Adaptive parameters selection for uplink grant-free URLLC transmission in 5G systems

Abstract

Ultra-Reliable Low-Latency Communications (URLLC) is a key service of 5G systems that imposes very strict Quality of Service (QoS) requirements. Typically, URLLC applications require successful delivery of at least 99.999% of packets with a packet delivery time below 1 ms. To satisfy these requirements for uplink URLLC traffic, 5G specifications introduce a grant-free channel access method. It allows a base station (gNB) to select transmission parameters for each User Equipment (UE) in advance. The algorithm for transmission parameters selection shall take into account the following factors: (i) various UEs may have significantly different channel conditions that can change with time; (ii) if several UEs share common channel resources, their transmissions can interfere with each other; (iii) the gNB can use sophisticated decoding mechanisms, such as Successive Interference Cancellation (SIC), to mitigate the interference problem. In contrast to the existing studies that take into account only some of these factors, this paper proposes an algorithm that considers all three factors and adaptively selects the transmission parameters for each UE based on the desired signal and interference measurements available at the gNB. Numerical results obtained with NS-3 show that the developed algorithm significantly increases the network capacity for both periodic and sporadic URLLC traffic compared with the state-of-the-art algorithms.