ABSTRACT
This chapter discusses nonorthogonal multiple access for OTFS technology. The multiple access (MA) technique can be broadly classified in two categories, namely orthogonal multiple access (OMA) and nonorthogonal multiple access (NOMA). In OMA, resource allocation orthogonality is maintained, that is, one resource unit is allocated to only one user. With reference to OTFS, two types of OMA-OTFS are known TF MA OTFS: where users are allocated different TF resources and De-Do MA-OTFS: where users are allocated different De-Do resources. The method power-domain NOMA (PD-NOMA) is realized using superposition coding at the transmitter along with successive interference cancellation at the receiver. Such schemes are known achieve the capacity of Gaussian broadcast channel. It is known that PD-NOMA outperform OMA as well as code-division NOMA schemes in terms of sum spectral efficiency performance.
