anyone know how to calculate the channel width

[kobesitu]

i have problem to calculate the channel width now. i know the modulation is 16QAM, and total bandwidth is 1200MHz, which is from 950MHz to 2150MHz. the symbol rate is 45MS/s, in general, it is 4 bit per symbol, i have no clue how to calculate the channel width base on these information, my superviser just tell me, he initially guess, base on what he know, is 22.5MHz ( the channel width), can somebody tell me the result or tell me how i can calcuate it or give me some useful information. thank you very much to everyone.

 

[m_llaa]

Hi
if you need precise calculation:
you should also specify your pulse shape, it is neccessary.
next you should calculate spectrum of M-QAM. it is not simple, so you can find it in digital communications books. for example Digital Communications by Proakis in chapter 4 or 5.

 

[kobesitu]

if not a precise calculation, how can i calculate it, because i have to show something as soon as possible, and use the channel width for other more complex calculations

 

[bulx]

22.5 Mhz is the theoretical minimum bandwidth required to do a 45 Msymbol/s transmission, which is usually unachievble in pracitce. Assuming and bandwidth requirement of 45 MS/s is more reasonable.

As m_llaa has already pointed out if you really want to calculate an exact value, in addition to knowing allowed bandwidth, modulation scheme and symbol rate, the pulse shape used for transmission _needs_ to be known.

- b

Added after 2 hours 53 minutes:

CORRECTION:

which is usually unachievble in pracitce. Assuming and bandwidth requirement of 45 MS/s is more reasonable.

SHOULD BE

which is usually unachievble in pracitce. Assuming and bandwidth requirement of 45 MHz is more reasonable.

-b

 

[kobesitu]

if i use raised cosine pulse shaping, so how can i do it, because i have no time to read the digital communication textbook now, so with the modulation is 16QAM, and total bandwidth is 1200MHz, which is from 950MHz to 2150MHz. the symbol rate is 45MS/s, in general, it is 4 bit per symbol,how to calculate the exact channel width? can anyone tell me?

Added after 2 minutes:

sorry, should i use bandwidth = Rb/2+beta ?

 

[correlator2006]

simply the bw of channel is symbol rate /2 ,after carrying signal on carrier frequency then overall BW will be Rs ,so channel width is 45 MHz.
the attached paint file may help you.