Sick of only having EDGE

[Wireless Junkie]

1. Show me one. Please. Just one. Antennas are just that, antennas, they don't know what the radio signal going through them is. Even antenna arrays for MIMO aren't tech specific really. For example, an AWS MIMO antenna array could be used for T-Mobile HSPA+ 84 or for AT&T LTE. Heck, it COULD even be used for non-MIMO (using just one antenna in it). Even beam-forming "smart" antennas, while they may be a unit designed for a specific technology, the antenna elements are, in fact, not. They're all just radio waves.

2. Gain means a LOT. A 3-sector site will cover more area than an omni. Plain and simple. The question is - WHAT area is covered? A high gain omni will have a fairly even flat "pancake" of coverage. Sectors shoot off something more like a cone shape of coverage - that includes more power getting lost to the sky and the ground. The coverage, all else being equal (same transmit power, receive sensitivity, etc - i.e. same radios turned up all the way) will be the same from EACH of the three sectors as from the single omni, just spread out differently. Now, accounting for overlap, and more signal lost to the ground and sky, the omni may well cover a larger TOTAL *land area* than the sectorized site. BUT - the pattern will be very different. Two sectors shooting up and down the road are much more useful than an omni throwing a ton of power off to the unpopulated sides of the mountain/valley/abandoned flatlands.

That's why you don't see omni's very often. They're not that useful. The flat round pancake of coverage wastes power covering places that don't need it in rural environments, and lower power, smaller sectors provide maximum capacity in urban environments.

The benefit to a single omni is one radio on the site. Dirt cheap. Poor capacity, poor coverage, but cheap.

1. When you start deploying new gen. radio technologies and are placing orders with vendors that supply RRU and antenna's then you will find all that you can imagine. But until then you can just pretend those antenna's don't exist. When you use an antenna designed for a specific technology, it yield better results. Yet again, you are running reiterating my point, the whole antenna unit may be designed for a specific technology........ When looking at an *antenna*, you don't just pick out pieces of the unit, they combine to form one entirety.

I am sure an LTE AWS MIMO antenna could be used for a technology that will never see the light of day here, but until then its an LTE antenna and if it has specific signaling processing properties, then all the features designed for THAT antenna will not work.

Sure you can run any tech over it, but its not going to be able to take advantage of all the features. You can run a premium car on cheap gas, but you definitely aren't taking advantage of all the potential of the car. You can run a car designed for gasoline only on E85, but again thats not what it was intended for

2. Most Omni setups that still exist in rural area's consist of 3 antenna's for maximum coverage, not just one single antenna. That's how rural networks are setup here, and you have proven my point, it does cover a larger TOTAL land area.

[Jordan T]

1. No doubt, but now you're talking antenna arrays, not antennas. The "smart antennas" are not antennas. Even a "MIMO antenna" isn't an antenna. It's an array, designed with a technology family in mind.

2. That doesn't make any sense. Granted, I've never seen the setups, but how would three omni's from one tower accomplish... anything? They'd all have the same pattern, and if on the same radio channel (in n=1 reuse UMTS, obviously in GSM they can't be), would accomplish... nothing. I'd love pictures/details on such a setup. Not saying I don't believe you, just that it doesn't make sense.

[TWX]

I had a conversation with a RAN engineer over on Wireless Advisor about omni antennas, and though I'd post it here just because.

Me: AT&T is planning on rolling out 3G in my area this year. As of now, my area is pure EDGE. However, many cell sites in my area use old omni-directional antennas (2 big antennas atop the cell site). Can they simply upgrade the base station in the cell hut and upgrade the backhaul a bit to get 3G going? Or do they need to replace antennas on top of the tower with ones that can broadcast a 3G signal?

RadioRaiders: Yea, the same antennas can be used for 2G and 3G, so long as the frequency is the same (ex. 850Mhz). if the base station is an old 2g one, then it would need to be swapped out. the newest base stations can house 2G/3G/4G in the same cabinet, just swap the cards for which technology you want.

Me: Very cool. Thanks for the reply! Another quick question, why would a sectorized array be better than an omni site?

Do sectorized sites handle network loads better or what?

RadioRaiders: With an omni antenna, it's one frequency that radiates in a circle. with a 3-sector site, each sector has it's own frequency, so you have 3x the frequencies (more capacity), plus you can direct the antennas to focus in certain directions, like for example along roads. So with sectorized antennas, you get more capacity and better coverage in areas you want to cover.

An omni site might be good to cover large areas with little population since it's cheaper and covers equally in all directions.

Me: Do they need to replace the coax cable that runs from the BS to the antennas when upgrading from EDGE-only to UMTS? Also, my home tower has 2 omni's on it. Does one send-only and the other receive-only? Or do both send and receive on different frequencies?

RadioRaiders: Coax can probably stay. If there's 2 omni's it could be like you said (space diversity), where only one transmits but both receive. with space diversity (2 receiving antennas) it takes both receive signals and combines them to negate any fading dips (makes the receive signal better). the uplink (phone to base-station) is usually the weakest link, so having 2 receive antennas helps reception.

