  Support massive connectivity is an important requirement in 5G wireless
communication system. For massive Machine Type Communication (MTC) scenario,
since the network is expected to accommodate a massive number of MTC devices
with sparse short message, the multiple access scheme like current LTE uplink
would not be suitable. In order to reduce the signaling overhead, we consider
an grant-free multiple access system, which requires the receiver facilitate
activity detection, channel estimation, and data decoding in "one shot" and
without the knowledge of active user's pilots. However, most of the "one shot"
communication research haven't considered the massive MIMO scenario. In this
work we propose a Multiple Measurement Model (MMV) model based Massive MIMO and
exploit the covariance matrix of the measurements to confirm a high activity
detection rate.
