Page 752 - 5G Basics - Core Network Aspects

2 Transport aspects

DS_ACK_WINDOW_SHIFT × Tsymb + Tg1' + DRMCus × Tsymb ≤ Tack_max_R

US_ACK_WINDOW_SHIFT × Tsymb + Tg1 + DRMCds × Tsymb ≤ Tack_max_O
The ACK window shift may be different for the downstream and upstream directions. The ACK window shift
parameter is selected by the receiver and communicated to the peer transmitter during the initialization in
O-PMS and R-PMS message, respectively.

Figure 9-8 – Example acknowledging downstream DTUs, U-R reference point

Figure 9-9 – Example acknowledging upstream DTUs, U-O reference point

The ACK field of the RMC message shall include acknowledgements for the received DTUs in the form of a
bitmap and an acknowledgement for the RMC frame. Each bit in the ACK bitmap relates to a DTU or group
of consecutive DTUs contained in the received data frames within the associated ACK window. The bitmap
shall include DTU acknowledgements starting with the first DTU ending within the ACK window and ending
with the last full DTU ending within the same ACK window. The ACK bitmap with no grouping shall
incorporate acknowledgements to all DTUs received in the ACK window. Bits of the ACK bitmap that relate
to DTUs that were not transmitted shall be set to "0". In case of grouping, the value of the ACK bits for
groups shall be determined only based on the received DTUs.
The ACK bitmap field size shall be 48 bits. The ACK bitmap shall be ordered according to the order of the
transmitted DTUs, where the acknowledgement to the last transmitted DTU in the ACK window shall be
represented by the LSB of the ACK bitmap field.

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