On Fri, Feb 08, 2008 at 03:37:19PM -0800, Ralph Becker-Szendy wrote: > I have been experiencing lots of receive errors on it, and reception > seems very position sensitive, so started playing with the antennas. > And at some point it occured to me that I have NO idea what it means > to have two diversity antennas. Are they electrically separate, and > the AP has two separate transmitters/receivers? How does it select > which packet goes where? Or if they are just connected to each other > electrically, wouldn't having two antennas in close proxomity cause > terrible interference effects?
Ralph, Ordinarily, the AP has just one transceiver. The transceiver connects to a solid-state switch that electrically connects to antenna 'A' in one position, and to antenna 'B' in the other position. Ordinarily, one position is the 'default' position. An AP will ordinarily "listen" for packets in default position. If the AP senses a carrier while the switch is in the default position, then it will measure the strength of the carrier in that position, and if the strength is not above a certain threshold, then it will switch to the second antenna and listen for a while (microseconds). Finally, it will switch to the antenna where the carrier was strongest in order to receive the transmission. An AP may use diversity in its transmission strategy. An AP may transmit in the default position, or it may transmit in the position where it last received a packet, or it may select the position based on the client that it is sending to. An AP may also try a transmission on a second antenna if the first transmission is not acknowledged. I have written 'ordinarily' a lot. That is because there is variation in designs. I hope that you get the gist of how diversity works from my description, but the details may be different for the particular device you are using. How your AP will work depends on the decisions of the WLAN designer, and the capabilities of the WLAN chip. If you are using open-source software, you may be able to find out how your AP will work by reading the source code. Dave -- David Young OJC Technologies [EMAIL PROTECTED] Urbana, IL * (217) 278-3933 ext 24 _______________________________________________ Soekris-tech mailing list [email protected] http://lists.soekris.com/mailman/listinfo/soekris-tech
