Ask Icepick about cell phones

[icepick]

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What is the range of a cell tower (i.e. generally, how far away can you get from a tower and still get a signal)?

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As with all things, it depends.

In the GSM world, the maximum distance is 63 timing advances, each 550m long, or about 21 miles. This is a very, very rare case.

In reality, it depends on the type of enviroment you're in. Out in the boonies, a really rural area, we'll have one site per town, spaced 10-15 miles appart. In a suburban area, they might be as close as a mile. In an urban area, they'll be blocks appart.

Two reasons we do it this way. People want to use their phones indoors, which makes it necessary to have sites near by to provide that kind of signal strength. The second is that each site can only handle so many calls at a given time. In high population or usage areas, it requires a increased number of sites to handle the traffic load.

[icepick]

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I used to talk a lot while driving cross country. Often calls would drop when I had full signal. I theorized that I was talking via a tower that was at it's saturation point for bandwidth and new calls took priority over existing calls (which would make sense from a business standpoint). Was that theory likely correct?

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In our network, existing calls take priority. Don't even know if we could set it up to be any different.

Now, if you were moving, it's possible you were in the process of switching from one site to the next, and the one you were trying to go to was at capacity.

Many carriers also have a maximum call duration, where they'll cut your call off after X minutes. We used to have that set for 120 minutes, and had to have a minor miracle to have management allow us to bump it to 180. I think it's stupid to have such an frivolous limit like that.

[xx44]

Cool job. NOt going to bash Tmob, but I would like to know why their sevice is notably subpar compared to the other major carriers. Though Tmobile claims to have coverage for most of Nassau County, LOng Isalnd, I frequently get no or low signal. The same with most of E florida b/w W palm and Miami.

Aside from this, when I do get a signal, if I walk inside, lets say into a casino, 20 feet past the doors, no siganl. I cant help be envious of the other players using their phones at the table.

So, what gives??

[BiPolar_Nut]

Thanks. I'm actually surprised, though. Seems it'd be better business to axe existing calls than to give someone a busy signal or other error. This was with Sprint and it's entirely possibly I simply was transferring to a "full" tower. Sprint had coverage on major interstates throughout most of the country at the time (I was driving 18 wheelers), and in rural areas obv they had as few towers as necessary. They had no time limit on calls. I'd frequently place a call at 6:59AM to go on line before the anytime minutes kicked in, and stay on line (used cell as a modem) til noon or even 2PM sometimes before dropping the call (while stationary). The entire call was billed according to the start time, so it was a free "night minutes" call.

[icepick]

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Cool job. NOt going to bash Tmob, but I would like to know why their sevice is notably subpar compared to the other major carriers. Though Tmobile claims to have coverage for most of Nassau County, LOng Isalnd, I frequently get no or low signal. The same with most of E florida b/w W palm and Miami.

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This is extremely dependent on the area you're speaking of. We may be weak in the areas you list, but extremely good in other markets, like Dallas, Minneapolis, Kansas City, etc. Every carrier has good and bad areas. We're well aware of our weaknesses and are working on improving them.

I'm not familar enough with the specific areas you mentioned to address them specifically.

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Aside from this, when I do get a signal, if I walk inside, lets say into a casino, 20 feet past the doors, no siganl. I cant help be envious of the other players using their phones at the table.

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Buildings are hard enviroments to cover. 70% of our complaints are regarding inbuilding coverage. It's our #1 focus at this time. The PCS carriers are at a slight disadvantage because the 1900 MHz band doesn't penetrate as well as the 800 MHz band. The carriers on the lower band will have better inbuilding coverage as a general rule.

I found 90% of the casinos in Vegas to be well covered last time I was out there.

[felson]

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i have service through your company and coverage sucks in my new house. anything i can do to make it better?

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Test your coverage before you buy a house.

Bitch to customer care, believe it or not, we do listen and prioritize new sites based on complaints.

Check your with your local city goverment about possible upcoming hearings reguarding site construction and show up in support of it.

Wait for the above mentioned UMA.

Eat the EFT and switch companies.

Suck it up and live with it.

Install a passive repeater ($20 in parts), which is unlikely to help.

Shell out $500+ for an active repeater.

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I think that installing your own repeater is a violation of FCC regulations.

[jackblack73]

[ QUOTE ]
[ QUOTE ]
What is the range of a cell tower (i.e. generally, how far away can you get from a tower and still get a signal)?

