Message Structure Reference

This document lists the control messages exchanged through the E2 and E3 interfaces, organized by service model and message type. Each table is split into Collective fields (carried once per message) and Per-UE fields (repeated for each UE in the payload). Messages with no per-UE payload are listed as a single table.

E2 Service Model

E2SM-KPM — RIC REPORT

Reported periodically from the O-DU to the near-RT RIC, carrying radio performance indicators.

Collective Message Content	Unit	Valid Range	Data Type	Per-UE Message Content	Unit	Valid Range	Data Type
Type	—	As defined	uint16	RNTI	—	—	uint16
Timestamp	ns	—	uint64	CQI	—	0–15	uint8
Frame Number	—	0–1023	uint32	Buffer Size	Bytes	—	uint32
Number of UEs	—	—	uint32	QCI	—	1–9	uint8
Total Buffer Size	Bytes	—	uint32	Achievable Rate	Mbps	—	double
Number of RBGs	—	0–Max RBG	uint16	Actual Throughput	Mbps	—	double
RBG Size	PRB	1–4	int	Total Bytes Served	Bytes	—	uint32
Link Direction	—	DOWNLINK / UPLINK	uint8	Packet Delay	ms	—	uint32
ID	—	—	uint32

E2SM-RC — RIC CONTROL

Sent from the near-RT RIC to the O-DU to override or configure MAC scheduling behavior.

Collective Message Content	Unit	Valid Range	Data Type	Per-UE Message Content	Unit	Valid Range	Data Type
Type	—	As defined	uint16	RNTI	—	—	uint16
Max UE Selection Size	—	—	uint32	Max RBG Allocation	—	0–Max RBG	uint16
Skip This Step	—	No / Yes	bool
Link Direction	—	DOWNLINK / UPLINK	uint8
ID	—	—	uint32

E2SM-DAPP — RIC REPORT

Reported from the dApp (O-DU) to the near-RT RIC, summarizing the executed real-time control step. This message carries collective (per-TTI) content only — no per-UE breakdown.

Collective Message Content	Unit	Valid Range	Data Type	Per-UE Message Content	Unit	Valid Range	Data Type
Type	—	As defined	int
Number of Selected UEs	—	—
Total Number of Allocated RBGs	—	0–Max RBG
RBG Size	PRB	1–4
Link Direction	—	DOWNLINK / UPLINK
ID	—	—

E2SM-DAPP — RIC CONTROL

Sent from the near-RT RIC to the dApp (O-DU) to override or configure the upcoming real-time control step. This message carries collective (per-TTI) content only — no per-UE breakdown.

Collective Message Content	Unit	Valid Range	Data Type	Per-UE Message Content	Unit	Valid Range	Data Type
Type	—	As defined	int
Max UE Selection Size	—	—
Total Available RBGs	—	0–Max RBG
Skip This Step	—	No / Yes	bool
Link Direction	—	DOWNLINK / UPLINK	int
ID	—	—

E3 Service Model

E3SM — E3 INDICATION

Reported from the MAC and RLC layers to the local dApp, carrying radio performance indicators including intent-related information shared by UEs.

Collective Message Content	Unit	Valid Range	Data Type	Per-UE Message Content	Unit	Valid Range	Data Type
Type	—	As defined	uint16	RNTI	—	—	uint16
Timestamp	ns	—	uint64	CQI	—	0–15	uint8
Subframe Number	—	0–9	uint32	Buffer Size	Bytes	—	uint32
Frame Number	—	0–1023	uint32	Content Criticality	—	1–10	uint8
Number of UEs	—	—	uint32	Content ID	—	Variant	char
Total Buffer Size	Bytes	—	uint32	QCI	—	1–9	uint8
Initial RBG	—	0–Max RBG	uint16	Achievable Rate	Mbps	—	double
Number of RBGs	—	0–Max RBG	uint16	Actual Throughput	Mbps	—	double
RBG Size	PRB	1–4	int	Total Bytes Served	Bytes	—	uint32
Link Direction	—	DOWNLINK / UPLINK	uint8	Packet Delay	ms	—	uint32
ID	—	—	uint32

E3SM — E3 CONTROL

Sent from the local dApp to the MAC scheduler to control its behavior on a real-time basis.

Collective Message Content	Unit	Valid Range	Data Type	Per-UE Message Content	Unit	Valid Range	Data Type
Type	—	As defined	uint16	RNTI	—	—	uint16
Number of Selected UEs	—	—	uint32	Initial Allocated RBG	—	0–Max RBG	uint16
Skip This Step	—	No / Yes	bool	Number of Allocated RBGs	—	0–Max RBG	uint16
Link Direction	—	DOWNLINK / UPLINK	uint8	MCS	—	0–28	uint8
ID	—	—	uint32