Enhancing massive machine type communication mMTC using grant free access mechanisms

Abstract

The Internet of things (IoT) is transforming our world owing to its compelling benefits across multiple industries and diverse applications. A prominent IoT scenario being supported in the fifth generation (5G) of wireless communication is the massive machine-type communication (mMTC), where a large number of devices require network access. The mMTC applications are predominantly low data rate and delay tolerant, thereby demanding solutions which are different from the conventional broadband applications. In terms of standardization, the narrowband Internet of things (NB-IoT) from the third generation partnership project (3GPP) is one of the main technologies considered for supporting IoT. While it has several advantages, such as being compatible with the long term evolution (LTE) standard and providing mechanisms for low data rate operation, the standard is still evolving to efficiently support mMTC applications. A key aspect of NB-IoT which is being modified or enhanced to support mMTC corresponds to the access mechanism adopted by the IoT users to connect to the network. newline newlineSeveral prior works have shown that using grant-free (GF) access for users would result in a lower signalling overhead and a reduced energy consumption when compared to the con- ventional grant-based access adopted in NB-IoT. Since GF access does not require the base station to grant specific resources to each user, and utilizes a pre-allocated set of resources in a contention based manner, a major challenge in GF communication would be to handle user packet collisions. This is detrimental for mMTC scenarios, since users experiencing collision will retransmit their packets, leading to an increased load on an already dense network. Thus, the probability of successful transmission of an individual user and that of all users become the key performance indicators (KPIs) of such systems. newline