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."