Troubleshooting Wireless LAN Installations

Range Considerations

When considering how to position wireless LAN hardware, the communication range of the units must be taken into account. Generally, three things will affect the range of an RF link: transmission power, antenna type and location, and environment. The maximum communication range of a wireless LAN link is reached when, at some distance, the link begins to become unstable, but is not lost.


Transmission Power

The output power of the transmitting radio will have an effect on the range of the link. A higher output power will cause the signal to be transmitted a greater distance, resulting in a greater range. Conversely, lowering the output power will reduce the range.


Antenna Type

The type of antenna used affects the range either by focusing the RF energy into a tighter beam transmitting it farther (as a parabolic dish antenna does); or by transmitting it in all directions (as an omni-directional antenna does), reducing the range of communication.


Environment

A noisy or unstable environment can cause the range of a wireless LAN link to be decreased. The packet error rate of an RF link is greater at the fringes of coverage due to a small signal to noise ratio. Also, adding interference effectively raises the noise floor, lessening the likelihood of maintaining a solid link.


The range of an RF link can also be influenced by the frequency of the transmission. Though not normally a concern within a wireless LAN implementation, frequency might be a consideration when planning a bridge link. For example, a 2.4 GHz system will be able to reach further at the same output power than a 5 GHz system. The same holds true for an older 900 MHz system: it will go further than a 2.4 GHz system at the same output power. All of these bands are used in wireless LANs, but 2.4 GHz systems are by far the most prevalent.