Connectionless access for massive machine type communications in ultra-dense networks

This paper proposes an approach for receiving small uplink data transmissions from a massive amount of machine type communication (MTC) devices in ultra-dense networks (UDNs). In particular, we propose using a beamforming based solution for distributing (broadcasting) uplink grants for small data transmissions. Receive beamforming is also employed in order to receive the subsequent uplink small data transmissions. The proposed approach is particularly useful in reaching high transmission success probability of MTC uplink traffic with low consumption of physical resources. Extensive numerical results are provided based on detailed system level simulations in an ultra-dense 5G context. Results show that low collision and decoding failure probabilities can be achieved by employing beamforming and orthogonal codes for connectionless uplink grant distribution. Additionally, it is shown that uplink transmissions can be received efficiently by utilizing receive filters designed to maximize the received power towards the directions where grants were broadcasted. The performance of the proposed scheme is analyzed with a typical uniformly distributed massive MTC (mMTC) traffic as well as with a peak access profile as an extreme case.