- This topic has 7 replies, 1 voice, and was last updated 6 years, 4 months ago by KIRAN.
26th March 2009 at 11:16 #56487RFOptimizerGuest
Hey All, my question is: why is the bandwidth for a single GSM channel equal to 200 kHz? Why couldnt it have been more or less? What are the factors that govern this?
Thanks/26th March 2009 at 20:03 #56488PixGuest
One channel is separated by 200kHz from its adjacent channel. The carrier itself has a very precise frequency. I don’t really like the term “bandwidth” in GSM, when talking about frequency, but that’s just me.
200kHz was chosen in order to provide enough room between channels to avoid interference – without the need of expensive filters in the TRX.1st April 2009 at 16:39 #56489MKTGuest
We don’t know what was given to “them”.
Whether 200KHz BW was given and “rest” are to be calculated?
Whether the “rest” was GIVEN and MINIMUM BW needed is to be ANSWERED??
“rest”= Selection of Speech codecs, Bit Rate at Air interface etc..
“Them”= ETSI13th May 2009 at 13:24 #56490sabahGuest
we have silent call in some sites please we need to now the real reason for it6th May 2010 at 06:42 #56491DsGuest
thanks for the ans.
in my opinion,requirement of expensive filters would have come later.
initially y 200khz was choosen, must have some other ans/technical calculation.6th May 2010 at 10:52 #56492paraHOGuest
The question about TDMA surely as GSM adopted it.
TDMA uses 200 kHz per radio channel in comparison to analogue cellular allocations btw 12.5 kHz – 30 kHz. TDMA reduces the allocation each traffic channel to 200 kHz / 8 = 25 kHz, roughly equal to typical analogue system. This perhaps tell us TMDA lloked to some quality and features over simply increased capacity. I suppose to put use the same approach for use for analogue systems would require significant increase bandwidth for analogue systems making it inefficient to operate maybe?
GSM as I seem to remember want ‘efficency’ as spec’d at the outset to prove digital communications introduced an enhanced pan-european digital service over localised and diverse analogue systems.
Quality those has its price. TDMA structure gives more capacity (when compare with analogue). MS burst every 4.615ms has underlying freq 216.6 Hz (1/4615ms) which is an audible range and frequency can be heard on radio/music system speakers etc – so risks and nuisances need to be designed out but costs to do that.
BR14th July 2010 at 07:29 #56493prashant gaurGuest
How we calculate the erlang?10th January 2015 at 17:15 #56494KIRANGuest
GSM system uses 200 KHz BW for each carrier. The target SNR at cell
edge is 5 dB (for voice delivery). Find the cell radius for the case when BS
transmitter power Pt = 10 watts for LOS and non-LOS cases, respectively.
Assume ht = 10m and hr = 1:5m, fc = 800MHz.