Abstract
Multiple input, multiples output (MIMO)-constant envelop modulation (CEM), has been proposed to be an efficient power alternative transceiver system to MIMO-OFDM. To attain a high power efficient MIMO transceiver, MIMO-CEM uses a constant envelope modulation at the transmitter (TX) side and an intermediate frequency (IF) based 1-bit ADC in the receiver (RX) side. Despite MIMO-CEM introduces low power consumption, it suffers from highly complicated MIMO detection due the use of IF-based 1-bit ADC in the RX. A decoder with low complexity is proposed in this paper for MIMO-CEM system in the presence of 1-bit ADC. In which, as a first step, an adaptive sphere decoder (ASD) rely on the affine linear transformation (ALT) model for MIMO-CEM system is proposed to adaptively select a small number of sequences from the all lattice states. Thereafter, the exceedingly accurate (the extra complex) maximum likelihood decoder (MLD) in the IF-band for MIMO-CEM is utilized to estimate the transmit sequence which is the most probable to be sent from the selected sequences. In the suggested adaptive SD scheme, the sphere radius is adaptively adjusted depend on the channel conditions, e.g., signal-to-noise power ratio (SNR). Simulation results confirm the high efficiency of the proposed adaptive SD in reducing the complexity of MIMO-CEM detection compared to other existing techniques.