Physical Planning for Wi-Fi Home Network

We will assume from here on that you’ve decided on Wi-Fi as the way to make your network. Even if you have an existing network using one of the other technologies, you can add Wi-Fi to it easily using CAT5 patch cords.

RJ-45-type connectors are a common denominator for all home network types. A Wi-Fi router, for example, will typically have four RJ-45 ports to accept input from wired PCs or other wired LAN hubs. As with the other wired methods previously described, every PC on your Wi-Fi network must have a specialized hardware interface.

These come in different shapes and sizes to fit the different PCs they were designed to work with. Special-purpose printer-sharing interfaces are also available. Modern PCs, especially laptops, come pre-equipped for Wi-Fi from the factory. The interfaces perform the same functions as for their wired equivalents, but they also include a small high-frequency radio transceiver and antenna.

Wi-Fi can be useful even if your home remains cut off from the World Wide Web. You may want to wirelessly connect your local PCs, laptops, and printers in the simplest way, which is called ad hoc mode. Each node communicates directly to every other node, as they might with infrared.

But because the medium is radio, they can all send and receive from room to room or around corners. When sharing data in this fashion, your PCs become a peer-to-peer network. This is one of the advantages of Wi-Fi. A group of business travelers who meet in a lobby or a customer who walks into your home office can immediately become a part of a network you create at a moment’s notice.

The alternative method of organization is known as infrastructure mode. If your Wi-Fi interfaces are configured this way, they will look for a central point at boot time and use that to relay data to the other devices on the wireless network. They will not communicate with the other stations, wired or otherwise, except through the wireless base.

While doing so, they divide the base station’s maximum throughput of 11 Mbps between them. Base stations can handle 50 or more wireless clients, but not if they are all trying to talk at the same time.

Once the wireless router station receives data, it selectively channels it out of the wired ports at whatever rate the destination station can accept. If the wireless router station is sending to wired PCs, this is most likely 100 Mbps.

If it is sending to the Internet over a DSL modem, the rate is 10 Mbps even though the modem can only communicate to the Internet at 1.5 Mbps. In every case, the chain of interfaces is only as fast as its slowest link.

You should give some thought to your system’s layout before you place the equipment. All your stations should be within the pickup pattern, but the pattern should not extend past the borders of your house. If you are starting from scratch, you can put your base station, be it access point or router, in a midpoint location.

If you already have a wired network, then you will probably want to centralize your Wi-Fi base station close to the existing hub. Likewise, it is often easier to move a wireless base closer to a DSL modem than to move the modem. In any case, you can connect nonmobile devices to a distant base station with a 100 Mbps LAN cable.

A connecting patch cord’s maximum length is 100 yards. That should be enough for all but the largest homes. Usually, long patch cords are unnecessary. Remember that walls, ceilings, floors, and other barriers will interfere with the signal and decrease the range.Wi-Fi is sometimes called a two-wall technology for this reason.

A typical line-ofsight range is given as 300 yards maximum, but it is actually hard to guess because the high-frequency signal bounces more than it is absorbed. At the very high frequency of 2.4 GHz:

  • Vinyl walls are radio transparent.
  • Drywall or wood paneling passes the signal, giving a range through five or six walls.
  • Cinderblock walls allow enough signal strength for three or four walls.
  • Precast concrete walls limit the range to one or two walls.
  • A metal wall, metallic wallpaper, aluminum-covered insulation, or chain-link fences block the signal.
  • Remember that most walls have metal pipes and wires in them. Stucco has embedded wire mesh

Other factors can spoil your plans, but you can do some quick tests first to ensure that your home PCs will work on the first try. Laptop PCs often come with Wi-Fi hardware and software built in, so if you have a laptop or can borrow one, they make ideal, simple test instruments for your less mobile desktop PCs.

Just call up the signal strength screen from the interface’s configuration menu and check out the site you plan to use. The antennas in laptops are typically less efficient than those attached on desktop wireless cards. If you get a strong signal from a laptop at a given location, then you should have an adequate margin for your desktop station as well.

Be aware that signal propagation on the 2.4 Ghz band is somewhat unpredictable, particularly at the weak fringes of the coverage pattern. As the signal degrades, the link will slow down to maintain the wireless circuit. Workstations that require high, dependable throughput, such as servers, should be closer together.

Those that are used for slower applications, such as email, need not be so close. Because the operating frequency is so high, it reflects off metal surfaces like a radar beam. Remember that the rear of most desktop PC chassis is metal so you may have to do some readjustment, particularly if your PC is backed up against yet another metal surface, such as a refrigerator or file cabinet.

One workaround for this problem is to use USB-compatible Wi-Fi interfaces for your desktops instead. These offer a few advantages over wired-inplace interface cards:

  • They can be unplugged from one PC and relocated to another USB PC on the fly.
  • The base antenna is at the end of a cord and can be easily moved for best coverage.
  • You can use it to interface a peer-to-peer Wi-Fi home network to a software Internet proxy.
  • It’s compact. You can use it in the corporate office and carry it home as well.