1.8. Identifying Wireless Service Performance Factors

Since wireless services are continuing to grow in popularity, we are beginning to see wireless devices used in many different types of environments. While most wireless protocols work properly in the "perfect environment," most of them also become challenged in the real world. In this section, we discuss the real-world factors that affect wireless communications.

1.8.1. Critical Information

You should know the factors that might affect the range and speed of wireless device that you use. In this section, we discuss the most common of these factors.

1.8.1.1. Radio Interference

To understand how radio interference can be a problem in a wireless network, you have to consider the access method that the wireless network uses: Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). This means that a device will wait until no other device appears to be using the frequency before it sends its data over the frequency. If the network is close to an operating 2.4GHz phone, a microwave oven, or a Bluetooth device, it might sense that the network is in use and wait for the offending interference to subside before it sends its data. Also, if the interference is sporadic, the communication might be interrupted during a transmission. This would cause the data to become corrupted and would force the device to resend the data. In this case, the device might still operate but much more slowly than normal. To keep radio interference from affecting your networks, identify the sources and try to eliminate them wher-ever possible. Also, keeping devices in close proximity to the WAP will help to reduce the effects of interference, since the true signal will overpower the interference.

1.8.1.2. Antenna Type

Because your wireless network operates using radio waves, the sensitivity of the antenna that is used in your network can increase the range and speed of the communication. A huge variety of antennas are available from commercial sources. These include directional and omnidirectional models for indoor andoutdoor use. Network enthusiasts have even developed operational antennae from common household objects such as a tin can or an emptied potato chip can. The type of antenna that you use in your network will depend on the placement of the computers that require connectivity to the network. Often, the antenna that is built into the WAP is the only antenna that you will need.

1.8.1.3. Environmental Factors

While radio waves do not require line of sight in order to communicate properly, they are affected by some environmental factors. Simple factors such as the materials with which the building was constructed can affect the range and speed of your wireless network. Since you cannot see the radio waves, you have to experiment a little to determine the best method of deploying your WAPs.

You can begin experimenting by placing WAPs in "best guess" locations and then walking around your network with a laptop equipped with a wireless NIC to determine where the signal is strongest and where it becomes weak. You can then change the location of a WAP or add another WAP as you begin to get a sense of the network's tendencies within your building.

Another way to optimize your network is to purchase equipment that will provide a spread spectrum analysis of radio transmissions in your building in a graphical format that allows you to "see" the radio waves as they travel through your building. This type of equipment can also identify and isolate other types of radio waves that might cause interference in your network. In either case, your goal is to eliminate as much interference as possible and keep signal strength to a maximum wherever possible.

1.8.2. Exam Essentials

Know the factors that might affect the range and speed of your wireless network communications. The range and speed of the network might be affected by interference, antenna types, and environmental conditions. You should be able to identify options that might improve these characteristics within your network.

Describe how wireless networks are affected. Wireless networks might be affected by such factors as interference, antenna type, and environmental factors. Be familiar with the methods of troubleshooting these factors to provide for the maximum range and speed of your wireless network.

Understand how radio interference can affect computer communication. Radio interference can keep wireless devices from communicating effectively. Part of the reason for this is the fact that the wireless devices use a CSMA/CA access method, which ensures that a medium is clear before trying to send information onto it. Know how to diagnose a problem caused by another wireless device, such as a Bluetooth device, and how to solve the problem by either removing the false signal or strengthening the real signal.

Know how antenna type can affect wireless communications. The type of antenna used in a wireless network can dramatically affect the range and direction of signal. Some antennas are designed to be very sensitive to signals in one direction only (directional), while others are designed to receive signals in the same manner in all directions (omnidirectional). The antenna that is included on the WAP is often the only antenna needed for a wireless network.

Understand how environmental factors can affect wireless communications. Environmental factors such as the type of building or the construction of walls in a building can have a dramatic effect on a wireless network. You can optimize your network by experimenting with the best placement of WAPs in the building so as to avoid the pitfalls caused by the environmental factors. In addition, you can purchase special software that will give you a graphical representation of radio wave behavior in your building and assist you in finding other sources of interference.