We have to many radios on our towers. I wish to have a GPS Synchronisation like Motorolla PTP600. With that I can put a lot more radius on our towers

Yes we need this for our sectors.

I think everyone needs this.

another vote.

Ubiquiti has it. We should have it.

This has been a long standing request from many people. My company's network is really starting to feel the strain without this feature. Self interference is starting to become one of our biggest challenges at our distribution tower sites.

+1 Vote for GPS Sync

Google earth cannot give you the actual location?

Google earth cannot give you the actual location?

it's not about position, it's about time

Yep it takes the time from the GPS and syncs the timing inbetween is access point at that location. Each access point takes turns using the same frequency. This enables the WISP to make use of the frequency more efficiently. Plus you can use 20-40 channels when you couldnt before because you maybe have sectorized for reliability.

i vote by this ++++ Timing syncronizaition.
for not doing much hardware change I suggest a software that can generate the clock and the other that can connect to it and synchronize their clocks

Thanks for the support guys

Each access point takes turns using the same frequency. This enables the WISP to make use of the frequency more efficiently.

Actually, it makes all access points transmit at the same time, and listen at the same time. This keeps them from desensitizing each other. It also allows access points with signal paths that don't overlap (from the client's point of view) to use the same frequency and polarization.

Since the radios don't have to worry about desensitization, they can also be placed right next to each other.

Desensitization analogy: If you are trying to hear someone shouting really far away, while someone right next to you is shouting (even if they are facing away from you), you won't be able to hear the far-away person, even if one is shouting in a low pitched voice, and the other is shouting in a high-pitched voice. If they are far enough apart in pitch (frequency), you might be able to make out what the far-away person is saying, but with more difficulty than if they weren't speaking at the same time.

I understand Desensitization now. Where are you getting your facts? Where can I read about this? I would like to learn more about what your talking about.

Each access point takes turns using the same frequency. This enables the WISP to make use of the frequency more efficiently.

Actually, it makes all access points transmit at the same time, and listen at the same time. This keeps them from desensitizing each other. It also allows access points with signal paths that don't overlap (from the client's point of view) to use the same frequency and polarization.

Since the radios don't have to worry about desensitization, they can also be placed right next to each other.

Desensitization analogy: If you are trying to hear someone shouting really far away, while someone right next to you is shouting (even if they are facing away from you), you won't be able to hear the far-away person, even if one is shouting in a low pitched voice, and the other is shouting in a high-pitched voice. If they are far enough apart in pitch (frequency), you might be able to make out what the far-away person is saying, but with more difficulty than if they weren't speaking at the same time.

I found docs on that type of gps sync. I like how that gps sync works. I. Vote for that type. I will post the facts later when I am not traveling. Thanks xxiii!

i vote for this too.

I understand Desensitization now. Where are you getting your facts? Where can I read about this? I would like to learn more about what your talking about.

Some of it comes from familiarity with another vendor's system, and their documentation.

Here is an article about desensitization: http://en.wikipedia.org/wiki/Desensitiz ... nications)

Thank you

Normis, is mikrotik working on this solution? I will beta test.

There is no need for a GPS unit to localy synchronize transmitters. A simple coax cord chained between radio units of the same tower is enough if a global sync reference between towers of different sites is not needed.

For this to work, radios need something like a 10 Mhz clock output, and 10 Mhz clock Input to daisy chain. If the chain is long, then it's better to have a master clock distributed through a splitter, to avoid added jitter at each node (and phase difference because of cable lenght).


For global synchronisation between tower sites, a central NTP server synchronized to the Atomic Time, and an optimized PPL loop associated to a high precision local Quartz oscillator and NTP client should be enough to keep sync.


The GPS or NTP server is only necessary if global synchronisation is mandatory, like in a GSM network or SDH synchronous network.

I think that removing the GPS unit, it should be possible to design lower cost sync radios than Ubiquity ones.

With or without GPS, for global sync, the most important part is the precision of the local oscillator, and the design of the PLL loop circuit that can keep a precise time between updates of the GPS or NTP references.

High precision local quartz oscillators and PLL circuits are not so expensive today.

I agree that having sync at a tower is most important even if we don't have remote sync. We can deal with that. We just need a solution.

I think all this GPS stuff is over hyped . It is because we are all operating in a license-free band and yes, you can get away from self-interference but your competitor again will be shouting in your ear a few meters away.

If we had operating in license-exempt bands, we could save spectrum and reduce interference with this technology. But it is not our case.

