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Cell Phones - Analog vs. Digital
"The point of digital is that it takes alot less power to transmit and if you've got 1 bar or 5, the signal should sound the same.. and there in lies the problem.. with the should. With an analog phone as your signal strength begins to go below 1 bar you start to hear static but you can still understand the person your talking to, though you may need to 'yell over the static'. However, with a digital system when the signal fades, there's no yelling because the signal isn't there, and packets that should be getting to your phone, just get dropped. As a result, Aunt Martha's 'Hello' on a crummy analog connection can still be made out.. but on a digital connection of the same strength might sound like 'He...o' with a gap of silence in the middle. (See my Cell-Phone Switch parody commercial on this site for an example if you don't know what I'm talking about).
Cell phone companies are boasting about how digital is good, but is it really? Analog signals work on the 900MHz band, which goes very well through houses, trees, your neighbors dog, etc. Analog works on the 1.9GHz frequency, which does not go through houses, walls, metal, trees, well at all. The question now becomes, why are they moving to 1.9GHz? The signal length is smaller, and therefore antenas on the phones can be smaller without worrying about chopping the signal from it's full height. However, the cell phone companies need to cover the area better for there to be as much coverage, especially in the city where there is lots of Multi-path (bounces and signal inversions), and buildings to go through. This is the same reason that your 900MHz portable (land line) phone will go further then your 1.2GHz portable phone.. (or it should anyway, but alot of companies are making illegal 1.2GHz phones and putting them on the market).
In addition, back to Aunt Martha, as long as her 'Hello' usually sounds like her 'Hello' on a land line, what difference does it make right? Well, unfortunately, the digital standards we have today are from years past. And while they work, they are by no means clear. If you are looking for clarity, you'll want to stick with an analog phone. For data communications, digital is the way to go. Cell phone companies will tell you that if you're in analog you won't get your voice mail notification and such, but the truth is they COULD do it if they wanted to. They just want you to switch over to digital. Why? For one, it takes less bandwidth off of their access points, so they can get more subscribers on per access point. Each analog cell antenna can carry only 56 simultaneous phone conversations, which just doesn't cut it in heavily populated areas. With digital they compress the signal and as a result can get many more people on a sectoral antenna. Digital cell phones use extreme compression of the sound that they transmit. The compression algorithms used are lossy; they're specifically designed around transmission of human voice to human ears, and take advantage of what the human ear will tolerate and what it won't.
What about the pros for digital? Digital is a bit more secure then analog as you can't hear it just by setting a scanner to the correct frequency, you also have to un-encode it from the digital, and smooth the signal out.
On last thing, the digital system works on 1.9GHz... your home microwave works on 2.4GHz.. It's close enough, you still want to hold that phone next to your head? Remeber what happens to an egg when you put it in the microwave, and then decide.
So with all that said, which do I prefer? I prefer the analog since it has better coverage, and the analog phone will keep the connection better in fringe areas. Digital phones are an all or nothing proposition. They either work or they won't. Analog phones can swish and cut out, without dropping the call. What do Slashdot readers use and like and why?"
On the frequency point... Digital cell phones use (at least GSM phones do, don't know the CDMA frequencies) both 900 MHz bands and 1.8 GHz bands (1.9 GHz in the US, because the 1.8 GHz band is reserved for .mil use in the US). It depends on what the base stations in the area are using.
In general, digital signals can get through a much worse signal-to-noise ratio (after all, all you have to pick up is a 0 or 1), and should therefore be more robust than analog, especially with basic error correction thrown in. You'd need to compare the transmission/reception power levels to see if the digital phone is really doing worse. If the digital base station is transmitting at X watts, and the analog base station is transmitting at 3X watts, yeah, the analog might come through better.
Of course, better battery life isn't a bad thing either...
Look here to find out: http://www.cnet.com/wireless/0-5939521.html I'll bet it's a lot less than your microwave. In addition, a microwave is a specially designed metal box that does it's best to make sure all that power gets into the food, your cell phone has at least a 180 degrees that isn't pointed at your head.
Digital signals are better, it helps to relieve congestion on the airways, it reduces the power of signals needed and increases battery life. Plus it's a hell of a lot easier to get IP working over it. (IP does dropped packets a lot better than garbled packets).
If radiation is really your concern. Get a head set. Bluetooth might not be the best idea. :)
I don't know what the point of this article is. It is re-iterating (in some cases exaggerating) stuff we already knew. The rest of the world had this discussion at least 10 years ago. As a result, we standardized on GSM.
