CATT's receiver-side HOL case list moves from Proposal 6 to Observation 7

RAN2 is the radio access network working group for radio interface protocols. At RAN2 #135, CATT's Proposal 6 asked the group to "discuss which causes of receiver-side HOL blocking should be addressed". Our reading: not treated means Proposal 6 was not discussed, and the register records no decision. At RAN2 #135-bis, CATT's Observation 7 says "Receiver-side HOL blocking arises from reordering and in-order delivery, which introduce additional buffering delay.". Our reading: its noted register status does not establish agreement on these cases.

Sources: R2-2604890, CATT, 3GPP TSG RAN WG2 #135. © CATT. R2-2606718, CATT, 3GPP TSG RAN WG2 #135-bis. © CATT.

Both lists describe blocking among quality-of-service (QoS) flows sharing one data radio bearer (DRB). Proposal 6 also describes blocking among multiple service data flows mapped to one QoS flow. Observation 7 describes missing packets blocking higher-priority, more important, or tighter-delay packets inside one QoS flow.

Proposal 6 splits transport-layer signaling blocking by direction, covering missing signaling blocking data and missing data blocking signaling. Observation 7 mentions Transmission Control Protocol acknowledgements (TCP ACK) but does not split its signaling case by direction. Proposal 6 separately describes a missing Packet Data Convergence Protocol (PDCP) control packet blocking data packets with consecutive PDCP sequence numbers. Our reading: Observation 7 does not mention that PDCP case, but this does not establish its withdrawal.