The 3rd Generation Partnership Project (3GPP) released the non-standalone (NSA) 5G New Radio (NR) specification last December. The NSA specification is associated with LTE/NR dual connectivity (DC). NSA deployment requires more complex hardware implementations to allow for simultaneous connections with both LTE and NR networks.
In the white paper, “Simulation for 5G New Radio System Design and Verification,” Keysight Technologies discusses some of the common technical challenges associated with 5G NR. Such challenges arise due to LTE/NR DC coexistence issues, as well as implementing millimeter-wave (mmWave) components in mobile devices.
Initially, the paper discusses the global spectrum landscape for 4G and 5G, explaining that the specific 5G spectrum bands zero in on mid-band frequencies (3.3 to 4.2 GHz) for longer distance service and high-band frequencies (24.25 to 29.5 GHz) for faster data speeds. The 3GPP specification defines different frequency ranges (FR), with the FR1 designator corresponding to frequencies between 0.45 and 6 GHz, and FR2 referring to operating bands between 24.25 GHz and 52.6 GHz.
Differences exist between 5G NR and 4G LTE that must be addressed in RF design, according to the paper. It also states that creating thousands of test cases to support increasing LTE frequency bands, defining various carrier-aggregation (CA) scenarios, and calculating intermodulation-distortion (IMD) and harmonics with different combinations of aggressor and victim bands all require a large amount of simulation and test time.
Included in the paper is a sub-6-GHz DC IMD case study. A behavioral model of a DC-enabled RF front end (RFFE) is shown; simulation results reveal the created IMD signals. Following that discussion, a mmWave front-end architecture is presented.
Over-the-air (OTA) simulation is also discussed, first getting into the configuration of an OTA test system before explaining the importance of performing simulations of an OTA environment. This simulation makes it possible to model the individual OTA building blocks, enabling the designer to divide the key functional blocks and better perform a root-cause analysis. An over-the-air (OTA) analysis example is provided as well.
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