Question For Cell Phone Technology Experts

[Shantanu]

Anyone here know a lot about cell phone technologies? Good, because I have some questions.

First, does your cell phone and the communications tower, transmit the signal equally in all directions? Or does the phone have some way of radially directing the signal at the communications tower (or to the phone, from the communications tower)?

Also, with phones that can handle multiple frequencies of the same communications sort (such as CDMA 1900, 800, or GSM 900/1800/1900), do the phones have a seperate communications device for communicating at each frequency? Or does it merely require a software switch to go from GSM 1900 to 900. Also, does it cost a whole lot more for the companies to manufacture a multi-frequency phone versus a single frequency phone (this does not include phones that have seperate technologies, like CDMA and AMPS)? The reason I ask is that there's not a huge price difference between multi-frequency and single-frequency GSM phones. But if adding extra bands is cheap, you would expect all GSM phones to be multiband (even if people aren't going to use the feature, its an appealing thing to have the brochure), but you quickly find that most of them sold in the U.S. are single band.

<-- Uses Nokia 5190 with Voicestream

Thanks.

 

[Pabster]

Shantanu wrote:

"First, does your cell phone and the communications tower, transmit the signal equally in all directions? Or does the phone have some way of radially directing the signal at the communications tower (or to the phone, from the communications tower)?"

Oh yes, you just need one of those miracle $19.95 gold pieces of paper to accomplish that

Seriously, no. The phone doesn't radiate the signal in any particular direction, or have any method to do so.

"Also, with phones that can handle multiple frequencies of the same communications sort (such as CDMA 1900, 800, or GSM 900/1800/1900), do the phones have a seperate communications device for communicating at each frequency? Or does it merely require a software switch to go from GSM 1900 to 900."

They just have multiple crystals for the different frequencies.

"Also, does it cost a whole lot more for the companies to manufacture a multi-frequency phone versus a single frequency phone (this does not include phones that have seperate technologies, like CDMA and AMPS)? The reason I ask is that there's not a huge price difference between multi-frequency and single-frequency GSM phones."

No, and the retail prices are a big racket anyway. As I noted above, adding support for an additional band is as easy as adding another crystal.

"But if adding extra bands is cheap, you would expect all GSM phones to be multiband (even if people aren't going to use the feature, its an appealing thing to have the brochure), but you quickly find that most of them sold in the U.S. are single band."

The problem with the U.S. is that so many (incompatible) technologies are being used and developed. There isn't really any standard. GSM is great technology, and it is a shame it hasn't been more widely adopted here in the U.S.

"<-- Uses Nokia 5190 with Voicestream"

I've got one now (the 5190) with VoiceStream. It's a bit too bulky for me ... got an 8290 I have to unlock this weekend and I'll be flying high

 

[Shantanu]

<< got an 8290 I have to unlock this weekend and I'll be flying high >>



8290, bah!

You should've held out for the 8390, or that cell phone of the Gods, the Ericsson T68!

 

[mk52]

<< cell phone of the Gods, the Ericsson T68! >>



I still drool all over when I see one of them at the local store.

 

[Shantanu]

<< "First, does your cell phone and the communications tower, transmit the signal equally in all directions? Or does the phone have some way of radially directing the signal at the communications tower (or to the phone, from the communications tower)?"

Oh yes, you just need one of those miracle $19.95 gold pieces of paper to accomplish that

Seriously, no. The phone doesn't radiate the signal in any particular direction, or have any method to do so. >>



I have a follow up question to that:

Isn't that enormously wasteful? The cell phone and the communications tower must be sending out billions of photons each, only 1 or 2 of which are intercepted by the other. Unlike a television or radio signal, which are utilized by millions, cell phone signals are only intended for one party. There's all this wasteful communication going out over several square miles, and for miles into the sky. It's mind boggling :Q

 

[Shantanu]

.

