A very common question occurs when people see their AP has 2 antenna ports and wonder why not attach a dish for picking up a remote WISP, and using the other port with an omni for local coverage.
This stems from a basic misunderstanding of what those ports are for.
Correct solution, don't be such a skinflint:
Use 1st AP with directional for p-t-p link, all TX/RX set to single antenna.
Use 2nd AP for local coverage.
The 2 ports you will notice, ship from the factory with IDENTICAL antenna installed. The reason we have 2 ports is for something termed "diversity", which in this usage means that the SINGLE radio looks at which antenna sees the strongest signal for the current client and uses that one. This helps with indoor multipath reflection issues in that it each timeslice it can evaluate which antenna is best and switch to it. It's a small but real improvement is solving indoor WiFi usage that costs little for the manufacturer to implement. Works well in a setup with a couple of low or medium-gain omni antenna.
Let's get back to the SINGLE radio point here. In practice, only one antenna is being used during a given time interval. The radio does not transmit or receive on both ports at once or anything crazy like that. So, what you are asking it do is WAY outside the design intention for the 2 ports. If the radio is very busy trafficking with YOU the local client, it is not going to be doing much with the dish connection. The vice-versa applies, if the point-to-point traffic is heavy then the local omni antenna will be largely ignored.
In practical usage, some people have done this very setup. The rule of thumb is that if both the p-t-p and the local clients are above -80 dBm signal strength it is what we would call "usable". Note that it is not IDEAL as there is still much neglect of one partner or the other, retransmits due to no response, etc. Most people find that the throughput suffers badly with a 50-75% reduction.
You may get it to kinda-sort work, and your usage may be sufficiently forgiving of its actual drawbacks to notice what a lousy hack it is. Good luck with that, but many find they are later having to add a 2nd AP to solve the issues.
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by vincentfox  edited by No_Strings
last modified: 2005-08-08 12:10:48 |