[Jordan T]

TWX, RadioRaiders is correct on this, but makes one major omission, the sectors are only on different channels (frequencies) for GSM and analog technologies. UMTS and LTE both are n=1 frequency reuse (same channel on every site/sector).

[Barry ATL]

Now, this is a discussion that is what HoFo used to be all about.

[TWX]

TWX, RadioRaiders is correct on this, but makes one major omission, the sectors are only on different channels (frequencies) for GSM and analog technologies. UMTS and LTE both are n=1 frequency reuse (same channel on every site/sector).

Right, I was asking him about the existing GSM omni antennas on the cell tower and how they act right now, not how the would act with 3G. Therefore, he did not omit anything. But thank you for pointing out how UMTS and LTE use frequency reuse

[Jordan T]

Oh okay, that makes sense. RadioRaiders is a smart guy

P.S. Off the top of my head, I can only think of three sites that have omni's on them (or did, haven't looked recently), and all three are Verizon sites, I believe. Though one I'm not sure, it could be an AT&T site or a Verizon site. The cost savings is minimal, and the coverage from an omni setup (which, like RadioRaiders describes, tends to be two antennas at least for the couple sites I've seen - receive diversity, that's why I called out guy-of-many-names on his "three antenna" omni description - especially the way he described it. There certainly aren't sites with three radios on the same channel being pushed into three separate omni antennas. That'd make no sense.) is NOT superior to three sectors (that's simple math). The coverage pattern is very DIFFERENT (a high gain omni is basically a pancake) and may work better in wide open flatlands... but literally it'd have to be like, North Dakota, LOL.

[Wireless Junkie]

Oh okay, that makes sense. RadioRaiders is a smart guy

P.S. Off the top of my head, I can only think of three sites that have omni's on them (or did, haven't looked recently), and all three are Verizon sites, I believe. Though one I'm not sure, it could be an AT&T site or a Verizon site. The cost savings is minimal, and the coverage from an omni setup (which, like RadioRaiders describes, tends to be two antennas at least for the couple sites I've seen - receive diversity, that's why I called out guy-of-many-names on his "three antenna" omni description - especially the way he described it. There certainly aren't sites with three radios on the same channel being pushed into three separate omni antennas. That'd make no sense.) is NOT superior to three sectors (that's simple math). The coverage pattern is very DIFFERENT (a high gain omni is basically a pancake) and may work better in wide open flatlands... but literally it'd have to be like, North Dakota, LOL.

For whatever reason, the Omni setups we have around here are 3 antenna's and the have amazing coverage. Sectorized setups can give *pockets* of no signal vs. a flat pancake, pancake works better in some area's. But yes, they are a lot cheaper, and are on older sites that used to be Analog only and is intended to only provide rural voice coverage, EVDO and LTE are sectored but drop out before voice does. Why don't they use sectors for voice, you will have to ask them. But ill get pictures of it.

[Jordan T]

I wonder what the antennas are, because I guarantee you they're not three radios. It could well be two with receive diversity. Possibly even some type of transmit/receive spatial diversity in CDMA (I don't know what's possible regarding transmit diversity on the site end in CDMA, I'm not a radio engineer).

Are you in an area where Verizon has EVDO on PCS and 1XRTT on CLR? That would be a reason for newer sector antennas for EVDO. It would also explain significantly worse EVDO coverage.

And yes, if you look at the pattern of a sector antenna, the gain isn't perfect, it has a sharp peak that's higher gain than your omni, and rapidly falls off at the sides of the sector. That's why I said a flat pancake could work well in VERY flat rural areas. For most of the rural world, you want two sectors - one shooting each direction up and down the highway. That's how most of the rural sites around here are. Two or three sectors (CellularOne seems to be the biggest user of two sectors on a site, shooting up and down highways, AT&T and Verizon seem to generally get three sectors on a site)

[Wireless Junkie]

I wonder what the antennas are, because I guarantee you they're not three radios. It could well be two with receive diversity. Possibly even some type of transmit/receive spatial diversity in CDMA (I don't know what's possible regarding transmit diversity on the site end in CDMA, I'm not a radio engineer).

Are you in an area where Verizon has EVDO on PCS and 1XRTT on CLR? That would be a reason for newer sector antennas for EVDO. It would also explain significantly worse EVDO coverage.

And yes, if you look at the pattern of a sector antenna, the gain isn't perfect, it has a sharp peak that's higher gain than your omni, and rapidly falls off at the sides of the sector. That's why I said a flat pancake could work well in VERY flat rural areas. For most of the rural world, you want two sectors - one shooting each direction up and down the highway. That's how most of the rural sites around here are. Two or three sectors (CellularOne seems to be the biggest user of two sectors on a site, shooting up and down highways, AT&T and Verizon seem to generally get three sectors on a site)

EVDO here is on both PCS and CLR, PCS would explain the newer sector antenna's.

As far as highways, most of the rural area's here are not highways but are wide open stretches of land like farms and lakes so I guess it would make sense for Omni's.

