This study considers an orthogonal frequencydivision multiple-access (OFDMA)-based multi-user two-way relay network where multiple mobile stations (MSs) communicate with a common base station (BS) via multiple relay stations (RSs). We study the joint optimization problem of subcarrier-pairing based relay-power allocation, relay selection, and subcarrier assignment. The problem is formulated as a mixed integer programming problem. By using the dual method, we propose an efficient algorithm to

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... ve the problem in an asymptotically optimal manner. Simulation results show that the proposed method can improve system performance significantly over the conventional methods. Index Terms-Two-way relaying, subcarrier pairing, resource allocation, orthogonal frequency-division multiple-access.