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A Novel Distributed Queuing-Based Random Access Protocol for Narrowband-IoT

Narrowband Internet of Things (NB-IoT) is a new communication technology designed for machine type communications (MTC), which needs to support much more devices compared to Long Term Evolution (LTE). But the random access (RA) process of it is also based on the slotted-ALOHA mechanism like LTE, which is not that suitable for machine to machine (M2M) communications. When a device's access attempt failed, the time of backoff and access class barring (ACB) is random. This would lead to a lot of meaningless failed attempts when the access load is heavy. And the access successful probability and energy efficiency will be very low. In this paper, we propose a novel access protocol based on resource grouping and distributed queuing (RGDQ) mechanism to effectively solve the massive access issue in NB-IoT. Firstly, we apply DQ mechanism into the access process of NB-IoT. Afterwards, we newly propose an arrival-based access resource grouping mechanism (RG) to reduce the access delay caused by the queuing process of DQ. In addition, we develop an analytical model to accurately estimate the access performance of the proposed protocol. Finally, computer simulations are also performed to validate the accuracy of the analytical model and verify the proposed protocol in comparison with the NB-IoT standard and conventional DQ access schemes.