Grant-Free Uplink Transmissions for Ultra-Reliable and Low Latency Communications
09 January 2018
Grant-based (GB) uplink transmissions offer reliable access. However, if the transmission fails, GB re-transmissions may not be possible, considering tight latency constraint of 1 ms even with New Radio (NR) 5G mini-slot numerology. To enable low latency access, Grant-Free (GF) transmissions can be targeted. It utilizes slotted ALOHA contention-based access in time- frequency resource. This eliminates signaling related to scheduling request (SR) and grant (SG), and saves significant time. However, reliability is undermined due to random collisions. We strive to enhance GF reliability by considering, e.g., repeated transmissions, GB access support, feedback control depending on traffic sporadicity, network implementations etc.
