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highrez
Joined: Jan 03, 2003
Posts: 3
From: Seattle, WA
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TDMA/GSM/CDMA: The US was infact ahead of europe, and the AMPS standard reflects that. Before there was GSM or talk about GSM there was AMPS. Original AMPS was simply analog FDM. Which means there was a frequency division. So your handset would send on one frequency and receive on another. This allowed "full duplex" comminication that we're all so used to. Anyways, GSM started to grow up around the same time as D-AMPS (IS-136) started be shaped. D-AMPS is what people call TDMA. D-AMPS used the same frequency and channel width as AMPS, but added the concept of time slots. This timeslot concept is TDMA (Time Division Multiple Access) and is the same concept that GSM is built off of. So when you say "TDMA" you're describing BOTH GSM AND D-AMPS (IS-136).
They differ however in implementation. Because early US cellular systems were analog, they only needed very small (30khz FD) ammounts of spectrum for transmit and receive (per channel). When they decided to go digital, they were required to maintain backwards compatability with old analog systems. To do so they needed to keep the size of their channels the same (to maximize their spectrum). Mixing GSM 200 KHz and D-AMPS 30KHz channels would create overlap or unused spectrum, and this is not acceptable.
Additionally, Europe first decided on the 900MHz band for thier TDMA implementation. For the US, this was not possible as that band is reserved for ISM (Industrual, Scientific, Medical) unlicensed use. Changing this would be no walk in the park.
I'm not sure which digital standard was ratified first, but its clear that both are very similar technologies. D-AMPS uses a 30KHz channel divided into 3 timeslots - GSM uses 200KHz channels with 8 timeslots. IIRC, the transmit time on GSM is very short on GSM (time per slot) compared to D-AMPS. However, in the end they do the same thing.
As far as 3G goes. I dont know of any major carriers that have genuine 3G fully rolled out anywhere. GPRS/EDGE/1xRTT are NOT 3G. These are 2.5G technologies (except GPRS which is 2G). UMTS (WCDMA) will be 3G (if my understanding is correct). Verizon has started to roll out EVDV in the US which is genuine 3G.
Others have properly explained why we pay for incoming calls (which is basically because local calls are free).
In general, despite what other posters have said, the US has always been ahead of the world in telecom issues (it was invented here, afterall). The fact that we're ahead sometimes dictates that we have to stay compatible with our legacy systems and can't always be jumping on the "international standards" bandwagon.
As far as the P900 goes, that has everything to do with consumer demand. People in the US dont spend that much on their phones. | |
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amagab
Joined: Oct 29, 2002
Posts: > 500
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Additionally, Europe first decided on the 900MHz band for thier TDMA implementation. For the US, this was not possible as that band is reserved for ISM (Industrual, Scientific, Medical) unlicensed use. Changing this would be no walk in the park.
As far as 3G goes. I dont know of any major carriers that have genuine 3G fully rolled out anywhere. GPRS/EDGE/1xRTT are NOT 3G. These are 2.5G technologies (except GPRS which is 2G). UMTS (WCDMA) will be 3G (if my understanding is correct). Verizon has started to roll out EVDV in the US which is genuine 3G.
In general, despite what other posters have said, the US has always been ahead of the world in telecom issues (it was invented here, afterall). The fact that we're ahead sometimes dictates that we have to stay compatible with our legacy systems and can't always be jumping on the "international standards" bandwagon.
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Yes, the mobile phone was invented in the US but then nothing happened. Other countries had national networks rolled out before the US. As in the popular case of the Scandinavian countries, where the NMT network covered the entire Scandinavian peninsula very early on and where the phone per capita penetration amassed very early on. Finland, Sweden, Japan, and Hong Kong were the countries that first could brag with having most of their population using the mobile phone technology.
GPRS is 2.5G and I would say that EDGE and 1xRTT is 2.75G to be exact. Anyway, there are several countries that now have WCDMA or UMTS fully rolled out including Austria, Sweden, Japan, Korea, and others.
As for a lot of other issues, US are often ahead in technology but lag behind when providing it to the general public.
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[ This Message was edited by: amagab on 2004-02-26 21:39 ] |
z200user
Joined: Feb 23, 2004
Posts: 19
From: new york city
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"As for a lot of other issues, US are often ahead in technology but lag behind when providing it to the general public."
You got it right.
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richy240
Joined: Jan 24, 2003
Posts: 465
From: Houston, Texas, USA
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What EXACTLY defines 3G?
AT&T US is advertising 3G access, but I know they are still using GSM, GPRS and some EDGE (total rollout yet?). I am meeting with some AT&T reps tomorrow and I want to know why they are advertising 3G when their services are obviously still 2G.
Someone help me make AT&T look like fools... They deserve it, if only because they call their GPRS and related services mMode. (Of course, T-Mobile is calling it T-Zones, which is just as stupid.)
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amagab
Joined: Oct 29, 2002
Posts: > 500
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A lot of companies in the US has advertised 3G when it's not. There was also an article in a wireless magazine that talked about 3G and there was a picture of the T68i. They couldn't have been more off topic.
3G is the technology that allows for video conference conversations or streaming video (without interruptions) broadcasting.
GPRS is considered 2.5G and is available on T-Mobile, AT&T, Cingular, and others.
EDGE is somewhat between GPRS and 3G. I guess you can call it 2.75G if you want term like that.
The terms used in the US has been a little off target because there is not nationwide standard as in other parts of the world. I would blame the confusion on the fact that US providers don't cooperate or talk to each other to come up with mutual standards. They all want to do their own thing. However, there have been some improvements lately between the US GSM providers.
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Posted: 2004-02-26 20:52
