A coordinate interleaved orthogonal design NOMA protocol for two cell-edge users

• Published in: Wireless networks 2023-02, Vol.29 (2), p.623-636
• Main Authors: Üstünbaş Gavas, Seda, Aygölü, Ümit
• Format: Article
• Language: English
• Subjects: Codes; Communications Engineering; Computer Communication Networks; Electrical Engineering; Engineering; Error analysis; IT in Business; Networks; Original Paper; Wireless networks
• ISSN: 1022-0038; 1572-8196
• DOI: 10.1007/s11276-022-03154-y

In this paper, two cell-edge users supported by two base stations from two adjacent cells, are considered. Base stations simultaneously send signals to the users according to the coordinate interleaved orthogonal design (CIOD) to provide diversity and to realize high spectral efficiency. Different from the classical two-antenna CIOD transmission matrix with non-zero entries only in the main diagonal, the proposed CIOD-NOMA matrix consists of two 2 × 2 superimposed CIOD matrices of two users whose signals are located at the two diagonals, respectively. At the receiver side, each user obtains its own CIOD matrix thanks to the NOMA technique. The theoretical bit error probability analysis for Nakagami- m fading channels is performed whose numerical outcomes are supported by computer simulations. The proposed CIOD-NOMA protocol provides full diversity for both users and significantly improves the bit error performance compared to the reference conventional downlink NOMA scheme. Moreover, the proposed CIOD-NOMA protocol is evaluated in terms of power allocation and fairness. It is shown that satisfactory fairness performance can be attained at acceptable BER values by appropriate power allocation.