Abstract
This paper presents an overloaded multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) scheme that realizes signal separation among terminals by orthogonal codes. In multi-user MIMO systems, block diagonalization has been well investigated. However, the calculation of weight coefficients requires the channel state information (CSI) of all the terminals. The accurate CSI feedback needs a large amount of frequency resources. In addition, if the channel correlation between the terminals is high, nulls cannot be formed at the same time. Thus, this paper proposes an overloaded MIMO-OFDM scheme with orthogonal codes that separates signals for different terminals without the CSI. The proposed scheme realizes orthogonality among the signals for the terminals while throughput reduction by spreading is compensated through with an overloaded MIMO technique. Numerical results obtained through computer simulation show that the proposed scheme achieves better bit error rate performance as compared to that of MU-MIMO on a Rayleigh fading channel when the number of users is two and each user has two receive antennas.
