Could this be correct? "Old" or "Aging" SIM Card affects Signal Strength?
 

I generally believe tech support people when they seem to honestly be trying to help me. That may be my first mistake.

But, today, I heard an interesting one. Both Mrs. jsnydcsa and I have exactly the model same T-Mobile ("T-Mo") BB Curve (8320) purchased same day about 2 months ago from T-Mo. We've both been T-Mo customers since about early 2004 and have had the same physical SIM cards since then (phones have changed, SIM cards have not).

We've noticed that my wife's BB gets significantly fewer signal strength "bars" than my BB and also, when my displays EDGE (all caps), her's displays edge (all lower case) or worse (e.g. GSM, gsm or just SOS).

So today, I spoke with T-Mo customer supports BB PDA department. I described the problem and, without missing a beat, the rep asked me how old Mrs. jsnydcsa's SIM card is. I told her and she said that that could be the problem. Since there's a T-Mo store right around the corner, I picked up a new SIM and tonight, will switch it out with her current SIM and see what happens.

Could this really be the case? Does an "old" or "aging" SIM Card affects signal strength I receive?

No, it has nothing to do with it but can't hurt to replace the SIM. More likely her Blackberry is defective.

Swap your card with hers and see what the signal strength is. If yours drops and hers goes up, it's the SIM card.

I would bet it's the way the sim is seated though, dirty contacts, whatever. The Iphone has had an issue with the sim card not seating correctly causing signal strength issues, there have been many stories about fixing your phone with scotch tape.

Would it actually affect received signal strength (as seen by the receiver circuitry) or just signal quality on the voice side? Seems odd that the SIM would affect received signal strength.

Cheers.

The SIM has nothing to do with signal strength or RF reception. The SIM is just a vessel that contains the subscriber ID (IMSI), private key (Ki), and phone number. The phone presents the data contained in the SIM to the network.

That said, if there is a bad electrical connection between the SIM and the phone or some other SIM problem, the phone could have trouble accessing network services.

I've heard that coloring the edge of the sim with green ink from a sharpie greatly improves reception.












"That's a joke... I say, that's a joke, son."

Actually, the sim card holds cell tower routing info. So, while it doesn't directly affect signal strength, it is possible that an old sim may connect you to towers that are farther away. IIRC, there is some GSM command to reset the sim routing table, but when this happened to me, it was easier to just have the sim replaced. FWIW, frequent travel can cause this as well - there is a limit to the number of cell towers that each sim can cache.

SIM

SIM cards store network specific information used to authenticate and identify subscribers on the Network, the most important of these are the ICCID, IMSI, Authentication Key (Ki), Local Area Identity (LAI) and Operator-Specific Emergency Number. The SIM also stores other carrier specific data such as the SMSC (Short Message Service Center) number, Service Provider Name (SPN), Service Dialing Numbers (SDN), Advice-Of-Charge parameters and Value Added Service (VAS) applications. (look to GSM 11.11)

It does not contain routing tables.

From the same wiki post... not routing tables - location area identity. Had heard this referred to as cell routing tables - similar in function to a network routing table.

IIRC, there was once a long discussion of this on Howardforums, but I get way too many hits searching to find the old thread.

Whatever the name, I've been told by T-Mobile CSR's and did see others with some explanations on Howardforums, that the sim can cause issues in connecting to the proper tower.

I had the same issues just this fall. Right after getting a BB 8820, the problems started. I tried a new SIM, a new BB, and still nothing. Mrs. UALfromMSN's ATT BB was getting amazing signal here in the apartment, while TMo gave me nothing.

When I finally called to cancel, the Tmo guy told me there couldn't be a problem, as I had made over a 1000 minutes of calls in the last 3 months, and then hung up on me.

As of that day, ATT was my new carrier, and has given me no problems.

The LAI is transmitted from the network to the phone, where it is stored in the SIM. Only one LAI is stored in the SIM at a time, and it shouldn't matter how old the SIM is - the SIM only gives 5 bytes for this information! (See GSM 11.11 10.2.17).

I was told the same thing by T-mobile. I went to the store, got a new SIM and it helped. I'm wondering if it was just the contacts on the SIM getting dirty or getting too scratched up?

Its a free swap, so mine as well try it.

I still use a 1999 Virgin Mobile SIM for the UK. It is not perfect shape and it works perfectly.

"You need a new sim" is code for "I don't know what the problem is, but I want to move on to my next caller".

CSR's use this excuse all the time when they can't come up with a reasonable solution.

EXACTLY!


RFTraveler// :D :D :D