User-Centric Cooperative Transmissions-enabled Handover for Ultra-Dense Networks

TL;DR

This paper introduces a user-centric cooperative handover scheme for ultra-dense networks that significantly reduces handover rates and costs by dynamically forming cooperative clusters based on user location and BS distribution.

Contribution

It proposes the GCHO scheme with a dynamic cluster boundary and the GCHO-S skipping scheme, providing analytical expressions and demonstrating substantial improvements over traditional methods.

Findings

GCHO reduces handover rate by up to 72.7%.

GCHO-S cuts handover cost by 50%.

Analytical handover rate expression derived using stochastic geometry.

Abstract

The user-centric cooperative transmission provides a compelling way to alleviate frequent handovers caused by an ever-increasing number of randomly deployed base stations (BSs) in ultra-dense networks (UDNs). This paper proposes a new user-centric cooperative transmissions-based handover scheme, i.e., the group-cell handover (GCHO) scheme, with the aim of reducing the handover rate in UDNs. In the proposed scheme, the boundary of the cooperating cluster depends on the distance among the user equipment (UE) and cooperating BSs. The new scheme captures the dynamicity and irregularity of the cooperating cluster topology resulting from randomly distributed BSs. Based on stochastic-geometry tools where BSs locations are modeled as the Poison point process (PPP), we derive an analytical expression of the handover rate for the UE with an arbitrary movement trajectory. Furthermore, a GCHO skipping (GCHO-S) scheme is proposed to minimize the handover cost, i.e., the percentage of time wasted in handover signaling in user-centric cooperative transmissions scenarios. The numerical results show that the GCHO scheme decreases the handover rate by 42.3% and 72.7% compared with the traditional single BS association and fixed-region cooperative network topology handover approaches, respectively. Moreover, under the same group-cell size and constant velocity, the GCHO-S scheme diminishes the handover cost by 50% against the GCHO scheme.