  With the explosively increasing demands on the network capacity, throughput
and number of connected wireless devices, massive connectivity is an urgent
problem for the next generation wireless communications. In this paper, we
propose a grant-free access protocol for massive connectivity that utilizes a
large number of antennas in a base station (BS) and is expected to be widely
deployed in cellular networks. The scheme consists of a sparse structure in
sparse code multiple access (SCMA) and receiver processing based on dictionary
learning (DL). A large number of devices can transmit data without any
scheduling process. Unlike existing schemes, whose signal schedulings require a
lot of overhead, the scheduling overhead required by the proposed scheme is
negligible, which is attractive for resource utilization and transmission power
efficiency. The numerical results show that the proposed scheme has promising
performance in massive connectivity scenario of cellular networks.
