Tower Locations and Improving Signal Strength

[wndrbees]

Since December my -77dBm signal has deteriorated to a -91dBm with an external antenna. Upon investigation found the base station which I am receiving from is only around 600m away at the Telkom exchange at the corner of Belmont and Queen in Rondebosch, confirmed with Cell C tech. So I pointed my antenna directly at the tower, note: I cannot get a direct view due to trees and buildings, and it did not make a big difference. I did however notice the Cell ID jumping between 40501 and 40502. Then when driving past the tower I noticed my location was right in the middle between two sectors as illustrated: http://mybroadband.co.za/photos/showphoto.php/photo/21949/title/tower-position/cat/500

I did tilt the antenna slightly to one side, to try and force on one cell and it does work to some extent however still a fairly poor signal strength. I am suspecting it is the combination of being in the center of two sectors and high apartment blocks to be the culprit, since driving about 50m down the road with my laptop the signal is -67dBm. I am also wondering if they have adjusted the cell transmitters around about December time, when I noticed a definite signal decrease.

Anyway, just wanted to share my pain and my diagram

 

[ginggs]

I think that's a different sector on the same tower.

See this post:
http://mybroadband.co.za/vb/showthread.php/273804?p=5661331#post5661331

 

[ajax]

I did however notice the Cell ID jumping between 40501 and 40502.

You can't maybe remember the Cell ID from December (the one with the good signal)?
Have you done speedtests when using each of the above sectors? I've experienced a similar issue described here

 

[wndrbees]

You can't maybe remember the Cell ID from December (the one with the good signal)?
Have you done speedtests when using each of the above sectors? I've experienced a similar issue described here

Yes, the Cell ID from December was the 40502 one and I can't remember picking up the other sector, 40501, before. Have not done explicit comparisons between the two sectors with speedtest, from experience both offer similiar poor performance with DL >1Mbps if I am lucky, but it is a good idea to determine which one to angle to, will update this post. I feel your pain.

 

[ajax]

from experience both offer similiar poor performance with DL >1Mbps if I am lucky,

Speeds drop off quickly when your RSSI is in the -90's of dBm, but it doesn't rule out congestion necessarily. To rule out cell breathing, have you checked the signal in the middle of the night too?

 

[TimTDP]

Speeds drop off quickly when your RSSI is in the -90's of dBm, but it doesn't rule out congestion necessarily. To rule out cell breathing, have you checked the signal in the middle of the night too?

What is the ideal dBm?

 

[ajax]

What is the ideal dBm?

The absolute value of the dBm should be 75 or less. But I've obtained around 6 mbit/sec in a speed test with a value of 83 (-83 dBm).

 

[1geoff99]

From this link:

Marginal - Levels of -95dBm or lower. At these sort of levels, it is very likely that you may suffer low throughput and disconnects due to cell loading/breathing even with an outdoor antenna.

Workable under most conditions - Levels of -85dBm to -95dBm. Probably worth considering an outdoor gain type antenna. Could suffer poor throughput and disconnects due to cell loading/breathing.

Good - Levels between -75dBm and -85dBm - normally no problem holding a connection with this sort of level (even with cell breathing) without the use of an external antenna.

Excellent - levels above -75dBm. Should not be affected by cell breathing/loading and should not require an external antenna.

 

[wndrbees]

Speeds drop off quickly when your RSSI is in the -90's of dBm, but it doesn't rule out congestion necessarily. To rule out cell breathing, have you checked the signal in the middle of the night too?

Signal stays very much the same, however I tend to get better DL early in the morning, peaks on MDMA around 1.6Mpps when download left overnight, slight increase nothing to write home about. So I take network congestion to be having an effect, just not the major problem, which I think is physical. As I pointed out, there is good signal (-67dBm) just down the road, which is not closer w.r.t. distance, but better positioned w.r.t. angle to the cell.

 

[lotus123]

How do I locate CellC towers in my area

I've set up my K4505-Z modem and Billion 7402-NX router, and connected my old Poynting high-gain antenna using a pigtail from an old Huawei E620 card (it fits). Using MDMA on the laptop I can see an improvement from -85db to >=51db using the antenna. A good Speedtest result (they vary somewhat) shows ping of 50ms, 7.5 & 2.5 mb/s.

I have not changed the direction of the aerial from it's original Vodacom tower (about 800m away). I'd like to know how to find the nearest CellC tower to re-orient the aerial.

Is there a map showing co-ordinates for these towers that I can refer to?

 

[jem]

In short, no.

Last time I tried to get that info from the call centre the guy kept telling me where the stores were instead

 

[ajax]

Erm with -51 dBm you really REALLY don't need to fidgit with your antenna any more! If it ain't broken, don't fix it!

 

[lotus123]

In short, no.

Last time I tried to get that info from the call centre the guy kept telling me where the stores were instead

Priceless!

I have an idea from reading posts (that I can never find again!) that one can do this using a suitable mobile phone.

 

[lotus123]

Erm with -51 dBm you really REALLY don't need to fidgit with your antenna any more! If it ain't broken, don't fix it!

True, but seeing as it's aimed straight at a very close by Vodacom tower it can probably improve a bit.

"If it ain't broken I can probably still fix it!" - Tim "the Toolman" Tyler

 

[ajax]

True, but seeing as it's aimed straight at a very close by Vodacom tower it can probably improve a bit.

If you really want to improve it then you will have to come up with some sort of attenuator. If you have access to the metal parts of the antenna you can try to short them out with a piece of wire. Basically if you can drop the gain of the antenna to 0, you would potentially end up with a signal of around -60 dBm giving you then an extra 9dB to read off of the RSSI on MDMA.

But again, this is really not necessary! There will come a point where the input signal is just too strong. The receiver will start to behave non-linearly and you could see your speed actually drop.

 

[lotus123]

There will come a point where the input signal is just too strong. The receiver will start to behave non-linearly and you could see your speed actually drop.

I can see your point here.

However, you don't think it would be better aimed away from the Vodacom tower, and more towards the CellC tower do you? As you say, it's not that I really need a better signal but I would like to optimise as far as possible. This area has a really high density of traffic, and around 16h30 until early evening there is a noticeable decrease in performance (far far worse with Vodacom 3G I might add). I can only imagine the stronger your signal the better your performance during those periods?

Thanks for your feedback, BTW!

 

[cedaw]

You could try querying your LAC and cell-id at http://www.location-api.com If your tower is in their database it should give you back the coordinates. The coordinates are not always pinpoint accurate, but it should be good enough

 

[lotus123]

You could try querying your LAC and cell-id at http://www.location-api.com If your tower is in their database it should give you back the coordinates. The coordinates are not always pinpoint accurate, but it should be good enough

Thanks - after a bit of to and fro-ing I deduced that the cell is not on their database. It is 19892, FWIW.

 

[1geoff99]

I learnt today that my antenna was pointing in the wrong direction. Cell C sent me a technical report related to a problem I logged with them. The report included a map of the towers in my area. From that I could tell that my antenna was pointing in the wrong direction by about 50 degrees! I don't know how that could have happened. Anyway, pointing in the right direction improved my signal strength by a further 10 dBm (from -74 dBm to -64 dBm). I think it shows the importance of having access to the tower locations.

Now that my antenna is pointing in the right direction...

This is what I was getting before in the early hours with the wrong antenna direction...

 

[Bundu]

I just noticed Cell C has updated/fixed the coverage map - You can now zoom in much closer to the area you want to check for coverage - Great, Thanks!