Slashdot Mirror
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?"
In a few years, the analog networks will be completely gone. Hell, a good number of phones sold today do not support analog.
For all its good points, what's the point of analog if I can't use my phone because the battery is dead?
I used to bulls-eye womp-rats in my pants
Yeah, I realize that microwaves are 2.4 ghz, etc. Cell phones are 1.9, yes. However, if there is proof that cell phones cause cancer, or some other awful problem - we haven't seen it yet. Does your head warm up when you're on the phone? Yes. Does it harm you? Don't know, and we might not know for some time.
If your analog phones signal drops below maybe -3- bars out of 5, you're gonna get static. If you have 1 bar or less of signal on an analog phone, no amount of screaming is going to help you. I can make a crystal clear digital call, on Verizon's network usually with 1 bar or more. I get a bit of dropping on 0 bars, but whenever the signal is THAT low, it should switch to analog ALREADY.
NOT all Digital systems operate at 1.9GHz either - Verizon's network is mostly 800MHz. (Also incorrect when he states that AMPS [analog] operates on 900MHz, it is in the 800 band) Digital phones are at -variable- power, anywhere up to 300mw. Analog phones run at 600mw for handhelds, and 3W for the larger mounted and bag phones.
Granted, with a 3W transmitter, I'd take call quality from an analog phone any day, but unless you're in a really crappy area, a digital handheld should outperform any analog handheld. At least, a good digital handheld.
Plus, any good digital handheld should also be a good analog handheld if it needs to be.
The Analog network will be going away in a few years, except for areas where there is NO digital coverage.
Use high quality phones. Verizon and AT&T have decent quality control for their phones, and strict standards as to what they will approve to be used on their network [i'd be willing to be Verizon is a bit higher than AT&T, since they don't have 8 million different handsets available]. T-Mobile, Sprint and Cingular's QC for phones is considerably inferior, though I have no personal experience with AT&T, T-Mobile, or Cingular's inner workings. I can't speak for Nextel at all, but I don't know anyone who personally wants to carry a phone as big and heavy as the analog ones from 5 years ago on their hips just to have neat walkie talkie functions.
"Champagne for my real friends - and real pain for my sham friends!" http://ericblade.postalboard.com/
The microwave comparison is bunk. First, microwave frequencies are chosen to be those best absorbed by food (ie. resonant with molecules such as H2O). Second, the power level of your phone is, at max output, a bit over a watt. The microwave is 600 to 1000 watts beamed into an enclosed space. It's like saying that you shouldn't play with a nerf launcher because getting hit with a rocket-propelled grenade is dangerous.
~~~~~~~
"You are not remembered for doing what is expected of you." - Atul Chitnis
... perhaps that answers your question.
Seriously, guys, get with the rest of the world. Even if it's just this one thing. In Europe GSM phones use either 900MHz or 1800MHz - why are you trying to push 1900MHz? Just use one of the normal frequencies.
US mobile phone networks seem really limited - if you go outside a given area, you might have coverage, but it's more likely you'll have to pay a fortune for it. In Europe, I can leave the UK and travel to damn near any other European country, and use the same phone. If I'm in Romania, my phone works just the same as it would in Scotland. Local calls cost about the same, international calls cost about the same. If you want to phone me, in Romania, dial the international dialling code for Romania then my mobile number. Simple as that.
Just use GSM, and get it the same as the rest of the world.
Stick with analog. The human ear cannot hear digital, only analog, so there isnt much better quality unless you have super ears.
http://phreakinb.com
They will take my analog network from me when they pry my dixie cups and kite string from my cold, dead hands.
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.
Many responders observe that the 600 mW of a phone
is about 1e-3 or less of the power of an oven, but
neglect to consider that you don't hold an oven
against your skull (hopefully). Holding a cell
at 600mW 5mm from your skull is like holding an
oven magnetron 6 inches from your skull, in terms
of the power density over the surface area at the
nearest point. I don't do either. I use a headset.
-I like my women like I like my tea: green-
- Statements about signal penetration indicate some knowledge of RF Engineering. Has the author ever worked in Radio Frequency engineering?
