E 2 suggestions NokiaATT contribution to WG 3

E 2 suggestions Nokia-AT&T contribution to WG 3 Paul Stephens, Alistair Urie, Thoralf Czichy, Rittwik Jana, Matti Hiltunen 9/24/2019

E 2 • E 2 AP: Application Protocol • Provides signaling procedures between a RAN node and RIC • Offers transport of one or more E 2 Service Model connections between RIC hosted x. App and RAN function • E 2 SM: Service Model • Defines the services exposed over E 2 by a given RAN Function • RAN Function specific service model handled by targeted x. App • Example: g. NB-X 2 part • E 2 SM used by the X 2 interface handler in g. NB and, in particular, the exposure of X 2 AP messages (3 GPP 36. 423) • Version for co-creation project release 1 supports REPORT only on

X 2 + E 2 Justifications • Near-RT RIC use cases can benefit greatly from data transported over X 2 • Majority of global operators have a large part of their network on LTE e. NBs; LTE will likely not sunset for many years to come • Near-RT RIC looks as if it is a “pseudo e. NB” when communicating to another e. NB or g. NB • Important consideration since this provides backward compatibility without changing/upgrading e. NB software • Reuse of X 2 information elements (load, status reports, etc. )

RIC to RAN (Directionality of E 2 connections) • Improving Resiliency and Load Balancing • If an E 2 Termination instance fails, the E 2 Manager can simply direct another E 2 Termination instance to connect to the RAN element • If E 2 Termination instance gets overloaded, E 2 Manager can migrate some RAN elements from that E 2 Termination instance to others (or possibly newly created ones) • If a RIC instance gets overloaded, a higher-level management system can move the management of some RAN elements from one RIC instance to another • Recommend that both directions are supported (RIC to RAN, RAN to RIC)

RIC E 2 Termination failure (current implementation) - E 2 Termination (instance) crashes - Platform restarts E 2 Termination - E 2 Termination wakes up and sends a new control message to E 2 Manager (we will add a new message type) - E 2 Manager determines that this is a recovery (versus the initial start) and determines (based on the R-NIB) which e. NB/g. NB the failed (and now recovered) E 2 Termination was responsible for - It will execute the (EN DC)X 2 SETUP flow for each of e. NBs/g. NBs - When a GNB returns EN DC X 2 SETUP RESPONSE, we also route the message to the Subscription Manager who then determines which subscriptions need to be resent to that g. NB. The x. Apps do not need to know about this interruption.

E 2 Termination failure recovery E 2 Termination E 2 Manager R-NIB Subscription Manager E 2 TERMINATION RECOVERY ACK EN DC X 2 SETUP REQUEST EN DC X 2 SETUP RESPONSE Get info about e. NBs/g. NBs served by the recovered E 2 Termination Determine which subscriptions need to be re-issued. Update R-NIB RIC SUBSCRIPTION REQUEST … 6

X 2 RESET from RAN handling E 2 Termination E 2 Manager R-NIB Subscription Manager X 2 RESET Update R-NIB EN DC X 2 SETUP REQUEST EN DC X 2 SETUP RESPONSE Determine which subscriptions need to be re-issued. Update R-NIB RIC SUBSCRIPTION REQUEST … 7

SCTP connection loss E 2 Termination E 2 Manager R-NIB Subscription Manager RIC SCTP CONNECTION FAILURE Update R-NIB EN DC X 2 SETUP REQUEST EN DC X 2 SETUP RESPONSE Determine which subscriptions need to be re-issued. Update R-NIB RIC SUBSCRIPTION REQUEST … 8