What does GSM mean in a cell phone?

[Toocool]

Probably the most useful thing to know about the Global System for Mobile communications (GSM) is that it is an international standard. If you travel in Europe and many other parts of the world, GSM is the only type of cellular service available. Originally, the acronym GSM stood for Groupe Spécial Mobile, a group formed by the Conference of European Posts and Telegraphs (CEPT) in 1982 to research the merits of a European standard for mobile telecommunications. Commercial service using the GSM system did not actually start until 1991. Instead of using analog service, GSM was developed as a digital system using TDMA technology.

Using TDMA, a narrow band that is 30 kHz wide and 6.7 milliseconds long is split time-wise into three time slots. Narrow band means channels in the traditional sense. Each conversation gets the radio for one-third of the time. This is possible because voice data that has been converted to digital information is compressed so that it takes up significantly less transmission space. Therefore, TDMA has three times the capacity of an analog system using the same number of channels.

http://www.krify.com/articles/uploads/adarsh/mmstdod.gif

TDMA is the access method used by GSM, as well as the Electronics Industry Alliance and the Telecommunications Industry Association for Interim Standard 54 (IS-54) and Interim Standard 136 (IS-136). GSM implements TDMA in a somewhat different and incompatible way from IS-136. Think of GSM and IS-136 as two different operating systems that work on the same processor, like Windows and Linux both working on an Intel Pentium III. GSM systems provide a number of useful features:

Uses encryption to make phone calls more secure
Data networking
Group III facsimile services
Short Message Service (SMS) for text messages and paging
Call forwarding
Caller ID
Call waiting
Multi-party conferencing

GSM operates in the 900 MHz band (890 MHz - 960 MHz) in Europe and Asia and in the 1900 MHz (sometimes referred to as 1.9 GHz) band in the United States. It is used in digital cellular and PCS-based systems. GSM is also the basis for Integrated Digital Enhanced Network (iDEN), a popular system introduced by Motorola and used by Nextel. The incredible growth of GSM is a big part of why the acronym is now commonly thought of as standing for the Global System for Mobile communications!

[carcomptoy]

You left out 1800 and 800MHz! Have something against the number 8?:p Anyways, so is GSM better than CDMA or is it the other way around? What are the pros and cons of each as compared to each other?

[jmax577]

CDMA is a more efficient echnology. it does not rely on time slots for data transmission, it simply breaks the signal into code and delivers. tdma in theory is supposed to be more efficient but in reality it isn't, i prefer gsm because i think call clarity and connectivity is far better than any cdma phone i have ever used.

[carcomptoy]

I'm not sure about clarity, but I know that connectivity is really good...I don't recall ever having a dropped call. BTW, has anyone else ever experienced an echo effect on their GSM phone? Sometimes though rarely it happens to me on my T-Mobile phone, but it never occured on my parents' Sprint phone...

[psykon99]

has anyone else ever experienced an echo effect on their GSM phone? Sometimes though rarely it happens to me on my T-Mobile phone, but it never occured on my parents' Sprint phone...


I have not experienced echo on GSM as I don't have it. :)
It does occur on TDMA and CDMA however for various different reasons:

1. In low cell areas. Calls are reasembled with missing information or distorted information due to interferance or an inability to get the entire call signal through.

2. Phone design. When a phone is not sheilded properly on the inside, sound can travel from the earpiece speaker through the phone back to the microphone and create a feedback that sounds like echo. It especially happens when your volume is up all the way and the callers volume is up all the way. Try turning volume down.

3. On CDMA, every phone has what we call "fingers" to listen to incoming signal. Each "finger" can be listening to its own signal source (multiple towers, bounced signal waves, etc...). The phone then reasembles the call from the various fingers. Occasionally, it gets confused on reassembly and you have echo. The nice thing about the "finger" setup is call clarity when there are obstacles, like in downtown situations. Big buildings interfere w/ signal quality, but CDMA phones can utilize bounced signal waves to reassemble the call.

[xc]

I'm not sure about clarity, but I know that connectivity is really good...I don't recall ever having a dropped call. BTW, has anyone else ever experienced an echo effect on their GSM phone? Sometimes though rarely it happens to me on my T-Mobile phone, but it never occured on my parents' Sprint phone...


__________________________________________________ ___________

I have experienced the echo effect on D-2 (now known as Vodafone de) about 3 years ago a lot on my V-60 Motorola :mad: . However now there are no echo problems nor have I had a call disconnected for any other reason then hanging up. :D