any network for that matter.

What really measures speed and performance is the throughput of a connection. You can calculate throughput by determining the amount of information sent over time. Many factors affect throughput, including number of users on a WLAN, interference, and latency of connections {latency is the amount of time it takes for data to travel between devices)

Throughput is always less than data rate, without exception. Often, actual throughput is less than half the data rate; therefore, users on an 11 Mbps WLAN may have an actual throughput of 6 Mbps or less. Being able to distinguish between these two terms will aid you when designing your WLAN, and will help you make smart buying decisions

802.11b also shares the 2.4 GHz band with other consumer electronic devices, including cordless phones and microwave ovens. When operating, these devices may interfere with 802.11b WLAN function.

802.11:

Another Wi-Fi standard, 802.11a, operates in the 5 GHz radio band, which is free from interference from other household electronic devices (for the time being). It has a maximum throughput rate of 54 Mbps almost five times faster than 802.11b. Unfortunately, 802.11a can only achieve this speed at a short distance from an access point; less than 30 feet is a good approximation. If you need to cover a wide area with Wi-Fi access, 802.11a may not be the best choice unless you are willing to invest in multiple access points.

Because it operates on a different frequency, 802.11a is not backward compatible with 802.11b, and upgrading requires you to purchase new equipment. Dual band equipment is available, these devices can operate on both 802.11b and 802.11a networks.

802.11g:

This is the newest addition to the 802.llx physical layer standards. 802.11g is an extension to 802.1 lb and provides the throughput of 802.11a, but operates in the same 2.4 GHz band as 802.11b. 802.llg is backward-compatible with 802.11b and devices for both standards can coexist on the same WLAN. However, for full throughput speed on a computer using 802.llg cards, you must have an 802.llg access point. An 802.llg access point can communicate with slower 802.11b cards, enabling you to continue to use them and upgrade as you see fit. 802.llg is susceptible to the same interference issues as 802.11b because it operates in the same 2.4 GHz band.

Insider insight: Because it offers the same speed advantages and is backward-compatible with 802.11 b, you may think that 802.11 g is a good alternative to 802.11a. In some cases it is, especially in a small WLAN in a home or SOHO environment, but when system capacity is important; 802.11a has the advantage. 802.11a has more channels available and can support more traffic. In a busy network environment 802.11a is a better choice, and ensures that you will be able to run mission-critical applications.

A wireless repeater can be a good solution to extend the range of an AP to areas of your house where the signal degrades due to distance or interference. However, clients communicating through a repeater typically get only half of the normal throughput of the WLAN and sometimes less. This is because a repeater has to handle each packet of data twice when transmitting and receiving between the access point and the client PC. If you don't move a lot of big files around on your network, this won't be too much of a problem

There is one thing to consider, though. When put in repeater mode, most access points no longer allow themselves to be administered via a wireless connection. You will have to connect to the repeater/AP through an Ethernet port to make changes or administer it. Keep this in mind when you are choosing a location for your repeater because you'll want to be able to reach it when necessary.

The antenna is one of the most important parts of your WLAN. Without antennas, the signal wouldn't get anywhere and you certainly wouldn't receive anything. Still, most people have no idea how an antenna works or which antenna is right for a particular job. This section addresses both of these questions and helps you make the right choices.

GPS satellites circle the earth in a very precise orbit and transmit signals to earth. GPS receivers receive this signal and, by calculating the time it takes to receive a signal from at least three satellites, triangulates the receiver's location anywhere on earth. If the GPS device receives a signal from at least four satellites, it can determine the user's altitude in addition to latitude and longitude.

With a GPS device, you can usually determine your position to within a few meters. Using a GPS device in conjunction with a wardriving setup, you can map the location of discovered networks as your sniffer discovers them. Your best bet is to use a National Maritime Electronics Association (NMEA) compliant unit, with a serial connector. Many popular GPS units are NMEA-compliant, including some Garmin units, although they require you to enable that option (by default Garmin units use their own proprietary format).

Depending on the sniffing software you use, the GPS data recorded by the sniffer usually corresponds to the location of the strongest signal. You can export location data from your sniffer into mapping programs, such as Microsoft Map Point 2004, and create location maps.

Increasing the power of your signal increases your access point's range, which enables clients that are further away from an AP to connect at a higher rate than they were originally. However, amplifying your AP's signal is not a perfect fix and has its own drawbacks.