In Australia we discouraged the use of Analog phones in the mid 90s, and the analog networks were shutdown in 99.
Before this time GSM was gaining huge momentum, with three GSM networks rapidly expanding their coverage. The majority of the urban population were pleased with the technology, however the rural population were less than amused. As a result, CDMA technology was deployed by Telstra which is a digital system, but offering performance characteristics closer to analog.
One problem with GSM in rural areas is the timing advance issue, which limits the maximum range of dedicated mode (2-way communication) to about 35km, typically. The GSM range limitation is not, contrary to popular belief, a power output limitation.
I'm getting a little offtopic here, but I'll quickly explain the problem: The timing advance problem is a result of using fine-grained timeslots. The timing advance parameter is the number of symbol periods the MS (phone) must advance the transmission to avoid colliding with other timeslots. The maximum value is 63 symbol periods, which was chosen to allow the MS plenty of time to measure other cells when not transmitting and receiving.
Additionally, GSM offers Short-Messaging-Service, GPRS (packet switched data), far more efficient spectrum use, EDGE (high speed GPRS using 8PSK modulation).
The population and population density of the US is far better for deploying GSM networks than Australia, so if Australia can do it, I can't see why the US can't.
and here - for a CDMA FAQ
and here for why CDMA is better than analog along with a whole lot of other shit as to why dropped calls are far less frequent on digital networks as opposed to analog ones...
'A lie if repeated often enough, becomes the truth.' - Goebbels
Hey Buddy!! - How do you generate 1 MW of energy out of 1.5 kW of electricty? Despite popular belief, microwave ovens don't "nuke" our food.
Dave
BTW, I have a perpetual energy machine to sell you, if you're interested.
FPGA, Wireless, ASIC, Verilog, VHDL, HW, 10yr exp, Team Lead, Ottawa (More? Email above. slashdotusername=dgmartin98 )
While you are correct that 2.4GHz is a resonant frequency of water, and thus the most efficient at causing materials with water to warm quickly, it is NOT true to say that off center frequencies will not warm things up.
If you doubt this, ask the guys that have to scrape dead birds from the tops of buildings with microwave transmitters. For that matter, consider the name of the first microwave oven - the "radarange" or, more accurately, "RADAR range". Early RF engineers figured out you could heat with radio frequencies pretty early on. If you put enough power behind it, you can make nearly any RF frequency toast something.
Where I work, we test a lot of prototype radar systems - and there are alarms and lighted perimeters all across the roof to keep people from walking in front of these beasties when they are transmitting. I can't tell you the exact frequencies, but I can tell you they aren't 2.4GHz either.
The trick with cell phones is that they are low power, and don't hit any known resonant frequencies of body tissues or water.
Sorry, but you're wrong - I suggest you read this. The important part for you to read:
" It concluded that the radio frequency signals emitted by phones generated heat in the brain, but said it was not clear whether this could have other biological effects, such as triggering cancer. "
When I said your head gets hot, this is what I was talking about. I doubt a tape player puts off enough raditation to heat your brain.
"Statements of coverage area indicate a knowledge of how the wireless companies have deployed sites. Which carriers have shared this information with the author? "
Actually, with info from the FCC, you can figure it out. For example...
Nextel Coverage Maps (Transmitter Locations)
Have fun!
While one will indeed find this "fact" listed in many places, including a few physics texts, it may well be a fallacy. I've looked up the frequency absorption spectrum of water, and 2450 MHZ was not a peak. Unfortunately my "classic" paper link is now dead (I'd really appreciate a currently active and stable link even if it supercedes the paper I had and proves me wrong)
The best I can do right now is " Absorption Spectrum of H2 18O in the Range 12 400...14 520 cm-1 [Journal of Molecular Spectroscopy 216, 77-80 (2002)]
Moreover, anyone with equipment to measure the relevant range can see that microwaves are not tuned to a tight band. The frequency of any one oven varies far more than any the reasonable expectation for an absorption band in that range (depending on temperature, use, etc.) and the variance between ovens is greater still.
That's actually one specific reason why a resonance frequency is not used: the increase in efficiency that would result from picking an absorption peak (vs. simply reflecting the microwaves around inside the cavity 10-1000 times until a significant fraction is absorbed) simply wouldn't have been worth the effort and cost of precisely tuning each unit (at the time when microwaves first came out) Further, we are all aware of the accounts (admittedly potentially apocryphal) that relate the discovery of microwave cookery to an accidental exposure to a military radar dish. Military radars (excluding weather radars) generally avoid the water bands, because water vapor in the air would limit range.
