In some circumstances, you might not be able use Wi-Fi in your home. You may have PCs that are so spread out that one access point will not cover them all. You may have a remote building, such as a barn, garage, or shop that you’d like to include. You may have already installed an isolated wired home network of some kind.

The term wireless usually refers to radio, but it can also be used to mean “no new wires.” Other ways exist for connecting your PCs without resorting to planting new utility poles on your property or drilling holes in the walls.You can interface these other media to a Wi-Fi access point to utilize the advantages of all of them. We’ll start with the simplest.

Infrared Links

Many PCs and personal data assistants (PDAs) are equipped with infrared ports, which transmit data between themselves in the same fashion that your TV remote control uses: over a modulated beam of invisible light.

These are fine for communicating from one to another, as long as they are in a line of sight, usually sitting right next to each other. Bright sunlight, however, can interfere with the signal. You can buy infrared adapters based on the Universal Serial Bus (USB) for desktop PCs, and some adapters will pick up diffused signals that have bounced off a wall.

But infrared ports cannot be used around corners or from room to room, as is the case with Wi-Fi. This also means that someone outside the house cannot pick up the signals, as is the case with Wi-Fi.

The transmission speed varies between 1 and 4 Mbps, depending on the manufacturer and on computer placement. The process of transferring files over a light link is known as beaming, and updating files back and forth is called synchronization.

Telephone-Line Home Networks

If you are reluctant to install computer cables, you can utilize the ones that the telephone company has already put in to connect your PCs. Your existing phone lines can be made to carry data as well, using the same technique (but not the specific audio frequencies) that DSL employs.

The process of using an impressed carrier signal to interface PCs in this way is known as the Home Phoneline Networking Alliance (HomePNA) method. With a HomePNA network, you can talk on your telephones and share resources over a network at the same time. The HomePNA interface cards will not interfere with a DSL connection.

About 50 devices can be connected to a phone-line network within a home while still maintaining the 10 Mbps speed. Additional devices can also be added, but may result in overall slower network speeds. The maximum separation between computers is about 1,000 feet. Your network should cover less than 10,000 square feet, an area that is larger than most homes.

Home phone-line networks use an inaudible carrier signal on the line that (usually) doesn’t interfere with voice communications or faxes. Specifically, the technique is called Frequency Division Multiplexing (FDM). FDM puts computer data on separate, discrete frequencies intended to avoid interference.

The protocol involved is a derivative of Ethernet, using a proprietary compression technique. It also uses Ethernet’s method of avoiding interference from multiple stations sending at once. This is abbreviated with the lengthy acronym CSMA/CD, which stands for Collision Sense Multiple Access with Collision Detect.

Simply put, each station listens for a clear channel before it starts transmitting. If the line is busy, the station will wait a random interval before trying again. The technical challenges to overcome are considerable, given the medium involved.

Unlike CAT5 wired networks that are built to exacting standards, a phone-line network can change randomly. Users can plug and unplug telephones and other devices, complete with extension cords. Every time this happens, another “branch” is grafted onto the phone-line wiring “tree.”

A transmitted signal is dampened and scattered as it reverberates on the wiring. In addition to added loads, the lines are sometimes unbalanced, or unterminated, as some phone sockets have nothing plugged in. The lines pick up high levels of noise from appliances, heaters, and air conditioners.

Finally, the interfaces must peacefully coexist with the customer’s existing equipment and with the telephone company’s gear, as mandated by the Federal Communications Commission (FCC). Nonetheless, it works well in 99 percent of the homes in which it is employed.

Network adapters for your home area network (HAN) are available in the usual variety of form factors: internal bus network interface cards (NICs) and USB connectors, but also the less common parallel port connectors. They are priced about the same as equivalent Ethernet components.

Every computer so networked must be placed near a telephone jack. If you aren’t totally opposed to running new wires, you have the option of running telephone cable from one room to another through the walls or along baseboards. You also have the option of using a telephone extension cord to daisy chain your PCs together and not use the in-wall wiring.

ability between different manufacturers. The equipment is available in 19 European nations as well as North America. The first of their standards was version 1.0, which transmitted data at a rather slow 1 Mbps. The latest is 2.0, originally developed by Broadcom, which sends at 10 Mbps.

The faster adapters will work with the slower ones, which are still on the market. A newer third-generation (3G) Home- PNA specification promises to deliver quality of service (QoS) at a throughput rate of up to 100 Mbps. HomePNA equipment has the following characteristics:

• It is standardized and interoperable, reliable, easy to install, and relatively cheap.
• If you don’t mind peer-to-peer mode, you can use it without buying other gadgets, such as hubs.
• You can interface it with other network technologies.
• It is available for Macs and older Wintel PCs.