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3G ATT Build out PICS

Discussion in 'Cell Tower Hunting Club' started by Eric47, Apr 8, 2008.

  1. Eric47

    Eric47 Bronze Senior Member
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    these are a few pics of a local area where they are adding 3G in the 3190* zips.

    this particular site, you can see where they have been working on adding Antennas to an existing tower on the 2nd row.

    [​IMG]

    [​IMG]

    [​IMG]



    In the other pics, if you look really carefully, between the bottom and the 2nd to bottom racks you can see 2 guys sitting up there and one on the bottom rack is standing moving back up to the top one.

    [​IMG]


    honestly these guys have some balls. my service is not that great right now, luckily im roaming on GSM Alltel so calling is fine but data services are slow as the Alltel gsm does not have EDGE.

    anywho. just thought id share.

    ill have more to add soon i think
     
  2. cellular_freak

    cellular_freak Senior Member
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    This may sound really dumb, but AT&T has to add new panels to have 3G? It's just kinda odd cuz it just seemed like when all the companies had AMPS and TDMA, they were all located on a tower with just one panel. So, does this mean that AT&T will have two panels on one tower now, one for GSM and one for 3G?
     
  3. Eric47

    Eric47 Bronze Senior Member
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    afaik from talking to the people that do this, they use the same antennas generally. in the pics i took however, one of those towers they are adding antennas because they were not on it previously.

    the other pictures just shows them working on it, from what i know, even when using the existing hardware antennas they still have to "plug in" the 3G as it uses its own hardware running in cunjunction with EDGE. they do this basically to increase capacity and data capabilities and still keep the consumer experience the same. its very similar to how CDMA/EVDO work together except its a little more advanced as its not just 3G data but 3G data and voice.

    i hope this helps, like i said im no expert but when radioraiders and telecomjunkie get to talking on here i pay attention lol
     
  4. TelcomJunkie

    TelcomJunkie Bad Handoff Investigator
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    Through all of these network upgrades the carriers are/have performed, it's often necessary to upgrade the antennas to meet particular signal levels and desired coverage patterns.

    Now all of these networks have had one major limitation, the uplink from the mobile device. Towers can put out from 40dbm on up, while the phones are putting out 20dbm (Remember that db's go exponentially, every three DB is twice the power). Quite often the device can hear the tower but the tower can't hear the phone making communications between the two impossible. With this limitation, it's often required that the antennas be upgraded to higher gain model, or tower top mounted amplifiers installed (often both) to achieve the needed signal levels back into the base station. Because of the importance of the link loss (the amount of loss between the base station and the antenna itself) it's desirable to install a separate feedline and antenna system to hook up to the new equipment instead of using a combiner down on the ground level.

    The other main consideration of swapping out the antennas during these upgrades are coverage patterns. Each technology's initial deployment may not be to every site so other sites will have to have wider broadcasting antennas, quite often at different azimuths than the other antennas on that same side of the tower to accomplish the needed propagation pattern.
     
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  5. Eric47

    Eric47 Bronze Senior Member
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    so a newer antenna and 3G can enhance current coverage in a given area even when using the same towers/terrain/and frequency?
     
  6. TelcomJunkie

    TelcomJunkie Bad Handoff Investigator
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    It can, if that's what it's intended to do. The GSM carriers appear, at least in my area, to be utilizing separate antennas for their UMTS deployments. Being that it's a different antenna system and in no way connected to the existing equipment, no 2G/2.5G coverage will be gained or changed.
     
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  7. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    It all depends on the Carriers Engineering Build Plan.

    If they have antennas there they may use them or if they own booth 850 or 1900 but the site is only 1900 they may change the antennas to dual band 850/1900 antennas.

    ATT is big on dual banding using diplexers which Im not a fan of. Diplexing kills the performance on the antenna cable (feedline) and alot of the sites I have put them on do not pass return loss testing (Sweeps).

    IMO dual banding is fine as long as each Band has its own feedline, the dual band antennas are fine as each Band is isolated from the other.

    I have only seen TMA (tower mounted amps) put on GSM. Has anyone seen it on CDMA/UMTS?
     
  8. TelcomJunkie

    TelcomJunkie Bad Handoff Investigator
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    I'm with you on that one! I've swept way too many of them that didn't pass because of the diplexor.

    For WiMax/UMTS I've seen them, for straight CDMA I've yet to see one installed. What I do see a number of are ground mount "Cell Extenders" which are effectively doing the same thing, just at the bottom of the tower.
     