I don't mean to criticize the Original Poster, since that "information" can indeed be found in reputable sources. I'd simply rather not see it repeated if it obscures and incorrectly explains the operation of microwave ovens and EM radiation.
Finally, even if the microwave radiation from a oven *did* operate on a resonance absorption band for water, the total power of a cell phone is tiny (mW-W). One would get orders of magnitude more tissue heating by stepping out into the sun or even another person (both things some techie types seem to avoid). In the absence of any specific epidemiological or other significant evidence of specific tissue or cellular disorders caused by the specific frequency bands used by cellular phones, their radiation can *only* be expected to produce nonspecific tissue heating.
Before you worry about microwaves, worry about other sources of energy like sunlight. Microwaves onlt *seem* "spookier" to certain people, while sunlight is far stronger in many, many specific bands than celphones over their entire range.
It might be wise to say say IANAMD, but I *am* an MD (with a degree in molecular biology). That doesn't make me an authority on epidemiology or molecular properties, but I like to think it does give me a small edge.
the digital system works on 1.9GHz... your home microwave works on 2.4GHz.. It's close enough, you still want to hold that phone next to your head?
You have a 850W mobile phone!? This is just a pile of FUD. The 900MHz analogue signals are at a higher power than digital, and since they're at a lower frequency will penetrate further into the skull.
True there is more cell phone coverage in Europe than in the US. However the US has a lot less people.
Hmmm, I guess this is is straying off-topic but I have to correct you on that. The population of the European Union right now is roughly 280 million. This will rise to around 360 million once the new members (mostly former Eastern Bloc states) join.
Compare that to the US population of roughly 300 million. Hardly "a lot less people" is it?
True, Europe is more densely populated than the US but most as Americans live in urban areas (cities, towns) it doesn't make that much difference.
Sure, if you live in a remote area of Utah then you're not going to find network coverage everywhere but the same is true of some places in Europe. However, it is fair to say that the percentage of land where you can't find coverage is far greater for the US than it is for the majority of Europe.
"Accept that some days you are the pigeon, and some days you are the statue." - David Brent, Wernham Hogg
So many things are misinformed/wrong about this...
Most have been posted by others, such as:
a) Digital can be in the 800 MHz band (same as analog) in addition to 1.9 GHz, and most of Verizon's CDMA network is low-band. 1.9 GHz is used because we ran out of 800 MHz spectrum.
b) Analog typically takes 3x as much power. Digital is good for the handset battery and good for your head. Digital phones peak at 200 mW, analogs are 600 mW for handsets, and some portables are 3W units. Analog is actually better for the provider power consumption wise - Analog FM signals can be amplified with around 70-80% efficiency or more, as opposed to around 14% for the absolute latest CDMA amplifiers. (FM signals do not need a linear amplifier, while CDMA requires an ultra-linear amplifier.)
c) RF cannot directly harm your body. (i.e. changing DNA nucleotides) The only way RF can harm your body is by heating it. Who cares if 1.9 GHz is close to 2.4 GHz? It's 200 milliwatts, which will cause negligible heating even if it is more efficiently absorbed than 800 MHz radiation. If RF were that dangerous, half of my coworkers would be dead after 10+ years of developing microwave transmitters and amplifiers. Yes, you have to be careful, and 45W of microwave directly into your body can do serious damage, but 200 milliwatts can't do diddly, even if you directly touch the antenna.
d) The author is severely wrong about quality vs. signal strength with analog vs. digital. Even at 4 bars of signal, an analog signal will have static. At 1-2, it will be almost unintelligible. I can get crystal-clear connections at 1 bar of signal, sometimes even 0 (i.e. on the verge of losing a connection) with my CDMA phone.
retrorocket.o not found, launch anyway?
A factor that is often ignored in this debate is also which vocoder is used. There are 2 main vocoders used in TDMA digital systems; ACELP and VSELP. ACELP is a more efficient (ie. better) encoding scheme and the difference can be heard when comparing the 2 schemes. VSELP was the main roll out system, and has not been replaced in many areas.
Analog mode transmission at 900Mhz maxes at 3W broadcast compared to a couple hundred mW for most digital phones (they vary by encoding method and distance to tower). Most phones today with analog mode won't get near the 3W output but they will still be several times higher than their digital mode, add to that the fact that broadcasted power does not come linearly and analog mode can easily drain the battery 10X faster than digital mode.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.