Fast Retrial for Low-Latency Connectivity in MTC With Two Different Types of Devices

In this letter, we consider co-existing two different types of devices in machine-type communication (MTC), namely type-1 and type-2 devices, where type-1 devices need short access delay for low-latency requirements, while type-2 devices are delay-tolerant. For short access delay, we study the use of fast retrial in preamble transmissions when a group of preambles is divided into two subsets to support two different types of devices. Stability conditions are derived using Foster-Lyapunov criteria in terms of arrival rates, the number of preambles, and the number of type-1 devices. We also propose an adaptive algorithm that dynamically decides the minimum number of preambles for type-1 devices under stability conditions.