# A queueing approach to the latency of decoupled UL/DL with flexible TDD and asymmetric services

## TL;DR

This paper models the latency of decoupled uplink and downlink in 5G networks with flexible TDD, using queueing theory to analyze benefits for heterogeneous traffic like eMBB and URLLC.

## Contribution

It introduces a queueing model for decoupled UL/DL access in flexible TDD, quantifying latency improvements for diverse traffic types.

## Key findings

- Decoupled UL/DL reduces queueing latency compared to coupled access.
- Provides an upper bound for latency in critical traffic scenarios.
- Quantifies latency gains through queueing analysis in Rayleigh channels.

## Abstract

One of the main novelties in 5G is the flexible Time Division Duplex (TDD) frame, which allows adaptation to the latency requirements. However, this flexibility is not sufficient to support heterogeneous latency requirements, in which different traffic instances have different switching requirements between Uplink (UL) and Downlink (DL). This is visible in a traffic mix of enhanced mobile broadband (eMBB) and ultra-reliable low-latency communications (URLLC). In this paper we address this problem through the use of a decoupled UL/DL access, where the UL and the DL of a device are not necessarily served by the same base station. The latency gain over coupled access is quantified in the form of queueing sojourn time in a Rayleigh channel, as well as an upper bound for critical traffic.