Three Challenges to 5G’s Military Success
Fifth-generation (5G) cellular extends the capabilities of critical communications, allowing 5G network deployment on bases, in emergency scenarios, and on the battlefield. Planes, ships, Humvees, and other vehicles will integrate 5G connectivity while 5G robotics allow for smart warehousing and telesurgery. Self-driving military vehicles will create new opportunities and use cases. Evolving 5G non-terrestrial networks (NTNs) promise to make all of these new applications a reality.
To guarantee performance, however, these applications require unique approaches to design and test. For aerospace defense applications, 5G must adhere to more strict performance requirements and overcome three key challenges: evolving NTN standardization, vehicles as user equipment, and 5G co-existence with radar and satellite systems. By taking a multistep approach, you can ensure that your product seamlessly integrates into a final design that meets 5G’s promise for military and government applications.
1. NTN Standards Development
Right now, questions around NTN form one of the first hurdles to predicting system performance. 5G NTN promises ubiquitous cellular coverage. Using space- or airborne assets, 5G can enable service in areas otherwise without coverage. Until now, base stations have been ground-based or terrestrial, but the Third Generation Partnership Project (3GPP) ratified NTN as a feature in Release 17.
The specific architectures will be finalized as the standard develops. No matter the final choice, the architecture will start with a user equipment (UE) block. Beyond mobile phones, UE now includes vehicles, sensors, and watches. The UE typically communicates with the base station, which in 5G is known as the gNodeB. You can refer to the 5G Core Network as the Next Generation Core (NGC).
The NTN standard remains in development, so commercial equipment and prototypes are not available. That means finding other ways to research, prototype, or develop. Unfortunately, available commercial-off-the-shelf (COTS) UEs and gNodeBs will not work with the amounts of Doppler and delay found in space-borne communications links (Figure 1).
To develop NTN, take a crawl-walk-run approach that starts with basic software modeling. The software tool should model the following:
- downlink and uplink transmit and receive chains of the UE
- the gNodeB
- the signal propagations to and from the satellite
- the satellite’s motion
- the antennas
- the delay and Doppler throughout the system
The UE will pre-frequency shift its transmission to counter the satellite’s Doppler shift. The gNodeB must also perform this task, but in a way that is common to all served UEs - no matter their location. When a UE attaches to the network and looks for a base station, it must assume a greater range of frequency offsets than it would in the terrestrial case. Although COTS prototypes are not yet available, you can simulate NTN links in software and prototype them with emulators. Use hardware emulators that are more easily customizable for mimicking NTN links. You can perform this prototyping in a lab or a chamber on a small-scale basis.
When NTN equipment becomes available, you should prototype this with real equipment in the lab or chamber on a small-scale basis. Follow that step with a full-scale implementation, deploying with actual equipment on the target platform. Then, engage in periodic maintenance testing.
2. 5G via Air, Land, or Sea
Outfitted with 5G for long-haul communications, aircraft, ships, Humvees, and other vehicles can use 5G to enable communications, high-data-rate video conferencing, and Internet of Things sensors. Eventually, these capabilities will evolve into self-driving or autonomous vehicles.
Ships, planes, and ground vehicles have different transmitters and receivers, including telemetry devices, communications transceivers, radar and satellite communications, and surveillance systems. They must all operate simultaneously without compromising the performance of other systems or damaging them. If not designed properly, for example, high-powered radar could damage sensitive satellite receivers. Planes, ships, and other vehicles with 5G also add complexity to the RF environment (Figure 2).
Vehicles with communications equipment, radar, surveillance systems, and other equipment pose potential electromagnetic compatibility issues. Careful planning must take place so that all systems can operate simultaneously and safely. Software modeling can help you discover potential issues by modeling the following: the UE’s downlink and uplink transmit and receive chains, the gNodeB, and the signal propagations of other vehicle communications systems.
