Evaluating Fast and Grant-Free Uplink Access in Next-Generation Cellular IoT Networks

Next-generation cellular communication technolo-gies must follow the trend of massive deployment and energy efficiency in the Internet of Things (IoT), preferably using existing network infrastructure. Narrowband IoT (NB-IoT) stands out as a promising candidate due to its low cost and easy installation because of its Long Term Evolution (LTE)-based architecture. However, the conventional random access procedure of NB-IoT limits its energy efficiency and predictability. To this end, this paper compares the achievable connection density and energy efficiency of the conventional random access scheme with novel grant-free and fast-uplink access techniques. Our findings reveal that optimal random access schemes can support three times as many devices as grant-free schemes and therefore perform the best in terms of connection density. However, when it comes to energy efficiency, random access performs the worst with energy consumption up to 12 times higher than grant-free schemes. Fast-uplink access fulfills its expectations as the most promising technique for next-generation IoT communication, supporting a connection density twice as high as grant-free access, at similar power consumption.