More on SA cell towers

Azimuth

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u2ygu3yd.jpg

Photograph by jcheek

I've created this thread to discuss cell towers/base stations, an overlooked aspect of mobile broadband that is not well understood by most. Some people understand how a WiFi router works in our homes (overly simple but comparable) but how do cell towers work?

With the current mobile data explosion (specifically LTE), a lot of us may try and improve our signal levels with the aid of antennas. With an outdoor (directional) antenna, one needs to identify an appropriate base station and not everyone knows what to look for.

This new section isn't the be-all and end-all without any mistakes. It would be greatly appreciated if any industry players/experts (strictly anonymous contributions) could visit from time-to-time and help with course corrections. ;)

Kicking things off:

Popular base station/cell tower locations:

- Schools (pre-schools, primary and high schools)
- Church grounds
- Shopping centres
- Roof-tops
- Petrol (service) stations, especially Total

Cell operators:

- MTN (often host Telkom Mobile and Cell C equipment)
- Telkom Mobile
- Vodacom
- Cell C (often outsourced to ATC)
- ATC (can cater for all of the above)
- Neotel (shares infrastructure with the Big 4)

Types of cells

- Macrocell (the great outdoors, large multi-tier towers; most sites are macro)
- Microcell (malls; also called minicell)
- Picocell (indoors, typically enterprise; also for outdoor hotspots)
- Femtocell (indoors, home use; ADSL/fibre backhaul; not used in SA yet, sadly)

Base station key features:

(Please help me establish who manufactures and supplies these?)

- Line-of-sight shrouded and unshrouded microwave dishes (parabolic dish, usually 1-2 on the tower)
- GSM sector antennas (elongated panels, 900/1800MHz, usually located lower down on the tower)
- LTE sector antennas (short panels, 1800-2300MHz, usually located at the top of the tower)
- Remote Radio Units (RRU bolted to the rear of a sector antenna); also called Remote Radio Heads (RRH)
- Tower Mounted Amplifiers (TMA) or Mast Head Amplifiers (MHA)
[Manufacturers: Powerwave Technologies, Alcatel-Lucent, Panasonic, Samsung, Ericsson, Huawei]
- RF Combiner/Splitter
- WiMax antennas (Neotel, iBurst, Telkom)
- WISP antennas (BitCo)

Edit: not sure on identifying antennas yet so please post a correction if you have inside info?

Purpose of each piece of equipment

- A microwave dish can either be for backhaul (up to 1Gbps) or to feed other nearby cells
- GSM antennas provide 2G or 3G
- LTE antennas provide next-gen LTE
- The RRU or RRH connects to the BTS on the ground via a fibre/power "Hybriflex" cable and relays signal via an antenna
- The TMA or MHA is able to receive and amplify weaker signals (two-way communications, send/receive) from the User Equipment (UE); it is also used when the cables between the antenna and receiver are too long or too thin
- The RF Combiner/Splitter boosts the signal going up to the antenna in the absence of an RRU or TMA

What makes up the rest of the cell tower:

- Cable clamps and accessories
- Earthing systems
- Insulation and weatherproofing
- Coaxial connectors
- Jumper cables
- Coaxial cables
- Aviation warning lights
- Cable ladders
- Steel palisade fencing
- BTS shelters (Poynting do the new-age subterranean BTS, CPS Technologies do the Cell C outdoor enclosures)
- Cellular towers (yes, the whole structure!)

Manufacturers: AlanDick, Amphenol Jaybeam, Rohn.

All aspects of power supply and backhaul still need to be detailed...

Cell identification

iPhone users:

Punch in *3001#12345#* on the Keypad to enter Field Test mode. Go to GSM Cell Environment > GSM Cell Info > GSM Serving Cell > Cell ID.

Android users:

Go to Settings > About or About > Network Info.



As a secondary discussion topic, please post photos of your local base stations with Cell ID and name (if possible). Not all base stations are easily identifiable e.g. roof-top cell towers look nothing like their ground cousins, while freeway/rural cell towers look like candy-stripe poles with forked omni antennas. Let's label these suckers and demystify their presence.


Resources:

Cell tower backhaul

Antenna installation and alignment

How to improve your wireless experience


Mybb articles

Telkom 100Mbps LTE rollout areas - new details

Telkom Mobile LTE Milestone

Telkom Mobile LTE 90Mbps peak speeds

Vodacom launches LTE in South Africa

MTN LTE network plans revealed

Cell C's LTE plans


External resources:

How cell towers work (Gizmodo)

Installation perspective - pretty cool (YouTube 720p video of a LTE install on a scary high tower)

Sprint 4G Rollout Updates Forum (This is going to be a very sweet resource)



A special shout out to the members of S4GRU forums for sharing their knowledge.
 
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K-Tech

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You are really serious about this stuff ;)

If I am not mistaken Telkom use to offer WiMax.
I think it was their first wireless offering...?
 
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MickeyD

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SA cell tower/site operators:

- MTN (often shared with Telkom Mobile)
- Vodacom
- Cell C (often outsourced to ATC)
- ATC (can cater for all of the above)
Telkom?
 

Azimuth

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You are really serious about this stuff ;)
Heh, it's a "hobby". :D

Thanks, MickeyD, I've added them.

So I'd like to start labelling these suckers as people submit photographs...please chime in if you can assist?
 
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garthvs

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Hi Azimuth

I can confirm that BitCo are indeed on mobile towers.

The regulations specify that all structures higher than 18m (I think) need warning lights for low level aircraft.
 

Azimuth

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Thanks for that. :) I hope there's no secret which panels are yours should we ask? The cell operators obviously won't point out anything. :(
 
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Azimuth

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I did three shoots the weekend - one MTN/TM/Cell C base station, one MTN/TM base station and finally a Cell C base station. I'll hopefully edit and share the photos this week.

