On the Performance Analysis of Full-Duplex Cell-Free Massive MIMO with
User Mobility and Imperfect CSI
Abstract
One of the candidate technologies for sixth-generation (6G) wireless
communication systems is cell-free massive multiple-input
multiple-output (CF-mMIMO) communication, which can control inter-cell
interference in MIMO systems. This paper investigates the performance of
a full-duplex (FD) CF-mMIMO system with practical limited-capacity
fronthaul links. The proposed system employs a large number $M$
distributed FD access points (APs), arbitrarily distributed $K_d$
downlink (DL) and $K_u$ uplink (UL) half-duplex (HD) single-antenna
user equipments (UEs), and a central processing unit (CPU). To exploit
energy efficiency (EE) and potential throughput gains of FD systems,
each AP is linked to the CPU by a fronthaul link with limited capacity
that handles the quantized UL/DL data to and from the CPU. On the same
spectrum resource, each AP is expected to support $K$ single-antenna
HD UEs, where $K = (K_u + K_d)$. Despite having a minimal signal
processing complexity, our approach offers a uniform quality of service
(QoS) to all UEs while providing improved spectrum efficiency and EE.
Imperfect channel state information and mobility of the UEs are also
considered. Closed-form expression for the outage probability is derived
using the optimal uniform quantization and maximum-ratio
combining/maximum-ratio transmission considering the Welch-Satterthwaite
approximation. Additionally, the asymptotic and infinite-$M$ outage
performance of the proposed system are analytically studied and verified
via Monte-Carlo simulation.