Successive Interference Cancellation for ISAC in a Large Full-Duplex Cellular Network

TL;DR

This paper explores the use of successive interference cancellation in a large full-duplex cellular network with integrated sensing and communication, analyzing how to optimally order decoding and detection to improve performance.

Contribution

It introduces a novel analysis of SuIC order selection in ISAC networks, considering practical factors like target distance, UE power, and SIC imperfections.

Findings

Optimal SuIC order depends on target distance and UE power thresholds.

Detecting first is better for short-range targets, decoding first for longer distances.

Imperfect SIC reveals vulnerabilities in the interference cancellation process.

Abstract

To reuse the scarce spectrum efficiently, a large full-duplex cellular network with integrated sensing and communication (ISAC) is studied. Monostatic detection at the base station (BS) is considered. At the BS, we receive two signals: the communication-mode uplink signal to be decoded and the radar-mode signal to be detected. After self-interference cancellation (SIC), inspired by NOMA, successive interference cancellation (SuIC) is a natural strategy at the BS to retrieve both signals. However, the ordering of SuIC, usually based on some measure of channel strength, is not clear as the radar-mode target is unknown. The detection signal suffers a double path-loss making it vulnerable, but the uplink signal to be decoded originates at a user which has much lower power than the BS making it weak as well. Further, the intercell interference from a large network reduces the channel disparity between the two signals. We investigate the impact of both SuIC orders at the BS, i.e., decoding $1^{st}$ or detecting $1^{st}$ and highlight the importance of careful order selection. We find the existence of a threshold target distance before which detecting $1^{st}$ is superior and decoding $2^{nd}$ does not suffer much. After this distance, both decoding $1^{st}$ and detecting $2^{nd}$ is superior. Similarly, a threshold UE power exists after which the optimum SuIC order changes. We consider imperfections in SIC; this helps highlight the vulnerability of the decoding and detection in the setup.