A low-complexity resource allocation algorithm in multi-cell DF relay aided OFDMA systems

This paper considers a multi-cell OFDMA downlink system with several decode-and-forward (DF) relay stations (RSs) aiding the base station (BS) transmissions. The opportunistic DF protocol proposed in [1] is applied. The problem considered is the maximization of the system sum rate with a total power constraint in each cell. An iterative low-complexity resource allocation (RA) algorithm is proposed to optimize mode selection (decision whether relaying should be used or not and which relay), subcarrier assignment (MSSA) and power allocation (PA) alternatively. During the MSSA stage, instead of the original objective function, a lower bound is maximized so that the problem is decoupled into subproblems which can be solved in linear time. During the PA stage, an algorithm based on single condensation and Lagrange duality PA (SC-LDPA) is designed to optimize PA with the tentative MSSA results. Through numerical experiments, the convergence of the low-complexity algorithm (LCA) as well as its benefit compared with a centralized algorithm (CA) are illustrated.