6G aims to connect the physical, digital, and human worlds through emerging technology focusing on new spectrum utilization, artificial intelligence (AI) integration into networks and devices, digital twins, and new network architectures. These elements enhance network programmability and automation across various 6G use cases.
While the commercial deployment of 6G seems quite far away, the research needs for 6G are already here, including growing efforts around the spectrum. New frequency ranges are needed to satisfy the bandwidth needs of the ever-growing throughput requirements. Frequency range 3, or FR3, is one of the new spectrum ranges where 6G is evolving. There were only two frequency ranges for 5G: FR1 and FR2. FR3 is between FR1, often referred to as sub-6 GHz, and FR2, the so-called millimeter-wave range, between 7 and 24 GHz.
6G Requirements: A Drive Towards Deterministic Channel Models
4G and 5G addressed radio channel modeling requirements using geometry-based stochastic channel models (GSCMs) for simulating and testing massive multiple-input and multiple-output (mMIMO) systems. However, 6G use cases and technologies are generating new requirements for radio channel modeling because of:
- Near-field (NF) and short-range communications using smaller cells.
- The need for accurate location-based services.
- Smart environments with multiple radio access (multi-RAT) technologies.
- Propagation challenges at sub-terahertz (THz) frequencies.
- Flexible adaptation and enhanced environmental awareness.
- Integrated sensing and communication (ISAC) and extreme MIMO (xMIMO).
6G FR3 Radio Channel Modeling
Antenna arrays with substantial apertures are under investigation in the 6G FR3 band for MIMO technologies, including MIMO, mMIMO, and xMIMO. xMIMO antenna arrays support narrow pencil beams and more MIMO layers than conventional mMIMO. Figure 1 shows an example of extreme hybrid beamforming, FR3 upper mid-band base station. As a result, the design and validation of xMIMO wireless systems necessitate accurate intra- and inter-cluster angular characteristics from the channel model.
Figure 1. An example of extreme hybrid beamforming, FR3 upper mid-band base station
Ensuring that the channel model accurately captures the intra- and inter-cluster angular characteristics is essential when conducting system simulations or testing the actual performance of xMIMO base stations in RAN and Open RAN configurations. In addition, dynamic channel models are necessary for evaluating beam management and precoding adaptation over user equipment movement. These channel models consider transitions between line-of-sight (LOS) / non-line-of-sight (NLOS) and blockage conditions.
However, the current 3GPP GSCM channel models lack the accuracy needed to develop extreme beamforming algorithms with highly directive pencil beams. To address that, a new 3GPP RP-234018 Release 19 technical study item on channel modeling enhancements for 7 to 24 GHz for New Radio (NR) was initiated.
To test the upper mid-band for FR3, test engineers need:
- Phase and time coherent multichannel emulation.
- Semi-deterministic and/or deterministic channel models.
- Accurately calibrated equipment for phase and amplitude measurements.
- Comprehensive measurement and analysis tools.
6G FR3 System Testing
6G FR3 system testing requires phase and time-coherent multichannel emulation using semi-deterministic and deterministic channel models. From the physical layer (PHY) to the application layer, key performance metrics for 6G FR3 testing include:
- Beam weight estimation and pointing metrics.
- Beam shape and gain.
- Sidelobe levels.
Figure 2. The three main channel modeling approaches necessary in 5G-Advanced and 6G system simulations, design, and product development and testing.
With a robust channel emulation solution, test engineers can reproduce a diverse propagation environment and emulate hardware impairments like phase noise and interference. They will need:
- Channel emulation capabilities to create realistic and highly accurate 6G FR3 environment models.
- Signal generation capabilities to provide the necessary 6G transmit waveform to the channel emulator.
- Performance metrics, including beamforming gain, beam width, and sidelobe levels.
- Software tools to perform phase and time-coherent multichannel emulation and create geometry-based stochastic channel models.
- Testing environment to reproduce propagation environments and ensure comprehensive testing.
The Keysight 6G FR3 system test solution
The Keysight 6G FR3 system test solution includes a channel emulator, channel emulation software, and an MXG signal generator. This solution creates realistic and highly accurate stochastic and deterministic models for mimicking 6G FR3 components and systems. The MXG signal generator provides the signal input to the FR3-capable channel emulator. The channel emulator also supports ISAC for detecting and tracking objects.
Figure 3. The Keysight 6G FR3 system test solution
The Bottom Line
Precise channel emulation is crucial for 6G FR3. Accurate channel models are needed to support advanced 6G features and allow for realistic testing of 6G technologies, such as mMIMO and beamforming, under various conditions to understand how these technologies will perform in real-world scenarios. Additionally, it supports advanced use cases like ISAC, which require detailed knowledge of the channel characteristics to function effectively.
Be prepared for 6G and the challenges it brings onboard and accelerate your 6G prototyping before releasing standards using Keysight solutions for channel modeling and emulation for FR3 MIMO, mMIMO, xMIMO, and ISAC.
Contact us for insights and advice on unlocking the frequency bands targeted by 6G and validating new spectral efficiency technologies.