IMHO, Careful channel planning and separation is still the way to go.

I think all this GPS stuff is over hyped . It is because we are all operating in a license-free band and yes, you can get away from self-interference but your competitor again will be shouting in your ear a few meters away.

If we had operating in license-exempt bands, we could save spectrum and reduce interference with this technology. But it is not our case.

IMHO, Careful channel planning and separation is still the way to go.

I agree to some extent, but if we can obtain better spectrum utilization / performance using TDMA based technology instead of CSMA/CA I think it would be beneficial to at least have the option.

I don't see anything negative coming from the time synchronization.

I think all this GPS stuff is over hyped . It is because we are all operating in a license-free band and yes, you can get away from self-interference but your competitor again will be shouting in your ear a few meters away.

If we had operating in license-exempt bands, we could save spectrum and reduce interference with this technology. But it is not our case.

IMHO, Careful channel planning and separation is still the way to go.

I agree to some extent, but if we can obtain better spectrum utilization / performance using TDMA based technology instead of CSMA/CA I think it would be beneficial to at least have the option.

I don't see anything negative coming from the time synchronization.

I totally agree. I bigger we get the more we need it.

I think all this GPS stuff is over hyped . It is because we are all operating in a license-free band and yes, you can get away from self-interference but your competitor again will be shouting in your ear a few meters away.

If we had operating in license-exempt bands, we could save spectrum and reduce interference with this technology. But it is not our case.

IMHO, Careful channel planning and separation is still the way to go.

To some of us that do careful planning, and realize what is occurring we understand what we are asking for.

GPS Sync between Sectors/Backhauls and tower sync between towers is not going to help me reduce any external interference hitting my system, its strictly for reducing self interference.

If I have 3 sectors at one tower site, mounted in a typical triangle fashion at 75 ft. The spacing between these antennas is in the range of only a few feet. Even if you are lucky enough to afford larger towers, spacing is still typically only 10-15 ft. Not all of us are lucky enough to deploy 300 ft towers where spacing is not an issue.

Now pretend that Sector1 transmits, while it is waiting for the CPE to answer back, Sector2 transmits at the exact moment the CPE answered. Now we have Sector1 hearing two signals one at -25 the other at -60. The -25 from Sector2 is noise and makes it very unreliable to use higher data rates as the self-interference we currently produce prevents reliable operation. Now scale this up, and add another 2-3 antennas working in the same frequency range, and add another tower 5km away that can be 'heard' and what you end up with is an inefficient system. The actual capability is far higher then real world performance, GPS sync is meant to help us recover this lost performance.

GPS sync is not a magic wand. For those just toss antennas and omni all over the place it will be of little help, but some of us operate large well planned out networks. We already space antenna's and frequencies appropriately, we use high quality antennas with very good Front-to-Back ratios, x-pol isolation, etc. We try to do everything to maintain fast and reliable networks, GPS sync is simply the next logical step to improve our networks.

Besides without GPS sync many of the larger purchasers of Mikrotik will be forced to look elsewhere.
Besides RouterOS can operate in licensed frequencies, so for those of use looking into that it an added bonus to not have to look elsewhere for a quality product.

Cheers

Yes I am looking to reduce self interference. Most wisp dont even though they are killing them selves. We can do without sync however. It makes life a lot easier. Plus all wireless providers are going to provide this. This is why mikrotik needs to implement it. Also it provides better utililization of the frequencies.

It does allow as well, when global sync is achieved, to get perfect roaming between towers.


If towers are not fully synchronised, then receivers need some time to resync to the channel with the PLL circuitry.


This explain why GSM or DECT roaming is almost perfect; but Wifi roaming is most of the time disastrous.


GSM and professional DECT access points are fully synched.

yes this is good idea.
+1 vote

Perfect Roaming is more complicated if the client is moving fastly, because of doppler effect. Then client position and tower positions needs to be known (by GPS ?) so that the client can compensate himself frequence adjustements during roaming.

An example of perfect roaming system is the GPS system himself.

Great idea but I still think we should get mikrotik to at least start on it. You know they will keep working on it once started. So lets keep it simple for them. Once a beta is out for sync then ask for toys lol.

Yes a simple sync between same tower radios would be a good start. Using for example a small coax cable with SMA connectors between cards.

hello guys, GPS synchronization is essential to improve our networks ... the question is .. WHEN?

C'mon, the ubnt already launched ... and mikrotik????

I agree. I need it as well. I using NV2 which helped me out but for how long until I need GPS?