What determines speed?

[Dolby]

I moved to Northriding about 7 months back and to my horror, Vodacom data was non-existenent rendering my contracts useless. The phone would display EDGE, but it wouldn't even connect - ZERO throughput.

I took out an 8ta 10GB special for my data needs, but at the same time moaned daily to Vodacom about lack of service. Someone was sent out, verified no signal, and Vodacom installed a booster/repeater on my roof - which allows me to use Vodacom data once again (On my iPad)

Tonight I thought I'd try both cards in my PC and get signals strength, RSSI etc - but I don't understand what gives performance? Tested with a 21mbps E1820 modem, my results :

8ta ... 67% HSDPA+ signal /-93dbi. Speedtest.net gets 80ms ping,and download at 3mbps (peak at 6+mbps)

Voda ... 99% HSDPA+ strength / -65dbi. Speedtest gets 150ms ping and download at 1mbps (peak at 1.5mbps)

These have been consistent with results from the past few months - so neither provider had a tower issue or anything negative impacting. On paper, the Vodacom should get great speeds - but it doesn't. I'm not too phased as it's my iPad data ... but I'm curious as to why?

 

[guest2013-1]

with wireless it's always OTHER users on the same tower as you that is a big contributor to what speed you'll get... and several little factors like backhaul from the tower to the DC etc.

 

[ginggs]

Voda ... 99% HSDPA+ strength / -65dbi. Speedtest gets 150ms ping and download at 1mbps (peak at 1.5mbps)

I'm guessing that's the strength of the signal you are picking up from the booster/repeater, not from the tower.

 

[Tiscanny]

Vodacom installed a booster/repeater on my roof

can that be done? and what was the cost?

 

[Sinbad]

I'm guessing that's the strength of the signal you are picking up from the booster/repeater, not from the tower.

Indeed.
What is the signal strength that the repeater is getting from the tower?

 

[Dolby]

That Voda signal is with it on ... But the speed (although ideal for me) is relatively slow with those specs. So I can assume its other users or backhaul?

With it off, it either registers nothing ... Or I get 0% signal with RSSI of between 105-113 ... Won't even connect

Tiscanny - only the networks the self can do it. A repeater or booster is seen as broadcasting on their frequency which is illegal. They retain ownership

 

[ginggs]

That Voda signal is with it on ... But the speed (although ideal for me) is relatively slow with those specs.

You don't know the signal strength that the repeater is getting from the tower, so you cannot say whether it is relatively slow or fast.

So I can assume its other users or backhaul?

No, your problem is signal strength:

With it off, it either registers nothing ... Or I get 0% signal with RSSI of between 105-113 ... Won't even connect

 

[Dolby]

Oh - I think I'm getting it now ...

So the modem is seeing the booster and that 99% if from booster to modem? Is the the same with RSSI?

 

[SteveO]

HS speed is not only determined by signal strength. The key aspect to look at is the "radio environment" this includes, signal strength, signal quality, external noise and interference etc. Essentially the closer to the tower you are the better the radio environment and thus the better the speeds. That said cell loading also comes into effect here in that there is a limit to the number of instantaneously simultaneous ( only way I can put it) users attached to the cell.

Then other factors come into the fold as well, back haul speed and quality, core network congestion and ISP throttling as well, these all effect your throughput

 

[sajunky]

Repeater boosted a signal, but it inreases background noise, so performance is not directly related to the signal strenght. On the other side I wonder how they managed to increase signal to such levels. Boosters I saw on the Web are rated from 12dBi to 24dBi. They have generally problems with stability, a technical limitation on amplifying signal.

Therefore I expect that the real boosting gives location of the antenna (better signal spot) and gain of the antenna.

If you decide to give up with Vodacom voice, you can take signal from the antenna and feed it directly to the modem or router. Then you can compare peers to peers.

 

[Dolby]

As the figures are skewed, I won't quote them - but this has taken my speed from 0kbps (unable to connect) to 1mpbs - ideal for browsing on my iPad.

It doesn't have a pig tail, antenna or anything connected to anything. Anything Vodacom in the house, now has 3G signal - so there's no way to feed it to the modem/router?

EDIT : On another note - how does this amplify the Vodacom signal only and does zero for 8ta?

