Throughput Enhancement of Dynamic Full-Duplex Cellular System by Distributing Base Station Reception Function

Abstract

In-band full-duplex (IBFD) is a promising technology for improving spectral efficiency beyond 5G and 6G. The dynamic duplex cellular (DDC) system has been proposed as a method for the phased introduction of IBFD into cellular systems while maintaining backward compatibility. Although previous studies have shown that DDC systems can improve the average user throughput, twice the spectral efficiency compared to half-duplex (HD), ideally expected for IBFD, has not been achieved. The main component that disturbs throughput enhancement is the residual component of self-interference (SI) at the base station (BS), which SI cancellers cannot entirely suppress. In this study, we propose a DDC system with a dedicated transmitter (DT) and multiple distributed receivers called remote receivers (RRs) for the BS to reduce the effective SI and enhance uplink reception quality. We implement user equipment scheduling and power control for the DDC system in the topology with DT and multiple RRs and evaluate its performance using computer simulations in a single-cell environment. The proposed DDC system with receiver-distributed topology achieves up to 96% improvement in average user throughput of uplink and downlink from the HD system with the same topology, which is close to the ideal performance improvement by IBFD.

Inter-User Interference Cancellation Scheme for 5G-Based Dynamic Full-Duplex Cellular System

“…In 4G and 5G systems, the proportional fairness scheduling (PFS) algorithm is commonly employed [28], [29]. The conventional DDC system also adopted a PFSbased algorithm [21], [22]. The UE allocated for UL communication in the 𝑛-th transmission time interval (TTI), 𝑢 UL (𝑛), is determined as follows:…”

“…However, the IUI must not deteriorate DL communication in a DL slot. A user scheduling scheme was proposed to overcome these limitations and apply IBFD [21], [22].…”

“…In 5G, the transmission power of the BS is not dynamically adjusted based on the path loss between the BS and the DL-UE. On the other hand, the conventional studies of DDC systems [21], [22] adjusted it based on whether the current slot is a DL or UL slot. In particular, reducing the transmission power of the BS in the UL slot mitigates the impact of SI on desired UL communication and facilitates the DL signal superposition (i.e., realization of IBFD).…”

“…In the above evaluations, the SI cancellation performance was set to 110 dB, following the previous studies on DDC systems [21], [22]. However, when the Tx power of the BS was 27 dBm, the interference-to-noise power ratio (INR) after SI cancellation became 8 dB owing to the -91 dBm noise floor of BS.…”

“…A dynamic full-duplex cellular (DDC) system can operate in an environment where some UEs have no function for IBFD operation and represents a pragmatic and incremental approach to FDC implementation employing the MAC layer method [20]- [22]. The DDC system operates based on the conventional HD system and activates IBFD when conventional communication in an HD system experiences less degradation owing to IBFD, enabling adaptive IBFD within a reasonable situation.…”