Truncated Channel Inversion Power Control to Enable One-Way URLLC with Imperfect Channel Reciprocity

TL;DR

This paper introduces a channel inversion power control scheme for one-way URLLC that reduces latency and overhead by eliminating the need for CSI feedback, leveraging channel reciprocity to improve reliability.

Contribution

It proposes a novel CIPC scheme that guarantees constant received signal power without CSI at the user, optimizing reliability and latency in one-way URLLC systems.

Findings

CIPC reduces feedback overhead and latency.

Analytical expressions for packet loss probability are derived.

Tradeoffs among reliability, latency, and resources are characterized.

Abstract

We propose to use channel inversion power control (CIPC) to achieve one-way ultra-reliable and low-latency communications (URLLC), where only the transmission in one direction requires ultra reliability and low latency. Based on channel reciprocity, our proposed CIPC schemes guarantee the power of received signal that is used to decode the information to be a constant value $Q$, by varying the transmit signal and power, which relaxes the assumption of knowing channel state information (CSI) at the user. Thus, the CIPC schemes eliminate the overhead of CSI feedback, reduce communication latency, and explore the benefits of multiple antennas to significantly improve transmission reliability. We derive analytical expressions for the packet loss probability of the proposed CIPC schemes, based on which we determine a closed interval and a convex set for optimizing $Q$ in CIPC with imperfect and perfect channel reciprocity, respectively. Our results show that CIPC is an effective means to achieve one-way URLLC. The tradeoff among reliability, latency, and required resources (e.g., transmit antennas) is further revealed, which provides novel principles for designing one-way URLLC systems.