Which modulation types are being used in GSM and it's successors

If we quit pre-GSM wireless technologies, we can specify the mobile technologies as followings:

GSM
An open, digital cellular technology used for transmitting mobile voice and data services 
GPRS

A very widely deployed wireless data service, available now with most GSM networks

EDGE

GSM Evolution (EDGE) technology provides up to three times the data capacity of GPRS 
WCDMA or 3G

The air interface for one of the International Telecommunications Union’s family of third-generation (3G) mobile communications systems.
HSPA
 The set of technologies that enables operators to upgrade their existing 3G/WCDMA networks to carry more traffic and at faster speeds.

LTE
Designed to be backwards-compatible with GSM and HSPA, Long Term Evolution uses the OFDMA air interface, in combination with other technologies, to offer high throughput speeds and high capacity.

Wireless or not we are using 2 types of signal. One of them is carrier signal and the other one is data signal.

  
We can consider this sinus wave as our carrier signal as an example.

And let's consider above figure is our data signal.

To be able carry our data, we have to use carrier signal in order to send it to long distances.
Let's put all together in PSK modulation

                                     

Note: we need only one carrier for PSK. Some of the modulation types requires  2 different carrier signals like FSK. 


Modulation may be done by varying the amplitude,phase, or frequency of a high frequency carrier
inaccordance with the amplitude of the message signal. 

Main goal of enhanging modulation is just inreasing the number of bits carried by Hertz or bandwidth.
Now, let's briefly see the modulation types for GSM technologies:

GSM GPRS uses GMSK type modulation.

Note: It is common way to explain modulation types by using polar graph. The letter I means a carrier 'In Phase' with the carrier signal. And in the letter Q means 'Quadrature' (or perpendicular). Do not worry you can consider I and Q as X and Y axixes for angle. Also please see the link for further information regarding symbol and quantization http://en.wikipedia.org/wiki/Quantization_%28signal_processing%29

EDGE uses  8PSK modulation

UMTS and WCDMA
Regarding UMTS Release 99 it was QPSK.  After 3GPP Release 7 introduced 64QAM modulation for HSDPA and 16QAM for EUL

The advantage of using QAM is that it is a higher order form of modulation and as a result it is able to carry more bits of information per symbol. By selecting a higher order format of QAM, the data rate of a link can be increased.
The table below gives a summary of the bit rates of different forms of QAM and PSK.

LTE
LTE stands for Long Term Evalution and really trembles me as my expectations is very high for it.
Actualy my operator is using UMTS based tech in Istanbul and it is sufficient to watch something from youtube. (maybewe do not have so much data traffic because of unwanted bills :) )
Regarding 3GPP spects  we will introduce with 128 QAM


Now, it is enough to talk about modulation to prevent to go into deeper :)
See you in next blog. Please do not hesitate me to contact if you have suggestions, reccomendations or questions.
Have a great day.


REFERANCES
http://www.gsma.com/aboutus/gsm-technology
http://www.exaltcom.com/
http://www.ilmondodelletelecomunicazioni.it/argomento.php?id_lezione=43&id_capitolo=287
http://biosonicstelemetry.com/resources.php
Prof. Robert Webber from following link:
http://www.youtube.com/watch?v=-_TWtJsgzlw&NR=1&feature=endscreen
http://www.telecomhall.com/what-is-modulation.aspx
http://staff.neu.edu.tr/~fahri/mobile_L7.pdf
http://wireless.arcada.fi/MOBWI/material/CN_4_4.html
http://mobile-telecom-networks.com/umts/general/17-modulation-schemes-used-in-umts
http://www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation
http://www.3gpp.org/ftp/Specs/html-info/36912.htm