Satellite phones get a fixed two-option way to share uplink capacity

Apple, Panasonic, InterDigital and Honor wanted satellite phones to combine two capacity techniques at once — Orthogonal Cover Codes (OCC) for sharing uplink resources among multiple users, and Transport Block over Multiple Slots (TBoMS) for spreading data across several time slots. Samsung and Xiaomi opposed the combination outright, and the moderator concluded there was 'not enough consensus' to proceed. The result is a gap: chipset makers cannot finalize how large data transfers over satellite links will work until this is revisited.

On the core capacity mechanism itself, phones will get two specific OCC schemes for satellite uplink: a length-2 code multiplexing 2 users, and a length-4 code multiplexing 4 users using Hadamard sequences. Two more flexible alternatives — intra-symbol OCC and a hybrid combination — were dropped. Networks can keep the 4-user scheme working well by grouping phones with similar frequency offsets, for example within 50, 100 or 200 Hz of each other; without that grouping, a 400 Hz mismatch costs at least 1 dB of performance. Phones will need separate certified capabilities for each code length, with the 2-user capability required before the 4-user one.

For 6G-era non-terrestrial coverage, RAN1 extended PDCCH repetition — used to help distant satellite devices decode critical system information — from a single SSB density setting to all three (M=2, 1, and 1/2), using a reserved bit in the broadcast channel to switch it on or off. A related proposal to let devices combine repeated control signals from two different satellite beams found no consensus: Spreadtrum, CATT, InterDigital, Honor, OPPO, Apple, Ericsson and Nokia were against adding it for this release, while Huawei and ZTE pushed for it.

For narrowband IoT devices on satellites, RAN1 fixed the TDD guard period at 48–50 ms and locked the downlink subframe pattern to match the legacy Iridium frame structure, and confirmed that NPRACH Format 2 won't be supported in this mode. But two related questions stayed open: whether multi-tone OCC transmission is worth the added complexity — backed by ten companies including Huawei, Apple and Xiaomi, opposed by InterDigital and Ericsson — and how to schedule random-access attempts that fall outside valid uplink subframes, where seven companies favor new access periodicities and seven others favor simply delaying the attempt.

The phase continuity rules that make OCC multiplexing reliable are still waiting on RAN4 to confirm whether existing DMRS-bundling requirements can be reused rather than written from scratch; that reply will determine how strict timing and power control need to be in silicon. NPRACH scheduling and segmented pre-compensation for satellite IoT remain split along similar lines and are expected to return at the next RAN1 meeting.