  6G wireless networks will require the flexibility to accommodate an extremely
diverse set of service types. This necessitates the use of mixed numerologies
to accommodate different quality of service (QoS) requirements. Non-orthogonal
multiple access (NOMA) techniques can potentially be used to accommodate users
with different numerologies while also gaining the performance benefits
associated with NOMA. To achieve the full performance benefits of a mixed
numerology NOMA (MN-NOMA) system, resource allocation among the users is
paramount. However, the coexistence of mixed numerologies changes the nature of
the interference that each user experiences. This means that techniques used in
single-numerology NOMA (SN-NOMA) are no longer sufficient. In light of this, we
approach the problem of optimizing subcarrier and power allocation for
maximizing the spectral efficiency of MN-NOMA while considering a minimum rate
constraint for each user. In this letter, we propose a two-stage sub-optimal
approach to solve the problem. We present numerical results which show the
superiority of our proposed method over existing benchmark schemes in both
spectral efficiency and fairness.

Signal Processing