View Full Version : GPS support
Are there any plans to offer a GPS sync with this new M gear. I would be VERY VERY VERY interested in this as an option for spectrum reuse. Mainly in the 5.8Ghz ISM band.
I wouldn't be as worried in the 5.4Ghz band, hopefully that will be certified soon.
-Cameron
twinkletoes
10-26-2009, 11:08 AM
There is no hardware capability to take in a GPS signal on existing M hardware. Companies like AFAR synchronize tower sites without GPS, by simply sending a synchronization packet over the ethernet port that all APs use to synchronize their timing. http://www.afar.net/technology/interference/
Perhaps UBNT's 5.1 software, which is supposed to produce a more exact TDMA interface without the need for ACK packets, will be able to use this type of mechanism. They need to shore up the TDMA interface and get rid of the vestiges of 802.11 (like CSMA) before they can hope to do something like this.
twinkletoes
10-26-2009, 11:10 AM
Also UBNT is using the Atheros high precision timer in their newer chips to make this all possible, with perhaps some other cool hardware features in the chips that i'm not aware of. I bet ethernet based TDMA tower synchronization is already on UBNT's upcoming feature portfolio.
i would love to see timing in some form soon, im sure it will be well recieved by the wisp community, i wonder if there would be a hardware appliance from ubnt that also provides PoE? 19 inch rack even....hope they are taking notes on this post....haha...keep up the good work ubnt...very pleased with this after the ethernet lockup was fixed.
twinkletoes
10-26-2009, 02:20 PM
You're looking for something like a Last Mile Gear CTM with remote reboot capabilities but without GPS, right?
twinkletoes
10-26-2009, 02:49 PM
The AFAR manual has more details on how their ethernet based synchronization works. It requires full duplex ethernet links, for instance. Cool stuff http://www.afar.net/manuals/PulsAR-24027_Manual_Apr08.pdf
A rackmount PoE that can take an IP for remote reboot and have GPS would get me so thrilled I think I would be speechless if UBNT did something like this.
I'm getting excited just thinking about the idea....
-Cameron
vicenteroca
10-27-2009, 02:51 AM
Hi!
One question. ¿ Is really worth the GPS system? I mean, ¿how important is the improvement?
¿Can you put some numbers here?
Thanks!
I believe GPS is huge. I also think it should be required by the FCC in the US for better spectrum efficiency and help eliminate inference. It may not be important or needed in some environments but if you ever had to deal with a lot of noise or have several 5.8ghz/900mhz AP the ability to reuse channels in a tight space could be the difference between you and the others guys as far as performance and reliability.
twinkletoes
10-27-2009, 09:36 AM
Given the current hardware offering, I wouldn't expect GPS synchronization, but if the "TDMA" system can be tightened up, they may be able to do something similar to what AFAR did. You could even centrally time it with GPS by using a GPS receiver plugged into the ethernet I suppose.
twinkletoes
10-27-2009, 12:33 PM
Is really worth the GPS system? I mean, ¿how important is the improvement?
¿Can you put some numbers here?
TDD TX/RX synchronization allows you to do two things:
1. Put APs/PTP links on adjacent channels with close physical proximity.
(Normally if you use channels that are adjacent, or even within 100MHz of each other, on antennas next to each other, you are going to get RF coupling between senders and receivers. You won't notice problems until you have higher traffic levels. Most people using non-synchronized TDD systems have to space the antennas far apart (30+ feet) or use frequencies that are over 100MHz apart to get around this effect.)
2. Re-use the same frequency in opposite directions on a tower. For instance, you could use 2415 MHz on a north sector, and a south sector. If you did this with a non-synchronized system, one would transmit on top of the other receiver all the time. (The way that people get around this right now is to use antennas with 30dB+ F/B ratio. But this is a poor solution because you rarely see that level of isolation in actual deployments.)
See the AFAR manual I linked to above for a better description of the RF coupling problem.
I hope to see GPS, I really think this would bump UBNT from just being another type of "Wi-Fi" product into a more carrier class. Obviously it still needs some firmware love, but they seem to be really working hard to impress us all with the M series.
So far, I'm impressed with the dedication to the project.
