Top view [Under GSM > Full rate speech coding illustration]
Now a 26 frame cycle means 26 slots, one go for SACCH, another one remain idle, and remaining 24 are used for carrying TCH. So here is top view of how speech frames are transmitted after interleaving.
Let us do quick calculations to check whether this result into our required bit rate of 13 kbps. As can be seen in above diagram, a 26-frame cycle carries 6 speech frames (half of N-1, N till N+4, and half of N+5). (6 speech frame = 260 x 6 bits) in (26 multiframe = 120 ms) gives us bit rate of 13 kbps !!
Further you can check Illustration for SACCH/SDCCH/BCCH/PCH/AGCH created in similar way.
References: GSM book by Mouly and Pautet.
© Copyright Samir Amberkar 2013
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