In this paper, a new subcarrier activation pattern (SAP) design for orthogonal frequency multiplexing with index modulation (OFDM-IM) system is proposed. It takes fairness and error performance into consideration to make each subcarrier activation probability as equal as possible, and we call it as the fair subcarrier activation method (FSAM). Furthermore, to reduce computational complexity, we divide the signal detection into two subprocesses: SAP determination and symbol demodulation, and develop a low complexity signal detection algorithm with negligible bit error rate (BER) performance loss. The simulation results show the effectiveness of the proposed algorithm over the conventional algorithms.