Downlink Repeated SACCH support
In 3GPP Rel-7 (?) of GERAN, the concept of "repeated SACCH" was introduced.
The rationale for SACCH improvement can be found in 3GPP TDoc GP-042668 Section 1/2 (even though if later sections have not been implemented as suggested there): Particularly with AMR as a voice codec, the voice quality performance is better than that of control channels (and estimated 5dB).
So in the end, even though the voice channel would still be acceptable, calls fail due to signaling failure, both on SACCH and FACCH.
Repeated SACCH support basically replaces downlink System Information on SACCH (or even pending SAPI3 frames) with re-transmissions of SAPI0 frames. Due to some related logic (and sigaling in the TS 44.004 header), the MS can then even combine the bursts from multiple transmissiosn to decode the SACCH block.