This letter investigates the coexistence between near-field (NF) and
far-field (FF) communications, where multiple FF users are clustered to be
served on the beams of legacy NF users, via non-orthogonal multiple access
(NOMA). Three different successive interference cancellation (SIC) decoding
strategies are proposed and a sum rate maximization problem is formulated to
optimize the assignment and decoding order. The beam allocation problem is
further reformulated as an overlapping coalitional game, which facilitates the
the design of the proposed clustering algorithm. The optimal decoding order in
each cluster is also derived, which can be integrated into the proposed
clustering. Simulation results demonstrate that the proposed clustering
algorithm is able to significantly improve the sum rate of the considered
system, and the developed strategies achieve different trade-offs between sum
rate and fairness