Gsm/cdma/tdma

[LRando]

For a cell phone novice, can someone explain exactly what these mean? I "believe" the tdma is the older analog/digital service? What are the others? Also if a tri mode phone will pick up both analog & Digital, why the push for All digital phones. Wouldn't that be the best of both worlds (for now), to be able to pick up both on one phone, just in case? I'm sure there is an obvious answer for this...but obviously I don't know it!
Thanks!

[Jay2TheRescue]

Originally Posted by LRando For a cell phone novice, can someone explain exactly what these mean? I "believe" the tdma is the older analog/digital service? What are the others? Also if a tri mode phone will pick up both analog & Digital, why the push for All digital phones. Wouldn't that be the best of both worlds (for now), to be able to pick up both on one phone, just in case? I'm sure there is an obvious answer for this...but obviously I don't know it! Thanks!

If I remember correctly CDMA is actually older. The push for all digital phones is to save bandwidth. Analog phones are bandwidth hogs. Analog service is going to be phased out in the next few years to free up the bandwidth. TDMA is already being phased out because TDMA carriers are switching to GSM technology. On a side note Nextel is going to phase out their iDen network as well so in a couple of years there will only be CDMA and GSM in the US. (provided they don't come up with a new standard.)

[Jerro]

Originally Posted by LRando For a cell phone novice, can someone explain exactly what these mean? I "believe" the tdma is the older analog/digital service? What are the others? Also if a tri mode phone will pick up both analog & Digital, why the push for All digital phones. Wouldn't that be the best of both worlds (for now), to be able to pick up both on one phone, just in case? I'm sure there is an obvious answer for this...but obviously I don't know it! Thanks!

1: TDMA is still out there but will yield to GSM in most cases, TDMA is less efficient, for GSM think Cingular and T Mobile. 2: Analog is scheduled to be shut off in about a year or so. It uses lots more space (spectrum) think radio frequencies or better yet channels, than digital. Digital talks computer talk, the over the air portion of the call is converted into digitized bites and reconverted in the phone and at the base back again. Digital is less prone to unintended eavesdropping.

So digital lets the carrier send more calls over the same channel space. Also analog uses more battery than digital. There are lot more in-depth explanations. Check the first page of Wireless Advisor on the right side. Your are on CDMA since you are using Verizon, Sprint also uses CDMA. The difference is noted on the front page of Wireless Advisor, check it out.

[LRando]

Thank you both for the input. I did check out the articles on the 1st page. Very helpful. Thanks again.

[Charlyee]

Originally Posted by LRando Thank you both for the input. I did check out the articles on the 1st page. Very helpful. Thanks again.

Just in case you didn't have your fill, here is some more information:

The world's first cellular networks were introduced in the early 1980s, using analog radio transmission technologies such as AMPS (Advanced Mobile Phone System). Within a few years, cellular systems began to hit a capacity. Dropped calls and network busy signals became very common.

So to handle more traffic within a limited amount of radio spectrum, the industry developed a new set of digital wireless technologies called TDMA (Time Division Multiple Access) and GSM (Global System for Mobile). TDMA and GSM used a time-sharing protocol to provide three to four times more capacity than analog systems.

Just as TDMA was being standardized, an even better solution was found in CDMA.The founders of QUALCOMM realized that CDMA technology could be used in commercial cellular communications to make even better use of the radio spectrum than the technologies. They developed the key advances that made CDMA suitable for cellular, then demonstrated a working prototype and began to license the technology to telecom equipment manufacturers.

The first CDMA networks were commercially launched in 1995, and provided roughly 10 times more capacity than analog networks and so much more than TDMA or GSM also.
__________________________________________________ _____________

Ok I will stop here, I don't want to bore you to death, but if you or anyone else is interested in more history, please let me know.

Hope this helps.

[Gideon H]

Originally Posted by Jay2TheRescue On a side note Nextel is going to phase out their iDen network as well so in a couple of years there will only be CDMA and GSM in the US. (provided they don't come up with a new standard.)

There are already new standards in the US... dont forget that AT&T started the UMTS rollout before Cingular bought them. Just so you know, LRando, UMTS is also knows as WCDMA, a new (new for Americans) 3G technology.

[Jerro]

Originally Posted by Charlyee Just in case you didn't have your fill, here is some more information: So to handle more traffic within a limited amount of radio spectrum, the industry developed a new set of digital wireless technologies called TDMA (Time Division Multiple Access) and GSM (Global System for Mobile). . __________________________________________________ _____________ Ok I will stop here, I don't want to bore you to death, but if you or anyone else is interested in more history, please let me know. Hope this helps.

I am; so Lets bore them even more, don't forget N-AMPS which was an analog system just before digital. It broke the channel up into 3 parts. It was a Motorola system, at first most often used by "A" carriers. Want to talk about IMTS?

[Charlyee]

Originally Posted by Jerro I am; so Lets bore them even more, don't forget N-AMPS which was an analog system just before digital. It broke the channel up into 3 parts. It was a Motorola system, at first most often used by "A" carriers. Want to talk about IMTS?

ofcourse the N-Amps, how could I miss that.

Sure let's talk about IMTS, but hey better yet let's start with MTS

You go first.

[Jerro]

Originally Posted by Charlyee ofcourse the N-Amps, how could I miss that. Sure let's talk about IMTS, but hey better yet let's start with MTS You go first.

Please tell me you read about MTS rather than actually experienced it.

