Fast Uplink Access in TDD Systems for Ultra Reliable and Low Latency Communications

Abstract

Fifth generation (5G) wireless networks are currently being developed to handle wide variety of use cases. In order to support these cases, new types of requirements other than throughput enhancement have been introduced. One such requirement is to reduce the latency down to a millisecond (ms) level in ultra reliable and low latency communications (URLLC). In case of uplink transmission, supporting this stringent latency requirement is quite challenging since the scheduling procedure is a time-consuming and complicated handshaking process. In time division duplexing (TDD) systems, satisfying the latency requirement is far more difficult since the mobile device cannot transmit the data when the subframe is assigned for the downlink. In this paper, we propose a low latency access scheme suitable for TDD-based URLLC. Key idea of the proposed scheme is to transmit the latency sensitive data immediately after the grant signaling. To support the fast uplink access, we introduce a fast grant signaling scheme based on the compressed sensing technique. Numerical results confirm that the proposed uplink access scheme is very effective in TDD-based URLLC systems.