Addressing the Mutual Interference in Uplink ISAC Receivers: A Projection Method

TL;DR

The paper tackles mutual interference in uplink DFRC receivers by introducing a projection-based framework that converts the ML joint detection of uplink data and target response into a multi-snapshot detection problem. A key result (Theorem 1) shows equivalence to a projected problem where radar interference is eliminated via orthogonal projection, enabling a nonlinear SDR detector to handle the ill-conditioned reduced problem. Compared to SIC, the projection method yields higher SNR and ergodic rate when radar power is non-negligible, and its rate approaches the interference-free comm-only benchmark as the number of snapshots $L$ grows. Simulations with a $4 imes8$ MIMO setup and QPSK corroborate the improved BER and rate performance and reveal the trade-off with computational complexity.

Abstract

Dual function radar and communication (DFRC) is a promising research direction within integrated sensing and communication (ISAC), improving hardware and spectrum efficiency by merging sensing and communication (S&C) functionalities into a shared platform. However, the DFRC receiver (DFRC-R) is tasked with both uplink communication signal detection and simultaneously target-related parameter estimation from the echoes, leading to issues with mutual interference. In this paper, a projection-based scheme is proposed to equivalently transform the joint signal detection and target estimation problem into a joint signal detection process across multiple snapshots. Compared with conventional successive interference cancellation (SIC) schemes, our proposed approach achieves a higher signal-to-noise ratio (SNR), and a higher ergodic rate when the radar signal is non-negligible. Nonetheless, it introduces an ill-conditioned signal detection problem, which is addressed using a non-linear detector. By jointly processing an increased number of snapshots, the proposed scheme can achieve high S&C performance simultaneously.

Figures (3)

• Figure 1: An uplink DFRC system.
• Figure 2: BER and ergodic rate versus the number of the snapshots.
• Figure 3: S&C performance evaluation under different $P_{\rm{r}}$.