[/ QUOTE ]

As with all things, it depends.

In the GSM world, the maximum distance is 63 timing advances, each 550m long, or about 21 miles. This is a very, very rare case.

In reality, it depends on the type of enviroment you're in. Out in the boonies, a really rural area, we'll have one site per town, spaced 10-15 miles appart. In a suburban area, they might be as close as a mile. In an urban area, they'll be blocks appart.

Two reasons we do it this way. People want to use their phones indoors, which makes it necessary to have sites near by to provide that kind of signal strength. The second is that each site can only handle so many calls at a given time. In high population or usage areas, it requires a increased number of sites to handle the traffic load.

[/ QUOTE ]21 miles is a lot longer than I was guessing. So cell phones can (at least theoretically) work on airplanes?

[BiPolar_Nut]

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The PCS carriers are at a slight disadvantage because the 1900 MHz band doesn't penetrate as well as the 800 MHz band.

[/ QUOTE ]

I'm not calling you a liar because you are clearly in the industry and I am not. That being said, I am an amateur radio operator and techy geek...and it's a very basic RF principle that higher frequencies penetrate better than lower frequencies (and have shorter range...so perhaps this is a range issue and not a penetration issue?).

Real world example: I live in an OLD apartment highrise w/ real plaster walls (not drywall). The chickenwire-like base the plaster sticks to basically creates a faraday cage. I'm less than 1 mile from a 50,000 watt AM radio station (< 1MHz) and cannot pick up the station on my clock radio. FM stations ( > 80MHZ) broadcasting w/ less power from farther away at lower altitudes come in better. Cell service works flawlessly, even in the elevator in the center of the building.

[icepick]

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I think that installing your own repeater is a violation of FCC regulations.

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I believe you're allowed upto a certain wattage. Dunno what the limit is.

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21 miles is a lot longer than I was guessing. So cell phones can (at least theoretically) work on airplanes?

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Provided it isn't moving, and you can penetrate the skin of the plane, more or less, yes. Moving planes have two problems, one is that the GSM spec only provides for a maximum speed (something like 180 mph), and secondly we design our networks to hand off from one site to another, and those sites are adjacent. In a plane, you could quite possibly go from one site on one side of town to another on the other, with miles in between them, skipping tens (hundreds?) of sites.

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I'm not calling you a liar because you are clearly in the industry and I am not. That being said, I am an amateur radio operator and techy geek...and it's a very basic RF principle that higher frequencies penetrate better than lower frequencies

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I'm not going to call you a liar, just misinformed. Lower frequencies do penetrate better. Higher frequencies do not. That's just physics.

Why do you think the guv'ment uses ELF (3-30 Hz) to talk to submarines? Besides the ground wave effect, they penetrate sea water, which higher frequency waves can not do.

[cliff]

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How common are those devices that let you listen in on cell conversations? I heard they are only made in china and are hard to get ahold of, still i'm curious how often my cell conversations are being listened to.

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That's a really good question.

To my knowledge, there is no device that will let you listen to live, over the air conversations that are using GSM or CDMA. To much math and frequency hopping going on to decode it realtime. Now, who knows what the NSA could do. I suppose, it could be possible to record the encoded conversation and then analyse it later, but that's pretty theoretical. Besides, a moving conversation will talk to many different cell sites, on many different frequencies very quickly. In any case it'd be expensive, big, and very very rare.

However, all providers have to comply with wiretap requests, and the FBI has equipment setup to allow them to tap lines at will. We as a company (or as individuals) can't and don't know who they're monitoring at a given time. Used to be that it was done manually, and we set it up for them, but they cut us out of the loop a few years back.

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I know of no comercially available devices that can listen to a cell phone conversation, but I would bet they exist (maybe not for sale though). Given enough processing power, it can be done (not cheaply). The only fundamentally hard problem is cracking the encryption on the data, the basic signalling (CDMA code, TDMA timing, etc.) has to be broadcast from the cell tower to the mobile (and hence can be intercepted), and the way this is done is specified in the standard for the technology (CDMA, GSM, WCDMA, etc.) If you can break the underlying encryption on the data, the rest is "easy". The business about CDMA being inherently secure is an exageration, like most security systems, anything but the base encryption just raises the bar on how much work it takes to eavesdrop.

If you had enough money and talent and had a way to crack hard encryption, you could do it. I think there are groups out there that meet these requirements.