For greedy block sparse recovery with unknown sparsity level, we theoretically derive a stopping condition to terminate the iteration process and thus to estimate the sparsity level. Focused on the block orthogonal matching pursuit (BOMP) algorithm, we model the energy of residual signals from a probabilistic perspective and we use its distribution to derive a threshold, the iteration process is terminated when the residual energy is below the given threshold. Specifically, a communication scenario of small packet transmission is considered, which uses the interference cancellation based BOMP (ICBOMP) algorithm to recover sparse signal, we apply the stopping condition to terminate the iterations, and thus to estimate the number of active users. Simulation results show that our derived condition can accurately estimate the sparsity level and at the same time guarantees a favorable recovery accuracy, both for the BOMP and ICBOMP recoveries.

Modern mobile terminals produce massive small data packets. For these short-length packets, it is inefficient to follow the current multiple access schemes to allocate transmission resources due to heavy signaling overhead. We propose a many-access scheme that is well suited for the future communication systems equipped with many receive antennas. The system is modeled as having a block-sparsity pattern with unknown sparsity level (i.e., unknown number of transmitted messages). Block precoding is employed at each single-antenna transmitter to enable the simultaneous transmissions of many users. The number of simultaneously served active users is allowed to be even more than the number of receive antennas. Sparsity-aware recovery is designed at the receiver for joint user detection and symbol demodulation. To better recover the transmitted block-sparse signal vector, interference cancellation based block orthogonal matching pursuit (ICBOMP) algorithm is developed upon the known BOMP algorithm for the recovery.Simulation results demonstrate the effectiveness of the proposed scheme in small packet services, as well as the advantages of ICBOMP in improving signal recovery accuracy and reducing computational cost.

Modern mobile terminals produce massive small data packets. For these short-length packets, it is inefficient to follow the current multiple access schemes to allocate transmission resources due to heavy signaling overhead. We propose a non-orthogonal many-access scheme that is well suited for the future communication systems equipped with many receive antennas. The system is modeled as having a block-sparsity pattern with unknown sparsity level (i.e., unknown number of transmitted messages). Block precoding is employed at each single-antenna transmitter to enable the simultaneous transmissions of many users. The number of simultaneously served active users is allowed to be even more than the number of receive antennas. Sparsity-aware recovery is designed at the receiver for joint user detection and symbol demodulation. To reduce the effects of channel fading on signal recovery, normalized block orthogonal matching pursuit (BOMP) algorithm is introduced, and based on its approximate performance analysis, we develop interference cancellation-based BOMP (ICBOMP) algorithm. The ICBOMP performs error correction and detection in each iteration of the normalized BOMP. Simulation results demonstrate the effectiveness of the proposed scheme in small packet services, as well as the advantages of ICBOMP in improving signal recovery accuracy and reducing computational cost.