Connect802 is a nationwide wireless data equipment reseller providing system design consulting, equipment configuration, and installation services.


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Fall 2008

   
Essential Wi-Fi
For those who are new to Wi-Fi networking...
Technology and Engineering
For the engineer and Wi-Fi network administrator...

Essential Wi-Fi

Determining the maximum range for 802.11 communication

In summary, transmit power, range, and data rate have a reciprocal relationship. If transmit power increases and data rate remains the same, range also increases. If data rate increases and transmit power stays the same, range decreases. If you want to increase data rate while keeping range the same, you'll need to increase transmit power accordingly.


 Technology and Engineering

How do directional antennas become directional? Why is it that amplifiers have separate receive and transmit gain, but antenna gain occurs equally well for both transmission and reception. The principle at work is called the "Law of Antenna Reciprocity" and it's what allows a high-gain antenna to not only send RF energy out over longer distances, but to pick up weak signals arriving from long distances, even though the weak transmitter has no particularly special antenna.

In order to fully understand the impact of the Law of Antenna Reciprocity, consider a different way of increasing a device’s coverage area, increasing the transmit power of the radio. If one radio has a higher transmit power than another, the weaker radio may hear the transmissions of the stronger radio, but the stronger radio will be too far from the weaker radio to hear its responses. This situation, which is known as the Unbalanced Power Effect, is irrelevant in one-way transmission, like television or radio, but in two-way data transmission, the link is effectively down when the Unbalanced Power Effect is occurring. The benefit of the Law of Antenna Reciprocity is that you can use higher gain antennas to increase the coverage of a radio without worrying about creating an Unbalanced Power Effect.