Our rural iDEN carrier SouthernLINC uses Omni's almost exclusively for whatever reason.

An example of a very rural site with 3 Omni

[Jordan T]

Thanks for the pic I actually do remember a Verizon site like that, but the antenna array has since been changed to a sectorized array. I'd love it if a radio engineer could tell us what the antennas are being used for. A transmit antenna plus receive diversity is the obvious answer - but what's the third antenna? Any engineers want to chime in? Or anyone feel like taking it over to RadioRaiders? He knows his stuff. Regardless, it's some form of a diversity scheme, NOT three radios one on each antenna

It's odd I forgot about the site like that because even at the time I wondered what the three antennas were used for... *now my brain wants to learn*. And - open stretches of farms and lakes you say? Sounds like the perfect place for an omni setup. It's hard for me to remember not everyone lives somewhere where every area ends in "valley" (the Flathead Valley, the Helena Valley, the Mission Valley, the Bitterroot Valley, the Swan Valley, etc.. those are the regions around me) and rural omni antennas are nothing more than power getting thrown needlessly into a mountain side. I actually remember a time (dunno if it still is) when one of Verizon's main cell sites serving Missoula, MT was omni antennas. LOL. Capacity issues would make that impossible today, but that's the site that I remember with three omni's like in your picture. Gosh I wanna know what the heck function those three antennas are serving. I almost wonder if it's some type of repeater setup with one antenna being used as a receive antenna for something else? C'mon anyone who knows...

As for SouthernLINC... well, being iDEN I can't imagine they have many users. Remember, omni's = 1/3 the number of radios as sectors (kinda... I mean I suppose you COULD feed all three sectors from a single radio through amps in a CDMA/UMTS world... but that'd be crazy).

[Wireless Junkie]

Thanks for the pic I actually do remember a Verizon site like that, but the antenna array has since been changed to a sectorized array. I'd love it if a radio engineer could tell us what the antennas are being used for. A transmit antenna plus receive diversity is the obvious answer - but what's the third antenna? Any engineers want to chime in? Or anyone feel like taking it over to RadioRaiders? He knows his stuff. Regardless, it's some form of a diversity scheme, NOT three radios one on each antenna

It's odd I forgot about the site like that because even at the time I wondered what the three antennas were used for... *now my brain wants to learn*. And - open stretches of farms and lakes you say? Sounds like the perfect place for an omni setup. It's hard for me to remember not everyone lives somewhere where every area ends in "valley" (the Flathead Valley, the Helena Valley, the Mission Valley, the Bitterroot Valley, the Swan Valley, etc.. those are the regions around me) and rural omni antennas are nothing more than power getting thrown needlessly into a mountain side. I actually remember a time (dunno if it still is) when one of Verizon's main cell sites serving Missoula, MT was omni antennas. LOL. Capacity issues would make that impossible today, but that's the site that I remember with three omni's like in your picture. Gosh I wanna know what the heck function those three antennas are serving. I almost wonder if it's some type of repeater setup with one antenna being used as a receive antenna for something else? C'mon anyone who knows...

As for SouthernLINC... well, being iDEN I can't imagine they have many users. Remember, omni's = 1/3 the number of radios as sectors (kinda... I mean I suppose you COULD feed all three sectors from a single radio through amps in a CDMA/UMTS world... but that'd be crazy).

This is HoFo >2008 lol. The only thing besides diversity I would think it could be for is capacity. As shocking as it may be in rural area's, SouthernLINC has others beat in a few area's and the network was designed especially for Southerncompany and AL, GA, and south MS and west FL power workers + public safety so in those areas where a single iDEN site covers 25+ miles a lot of use can be on a site at a single time.

[Jordan T]

Additional capacity doesn't require more antennas, since it's on different channels. Just like you don't need one antenna for each TV station you pick up. Odd, I'd really love to talk to a tower engineer about what those three-omni-antenna arrays are/were used for. Most curious.

[Wireless Junkie]

Additional capacity doesn't require more antennas, since it's on different channels. Just like you don't need one antenna for each TV station you pick up. Odd, I'd really love to talk to a tower engineer about what those three-omni-antenna arrays are/were used for. Most curious.

Ahh, its not sector site, forgot. Hmm, one radio per antenna? I am really curious too, they are still used in remote area's here. Our newest AT&T site is a 3 Antenna Omni as well, I am going to snap some pics of it too and try and catch an engineer and ask what the deal is. The 3 Omni AT&T site actually kicks out HSPA/EDGE and at night they are pretty ok speeds.

[Jordan T]

That'd be great if you could catch an engineer. One radio per antenna would make no sense, really. I mean I suppose in GSM/iDEN/AMPS/DAMPS it could reduce interference, but would serve no purpose in UMTS/CDMA (since the channels have a reuse factor of one). Two antennas would provide receive diversity. But three? Odd stuff there...

UPDATE
A quick Google search got our answer. The common arrangement is apparently 1 transmit 2 receive. What I wasn't accounting for is they're using separate Tx and Rx antennas. Which brings me to - what are the sites with TWO omnis I've seen? No receive diversity?