RLC Reset procedure

The Reset procedure is used to reset the two RLC entities. It uses the RESET and RESET ACK PDUs, as shown in the figure. These PDUs have a higher priority than AMD PDUs. During the Reset procedure the hyper frame numbers (HFN) used for phering in UTRAN and UE are synchro-nized1.
The Reset procedure can be triggered by a number of events:

The Discard function is using the No_Discard after x number of transmissions variant and the VT(DAT) variable for an AMD PDU equals the value of the Max-DAT parameter.

The variable VT(MRW), which counts the number of attempts for success-fully sending a Status PDU with a MRW SUFI, equals the value of the Max MRW parameter.

A Status PDU (or piggybacked Status PDU) with erroneous sequence numbers in the status report (LIST, BITMAP, RLIST or ACK SUFIs) is re-ceived.

A Status PDU (or piggybacked Status PDU) with erroneous sequence numbers in the status report
(LIST, BITMAP, RLIST or ACK SUFIs) is re-ceived.

If the RESET PDU received by the Receiver has an RSN value that is different than the last RESET PDU, and consequently is part of a new Reset procedure, (or if it is the first one the Receiver receives since its establishment or re-establishment) then the Receiver must reset itself. This includes the following:

·         Resetting all its state variables (except VT(RST)) to their initial values.

·         Stopping all timers except Timer_RST, Timer_Discard, Ti-mer_Poll_Periodic and Timer_Status_Periodic.

·         Resetting all configurable parameters to their configured values.

·         Discarding all RLC PDUs in the receiving side of the AM RLC entity.

·         Discarding all RLC PDUs that were transmitted before the reset in the

·         Transmitting side of the AM RLC entity.

·         Synchronizing its HFN numbers with the ones in the RESET P

·         Informing the upper layers of the reset, if configured to do so.

·         Submitting a RESET ACK PDU to the lower layer with its RSN field set to

·         The same value as the corresponding received RESET PDU.

When the Sender receives the RESET ACK PDU, it checks its RSN to determine if it corresponds to the last RESET PDU it sent. If it does not, then the PDU is discarded. Otherwise, the Sender resets itself similarly to the Receiver. This includes the following.

• Resetting all its state variables to their initial values.
• Stopping all timers except Timer_Discard, Timer_Poll_Periodic and
• Timer_status_periodic
• Resetting all configurable parameters to their configured values.
• Discarding all RLC PDUs in the receiving side of the AM RLC entity.
• Discarding all RLC PDUs that were transmitted before the reset in the
• Transmitting side of the AM RLC entity.
• Synchronizing its HFN numbers with the ones in the RESET ACK PDU.
• Informing the upper layers of the reset, if configured to do so.

Re-establishment function

The RLC entity can be re-established by upper layers. In this function, it resets state variables and configurable parameters and discards the AMD PDUs in the receiving side, among other things. This function was not implemented or used in our simulation since there is no support for such a function from the upper layers in our simulated environment.

Reconfiguration of RLC parameters by upper layers

The RLC parameters for an RLC entity can be modified by upper layers. The parameters that can be reconfigured include the Configured_Tx_Window_Size parameter (which affects the VR(MR) variable) and Configured_Tx_Window_Size parameter (which affects the VT(WS) and VT(MS) variables). This function can cause a number of PDUs to be discarded at the UE due to limited memory. This function was not implemented or used in our simulation since there is no support for such a function from the upper layers in our simulated environment.