for the TDD mode. Configuration of the Number of the subf-rame during Sub-frame_Offset sub-frame the SPS activation sans objet 2 and 7 3 and 8 2 and 3 sans objet sans objet Table 4.6. Value of optional parameter Subframe_Offset 136 VoLTE and ViLTE 4.2.2.4. HARQ function In case of error, the retransmission implements two mechanisms: - the automatic repeat request (ARQ) mechanism elaborated by the RLC layer; - the hybrid ARQ (HARQ) mechanism established at the physical layer level, under the MAC layer control. The ARQ mechanism takes over from the HARQ mechanism if the retransmissions at the physical layer level have failed. The ARQ is applied only to the flow of traffic and signaling using the acknowledged mode (AM) of the RLC protocol. On the other hand, taking its speed into consideration, the HARQ mechanism is applied to the flow using the AM mode and unacknowledged mode (UM) of the RLC protocol. A different redundancy version facilitates the retransmission of selected data: - for the chase combining mechanism, the retransmission contains the same sequence. The improvement of the error corrector code is due to the increase of the signal to noise ratio; - for the incremental redundancy mechanism, the retransmission contains some different sequences. The improvement of the error corrector code is due to the increase of the number of redundancy bits. The first transmission corresponding to the redundancy version (RV0) contains the initial sequence to transmit and redundancy bits generated by the error corrector code, whose number is determined by the coding rate. The HARQ mechanism functions with a window of one data unit. When a transport block is transmitted, the transmitter must wait for the reception of the acknowledgement before sending the following transport block. This disposition penalizes the rate of the mobile and this restriction is removed thanks to the implementation of several HARQ parallel processes. Radio Interface Procedures The combination of HARQ parallel processes and of the retransmission me