5G Hardening Against Smart Jammer Attacks

Overview

This white paper by Rohde & Schwarz addresses enhancing 5G network resilience against smart jammer attacks by implementing frequency hopping (FH) using the existing handover (HO) feature in 5G devices. Smart jammers pose a critical threat due to their ability to detect operating frequencies and selectively disrupt communications, especially impacting mission-critical, public safety, and military scenarios where reliability is paramount.

The core concept involves rapidly switching the carrier frequency of communication links between multiple 5G cells operating on different frequencies. This frequency hopping complicates a jammer’s ability to track and disrupt signals, increasing communication security. Unlike traditional military radios that require specialized equipment, this solution leverages the standard handover process specified in 3GPP protocols, making it compatible with all commercial 5G-compliant devices.

Two implementation approaches are evaluated: one where many cells remain active simultaneously, and another more secure method activating only one cell at a time, dynamically configuring inactive cells just prior to handover. This approach aims to obscure the next operating frequency and reduce predictability for attackers.

The study employs a Rohde & Schwarz CMX500 5G network emulator to create controlled multi-cell frequency hopping scenarios using different frequency bands (n41, n78, n79) and user equipment (UE) modems. Key performance indicators such as handover interruption intervals, round-trip time (RTT) latency, data rate throughput via iPerf, and real-world application testing with a Microsoft Teams video call were recorded to assess the impact of frequent handovers.

Results indicate that handover interruptions cause brief data gaps generally below 75 ms in 99% of cases, which although introducing minor latency and throughput fluctuations, are manageable by modern real-time applications through buffering and error correction. The network achieved stringent 3GPP QoS requirements, meeting delay and reliability levels suitable for mission-critical voice and video services. Specifically, average RTT was observed around 128 ms during a sustained video call, with packet loss under 0.01%, demonstrating very high reliability despite frequent frequency changes.

Conclusively, using handover-based frequency hopping is a feasible and effective overlay solution to harden 5G communications against smart jamming without the need for specialized hardware. Future work is suggested to explore advanced QoS metrics, randomized frequency patterns, multi-connectivity scenarios to eliminate handover interruptions, and integration with newer handover features such as dual active protocol stack (DAPS).

Overall, this approach represents a promising step towards secure, reliable 5G networks tailored for mission-critical applications, leveraging existing standards and commercial technology for practical deployment.