Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

RACH-less Handover with Early Timing Advance Acquisition for Outage Reduction

Subhyal Bin Iqbal, Umur Karabulut, Ahmad Awada, Philipp Schulz, Gerhard P. Fettweis

TL;DR

A RACH-less handover signaling scheme for the 3rd Generation Partnership Project (3GPP) conditional handover (CHO) mechanism that exploits the decoupling between the CHO preparation and execution phases to establish initial synchronization between the UE and the target cell through an early acquisition of the timing advance.

Abstract

For fifth-generation (5G) and 5G-Advanced networks, outage reduction within the context of reliability is a key objective since outage denotes the time period when a user equipment (UE) cannot communicate with the network. Earlier studies have shown that in the experimental high mobility scenario considered, outage is dominated by the interruption time that stems from the random access channel (RACH)-based handover process from the serving cell to the target cell. A handover by itself is a necessary mobility process to prevent mobility failures and their associated outage. This paper proposes a RACH-less handover signaling scheme for the 3rd Generation Partnership Project (3GPP) conditional handover (CHO) mechanism. The proposed scheme exploits the decoupling between the CHO preparation and execution phases to establish initial synchronization between the UE and the target cell through an early acquisition of the timing advance. This significantly curtails the RACH process and therefore the handover interruption time. Results based on a system-level simulation-based mobility study have shown that the proposed scheme significantly reduces the outage and its constituent handover interruption time relatively by 18.7% and 43.2%, respectively.

RACH-less Handover with Early Timing Advance Acquisition for Outage Reduction

TL;DR

A RACH-less handover signaling scheme for the 3rd Generation Partnership Project (3GPP) conditional handover (CHO) mechanism that exploits the decoupling between the CHO preparation and execution phases to establish initial synchronization between the UE and the target cell through an early acquisition of the timing advance.

Abstract

For fifth-generation (5G) and 5G-Advanced networks, outage reduction within the context of reliability is a key objective since outage denotes the time period when a user equipment (UE) cannot communicate with the network. Earlier studies have shown that in the experimental high mobility scenario considered, outage is dominated by the interruption time that stems from the random access channel (RACH)-based handover process from the serving cell to the target cell. A handover by itself is a necessary mobility process to prevent mobility failures and their associated outage. This paper proposes a RACH-less handover signaling scheme for the 3rd Generation Partnership Project (3GPP) conditional handover (CHO) mechanism. The proposed scheme exploits the decoupling between the CHO preparation and execution phases to establish initial synchronization between the UE and the target cell through an early acquisition of the timing advance. This significantly curtails the RACH process and therefore the handover interruption time. Results based on a system-level simulation-based mobility study have shown that the proposed scheme significantly reduces the outage and its constituent handover interruption time relatively by 18.7% and 43.2%, respectively.
Paper Structure (13 sections, 4 equations, 7 figures, 2 tables)

This paper contains 13 sections, 4 equations, 7 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Network Model
  3. Inter-cell Mobility
  4. Intra-cell Mobility
  5. SINR Model
  6. RACH-less Handover System Model
  7. Handover Interruption Time Breakdown
  8. Proposed Model for Early TA Acquisition
  9. Simulation Scenario and Parameters
  10. Performance Evaluation
  11. KPIs
  12. Simulation Results
  13. Conclusion

Figures (7)

  • Figure 1: Illustration of CHO mechanism from serving cell $c_0$ to target cell $c^{\prime}$.
  • Figure 2: Depiction of the handover interruption time for the CHO mechanism. The control and data plane signaling is indicated in italic and roman font, respectively.
  • Figure 3: Signaling diagram depicting the proposed enhancement (shown in red) for early acquisition of the TA in CHO to execute a RACH-less handover. The solid and broken lines represent ideal and non-ideal links, respectively.
  • Figure 4: Simulation scenario consisting of seven hexagonal sites, where each site is serving three cells with 120$^{\circ}$ coverage. The effect of shadow fading is also visible in the form of coverage islands.
  • Figure 5: A depiction of the mobility performance of the proposed RACH-less handover scheme.
  • ...and 2 more figures