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Air-to-Ground Communications Beyond 5G: CoMP Handoff Management in UAV Network

Yan Li, Deke Guo, Lailong Luo, Minghua Xia

TL;DR

A computationally efficient CoMP transmission method based on the theory of Poisson-Delaunay triangulation is developed, where an efficient subdivision search strategy for a CoMP UAV set is designed to minimize search overhead by a divide-and-conquer approach.

Abstract

Air-to-ground (A2G) networks, using unmanned aerial vehicles (UAVs) as base stations to serve terrestrial user equipments (UEs), are promising for extending the spatial coverage capability in future communication systems. Coordinated transmission among multiple UAVs significantly improves network coverage and throughput compared to a single UAV transmission. However, implementing coordinated multi-point (CoMP) transmission for UAV mobility requires complex cooperation procedures, regardless of the handoff mechanism involved. This paper designs a novel CoMP transmission strategy that enables terrestrial UEs to achieve reliable and seamless connections with mobile UAVs. Specifically, a computationally efficient CoMP transmission method based on the theory of Poisson-Delaunay triangulation is developed, where an efficient subdivision search strategy for a CoMP UAV set is designed to minimize search overhead by a divide-and-conquer approach. For concrete performance evaluation, the cooperative handoff probability of the typical UE is analyzed, and the coverage probability with handoffs is derived. Simulation results demonstrate that the proposed scheme outperforms the conventional Voronoi scheme with the nearest serving UAV regarding coverage probabilities with handoffs. Moreover, each UE has a fixed and unique serving UAV set to avoid real-time dynamic UAV searching and achieve effective load balancing, significantly reducing system resource costs and enhancing network coverage performance.

Air-to-Ground Communications Beyond 5G: CoMP Handoff Management in UAV Network

TL;DR

A computationally efficient CoMP transmission method based on the theory of Poisson-Delaunay triangulation is developed, where an efficient subdivision search strategy for a CoMP UAV set is designed to minimize search overhead by a divide-and-conquer approach.

Abstract

Air-to-ground (A2G) networks, using unmanned aerial vehicles (UAVs) as base stations to serve terrestrial user equipments (UEs), are promising for extending the spatial coverage capability in future communication systems. Coordinated transmission among multiple UAVs significantly improves network coverage and throughput compared to a single UAV transmission. However, implementing coordinated multi-point (CoMP) transmission for UAV mobility requires complex cooperation procedures, regardless of the handoff mechanism involved. This paper designs a novel CoMP transmission strategy that enables terrestrial UEs to achieve reliable and seamless connections with mobile UAVs. Specifically, a computationally efficient CoMP transmission method based on the theory of Poisson-Delaunay triangulation is developed, where an efficient subdivision search strategy for a CoMP UAV set is designed to minimize search overhead by a divide-and-conquer approach. For concrete performance evaluation, the cooperative handoff probability of the typical UE is analyzed, and the coverage probability with handoffs is derived. Simulation results demonstrate that the proposed scheme outperforms the conventional Voronoi scheme with the nearest serving UAV regarding coverage probabilities with handoffs. Moreover, each UE has a fixed and unique serving UAV set to avoid real-time dynamic UAV searching and achieve effective load balancing, significantly reducing system resource costs and enhancing network coverage performance.

Paper Structure

This paper contains 32 sections, 8 theorems, 55 equations, 18 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. Related Works and Motivations
  3. Major Contributions
  4. Paper Organization
  5. System Model
  6. The CoMP Set of a UE
  7. Mobility Model
  8. Channel Model
  9. Performance Metrics
  10. The Subdivision Search Strategy
  11. The Minimal Search Radius
  12. Subdivision Search Strategy For A CoMP Set
  13. CoMP Handoff Strategy and Performance Evaluation
  14. CoMP Handoff Strategy
  15. CoMP Handoff Probability
  16. ...and 17 more sections

Key Result

Lemma 1

Let $v$ be a non-negative random variable denoting the speed of a UAV, with the cumulative density function (CDF) $F_v(x)$ and probability density function (PDF) $f_v (x)$, then the difference set $\Phi(t)\setminus U_0(t)$ forms an inhomogeneous PPP with intensity computed by

Figures (18)

  • Figure 1: The proposed A2G network based on the Poisson-Delaunay triangulation, where the typical terrestrial UE is served by the UAVs in the CoMP set $\{A_0, B_0, C_0\}$ with distances $d_i$, $i = 1, 2, 3$.
  • Figure 2: An illustrated Poisson-Delaunay triangulation network where CoMP sets consist of the UAVs at the vertices of Delaunay triangles with blue dash boundaries. The projected UAVs (denoted by blue solid triangles) are distributed as a PPP, and the UEs (denoted by red stars) are uniformly distributed in a normalized coverage area of one square kilometer.
  • Figure 3: An illustration of the different moving speed (DMS) mobility model.
  • Figure 4: Illustration of a subdivision searching process for a CoMP set.
  • Figure 5: Illustration of the handoff from CoMP set $\{A, B, C \}$ to $\{A^{\prime}, B^{\prime}, D^{\prime}\}$ due to UAV mobility.
  • ...and 13 more figures

Theorems & Definitions (11)

  • Lemma 1
  • Lemma 2
  • proof
  • Corollary 1
  • Theorem 1
  • proof
  • Lemma 3
  • Lemma 4
  • proof
  • Lemma 5
  • ...and 1 more