8.3.19 Radio Link Congestion

25.4233GPPRelease 17TSUTRAN Iur interface Radio Network Subsystem Application Part (RNSAP) signalling

8.3.19.1 General

This procedure is started by the DRNS when resource congestion is detected and the rate of one or more DCHs, corresponding to one or more radio links, is preferred to be limited in the UL and/or DL. This procedure is also used by the DRNC to indicate to the SRNC any change of the UL/DL resource congestion situation, affecting these radio links. This procedure shall use the signalling bearer connection for the relevant UE Context.

The Radio Link Congestion procedure shall not be initiated if a Prepared Reconfiguration exists, as defined in subclause 3.1.

8.3.19.2 Successful Operation

Figure 26C: Radio Link Congestion procedure, Successful Operation

Start of an UL/DL Resource Congestion Situation

When the DRNC detects the start of a UL/DL resource congestion situation and prefers the rate of one or more DCHs for one or more Radio Link(s) to be limited below the maximum rate currently configured in the UL/DL TFS, it shall send the RADIO LINK CONGESTION INDICATION message to the SRNC. The DRNC shall indicate the cause of the congestion in the Congestion Cause IE and shall indicate all the Radio Links for which the rate of a DCH needs to be reduced. For each DCH within the RL with UL congestion, the DRNC shall indicate the desired maximum UL data rate with the Allowed UL Rate IE in the Allowed Rate Information IE. For each DCH within the RL with DL congestion, the DRNC shall indicate the desired maximum DL data rate with the Allowed DL Rate IE in the Allowed Rate Information IE.

[FDD – For each E-DCH MAC-d flow within the RL with UL congestion, the DRNC shall indicate all the MAC-d flows for which the rate cannot be fullfilled.]

When receiving the RADIO LINK CONGESTION INDICATION message the SRNC should reduce the rate in accordance with the Congestion Cause IE and the indicated Allowed DL Rate IE and/or Allowed UL Rate IE for a DCH.

[FDD – If the RADIO LINK CONGESTION INDICATION message includes the DCH Indicator For E-DCH-HSDPA Operation IE, then the SRNS shall ignore the DCH Rate Information IE in the RADIO LINK CONGESTION INDICATION message.]

Change of UL/DL Resource Congestion Situation

The DRNC shall indicate any change of the UL/DL resource congestion situation by sending the RADIO LINK CONGESTION INDICATION message in which the new allowed rate(s) of the DCHs are indicated by the Allowed Rate Information IE. In the case that for at least one DCH the new allowed rate is lower than the previously indicated allowed rate for that DCH, the Congestion Cause IE, indicating the cause of the congestion, shall also be included.

When receiving a RADIO LINK CONGESTION INDICATION message indicating a further rate decrease on any DCH(s) on any RL, the SRNC should reduce the rate in accordance with the indicated congestion cause and the indicated allowed rate(s) for the DCH(s).

End of UL/DL Resource Congestion Situation

The end of an UL resource congestion situation, affecting a specific RL, shall be indicated by including the TF corresponding to the highest data rate in the Allowed UL Rate IE in the Allowed Rate Information IE for the concerned RL. The end of a DL resource congestion situation, affecting a specific RL, shall be indicated by including the TF with the highest data rate in the Allowed DL Rate IE in the Allowed Rate Information IE for the concerned RL.

8.3.19.3 Abnormal Conditions

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