SACCH Frame holds special importance in GSM as it contains vital control information regarding the network. The SACCH is transmitted after 12 frames (no 13) of a 26 Traffic Multiframe. 12 frames before and after SACCH carry voice traffic whereas the 26th frame is idle that distinguishes two traffic MFs. SACCH is thus called an associated channel as it traverses along with the voice traffic.
SACCH contains signaling information such as Power control information, timing advance (TA) and other control related data. 4 SACCH frames form a SACCH Multiframe (480 ms). SACCH frames are used in the triggering of Radio-Link Timer (RLT) Counter that is directly related with the quality of a call. If a SACCH frame is not decoded sucessfully, RLT Counter is decremented by 1, whereas successful decoding of the counter increments it by 2. The call drops when RLT Counter is reaches the value of zero.
SACCH contains signaling information such as Power control information, timing advance (TA) and other control related data. 4 SACCH frames form a SACCH Multiframe (480 ms). SACCH frames are used in the triggering of Radio-Link Timer (RLT) Counter that is directly related with the quality of a call. If a SACCH frame is not decoded sucessfully, RLT Counter is decremented by 1, whereas successful decoding of the counter increments it by 2. The call drops when RLT Counter is reaches the value of zero.
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