- Statements of coverage area indicate a knowledge of how the wireless companies have deployed sites. Which carriers have shared this information with the author?
- Is there any evidence that isn't anecdotal in the author's statements?
Since no credentials are given for the author, I am quite curious to see if this is an amateur opinion or an educated one. Being a technical field, only the latter matters.There are a lot of things to dislike about wireless companies - the weak regulatory bodies that have failed to force standardization or universal coverage, or the amount the industry is steered by market analysts with no experience or knowledge of the field both spring to mind. But the adoption of digital technologies is not one of them.
--Gus
I've been using various digital cellphones lately, from an LG-T520 to an Audiobox 9000 or something (stupid loaner phone while I'm getting some repairs done to my LG), and here's my refutations of what's the dilly, yo:
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.
Even with the worst digital signal I could find, I've never had a problem at all hearing someone else's voice. I've been told that some voicemail I left once dropped out a word, but that's the only comment I've ever had. Other than that, no problems.
he question now becomes, why are they moving to 1.9GHz?
Among the other reasons mentioned, it provides more bandwidth as well, which means a lot of things - more users, more data, more whatever you're sending.
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.
I live in Fredericton, NB. We have digital, but barely, since the telco just decided fairly recently to cover the area with digital. There isn't great digital coverage, but see my comment above for the impact this has made. The worst problem I've had is that I get bumped to analog (usually four or five out of six bars) when I'm in a basement room two minutes' walk from daylight, or I get no signal whatsoever, in worse circumstances. Even if digital coverage were hopeless, my phone can not only fall back to Analog from digital, it can do so in the middle of a call. It can't fall forward to digital during a call, but that's ok.
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.
I don't know about you, but my phone uses 3G CDMA (hooray Qualcomm), which is a fairly new standard, and most people (even people who KNOW that my only phone is a cellphone) often ask whose house I'm at - because I sound like I'm on a land line, and everyone knows cellphones are horrible, right?
Another related comment: I was standing in Starbucks, of all places, surrounded by a crowd and with the espresso machine going, while I was on my cellphone, but the person on the other end could only hear me. When I wasn't talking, there was no sound. When I was, there was only me. Hooray active noise reduction. That being said, it was the phone itself doing it, and not CDMA's built-in anti-background filter (though that can't have hurt).
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.
Don't forget to mention that, in the case of CDMA, it just doesn't transmit while you're talking, and doesn't recieve when the other person isn't. This saves battery power, bandwidth, radiation, everything. Analog, on the other hand, is always doing what it's doing all the time, by nature of it being a connection, as opposed to packets.
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.
Not to mention battery life. I can go for literally a week and a half without charging my phone, as long as I'm not stuck in that stupid room in the forestry building I had class in last semester. When I am, and I get bumped to analog, my battery drains almost 80% in a day. This is partly because I get poor reception, but even in one-bar digital areas, I don't have any sorts of issues (and I should know, Chapters/Starbucks is one such area).
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.
Oh yeah, and by the way, wireless networking is going to give you testicular cancer, because it uses 2.4 GHz, just like your home microwave. And it'll fry your brain! And eat your fish! And salt your lawn! Fearmongering is pathetic, let's get real.
I use and like my 3G CDMA LG T520, serviced by Telus Communications, 800 MHz digital network by Aliant Telecom. Rare dropped packets, rare analog service, even though there are very few towers around here, and yet the data service is entirely reliable. They're putting up a 1900 MHz digital tower soon, which will provide us with '1x service' (the full 3G shebang), but in the meantime, my phone rocks anyway, and will gladly switch from 1900 MHz digital to 800 MHz digital to analog depending on what it can find.
So why is there such a complaint? Are people getting stuck with digital-only phones? Do Americans have to make this choice actively when they get a cellphone? Every phone Telus sells is 3G CDMA, tri-mode, and cool to boot. No old-school audiobox, no Nokia phones, just good-looking, good-working, sturdy, quality phones, and you know what? They work great, even here.
--Dan
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?