The basic multiple access scheme for NR is orthogonal for both downlink and uplink data transmissions, e.g., time and frequency physical resources of different users are not overlapped. On the other hand, non-orthogonal multiple-access schemes recently gained wide interest.
Non-orthogonal transmission can be applied to both grant-based and grant-free transmission. The benefits of non-orthogonal multiple access, particularly when enabling grant-free transmission, may encompass a variety of use cases or deployment scenarios, including eMBB, URLLC, mMTC etc. In RRC_CONNECTED state, it saves the scheduling request procedure assuming UE is already uplink synchronized. In RRC_INACTIVE state, data can be transmitted even without RACH procedure or with 2-step RACH. The saving of the signalling naturally also saves UE's power consumption, reduces latency and increases system capacity.
This document is intended to gather all technical outcome of the study item "Study on non-orthogonal multiple access (NOMA) for NR" , and draw a conclusion on a way forward.
This activity involves the Radio Access work area of the 3GPP studies and has impacts both on the Mobile Equipment and Access Network of the 3GPP systems.