Multiuser subcarrier and bit allocation along with adaptive cell selection for OFDM transmission

A dynamic multiuser subcarrier-and-bit allocation algorithm with low computational complexity for wideband OFDM downlink transmission is proposed to exploit the multiuser diversity in this paper. Our objective is to maximize the overall spectral efficiency in terms of the number of bits per subcarrier while simultaneously satisfying the requirements on each user's data rate, bit error rate (BER), and the total transmit power. Our results show that the proposed dynamic subcarrier-and-bit allocation algorithm offers about 6 dB performance gain over OFDM using adaptive modulation with fixed subcarrier allocation. Since outages may occur when users happen to be located near the boundary of the cell, a novel adaptive cell selection scheme is proposed to further reduce the probability of outage. Our results show that the probability of outage can be reduced by one order of magnitude.