Satellite IoT devices get a way to share channels, but collision rules still split vendors

Satellite IoT capacity now hinges on a fight over what happens at the edges of a transmission. Huawei, OPPO and Qualcomm want the scheduling pattern for multi-transport-block traffic scaled to match the orthogonal cover code length so devices sharing a channel don't step on each other; Nokia and Apple instead insist that any codeword touching a timing pre-compensation gap should be dropped outright, while vivo and Qualcomm counter that smart scheduling alone avoids the collision. Unlike terrestrial 5G, where interference is a capacity nuisance, on a satellite link with heavy Doppler shift it can silently erase the gains the whole feature was built to deliver.

The core win this quarter was confirming inter-slot orthogonal cover codes for satellite IoT: a code length of 2 multiplexes two devices, length 4 uses Hadamard sequences to multiplex four, and networks group devices by carrier frequency offset windows as tight as 50 Hz to keep the codes aligned. RAN1 also fixed a concrete edge case — when an uplink transmission collides with a random-access occasion, devices restart at a slot where (5×nf + ns) mod 4 = 0, keeping the 4-slot repetition pattern intact. Chipmakers get a stable rule instead of ambiguity, but three other pieces — dropping entire OCC groups on cancellation, CSI-report timing, and the beta-offset overhead cut — stayed unresolved despite broad support from Vivo, Samsung, DoCoMo and Panasonic.

A parallel study opened on what happens when satellite phones lose GPS entirely. 3GPP agreed to test two scenarios — total GNSS loss and gradual position drift — across geostationary orbit, 1200 km and 600 km low-earth orbit, at elevation angles down to 12.5 degrees and speeds up to 1500 km/h for aircraft terminals. But Apple, ST Engineering iDirect, InterDigital and CMCC want both cell-wide and per-device GNSS failure studied, while Nokia, Samsung, CEWiT and Lenovo argue only the per-device case matters; the split determines whether future fixes need network-wide signaling or just individual device logic.

NB-IoT over satellite got its TDD frame structure locked: 8 downlink subframes, a 50-subframe guard, 8 uplink subframes, then a 24-subframe guard, all within a 90-millisecond cycle. Nokia and Xiaomi pushed to shorten the scheduling delays to reclaim wasted resource inside that tight 8-subframe window, but Lenovo, Ericsson, ZTE, Huawei and Iridium — ten companies against two — kept the existing terrestrial delays, judging the change unnecessary in a maintenance release. A separate push by Qualcomm, Nordic and Iridium to relax reference-signal assumptions for better channel estimation was blocked by eight opposing companies including OPPO, Huawei and Nokia.

One dependency now blocks further progress: OPPO and Xiaomi want RAN1 to specify how devices pre-compensate timing across each block of 8 TDD uplink subframes, but Lenovo, Vivo, Huawei, Nokia and seven others say this belongs to RAN4, the group handling radio performance requirements. Until RAN4 weighs in, TDD-mode satellite IoT devices lack a finished timing procedure — a gap that matters for whether early chipsets ship with FDD-only assumptions baked in.