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  9. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    ground mounted AMPS would be nice, but I wonder what the difference in gain is a 0 Feet vs the 250 to 300 feet average in my area.
     
  10. TelcomJunkie

    TelcomJunkie Bad Handoff Investigator
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    In our cell extender deployments we get about a 3db gain in received power from the mobile. I'm not quite sure how much gain the GSM tower top models provide, but I'm sure either way it ends up about the same.
     
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  11. Eric47

    Eric47 Bronze Senior Member
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    is adding extenders a typical install or not? we could probably use the for att here but i wonder if they will use them.. what about on new towers?
     
  12. TelcomJunkie

    TelcomJunkie Bad Handoff Investigator
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    On CDMA, no. GSM carriers heavily utilize tower top amplifiers.
     
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  13. Eric47

    Eric47 Bronze Senior Member
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    gotcha. man i have so many random questions about this type of stuff its crazy lol.
     
  14. TelcomJunkie

    TelcomJunkie Bad Handoff Investigator
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    Feel free to ask away, there are plenty of us here to answer.
     
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  15. Eric47

    Eric47 Bronze Senior Member
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    is there a way to set a 3G phone to "lock on" to 3G only? at what dbm does 3G try to fall out and EDGE come back in? why does it do this?

    the whole way 3G and EDGE cross back and forth over and when they do is bewildering to me and i guess i just wanto know if its going to be something controllable or not.
     
  16. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    You think is would still be beneficial for CDMA as well being it only amplifies the mobiles transmit which is the weakest link.

    Basically in GSM land the TMA sort of bridges the GAP between CDMA and GSM

    CDMA out performs GSM in low signal environment due to the Soft and softer handoff and CDMA can easily hold a call at 1 bar as long as there are decent SHO candidates which isnt a problem unless in a mega rural area.

    TMAs allow the GSM handset to run at lower signal levels so where before a TMA if you had less than 2 bars you were guaranteed to drop.

    I think it was the same ball park on Gain 3-5 DB based on Feedline and jumpers size and quality, 7/8 1 5/8 etc
     
  17. Eric47

    Eric47 Bronze Senior Member
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    so can WCDMA/UMTS hold a call at 1 bar well like a CDMA ? assuming you set the phone to do so?
     
  18. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    Yes UMTS Is based on CDMA so alot of the same principles exists.
     
  19. Eric47

    Eric47 Bronze Senior Member
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    so why does ATT 3G always try to switch back to EDGE (i know im beating a dead horse a bit). im just confused.


    is it possible to lock a phone down onto UMTS for voice?
     
  20. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    Depends on the way the engineers have the handoff set up.

    There arent as many 3G sites as GSM. Consider 3G as sort of a hot spot technology until ATT overlays all towers. Basically main focus is top 200 cities and main highways etc then move on to other cities and areas.
     
  21. RadioRaiders

    RadioRaiders RF Black-Belt
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    I've never seen "dual-band" antennas for the same band, do they exist :confused: (ie: an antenna with seperate feeder connections for GSM850 and UMTS 850)

    "Real" dual-band antennas have seperate connections for each band. For exapmle, here's a popular antenna in Europe that is actually triple band (GSM 900/1800 and UMTS 2100). You see on the last page it has 6 feeder connectors, 2 for each band (plus elect tilt can be controled independentaly in each band)

    http://www.kathrein.de/de/mca/produkte/download/9363227a.pdf

    ...but, since AT&T has GSM850 and UMTS 850, this doesn't really apply. Either they need seperate antennas for each (the technically better but more expensive solution), or they can put both on the same antenna with duplexers and rejection filters (the cheaper solution)

    I've seen operators cram 2 technologies into one band (ex. GSM850/UMTS850) using dual-duplexers and filters, and in theory it should work OK, accepting you can live with a few dB reduced output power. But in reality, as you've said, it's a headache for techs (intermodulation or VSWR problems, like you said) and it's not the best solution for the engineers either (can't independently control tilt/azimuth). The only people who favor this solution are the bean-counting managers who see they can save a few $$ by re-using an existing antenna :rolleyes: Or if they want a quick roll-out and not have to wait for new antennas to arrive.....well, OK to be fair, sometimes you also have to go this route if you can't add new antennas to an existing site, then you're stuck with it.

