Bit-interleaved coded multi-user multilevel modulation for OFDMA systems

Recently the demand for high data rate has been increasing along with the need to connect many users to an access point (AP) or a base station (BS). In this paper, we propose a bit-interleaved coded multi-user multilevel modulation (MU-MLM) for orthogonal frequency division multiple access (OFDMA) systems. MU-MLM is multilevel modulation (MLM) incorporating multiple users at each modulated symbol. This allows each channel resource of OFDM system to be optimized with higher order modulation (HOM) as well as carry data to multiple users. At the receive side, the received signal is MMSE equalized and successive decoding is done until the level of MLM that is assigned to respective user is decoupled. The equalization at the receiver for the proposed system is far less complex as the same signal is transmitted to all the users. Simulation results show that the proposed system has better BER performance compared to conventional M-ary Quadrature amplitude modulation (M-QAM). The performance is further improved for HOM like 1024-QAM.

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