Single versus multiple uplink SPS configurations for NB-IoT NTN voice

The proposals concern semi-persistent scheduling (SPS) for voice over narrowband Internet of Things (NB-IoT) non-terrestrial networks (NTN). RAN2 is the working group for radio layer 2 and radio resource control. These contributions were submitted for RAN2 #135-bis. ZTE with Sanechips proposed one uplink (UL) SPS configuration using dedicated radio resource control (RRC) signaling. Their proposal states "only one SPS periodicity can be provided in this UL SPS configuration". Quectel's proposal calls for "the configuration of multiple UL SPS via RRC". Each configuration would carry at least a periodicity and grant parameters related to transport block size.

Sources: R2-2607166, ZTE (with Sanechips), 3GPP TSG RAN WG2 #135-bis. © ZTE, Sanechips. R2-2606748, Quectel, 3GPP TSG RAN WG2 #135-bis. © Quectel.

China Mobile called one periodicity and one transport block size with over-provision simplest for long-latency geostationary orbit (GSO) scenarios. Our reading: Over-provision allows more transport block capacity than a packet immediately needs.

The cited meeting agreement uses the same SPS cell radio network temporary identifier (C-RNTI) for uplink and downlink scheduling. It can be configured in a common SPS location, for example outside the separate uplink and downlink configurations. Whether its value matches the identifier for SPS used for buffer status reports (BSR) remains for further study (FFS). The report also says Samsung thinks "we can also consider reverting the previous agreement".

Source: R2-2607784, Session Chair (ZTE), 3GPP TSG RAN WG2 #135-bis, meeting report, agenda item 8.7.2.