 

[UnUnOctium]

8ta ... 67% HSDPA+ signal /-93dbi. Speedtest.net gets 80ms ping,and download at 3mbps (peak at 6+mbps)

Voda ... 99% HSDPA+ strength / -65dbi. Speedtest gets 150ms ping and download at 1mbps (peak at 1.5mbps)

Sounds like tower backhaul is quite saturated (or they have stricter bandwidth management policies) for the Vodacom tower.

As for signal, don't you mean dBm? dBi is used for antenna gain as a power ratio from isotropic.

As for the booster, there are a few types, as sajunky mentioned, there's the ones which make no attempt to demodulate the signal and just amplify (increases signal power and noise, SNR remains approximately the same). And there's also ones which do a demodulation and then modulation such that they exploit the higher sensitivity of their receivers to increase the SNR.

I honestly have no idea which one of those two it is since I don't know the make/model but to answer your question as to how it works for vodacom and not 8ta, they're simply in different bands. This one has been set to operate in Vodacom's bands.

BTW. It's also not impossible that something's up with the repeater. Try switching it off and do some throughput tests (if possible at all without it).

 

[Dolby]

Hi,

Yes - I probably do mean that dBm

I did switch it off : signal is 0% with RSSI at between -105 and -113 ... it won't even connect. That's the reason they gave me this thing anyway, as I had multiple Vodacom contracts which were all useless.

This booster takes it from 0 to 1mbit ... so usuable when on.

My main query was why - with it on - I get awesome figures and a slow speed relative to 8ta. But as ginggs told me, it's picking up the signal from the booster and not the tower.

Perhaps I should try get on the roof and check if I can see a make/model

 

[sajunky]

As for the booster, there are a few types, as sajunky mentioned, there's the ones which make no attempt to demodulate the signal and just amplify (increases signal power and noise, SNR remains

If it is demodulating one, it explains high gain. Then is a question whether it is just demodulating to the intermediate frequency and transfers it to different cell or tries to decode to the digital data stream too. If the later, it comes to the question on capability of the decoder (HSPA+, HSDPA 7.2 or 3.6 ...).

 

[Dolby]

Man, my head is going to pop ... :/

 

[ginggs]

Perhaps I should try get on the roof and check if I can see a make/model

Just out of interest, could you make a note of the cell IDs that you pick up indoors and outdoors please?

 

[UnUnOctium]

Hi,

Yes - I probably do mean that dBm

I did switch it off : signal is 0% with RSSI at between -105 and -113 ... it won't even connect. That's the reason they gave me this thing anyway, as I had multiple Vodacom contracts which were all useless.

This booster takes it from 0 to 1mbit ... so usuable when on.

My main query was why - with it on - I get awesome figures and a slow speed relative to 8ta. But as ginggs told me, it's picking up the signal from the booster and not the tower.

Perhaps I should try get on the roof and check if I can see a make/model

The repeater simply forwards transmissions between you and the tower. It would only improve signal strength and maybe SNR (depending on the type). Whether the base-station or its backhaul can provide you with more speed is a completely out of your or the repeater's control. That's why I think the bottleneck lies in the base-station.

If it is demodulating one, it explains high gain. Then is a question whether it is just demodulating to the intermediate frequency and transfers it to different cell or tries to decode to the digital data stream too. If the later, it comes to the question on capability of the decoder (HSPA+, HSDPA 7.2 or 3.6 ...).

I doubt it would decode it, too much overhead and not necessary at all. Just the modulating signal sampled quickly enough and then remodulated is all it needs to do IMO. Of course, a little bit of phase compensation wouldn't hurt either so that you don't get destructive interference.

 

[Dolby]

Thanks guys,

I will do more tests tonight and get the cell ID's

 

[Sinbad]

The repeater simply forwards transmissions between you and the tower. It would only improve signal strength and maybe SNR (depending on the type). Whether the base-station or its backhaul can provide you with more speed is a completely out of your or the repeater's control. That's why I think the bottleneck lies in the base-station.




I doubt it would decode it, too much overhead and not necessary at all. Just the modulating signal sampled quickly enough and then remodulated is all it needs to do IMO. Of course, a little bit of phase compensation wouldn't hurt either so that you don't get destructive interference.

* Dolby wishes he'd never asked *headspin*

 

[SteveO]

you need to compare the 8ta signal level with the signal level received by the repeater. The BTS will use this level to decide when to schedule packets to you and thus what your speed will be like.