Question QUESTION: why the bandwith in gsm is 200khz or more or less than this value?
ANSWER: The modulation method used for GSM signals are GMSK.
The objective is to find the bandwidth that contains about 99% of the radio signal power.
The relationship of the transition time is usually expressed in an indirect way, by stating the product of the 99% bandwidth (called B), and the total bit or symbol duration (called T). This product is called BT. In GSM, a transition time giving a BT product of about 0.3 was chosen by the designers. It puts 99% of the signal power into a 200 kHz bandwidth centered at the carrier frequency. It also allows an almost error-free (about 1% bit error rate -- BER) demodulation of the binary data in the presence of noise at the ratio of 8 to 1 (signal power to noise power). Power ratio of 8/1 corresponds to 9 dB signal to noise ratio in logarithmic decibel units. This 1% BER can be handled adequately by the forward error correcting codes and other error protection methods used in the GSM system design.
GSM system, with BT=0.3, the spectral efficiency is therefore about 1.35 bits/second/Hz (270/200). GMSK designs with different BT values have a different spectral efficiency value as well.
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QUESTION: thanks a lot for your answer please write me more detail.
ANSWER: Send me your e-mail address and i will try to give you some more information.
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QUESTION: i don't understand my email address is
shahrzad_ahmadi51@yahoo.com
Answer I have received your e-mail address, shahrzad_ahmadi51@yahoo.com
For your information; your e-mail address do not appear with your question here on allexpert, all correspondence are kept within the environment of allexpert.
I will try to give you somemore light on the issue of GSM bandwidth.
