  In this paper, we investigate the coexistence of a single cell massive MIMO
communication system with a MIMO radar. We consider the case where the massive
MIMO BS is aware of the radar's existence and treats it as a non-serviced user,
but the radar is unaware of the communication system's existence and treats the
signals transmitted by both the BS and the communication users as noise. Using
results from random matrix theory, we derive the rates achievable by the
communication system and the radar. We then use these expressions to obtain the
achievable rate regions for the proposed joint radar and communications system.
We observe that due to the availability of a large number of degrees of freedom
at the mMIMO BS, results in minimal interference even without co-design.
Finally we corroborate our findings via detailed numerical simulations and
verify the validity of the results derived previously under different settings.