First, when you amplify the power of a signal, you also are amplifying any noise that was originally present in the signal as well. This usually won't cause problems for most clients on your WLAN, but it can affect connectivity and quality of service for clients with a weak signal.

Adding an amplifier to an access point only increases the output signal of that unit; it doesn't improve reception of the signal from wireless clients. If you are trying to improve service for clients with a weak signal, and then an amplifier only takes care of half of your problem. Because Wi-Fi networking requires two-way communication, your best bet may be to add a high-gain antenna. An antenna doesn't add noise to the signal and improves reception of client signals at the AP.

Boosting your signal also may extend it to neighboring houses or apartments. This can cause problems in two ways. First, it is more likely that your WLAN will be discovered and possibly used by wardrivers or neighbors. Second, you may interfere with the operation of a neighbor's WLAN and get an angry knock on your door (or head) as a result.

Both of these problems can be fixed both by properly securing your WLAN and by using directional antennas to minimize propagation of your Wi-Fi signal outside the boundaries of your property.

The Google WAP page has limited functionality compared to the HTML version, and it doesn't support some advanced features like spellchecking. Another difference is the search results; the Google WAP page only returns results for pages that you can access from a WAP browser. Makes sense, doesn't it?

Information on the wireless Web is also organized into several portals that make finding related information easier. An example of a wireless portal is the MSN Mobile portal. The MSN Mobile portal lets you access Hotmail, Messenger, MSN alerts, ring tones, and more. The site is organized so that you can get around quickly and easily. A WAP portal can help you save time by giving you access to things that you need all in the same place.

The problem you are having is that the receivers you can't control are on a different leg of your house's electrical circuit than your controller is. In the U.S., most houses have a 220-volt power supply that enters at the house's circuit breaker panel and then splits into two separate 110-volt phases.

The signal from your controller is having trouble going from one phase to the other. There are two ways to deal with this; one is to hire an electrician to install a hardwired signal bridge across the breaker for each phase. The other way is to install an X10 phase coupler/repeater.

An XI0 phase coupler plugs into 220V dryer outlet and allows XI0 signals to cross both 110V phases

An X10 phase coupler/repeater plugs into a 220-volt outlet like the kind used for electric clothes dryers. The 220-volt outlet is one place where both 110-volt phases meet. The coupler/repeater transmits the X10 signal across both phases and boosts the signal to help ensure reception on the opposite phase. You can also get a phase coupler that doesn't repeat the signal but does bridge it across both phases. (Your dryer plugs back into the 220-volt outlet through the phase coupler.)

Maintaining Your Security and Privacy:

Like any wireless technology, home automation has its own set of security problems, whether it involves wireless cameras or power line home control units.

The PC used as an SAP must remain running and available or network clients will be unable to connect. If you are sharing an Internet connection, the computer acting as the SAP may have to run connection-sharing software (see the following section, "Secret #30: Sharing an Internet Connection via Software") to enable clients to connect to the Internet if the computer also is directly connected to the Internet. For best performance, a hardware AP is a better selection, but if you can't afford one or need a quick substitute, an SAP is a possibility. Even then, the PC running ICS software and sharing the Internet connection should be dedicated to that purpose for best performance.

Insider insight: Because signals travel at the speed of light latency increase due to distance is not noticeable on a WLAN. Latency caused by distance is only an issue if the signal is traveling extremely far, as with a satellite Internet connection.
Even then, the latency increases only by a few hundred milliseconds.

Latency caused by retransmission of lost and corrupt packets increases because the weaker signal is subject to greater interference than a strong signal would be. Because of this, users at the edge of an access point's coverage area are more likely to experience "slower" throughput than those positioned closer to the access point.

This is the reason that you can set the minimum connection speed high as a security measure. Fast connections require a strong signal, and a strong signal usually requires that you be reasonably close to an access point. If you require WLAN clients to connect at a high speed, war drivers are less likely to be able to connect without getting close to your home or building, and making themselves obvious.

Increasing signal strength

Now that you have more information than you wanted to know about the problems of signal strength, here are some suggestions for boosting your signal. Most solutions for extending a WLAN require increasing signal strength by some means. If done correctly, with full consideration for the risks and drawbacks, increasing signal strength is an easy way to increase the coverage area of your network. This section helps you decide whether this is the way you want to go, and, if so, how to determine the best way to achieve it.