3GPP Interworking and Multicast retransmission Group Name: ARC Source: KETI and Hyundai Motors – JaeSeung Song, Lewis Nkenyereye, Youngjin Ra, and Minbyeong Lee Meeting Date: 2018-12-03

Motivation and Background

Issues and Use Case oneM2M IN-CSE, Group Hosting CSE, should aware of MBMS status of a multicast message to be delivered so that it can provide an exact information which members were failed to get the multicast message. If such information is available at the Group Hosting CSE, Contents provider (AE) can perform retransmission of the message only to the members failed to receive the message Use Case for a periodic and/or planned file delivery to a large number of vehicles. Smart vehicles are moving various places. These smart vehicles are receiving many multicast services such as traffic condition, accident information, detour information. Based on growing amount of data, the system configuration is adjusted, requiring the delivery of small configuration updates to all vehicle devices. As vehicles move fast, there will be high chance not to get the delivered multicast message If some of these multicast delivery fails, the message should be retransmitted to users

Current Status What about some members didn’t receive the multicast msg properly?  Retransmission should be performed

How to support? Required enhancements for multicast retransmission oneM2M should support the reliable delivery of multicast message The <group> resource should know the detail information about the MBMS delivery status (i.e. delivery failure) The <localMulticastGroup> resource should also know the detail information about the MBMS delivery status oneM2M system should be able to retransmit multicast message to failure MBMS nodes Two available mechanisms Unicast to MBMS failure member nodes If the number of failure member nodes are low, this mechanism is good to be selected Multicast the same message to the MBMS failure member nodes If the number of failure member nodes are high, this mechanism is good to be selected Different multicast group (TMGI) for retransmission is needed

Retransmission using Unicast Member Hosting CSE 3GPP Group Hosting CSE AE 15. Response Retransmission using Unicast If there are failures of multicast delivery, <group> hosting CSE retransmit the message to failed nodes via unicast CSE sends unicast message delivery to the members in the memberNotDelivered attribute If unicast delivery is successful, CSE deletes the member from the memberNotDelivered. After the given number of retransmission, CSE considers the failure nodes are not available anymore and removes the member from the <group> resource 16. Update retransmission related attributes 17. Response 18. retransmit 19. Check failure members 20. Retransmit using Unicast 21. Response 22. Remove members that receive delivery successfully 23. Response 24. If there exist member CSEs that didn’t get the message successfully, AE can repeat again until the given maxRetransmission number

Retransmission using Multicast Member Hosting CSE 3GPP Group Hosting CSE AE Retransmission using <Retransmission> 16. Record failure member hosting CSEs 17. Response to AE 18. AE requests retransmission for the message (maxTime, maxNumber, etc), 19. Group Hosting CSE creates <retransmission> resources with other relevant attributes, incl. allocate a new TMGI for retransmission 20. CSE sends unicast message delivery to the members in the memberNotDelivered attribute 21. Response from member hosting CSE 22. Update <Retransmission> resource based on the If unicast delivery is successful, CSE deletes the member from the memberNotDelivered. Increase currentNrRetransmission. 23. Response to AE 24. After the given number of retransmission, CSE considers the failure nodes are not available anymore and removes the member from the <group> resource 15. Response 16. Local processing 17. Response 18. retransmit 19. Prepare retransmission 20. Retransmit using Unicast 21. Response 22. Update <retransmission> for example, remove members that receive delivery successfully 23. Response 24. If there exist member CSEs that didn’t get the message successfully, AE can repeat again until the given maxRetransmission number

Retransmission using Multicast Retransmission using <Retransmission> resource <Retransmission> resource can be introduced to support multicast retransmission If there are failures of multicast delivery, <retransmission> resource is created as a child resource of <group> CSE performs multicast to the members listed in <retransmission> group for the given number of times For each retransmission, if nodes receive the message properly, these members should be removed from the <retransmission> resource After performing multicast to the given number of times, the created <retransmission> resource is removed In this case, 3GPP MBMS TMGI and relevant information to perform 3GPP MBMS should be created and configured for the members specified in <retransmission> resource