Sharif University of Technology Scientia Iranica 1026-3098 Articles in Press 2025 11 15 Spectral-Efficient User Association in Two-Way Network-Coded D2D Communications with Multiple Antenna Relay 24050 10.24200/sci.2025.66769.10243 EN Abubakr Mohammadian Department of Electrical and Computer Engineering, Urmia University, Urmia, Iran Mahrokh G. Shayesteh Department of Electrical and Computer Engineering, Urmia University, Urmia, Iran Wireless Research Lab, ACRI, Electrical Engineering Department, Sharif University of Technology, Tehran, Iran Hashem Kalbkhani Faculty of Electrical Engineering, Urmia University of Technology, Urmia, Iran Azadeh Khazali Department of Electrical and Computer Engineering, Urmia University, Urmia, Iran Journal Article 2025 04 24 A two-way relay network refers to a communication scenario in which two nodes exchange information with each other, but they are out of transmission range of each other. In this scenario, a relay node can facilitate the information exchange between the two communication nodes. The relay node receives signals from both nodes, processes them, and then forwards the processed signals to the nodes. Interference is the fundamental challenge of two-way relay channels which reduces the received signal quality, where beamforming reduces the interference. Further, when the number of pairs of users increases, the spectral efficiency (SE) decreases dramatically. The purpose of this study is to spectrally efficient user association in two-way network-coded device to device (D2D) communication with multiple antennas relay. We optimize the beamforming vectors at the relay to maximize the achievable sum-rate. In the proposed method, D2D users are selected from the pairs that have the highest correlation channel gains. However, to increase the efficiency of transmission, those pairs whose average data rate does not reach the threshold rate, are removed and other pairs are replaced. The results show that the proposed method can improve the outage probability and spectral efficiency in two-way communication in comparison with other methods. https://scientiairanica.sharif.edu/article_24050_9a8bf55dbb149d31677a2bb1a3370224.pdf