TDD-sparse index multiple access for joint data detection and device identification in MTC

In this paper, we study pre-equalization for sparse index multiple access (SIMA), which was proposed to enable one-shot identification and detection in random access, over frequency-selective fading channels in time division duplexing (TDD) mode. Each device is to decide a transmit vector to adapt to its channel for pre-equalization based on the channel reciprocity. Due to pre-equalization, the receiver does not need to estimate the channel state information (CSI) of active devices. We further modify pre-equalization with multiple precoding matrices for a better performance with a lower transmission power. For low signaling overhead in random access, we also consider one-shot identification and detection to perform active device identification and their signal detection simultaneously with a low-complexity algorithm by exploiting the sparsity of device activity as well as unique identification sequences.