Abstract

As the mobile networks become even denser and the traffic demand is increasing drastically, it is becoming more heterogeneous. Recently, it is intensive to investigate the Cell-Free Massive multiple-input multiple-output Massive (MIMO) system, where a large number of access points (APs) simultaneously serve a much smaller number of users, and the APs and users are clustered to provide good service for all users. This paper designs a mobile base station (MBS)-assisted Cell-Free Massive MIMO system: Utilizing an MBS deployed on the unmanned aerial vehicle (UAV) to form an air-ground heterogeneous system with the Cell-Free Massive MIMO system and offload part of traffic to the MBS to further improve the system performance. To provide better service to all users, this paper design an MBS flight trajectory optimal method to improve the wireless coverage performance and user experience, and proposed a joint power allocation algorithm based on the consideration of the fairness of the service quality. The simulation results indicate that the performance of the system designed in this paper has a significant improvement compared with the normal Cell-Free Massive MIMO system.

Highlights

  • The Cell-Free Massive multiple-input multiple-output (MIMO) system has already been a crucial research topic [3], [7], the system deploys a large number of access points (APs), the ensemble of APs forms a massive MIMO array [16]

  • The results indicate that the performance of the mobile base station (MBS)-assisted Cell-Free Massive MIMO system has been significantly improved compared with the normal Cell-Free Massive MIMO system

  • This paper studies the application of MBS in the mobile networks, and uses unmanned aerial vehicle (UAV) as the carrying platform for MBS

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Summary

INTRODUCTION

The Cell-Free Massive multiple-input multiple-output (MIMO) system has already been a crucial research topic [3], [7], the system deploys a large number of access points (APs), the ensemble of APs forms a massive MIMO array [16]. [10] designed a power control algorithm aiming at improving energy efficiency The researches such as [3]–[11] are based on the traditional Cell-Free MIMO structure, which does not provide much attention to the actual scenario. A new hybrid network was proposed in [22], the authors use a UAV as an aerial mobile base station, designed a trajectory that cyclically along the cell edge to offload data traffic for cell-edge users, and aimed at maximizing the minimum throughput of all users, by joint optimizing the spectrum sharing and cyclical multiple access methods. The authors of [24] designed a hybrid optimization scheme including user selection, trajectory optimization and power allocation optimization scheme aimed at maximizing the minimum user throughput, and proposed an iterative optimization algorithm based on the block coordinate descent and successive convex optimization algorithm.

SYSTEM MODEL
CHANNEL MODEL OF AP-USER
CHANNEL MODEL OF MBS-USER
CELL-FREE MASSIVE MIMO SYSTEM DOWNLINK DATA TRANSMISSION
DATA TRANSMISSION PREOCESS OF THE HETEROGENEOUS SYSTEM
TRAJECTORY OPTIMIZATION AND POWER ALLOCATION
TRAJECTORY OPTIMIZATION SCHEME OF MOBILE BASE STATION
JOINT POWER ALLOCATION
CONCLUSION
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