 

[digme]

<< have a follow up question to that:

Isn't that enormously wasteful? The cell phone and the communications tower must be sending out billions of photons each, only 1 or 2 of which are intercepted by the other. Unlike a television or radio signal, which are utilized by millions, cell phone signals are only intended for one party. There's all this wasteful communication going out over several square miles, and for miles into the sky. It's mind boggling >>




i don't think dude gave u the full answer.... antenna to antenna transmission are set usually on line-of-sight paths....though this doesn't mean there aren't vectors that are diverted due to propagation medium etc etc...... so not everything is just out there being wasted.... even from what i understand, cellphones establish a line-of-sight to comm tower once the connection is made...... now, the towers have these excellent antennas that pick up the slightest twiches of 0&1.... (specifically one frequency is chosen for propagation transmission b/n cell and tower)..........

 

[Shantanu]

<< i don't think dude gave u the full answer.... antenna to antenna transmission are set usually on line-of-sight paths....though this doesn't mean there aren't vectors that are diverted due to propagation medium etc etc...... so not everything is just out there being wasted.... even from what i understand, cellphones establish a line-of-sight to comm tower once the connection is made...... now, the towers have these excellent antennas that pick up the slightest twiches of 0&1.... (specifically one frequency is chosen for propagation transmission b/n cell and tower).......... >>



That response is the exact opposite of what Pabster said.

 

[alpineranger]

Cell phone antennae are omnidirectional.

Edit: ... and transmit equally strong signals towards your skull and towards everything else. Wonderful, isn't it?

 

[Deeko]

<< You should've held out for the 8390, or that cell phone of the Gods, the Ericsson T68! >>


I've got one of those (the T68)...let me tell you, it is the greatest phone ever lol...it basically never leaves my sight if its not in my pocket

 

[DAWeinG]

<<

<< got an 8290 I have to unlock this weekend and I'll be flying high >>



8290, bah!

You should've held out for the 8390, or that cell phone of the Gods, the Ericsson T68! >>



<-- 8890 Can't wait until the 9290 communicators come

 

[Deeko]

I was thinking about the 8890 before I got my T68...but really, in the end, its a waste, it costs so much more than the 8290 and for what, the extra band that I would never use and a metal faceplate I could get for $30 online somewhere?

 

[glen]

"Edit: ... and transmit equally strong signals towards your skull and towards everything else. Wonderful, isn't it? "

How are radio waves bad for you?
They aren't
If you are really worried about electromagnetic waves, worry about UV rays from the sun.

 

[Spike]

unlocking a 8290? what do you mean by that

 

[Shantanu]

<< "Edit: ... and transmit equally strong signals towards your skull and towards everything else. Wonderful, isn't it? "

How are radio waves bad for you?
They aren't
If you are really worried about electromagnetic waves, worry about UV rays from the sun. >>



Actually I wasn't concerned about that. My main concern is that if phones can give you 3 hours of talk time if they transmit the signal in all directions, how long they would last if they just directed the radio signals directly at the communications tower (thereby not wasting nearly as much energy). The current setup just sounds very inefficient to me.

 

[alpineranger]

A system to intelligently and automatically direct the waves in the correct direction would add unacceptable cost and complexity. Keep in mind that often cell phones have to communicate with multiple towers simultaneously (when the signal is being handed off from one cell to the other), so the problem is not trivial.

 

[911paramedic]

Actually I wasn't concerned about that. My main concern is that if phones can give you 3 hours of talk time if they transmit the signal in all directions, how long they would last if they just directed the radio signals directly at the communications tower (thereby not wasting nearly as much energy). The current setup just sounds very inefficient to me.

Think of the phone broadcast like you are yelling, it goes in all directions, not just one. If you (not you, anybody) could focus your voice to the person you were speaking with nobody else would have to hear it either. That is the way that waves work, radio or voices.

 

[alpineranger]

The way I understand it, the thing that limits phone size in the US is the fact that the batteries have to be larger than they do in cell phones in lets say, Japan. It's my understanding that Japanese cell phones use less power to transmit signals because they have a much higher cell density. In my mind, this would at the moment be the best way to reduce power requirements, which is what I assume you are ultimately trying to get at with the efficiency question.