In modern warfare, electronic warfare (EW) has become a key element in ensuring the protection of armored vehicles, logistical columns, and assault

groups. Of particular urgency is the issue of defense against FPV drones, which are controlled over long distances using secure digital radio protocols.

For owners and engineers involved in the development, testing, or marketing of vehicular EW systems, it is critically important to understand the physics and mathematics of the jamming processes. In this article, we will examine in detail why standard communication protocols lag behind military modifications, and provide precise calculations of the effectiveness of dome EW systems depending on packet rate, time-on-air (ToA), and frequency-hopping spread spectrum (FHSS) algorithms.

1. Architectural Differences Between Protocols: ERLS vs. MilERLS

To understand how a vehicular EW system affects a drone's control channel, it is necessary to analyze the underlying transmission architecture of both protocols.

Standard ERLS Protocol (Express Long Range System)

This protocol was designed as a high-speed and sensitive solution for civilian and basic military applications.

·         Packet Rate: Most commonly configured between 250 Hz and 500 Hz. This means the remote control and drone receiver exchange data packets every 2 - 4 milliseconds.

·         Time-on-Air (ToA): Due to the high bitrate speed, the duration of each individual packet is minimal (around 1 - 1.5 ms).

·         Operating Logic: High packet frequency ensures extremely smooth control and minimal latency (latency under 5 ms). However, this creates an intensive, continuous stream of micro-packets in the radio spectrum.

Military MilERLS Protocol

Created specifically for harsh electronic countermeasure conditions. It shifts the focus from ultra-low latency to maximum energy resilience and anti-intercept protection.

·         Packet Rate: Reduced to critically minimal or adaptive values (e.g., 44 Hz or dynamic adjustment depending on channel conditions). The interval between packets (T_int) increases to approximately 22.7 ms (at 44 Hz).

·         Energy per Bit and Processing Gain: By lowering the packet rate, the protocol concentrates more energy into each transmission and uses advanced spread spectrum techniques with a wider data packet.

·         Operating Logic: The drone does not "clog" the spectrum with frequent packets, but transmits them less frequently while maintaining a higher level of cryptographic protection and structural resilience against interference.

2. Mathematical Model of Vehicular EW Impact

The effectiveness of electronic jamming (Jamming Effectiveness, $E_j$) depends directly on the Jamming-to-Signal Ratio ($J/S$), as well as the temporal characteristics of the interference interacting with the data packet (Dwell Time).

Signal-to-Noise Ratio Formula with Interference

In the coverage zone of a vehicular dome EW system, the resulting signal-to-noise ratio at the input of the FPV drone receiver is described by the equation:

Where:

·         P_tx — transmitter power of the remote controller;

·         P_j — output power of the vehicular EW system;

·         W — channel bandwidth;

·         G_j — antenna gain of the EW system directed toward the drone;

·         -  path loss gradient depending on the distance to the jammer and the drone.

Packet Loss Probability (P_loss)

To estimate whether the drone can maintain control, the probability of successfully jamming an individual data packet is used. It depends on the jammer's dwell time (T_dwell) relative to the packet interval T_int:

where $\mu$ is the energy excess coefficient of the jammer over the useful signal within the bandwidth.

3. Detailed Comparative Calculation for ERLS and MilERLS

Let us examine how the mathematical model above works in practice when an FPV drone enters the coverage zone of a vehicular EW system with an output power of several hundred watts and a dome radiation pattern.

Scenario A: Drone Using ERLS Protocol (500 Hz)

1.      Time Parameters: The interval between packets is only 2 ms.

2.      EW System Response: Due to broadband or fast dome sweep jamming, the vehicular EW covers the entire frequency range with an update period of less than 1 ms.

3.      Link Failure Calculation: Since packets flow continuously and their duration is minimal, the link protection algorithm fails to accumulate a complete frame. Losing 3–5 consecutive packets (>10 ms) is treated by the receiver as a critical failure.

4.      EW Efficiency Coefficient: Due to the high packet rate, ERLS becomes an easy target for vehicular systems. The probability of successful suppression is 92–98%. The drone quickly loses control and enters a failsafe emergency landing or crash mode.

Scenario B: Drone Using MilERLS Protocol (44 Hz)

1.      Time Parameters: The interval between packets is significantly larger—approximately 22.7 ms. The packet structure itself is temporally stretched to provide higher energy per bit.

2.      Dwell Time Requirement: To completely block such a packet, the vehicular EW must hold or cover a specific narrow frequency for an extended duration (≥ 20 ms), or create excessively powerful interference across the entire channel width.

3.      Packet Transmission Calculation: If the jamming generator operates in a fast sweep mode, its "beam" passes through the operating frequency in milliseconds. The infrequent MilERLS packet manages to "slip through" the time gap between jamming scan cycles.

4.      EW Efficiency Coefficient: Due to the adaptability and low packet rate, the effectiveness of a standard vehicular EW drops to 45–60%. To guarantee suppression of this protocol, the vehicular system must feature either ultra-high power density in the kilowatt range or intelligent digital interception modules with adaptive frequency tracking.

4. Conclusions for Developers and Buyers of Vehicular EW Systems

Summarizing the mathematical calculations and field data, several strategic conclusions can be drawn for the vehicular counter-measures market:

·         Standard Countermeasures are Ineffective Against Upgrades: Classic vehicular EW systems designed solely to jam older analog channels or high-frequency civilian protocols (like standard ERLS at 500 Hz) show excellent results (up to 95% effectiveness).

·         The Need for Equipment Evolution: The proliferation of the MilERLS protocol requires manufacturers of vehicular systems to transition to new jamming generation algorithms — increasing dwell time, implementing feedback systems, and expanding the energy potential of dome antennas.

·         Commercial Value: Having reliable protection against modern adaptive protocols is a key competitive advantage for commercial EW systems supplied for frontline vehicle equipment.