3G question regarding cell towers

[brandonb]

Not sure how highly technical this is, but have a question:

I have a wireless 3G datamodem for internet at home that I've been trying to get working. My home is about 7 miles from the closest tower. I use a Yagi antenna to gain signal. When using the antenna, I recieve a 80-90dbm noise level to that tower. When connected to that tower, any HSDPA connections are working just great, and I'm receiving up to 300k/s with under a 100ms ping.

However, due to the nature of 3G, once you are not passing traffic, you get downgraded to a UMTS connection. This is not working at all on this tower. And the datamodem will transfer me to another tower which is 10 miles away in the same direction which is too far to transfer traffic (about a 113dbm). Then I get nothing.

To combat this: This forces me to once connected to continously download traffic (usually a 10 gig torrent file set at a 32k/s max transfer rate) to keep from being downgraded into UMTS. Which works fine, but I have to have the computer on all the time. Once I'm down with UMTS, it can take up to a day to get back into HSDPA on the main tower. I only have an uptime of maybe 50% of the time, and that is only if I'm downloading contantly.

When I unplug my data modem from the antenna, it does not see the further tower which is 10 miles away, and does not transfer in UMTS to the original tower, and I run into the same problem, and have the same issue.

I keep trying to tell the company that UMTS is not working on the tower which is 7 miles away, and if they can look into it. But they keep telling me to piss off and that is not it, and they can't figure out why it keeps transferring me to the next tower. They said they lowered the antenna on the tower (10 miles away) for a day or two to see if it would help (not be detected by my yagi) but it cut out some other of their customers so they tilted it back up. (It did not make a difference on my end)

The question being:

Is there any other circuitry or anything different in cell phone towers between UMTS and HSDPA? Could one technically be fried out while the other worked?

 

[Mark R]

Most modern cell equipment is split into 2 components:
A baseband unit (BBU) and a remote radio unit (RRU). The BBU is an all-digital CPU, which is connected over a high-speed digital link to the RRU. The RRU essentially just a DAC/ADC and frequency shifter connected to an antenna.

In effect, all the processing is done in software on the BBU. In fact, upgrading from UMTS to HSDPA/HSPA+ can be done by a simple firmware update (or replacing the BBU if the incumbent's CPU isn't strong enough)

As a result, a hardware failure would seem most unlikely as the cause.

 

[Lemon law]

As some one whose only broadband options are either 3G evdo or satellite internet, I have been somewhat been forced to better understand 3G internet issues. And as I result I have joined some 3G internet forums as educational tools.

Quite frankly, the issue of UMTS Or HSDPA have never surfaced in any of these forums.
Leading me to speculate our OP is barking up the totally wrong causal tree.

First of all, seven miles from a cell phone tower is usually a bridge way too far for 3G EVDO, even if an added Yagi antenna might hep if its still LOS. Ten miles is usually hopeless.

But without knowing what 3G provider our OP's modem expects, the frequency that 3G modem expects, if its the the 3G tower 7 miles away, or that tower 10 miles away, I am being given nothing to go on.

But fact one, 3G EVDO can swing in two basic ways, the more modern 3G EVDO revision
Rev A, which can deliver best case scenario download speeds of more than 1 MBits/sec down. Or degenerate to the more primitive 2G standard of 1xRTT which might at best deliver something on the order of 300 kbits/sec down. Your connection manager software should tell you if you connect at EVDO rev A or at 1xRTT at any given time.

After that, it gets weird, even if two different EVDO providers operate on the same frequency, you can only get EVDO revsion A if you can connect to your modem's tower network. So if you have say a Tmobile modem that best connects to a closer sprint tower, you are fucked on getting TMobile 3G REV A and vice versa. Because piggish providers do not share their better 3G Rev A.

But the story changes for the older 2G standard of 1XRTT, because any 3G modem is allowed to contact and share the older and slower 2 G standards in a 1XRTT connection.

Then the plot further thickens, as many cell phone towers do not have the front haul and back load haul capacity to service all users when demand ramps up. With peak demand hours usually between 1 PM and 1 AM for many towers.

And as some towers can no longer handle the demands, they drop users, not on the weakest signal levels and instead on the most distant first criteria. Which could explain why our OP is screwed so often.

After that, if our OP wants more insights, he or she is welcome to PM me. I have written enough already.

 

[jersiq]

I'll preface this with:
I am a CDMA/LTE guy, I have never worked with UMTS.

However, there are some comparisons in CDMA that could be at play here.
There is a problem called PN masquerading, where the far tower has a different PN, but due to time shifts it appears as the same PN as the near tower.

In a very generic sense, the PN identifies the sector of the BTS that is transmitting. Of course, you can then see a problem as the phone will lookup the SiNR associated with that PN and actually find two different values.

Also, there could be an idle mode reselection problem with your handset/aircard where it is not properly reselecting the appropriate air interface after going idle. Generally, this is actually a handset/aircard problem. You may need to investiagte this from an aircard perspective rather than a provider perspective.

For any troubleshooting, do you have access to other aircards (different manufacturer and model) to see if the problem can be recreated with those?

Because piggish providers do not share their better 3G Rev A.

Dude, roaming agreements are for just that, roaming. Instead of complaining about not being able to roam while in native coverage, rally your provider to give better service in their native coverage.
If your phone is automatically roaming within native coverage, then you need to have your provider address their PRL's. It's the original providers fault, not the roaming provider. The phone does constant lookups for system ID's and will select preferred networks based upon the lists.
Besides, providers don't "share" spectrum. They purchase blocks of spectrum from the FCC (or whoever previously owned the spectrum), and transmit solely within those frequencies. In fact, it's a 10,000 per day fine for transmitting in another providers band without any agreement between the providers.[/quote]

Then the plot further thickens, as many cell phone towers do not have the front haul and back load haul capacity to service all users when demand ramps up. With peak demand hours usually between 1 PM and 1 AM for many towers.

And as some towers can no longer handle the demands, they drop users, not on the weakest signal levels and instead on the most distant first criteria. Which could explain why our OP is screwed so often.

They never had all that capacity and they never will, unless you are willing to charge customers $500.00 for service. Cellular has always been an oversubscribed network (with the sole exception of TLDN) and always will be.

And unless the provider is providing any form of QoS, it's a first-come fist-served basis. No one is dropped, even in the case of Wireless Priority Systems.

 

[brandonb]

Hi guys.

Thanks for the input.

I talked to my provider again this afternoon. I tried talking to them more technically (which I fail at miserably when it comes to this subject) and they mentioned that there may be some tower forwarding issue at play. So while my signal is based on the better tower, the better tower is telling the other one to forward me the message, and that may be the reason why even though supposedly on UMTS with the near tower, that the forwarding is actually causing the other tower to send me the message with UMTS which is why the connection is dying.

They did say that they contacted the modem manufacturer (GlobeSurfer 3 FYI) and asked for a BIOS which would allow the modem to opt-out of the tower forwarding awhile back, and they recieved the patch to fix that. And that they installed it on my modem from remote today. I'm stuck at work so I have no idea what the result will be for this, but I will find out.

 

[Lemon law]

Jersig, you may be confused here, we are talking EVDO wireless internet access for computers and you basically seem to be talking about cell phones.

 

[Mark R]

Jersig, you may be confused here, we are talking EVDO wireless internet access for computers and you basically seem to be talking about cell phones.

We're talking about UMTS/HSDPA aircards. Not EVDO.

 

[brandonb]

So far the BIOS update has been working fine. It hasn't dropped a connection yet. So it's looking good.