    In theory, AT&T would be better off with seperate antennas for GSM850 and UMTS850. But it's not a perfect world and everyone has to make sacrifices and compromise. I'm sure antenna sharing will work for them, they'll just hit a few sangs now-and-then.

    PS- Sure, UMTS uses TMA's also.
     
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  22. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    There not called Dual Band. Their call single band dual pole. The come as a dual or quad ant and has 2 or 4 feedline connectors. These are most commonly used on building or places where leasing doesnt allow more antennas or weight loading fails on a tower.

    850 antennas are just generic 824-896 A and B band and doesnt matter if Analog, CDMA, GSM or UMTS.

    The also make dual Band dual pole Ants and they make dual band quad pole (2 1900 and 2 850)

    One on the dual banders I had to do with diplexors was on a water tower that didnt have space for individual feedlines. Most of the dual band sites I have done have dedicated feedlines.

    In my area when we first put in GSM some areas had to share antennas with TDMA and at the time where omni sites. Some antennas where shared by using external input and outputs on both technologies combiners. Regardless to say antenna sharing that way throw the daily reporting metrics out of whack. It makes the Link Balance look like crap and has to be adjusted for similiar to the same was as using TMAs.
     
  23. RadioRaiders

    RadioRaiders RF Black-Belt
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    Oh, ok, you mean it's just a single band cross-ploarized antenna, and they connect (for example) GSM to veritcal and UMTS to horizontal? Ok, that's pretty simple, but then you're losing even more dB's because you don't have the cross-polarization gain on the receive path. If you use dual-duplexers and receive filters, you can still keep the x-polarization (I think, I don't remember exactly, but I know there's a way)
     
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  24. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    I think there standard polarization.

    The dual band antennas we have are huge like the Nextel antennas.

    The dual band antennas are about 6 foot tall and have the 1900 mounted on the top and the 850 on the bottom and are technically 2 antennas but in the same housing. I have had sweeps on both sides -23dbm before lightning protection.

    If you use individidual feelines to both sides of the antennas you dont need any external duplexing or diplexing.

    If I ever run into a bad antenna I will take the cover off and see what the guts look like.
     
  25. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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  26. spleck

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    Just a side question on that: How did ATT handle bandwidth when running TDMA and GSM? Can they split just a few channels to TDMA in the same block, or do they need separate blocks? ie A block for GSM, D block for TDMA?
     
  27. RadioRaiders

    RadioRaiders RF Black-Belt
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    That's a funky antenna! Really thick :eek: ...don't you guys use Andrew in the USA? :confused:
    Yea, that Swedcom antenna is x-polarized (says "2x vertical") I shouldn't have said Vertical/Horizontal before, that's more for microwave TX, Cellular is Vertical +/-45°. Yea, if you plug GSM into +45° and UMTS to -45° then you don't get the x-pol RX gain. But with a duplexer/diplexer you can/should get the gain.

    If you open a dual-band 850/1900 antenna you'll see it is 2 seperate physical antennas built into one. The larger diploes are for the lower band (850) and the smaller dipoles are for the higher band (1900). I think it's 1/2 wavelength, a full wavelength for 900Mhz is 13".

    Sure, they should be able to split up the spectrum however they want (ie: put GSM and UMTS on the same block) Well, I mean it's technically possible, but I don't know what FCC regulations they have to abide by.
     
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  28. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    ATT wireless when it first started GSM it was only 1900 MHZ at TDMA was still the primary technology and still using 850 mhz. When GSM first came to the states it was available only in 1900. At more people switch to GSM from TDMA is cleared room on the 850 to move GSM over to it. TDMA is no more but toward the end not much bandwidth was used at all with most of it going to GSM. In alot of areas ATT has alot of 850 and 1900 and GSM easily handoffs between the two so a sort of capacity sharing occurs between them. As UMTS become more popular the same will occur and the 700 MHZ picked up will help out in the more Metro environments were congestion can be a problem.
     
  29. spleck

    spleck Tool
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    I ask because it came up in another discussion. A poster had claimed that in order to support TDMA customers until the cut-off, AT&T had to use a whole 5 MHz block running TDMA. I was under the impression they could run a 1.25 MHz chunk (or smaller) as TDMA with the rest running GSM. Just wondering if anyone else was familiar with the equipment capabilities during the transition.
     
  30. RadioFoneGuy

    RadioFoneGuy Powered by HTC FUZE
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    In rural areas towards the end you could use less that 1 mhz, I would venture to say 500-800 khz.
     

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