Scheduling Versus Contention for Massive Random Access in Massive MIMO Systems

Massive machine-type communications protocols have typically been designed under the assumption that coordination between users requires significant communication overhead and is thus impractical. Recent progress in efficient activity detection collision-free scheduling, however, indicates cost of can be much less than naive scheme for scheduling. This work considers a scenario which massive number devices with sporadic traffic seek to access multiple-input multiple-output (MIMO) base-station (BS) explores an approach device followed by single common feedback broadcast message, used both schedule active different transmission slots assign orthogonal pilots channel estimation. The proposed coordinated compared two prevalent contention-based schemes: coded pilot access, based on principle slotted ALOHA, approximate message passing joint user Numerical results indicate scheduled provides gains successful transmissions per slot sum rate, due reduced interference, at only small feedback.