Any comment on my opening post? Any corrections?
 

Azimuth

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View attachment 133967
From afar.

nhplcRG.jpg

Up close. This is my base station I have clear LOS to. It's 1622m away.

RSSWD7F.jpg

What is what here? Anyone that is in the know, feel free to chime in.

VjYi5uX.jpg

All the sector antennas seem old yet this site was upgraded within the past year to 100Mbps LTE.

BogLMAF.jpg

Again, not sure what antenna this is, or what belongs to who.

2TAz1Lu.jpg

MTN owns this site but also hosts Telkom Mobile (Cell ID 174) equipment. There is only one large BTS shelter from what I could see. While I saw no Vodacom signage, I did see a box on the wall with label "Vodameter"... (???)

T7MoqLZ.jpg

An active GPS antenna.

LwuHaev.jpg

When looking carefully you can see the frequency on the side of the unit is 1574.42 MHz. This is the L1 band used in the GPS system. This GPS will provide both a time and location reference to the cell operator. This is used for TDD time guard interval (Telkom Mobile only at this stage).

[Thank you AntennaMan, jcheek and SteveO for identifying and explaining this.]

bOhinxS.jpg

"Feeder" cables.

Thanks SteveO.
 
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Azimuth

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HA6qUS3.jpg

Feeder cables on their way to the cell tower.

oEvug18.jpg

Company that provided the cooling for the BTS shelter.

pzEixiE.jpg

The cabling is a combination (Hybriflex) of fibre and DC power to link the BTS to the RRUs. More correctly termed "feeder cable" or FTTA (Fibre-to-the-Antenna).

utacpDM.jpg

This is a Diplexer that allows the use of one set of feeder cables to carry the RF for two frequency bands.

Thanks SteveO for the correction!

v0nnQ7B.jpg


XrHluOX.jpg


ZxTCFLP.jpg
 
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Azimuth

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ysiCMa4.jpg

Cables between the RRU and sector antennas are coax jumper cables.

mb6BSkB.jpg

Damn this tower is high, higher than the moon. :p

Notice how there are no microwave dishes hence this base station is running off fibre backhauls *and/or* not feeding any other cells. Both MTN and TM must each have their own fibre backhaul here. (Still not sure if VC is at this site or not...)
 
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AntennaMan

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T7MoqLZ.jpg

Interested to know what this is...

LwuHaev.jpg

Close-up. I hope the high resolution photo I took is in tact because I can read the writing on the original.

That is an active GPS antenna. When looking carefully you can see the frequency on the side of the unit is 1574.42 MHz. This is the L1 band used in the GPS system.

The fact that it requires 5V and there is a current specified means that it is active. Using a device called a bias-tee, you can feed DC through the coaxial cable and thereby power the amplifier inside this antenna.

It is difficult to see the gain on the label, but a lot of commercially available active GPS antennas has 20 - 30 dB amplifiers inside. The size of the enclosure also leads me to believe that it uses a patch antenna. Patch antennas are used for a lot of these types of applications since it will always point upwards. The radiation pattern of a patch is ideal since you don't need a lot of gain on the horizon, but from about 20 degrees above horizon you want decent gain.
 

Azimuth

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Much appreciated AntennaMan! Where have you been hiding all this time? :p
 

AntennaMan

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Much appreciated AntennaMan! Where have you been hiding all this time? :p

I have been lurking...

I recently had to fight because of bad active GPS antennas. The company that made good quality ones and were funded by DARPA went out of business. Trying to stay afloat, they cut costs by removing the SAW filters inside the amplifier. This caused us significant headaches... and they went bankrupt anyway.
 

Azimuth

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Fantastic! I hope you can create a few interesting threads without ending up on a hit list. :)
 
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jcheek

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That is an active GPS antenna. When looking carefully you can see the frequency on the side of the unit is 1574.42 MHz. This is the L1 band used in the GPS system.

The fact that it requires 5V and there is a current specified means that it is active. Using a device called a bias-tee, you can feed DC through the coaxial cable and thereby power the amplifier inside this antenna.

It is difficult to see the gain on the label, but a lot of commercially available active GPS antennas has 20 - 30 dB amplifiers inside. The size of the enclosure also leads me to believe that it uses a patch antenna. Patch antennas are used for a lot of these types of applications since it will always point upwards. The radiation pattern of a patch is ideal since you don't need a lot of gain on the horizon, but from about 20 degrees above horizon you want decent gain.

Yip, AntennaMan is spot on with that.
I have a couple of these antennas in my cupboard, but more the consumer-grade variety. Many of the more "serious" consumer GPS receivers support the connection of an external active antenna to improve accuracy. The company Trimble was (and maybe still is) big in that game.

I'm interested to know what it's used for on a cellular base-station - apart from telling the station equipment where it is :p
My guess would be that it's used to provide a very accurate time reference, since the time-sources in the GPS satellites are deadly accurate.
 

AntennaMan

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Fantastic! I hope you can create a few interesting threads without ending up on a hit list. :)

I won't go into details regarding my work, but I will be happy to answer antenna related questions if I can.
 

AntennaMan

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Yip, AntennaMan is spot on with that.
I have a couple of these antennas in my cupboard, but more the consumer-grade variety. Many of the more "serious" consumer GPS receivers support the connection of an external active antenna to improve accuracy. The company Trimble was (and maybe still is) big in that game.

I'm interested to know what it's used for on a cellular base-station - apart from telling the station equipment where it is :p
My guess would be that it's used to provide a very accurate time reference, since the time-sources in the GPS satellites are deadly accurate.

My guess would be both time and location reference. For example, Google maps can triangulate your position from the position of the cell tower your phone connects to. That is if your phones GPS and Wifi is turned off.
 
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