Jammer-Resilient Time Synchronization in the MIMO Uplink

TL;DR

Jammer-Resilient Time Synchronization in the MIMO Uplink introduces JASS, a novel method to achieve reliable time synchronization under smart, multi-antenna jamming. By formulating a Grassmannian-structured optimization that fits a spatial filter to a time-windowed receive signal, JASS effectively nulls jammer subspaces while preserving the synchronization signal, and uses a Dinkelbach-like algorithm to compute an approximate solution. A theorem guarantees correct detection of the randomized synchronization sequence under intuitive conditions, and experiments show robust performance (TER around 1%) across six jammer types and various channel models. This approach enables dependable uplink synchronization in adversarial environments, with implications for robust MIMO detectors and secure link establishment in future wireless systems.

Abstract

Spatial filtering based on multiple-input multiple-output (MIMO) processing is a promising approach to jammer mitigation. Effective MIMO data detectors that mitigate smart jammers have recently been proposed, but they all assume perfect time synchronization between transmitter(s) and receiver. However, to the best of our knowledge, there are no methods for resilient time synchronization in the presence of smart jammers. To remedy this situation, we propose JASS, the first method that enables reliable time synchronization for the single-user MIMO uplink while mitigating smart jamming attacks. JASS detects a randomized synchronization sequence based on a novel optimization problem that fits a spatial filter to the time-windowed receive signal in order to mitigate the jammer. We underscore the efficacy of the proposed optimization problem by proving that it ensures successful time synchronization under certain intuitive conditions. We then derive an efficient algorithm for approximately solving our optimization problem. Finally, we use simulations to demonstrate the effectiveness of JASS against a wide range of different jammer types.

Figures (8)

• Figure 1: Performance against barrage jammers ([inner color=white, fill color= gray, outer color=gray]1) with different transmit powers. The jammers have $I=4$ antennas; the receiver assumes $\hat{I}=4$.
• Figure 2: Performance against reactive jammers ([inner color=white, fill color= gray, outer color=gray]2) with different transmit powers. The jammers have $I=4$ antennas; the receiver assumes $\hat{I}=4$.
• Figure 3: Performance against different jammers with a transmit power of $\rho=30$ dB. All jammers have $I=4$ antennas; the receiver assumes $\hat{I}=4$.
• Figure 4: Performance against barrage jammers ([inner color=white, fill color= gray, outer color=gray]1) with a transmit power of $\rho=30$ dB when there is a mismatch between the number of jammer antennas $I$; the receiver's guess $\hat{I}$ about the number of jammer antennas.
• Figure 5: Ablation studies. Default values are $K=16$, $B=16$, $\textit{SNR}=0\,\text{dB}$, $\rho=30\,\text{dB}$, $I=\hat{I}=4$, $t_\textnormal{max}=4$. The jammer is a barrage jammer in all cases.

Theorems & Definitions (1)

• Theorem 1