Anyone here versed in cellphone technology?

[TillEulenspiegel]

I have a question about the protocols used in the handoff between a "local" call designation and "roaming".
I looked at my wifes cellular bill and wondered why it was so high, she only uses it locally and even then only when on a job sight. I looked at the bill and there were charges for roaming that's why the bill was high. I showed her the bill a she explained that even standing still at home with a fully charged battery the phone will slip in and out of roaming mode. I opened up the phone and sure enough the thing was in roaming mode and stayed there. It's not the phone , this is the second phone and the first one acted the same way I am on the outskirts of Tampa,FL ( which is flatland anyway) at a high point for the area, so there shouldn't be any dropouts because of terrain.

Altho I'm not a conspiracy theorist, I'm beginning to think that this "feature" was engineered that way, for obvious reasons.
Any Ideas?

 

[Aoidoi]

(Note, not really an expert on cell phones, I work on the infrastructure side of the business. Others are likely better from the phone end. )

What plan are you on? i.e. what does your plan say roaming is, geographically... SE US, Florida only, Tampa area, etc. Maybe your home is at the edge of their coverage? (seems unlikely)

Does your cellphone company have deals with other providers for broader coverage? The first thing that springs to mind is that the phone could be picking up a competitor's signal as stronger and camping on them instead, which would then likely result in roaming charges regardless of location. I would think the phone would be set to try to camp on your providers equipment if available, but maybe you happen to be at the limits of whatever tower is around for your provider so the phone goes looking for other options. I believe most phones will say who's network you're on, if it's not your provider that's likely the reason for roaming.

Other random info questions:
- what technology is the phone? CDMA, GSM, TDMA etc. You might not know, somewhat oddly the providers rarely seem to mention this.
- Who's your provider? I'm not real familiar with most of them, but maybe others have had similar experiences with their services.

 

[wayrad]

I'm no expert, but are you using a dual band phone that is slipping into analog roam? Can you just disable analog roam, or set it so it will ask for confirmation before switching?

 

[a_unique_person]

I bought my wife a CDMA phone. It is new here in Australia, because a lot of the country is sparesly populated, so the GSM system doesn't work too well once you leave the populated areas.

It also has roaming, and I turned on the option of beeping when it entered an left roaming. After a few days, it was driving us crazy. So I turned it off again. Note that we don't get charged for it going into/out of roaming, we just lose the cheaper rate when we make a call if it does.

The battery life has not been too good, so I thought it might have something to do with going in/out of roaming mode all the time. I disabled the ability to roam, and this was fine, till we did go out to the country for a few days, and couldn't work out why it didn't get a signal. I turned on roaming again, and it is worked fine.

I really should disable the roaming again.

When my wife complained about the roaming, she was told some of the phones, (They are Hyundai), have a problem, and to bring it in to be fixed. I would guess that this would be to get a firmware upgrade.

 

[Luceiia]

Till,

1) Is the phone CDMA, TDMA, or GSM?

2) What brand and model is the phone?

3) Who is your carrier?

4) It's most likely a bad antenna or antenna circuit, but could be a bad NAM file, bad phone setting, or a glitch with where your carrier thinks you wish to use the phone. Best bet is to take the phone to your carrier and ask them to fix it.

5) Those little antenna amplifiers that are sold...
http://cellphones-accessories.com/cell-accessories/antennabooster.html

as well as the radiation guards...
http://cellphones-accessories.com/cell-accessories/anprod.html

are pure claptrap.


Luceiia

 

[TillEulenspiegel]

The carrier is Sprint, so ......
The phone is Kyocira (sp ) sold in any circuit city or best buy store.
The transmission scheme is ( Duh, we'll have to get back to you) unknown .
As I stated there were two phones that acted identically. ( first one was a loss to gravity. =) ) So it's not a peculiar case. I think it may be related to the handoff threshold in regards ( as was mentioned Aoidoi ) by to cooperative companies that split the services with the subscribed carrier , which would be beneficial to both.

The fact that this handoff can exist in favor of the cell companies is in and of it self not suspicious, that it seems to be prevalent in " covered areas" does , if you can be in a topographically flat environment , at the subscribed address, 7 miles from the carriers office smells funny to me , I don't live in podunk, Montana.

 

[wayrad]

The carrier is Sprint, so ......

It's CDMA, then. I have it too. Reception was lousy where I used to work (constant dropped calls, constantly trying to go into roaming) but a firmware upgrade helped a little. However, I'm now working in a location with even worse reception, and plan to switch to Verizon as soon as I can. Seems like there are a lot of dead/intermittently bad spots even in areas that Sprint claims are covered (IMO, YMMV).

 

[Cinorjer]

It sounds like you're on the edge of the company's coverage area, or in a spot that's weaker than it should be. If their map shows your location should be covered, then you have a case for getting those roaming charges eliminated from your bill.

The programming in the cellphone searches for another carrier when its primary service signal falls below a certain parameter. But it continues to monitor for the assigned signal and switches back when it's seeing that one again. Your primary assigned frequency seems to be right at the threshold, causing it to toggle back and forth.

Technically, they have a problem with their signal area. But every carrier has these dead zones and can't do much about it unless they put up a bunch more antennas. You might have to change services, and turn off the roaming feature on your cellphone unless it's needed for a trip.

 

[Luceiia]

The carrier is Sprint, so ......

Most likely CDMA, as wayrad indicated. I'd take it to Sprint's office and ask them to make sure it has the latest and greatest PRL file, the correct NAM data, and to check the sensitivity just to make sure the phone is operating up to snuff.

The PRL is an acronym for Preferred Roaming List and it contains a list of tower ID's to look for and other data about previous attempts to connect to those tower ID's.

The NAM is the Number Assignment Module that contains the ESN (unique ID number) as well as the phone's telephone number and home location and some other configuration data.

The fact that this handoff can exist in favor of the cell companies is in and of it self not suspicious, that it seems to be prevalent in " covered areas" does , if you can be in a topographically flat environment , at the subscribed address, 7 miles from the carriers office smells funny to me , I don't live in podunk, Montana.

You could live in a 'dead spot' or too far from their nearest tower. You could call and ask to speak with one of their engineers and ask if he/she has any idea why you're roaming when you clearly should not be.


Luceiia