Yes, I had a IMTS Motorola Pulsar phone with a dial in 1977
The head had several switches I think about 16 for roaming, each representing a channel. We had 8 home channels in Philadelphia. The base antenna was on top of the PSFS building in Center City. There were polling receivers in the suburbs but not transponders or transmitters. So service was pretty good for about 18 miles of center city and farther in high spots. For instance high on a mountain ridge in Reading Pa. a good 45 miles or more, I could hit the Philly antenna on the 450 MHz band. The phone was duplex but allowed simplex with a push to talk option for really rural, service.

Some common carriers, who mostly operated paging companies also provided a competing service with each phone company. There were other bands too, 152, and 35 MHz. The 35 was simplex, it was before my time but was still in service in the 70's.

With MTS, often operator assisted and some simplex. But I got in with IMTS and a "solid state" trunk unit. Then upgraded to a pulse dial Pulsar 2 head with a speaker. For those who don't know; all the calls were in the clear, any one with another phone, or a scanner could listen.

To make a call of course one needed a clear channel. The pulsar 1 had a green and red indicator; picking up the receiver would give either a green or red light. Green would give a DIAL TONE, for a free channel. Red a fast busy.

The Pulsar 2 and some Harris and Glynair units would ring back when green otherwise it was necessary to keep pushing the switch hook in hope of getting a green light.

IMTS would hunt for an idle tone (free channel) automatically, SMR's and MTS channels were select manually. But the green light would still indicate an open channel.

That's the short version.

[Charlyee]

LOL, Jerro yes I did read about both MTS & IMTS & no personal experience, but I have always been intrigued by them and have read quite a lot. It is great to get your experience with IMTS, thanks very much. I wanted ask/add a couple things on MTS, I will do that tomorrow.

Thanks again for the details.

[Charlyee]

Ok here is my 2 cents on MTS:

MTS was introduced on June 17, 1946 in Saint Louis, Missouri, by AT&T and Southwestern Bell. This was the first American commercial mobile radio-telephone service. It operated on six channels in the 150 MHz band with a 60 kHz channel spacing, twice the size of today's analog cellular. Very soon after bad cross channel interference, forced Bell to use only three channels. In a rare exception to Bell System practice, subscribers could buy their own radio sets and not AT&T's equipment.

There was a centrally located antenna transmitting 250 watts that paged mobiles when a call was for them. Automobiles responded not by transmitting to the headquarters building but to a scattering of receiving sites placed around the city, mainly because the automobiles used lower powered transmitters and could not always get a signal back to the middle of town. These central offices relayed the voice traffic back to the manually operated switchboard at the HQ where calls were switched. So, although the receiver sites were passive, merely collectng calls and passing them on, they did use the idea of the cellular network of distributed, interactive cell sites.


Only one party talked at a time with MTS. You had to push a handset button to talk, then released the button to listen. This eliminated echo problems which took years to solve before natural, full duplex communications were possible. This is not simplex operation as many people say it was. Simplex, used in business radio, shares a single frequency for both people talking. In MTS and IMTS transmitting and receiving frequencies were different, and offset from each other to prevent interference. Base to mobile might be on 152 MHz and mobile to base might be on 158. This is what was called half duplex, whereby different frequencies for transmit and receive are employed, but only one party talks at a time.

Operators placed all calls so a complex signaling routine wasn't necessary.

Here is my questions for you...Is it true that even though IMTS was introduced in 1964 by Bell System, Pacific Bell didn't implement it until 1982?This seems to me a long gap and also 1982 was the start of Cellular, so why?

PS: If we have not thoroughly bored everyone yet, We could talk about Motorola 2 way radios from the early '80s. My full time Summer job and part time during the semester was that of a bench tech, doing warranty repair work mostly for the one's issued to the local police fource.

[omni]

Originally Posted by Charlyee PS: If we have not thoroughly bored everyone yet, We could talk about Motorola 2 way radios from the early '80s. My full time Summer job and part time during the semester was that of a bench tech, doing warranty repair work mostly for the one's issued to the local police fource.

I'd love to hear about it actually, the store I work for is thinking selling them and hiring a tech to work on them.

[Charlyee]

Originally Posted by omni I'd love to hear about it actually, the store I work for is thinking selling them and hiring a tech to work on them.

So are you offering me a job?...LOL.

Why are they thinking of selling 2 way radios from the early '80s..that sounds interesting, why don't you elaborate some more, I would love to hear about it.

[Jerro]

[QUOTE=Charlyee]Ok here is my 2 cents on MTS:

Here is my questions for you...Is it true that even though IMTS was introduced in 1964 by Bell System, Pacific Bell didn't implement it until 1982?This seems to me a long gap and also 1982 was the start of Cellular, so why?


I don't know what Pac bell did in that regard, I has IMTS beginning in 1977 and kept it until about 1988 in one car, although I started with Bell of Pa. then had the trunk unit reprogramed to a RCC. It worked better than cellular in 84 to about 87 because everyone was jumping off of IMTS to get on cellular so more channels were open most of the time and many cellular towers were not yet built. And it was loud and clear. Bell of Pa. was still supporting it for 10 years, but I think only telco people were using it. Now the 152 and 454 are mostly paging channels.

By the way the solid state (that meant no vacuum tubes) trunk unit weighed a lot more than even first generation analog cellular trunk units. Perhaps 35 pounds with the heavy metal alloy case. The whole thing was hard wired.