. 3GPP TS 38.104; 5G; NR; Base Station (BS) radio transmission and reception. 8. Andersen, O.; Björsell, N.; Keskitalo, N. A Test-Bed Designed to Utilize Zhu's General Sampling Theorem to Characterize Power Amplifiers, I2MTC 2009 - International Instrumentation and Measurement Technology Conference, Singapore, 5-7 May 2009. 9. Zhu, Y.-M. Generalized sampling theorem. IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing 1992, 39,587-588. 10. Analog Devices. AD9375 Digital Pre-Distortion. <https://www.analog.com/en/applications/technology/ 3dr-radioverse-pavilion-home/wideband-transceivers/digital-pre-distortion.html>. 11. 3GPP TR 38.803; Study on new radio access technology: Radio Frequency (RF) and co-existence aspects. 12. Octasic. OCT3032W. <http://www.octasic.com/product/oct3032w/>. . 13. <https://github.com/intel/FlexRAN>. . 14. Arm Developer. Arm RAN Acceleration Library. <https://developer.arm.com/solutions/infrastructure/ developer-resources/5g/ran>. System software We try to identify the minimum required Linux features that are needed to constitute a "Distributed Unit viable image," whilst keeping in mind that the actual features depend per instantiation-it is difficult to do a broad sweep requirements definition. Operating system Bare metal/RTOS versus embedded Linux Before we delve into details on the Linux Operating System (OS), let's quickly evaluate what the options for device and (partially by implication) os are. When building an embedded system, we have two options for choice of target device: design on a microcontroller-with a traditional Digital Signal Processor (DSP) as an example of a microcontroller-or design on a microprocessor. The difference between the two (Table 5-1) is that a microprocessor is defined to run a higher order os (like Linux) that is characterized by a larger size image and near infinite (software) capacity. A microcontroller, on the other hand, typically executes os and application image from an embedded (and size-bound) memory with a small fo