In the planning phase, simulating signals in software determines electromagnetic compatibility using a 3D model of the deployment platform. The finite-difference time-domain (FDTD) method is based on volumetric sampling of the electric and magnetic fields throughout the complete space. This method updates the field values while stepping through time, following the electromagnetic waves propagating throughout the structure. As a result, a single FDTD simulation can provide data over an ultra-wide frequency range.
To increase confidence, you can prototype signals in the lab on a small scale to gauge performance in the field. Use hardware emulators in place of COTS equipment, as they are easy to customize and adapt. The prototyping is conducted in a lab or chamber on a small-scale basis. Once you are satisfied, follow up with full-scale implementation, deploying with actual equipment on the target platform. Follow with periodic maintenance testing.
In the prototype phase, simulate signals with signal generators and other emulation equipment. You can adjust signal levels to simulate the real-world environment, but on a much smaller scale inside a chamber. The measurements determine electromagnetic compatibility.
3. Coexistence: The Battle for Priority
For radar and satellite applications specifically, 5G raises another challenge: coexistence. Because these applications may use the same spectrum as 5G, they can impact one another, leading to service disruption or performance degradation. Coexisting signals have the right to operate in the same frequency range, but one signal usually takes priority. For example, radar signals typically take priority over 5G signals. As a result, 5G needs to shut off or move to another frequency.
Satellite signals can also coexist with 5G signals. For example, 5G NR FR2 overlaps with fixed-satellite services (FSS) Earth station uplinks at 27.5 to 29.5 GHz and FSS downlinks at 37.5 to 40.0 GHz. This overlap creates questions around how interfering waveforms interact and how much in-band and out-of-band suppression is needed. You also need to determine how much guard band is necessary and what metrics to consider in assessing impact.
To test the impact of radar or satellite on a 5G network, you can use a 5G test UE in the field. This approach provides a detailed view of the quality and throughput metrics of the 5G network. To test the impact of 5G on a coexisting signal, you can use a signal analyzer to measure many signal types including radar, satellite, and 5G.
You can simulate radar signals in several ways, depending on the fidelity and emitter parameters required. By leveraging software, you can generate single radar emitters or high-density emitter environments. These simulations create threat environments that let you specify parameters such as amplitude, frequency, pulse width, modulation-on-pulse, pulse repetition interval, coherent processing intervals, and antenna scan modulation.
Creating satcom simulated signals is as easy as using a vector signal generator with digital video broadcast (DVB) software. Today’s software can generate a number of DVB signal standards. The signal-creation process allows you to simply enter the signal parameters, including pseudo-noise (PN) sequencing and user-defined data patterns.
For scenarios in which it is difficult to generate realistic conditions with signal generators and software, use a record and playback system. Here, a system records the signals live on a platform and brings the recording back into the prototyping platform lab. It replays them with a vector signal generator.
With a 5G network, you face unknown coexistence vulnerabilities. Monitoring 24/7 can help you secure the network from coexistence conditions. By prototyping those conditions for research, you can expose those conditions and make sure they will not negatively impact your 5G system.
A Successful Path Forward
Use cases for 5G in aerospace and defense will quickly expand as support for their development grows. As theoretical advancements evolve, you can use software to simulate their features. Examples of such features include NTNs, where the 5G satellite link is simulated; UE-to-UE communication; and connected vehicle to anything. 6G technology will also necessitate a software simulation feature as hardware development becomes defined. Once the concept is investigated in software, you can use hardware-in-the-loop to prototype the new feature with off-the-shelf solutions.
Next, development and integration testing offers control, observe, and repeat functionality. You then move on to performance characterization of the complete 5G system. In the final use case, you test and assess the security of the finished solution.
Military and government applications demand the highest levels of reliability and security. Resist the temptation to take big leaps. Instead, rely on gradual steps to ensure performance through validation and emulation. Verify your 5G and eventually 6G system to gain confidence in the new use cases and network capabilities set to transform the aerospace and defense landscape.
This article was written by Nancy Friedrich, Industry Solutions Marketing, Aerospace Defense, Keysight Technologies (Santa Rosa, CA). For more information, go here .