5G-Advanced phones will get channel reports from a fixed SIB1 recipe, not on demand

Getting a phone's channel quality report to the network fast after it connects sounds like plumbing, but it splits vendors into camps with real implementation costs. Samsung, Huawei, Xiaomi, MediaTek and six others wanted the configuration for early channel and sounding reports broadcast in SIB1, the block every phone reads before it even sends its first uplink message — guaranteeing the setup is always there. CATT, ZTE, Ofinno and 1Finity argued for a dedicated new SIB instead, which would keep SIB1 leaner but adds a new broadcast channel for chipsets to parse. 3GPP sided with the SIB1 camp in May, closing a debate that had run since the previous meeting.

The same session locked the trigger mechanism: the network signals which pre-configured report to use via a MAC control element riding inside MSG4, the fourth message of the random-access handshake. InterDigital, Nokia, vivo, ZTE and ETRI wanted this MAC-CE to also dynamically carry parameters like the SRS repetition factor and the number of tracking-reference-signal bursts, giving the network per-device tuning. Samsung, Huawei, Qualcomm and six others won the argument for keeping those values static in system information instead — a simpler MAC-CE, but one-size-fits-all coverage settings for every device joining the cell.

For massive-MIMO deployments running 48, 64 or up to 128 antenna ports, 3GPP confirmed that low-density channel reference signals — as sparse as one resource element in eight per port — must still land within one or two consecutive time slots, a restriction carried over from Release 19. But the group found no consensus to also restrict which frequency resource blocks these signals can occupy, despite a coalition of LG, Huawei, vivo, Samsung, Qualcomm, NTT DOCOMO and others pushing new subband sizes, like a 12-PRB subband for 24-72 PRB carriers. CATT was the lone objector, and the proposal stayed parked without a stated reason.

Uplink sounding got its own tug-of-war. 3GPP agreed the network will set, via RRC signaling, how many frequency starting positions (K) an SRS signal can hop to within a repetition, and clarified exactly how a sounding resource spanning two slots aligns its start. ZTE and ETRI then asked for pseudo-random hopping patterns on top, to scatter interference between users in dense cells; Samsung, Qualcomm, Sony and Xiaomi rejected it, saying existing hopping rules already sweep all resource blocks. The interference-randomization feature stays off the table for now.

Two threads carry into the next rounds. RAN4 has already picked 35, 70 and 140-second switching periods for the enhanced low-band carrier-aggregation mode that lets a phone receive on two carriers at once without transmitting on both — 3GPP agreed a change to TS38.213 is needed to support it, with only Huawei dissenting. Separately, UE-triggered beam reporting still lacks rules for what happens when its uplink control message collides with other signals; the chair has asked proponents to justify the change with concrete numbers before RAN1 revisits it.