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plannerguy
2009-05-30, 12:58 AM
Hi freinds

i have next doubt .......

why were limited to 8 time slots not more?, and similarly 26 tdma frame,
52 frame for Control channels?

any specific reason .......


regards
Plannerguy

zaebolll
2009-05-30, 04:33 AM
why 8 TS.
the reason is certainly related to the fact that the speech is put in frame of 20ms. And when the GSM was invented, 20ms could be encoded/compressed/etc. into 4x0.577 ms.
20ms => 4x0.577ms = 2.3ms
each 20ms, one user needs 2.3ms.
So during 20ms on the air, only 8 calls can be multiplexed.

20/2.3 = 8.7

The remaining is used for in band signalling (sacch).

chovocoi
2009-05-30, 02:28 PM
@zeaboll

Can you explain deeply about 4*0.577ms in 20ms.
I don't undersatand.
Tks!!!!111

kahnoie
2009-06-13, 10:03 PM
Bandwidth of GSMK filter is 67.5 Hz and the output of the mobile is at 270.333

270/67.5 = 4 i.e. -4 channels in UL and 4 channels in DL thus giving us 8 timeslot per TRX.

Regards,
Amit
agarwalamit081@gmail.com

m2m
2009-09-16, 03:57 AM
for reason of 8 ts, i don't know

m2m
2009-09-16, 03:57 AM
There are 2 types of multiframe 26 multiframe, and 51 multframe.

in 1 super frame there are 51 - 26 frame multiframe and
also in 1 super frame there are 26 - 51 frame multiframe

The reason why we need to have different between 26 and 51 due to the concept of sliding multiframe, to let mobile during idle can detect BSIC of neighboring cells

If u like my answer thanks and reputation would be great

ghassen
2009-09-16, 06:36 AM
why 8 TS.
the reason is certainly related to the fact that the speech is put in frame of 20ms. And when the GSM was invented, 20ms could be encoded/compressed/etc. into 4x0.577 ms.
20ms => 4x0.577ms = 2.3ms
each 20ms, one user needs 2.3ms.
So during 20ms on the air, only 8 calls can be multiplexed.

20/2.3 = 8.7

The remaining is used for in band signalling (sacch).

the reason is related to bandwith capacity no more