Hyperparameter-Free Receiver for Grant-Free NOMA Systems With MIMO-OFDM

We introduce a new grant-free non-orthogonal multiple access (GF-NOMA) scheme, which unlike conventional approaches, spreads over the frequency domain instead of the time domain to reduce access latency. Most conventional receivers for GF-NOMA require the pre-tuning of hyperparameters to achieve superior performance. To avoid such pre-tuning, we propose a hyperparameter-free receiver for the proposed architecture, exploiting the sparsity of channels in the delay domain. Simulation results demonstrate the superior performance of the proposed receiver in terms of the normalized mean-squared error and the activity error rate.