# [Intern] 22/07/2022 O-DU emulator.
###### tags: `BMW-Lab`, `Intern`

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**Goal:** To understand how O-DU emulator works.
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**References**
- [O-DU emulator](https://www.keysight.com/us/en/assets/3121-1107/data-sheets/DuSIM-O-DU-Emulation-Solution-for-O-CU-Testing-over-F1-Interface.pdf)
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## O-DU emulator

The O-DU emulator requires the test engineer to build a real 5G waveform with one or more frames. The waveform generation capability is similar to software packages used in many signal generators to construct test signals. It enables you to build wave forms that include all the features in a 5G frame. These waveforms include synchronization signals, multi-layer multiple-input / multiple-output (MIMO), demodulation reference signal (DMRS), physical downlink control channel (PDCCH), and physical downlink shared channel (PDSCH) channels. It also has the functionality to control power levels, build uplink and downlink signals, and the ability to automatically make 3GPP compliant frames since the O-RAN conformance test specification uses these as test signals.Wave form generation capability can also generate frequency-domain I/Q data.
When completed, the O-DU emulator takes the signal created and automatically breaks it down into appropriate section types. The tester then needs to adjust the O-RAN specific parameters, such as compression type and method. For example, whether to use static or dynamic, block floating point, beam identification, or weights. This process includes optional section types such as section type 0, extended antenna carrier (eAxC) values, mixed numerologies, and any I/Q power scaling. The O-DU emulator needs to recognize downlink signals and construct U-plane and C-plane messages. It must also recognize uplink signals and only construct correct C-plane messages. The O-DU emulator enables you to specify timing constraints to test the boundaries of the radio’s delay windows. When this process is complete, the O-DU emulator stores the downlink C- and U-plane messages and the uplink C-plane messages as a single test. When you begin the test, the O-DU emulator sends the O-RAN fronthaul packets to the O-RU following the timing constraints set during signal construction. It will also adjust the frame and subframe numbers and check the sums in real time. Simultaneously, the O-DU emulator triggers the signal source to send uplink RF after an appropriate delay. The delay allows the O-RU to decode and interpret the uplink C-plane messages it just received before recognizing any RF signals. If required, it can also trigger the signal analyzer to begin analyzing downlink RF; the O-DU emulator coordinates the entire test. Triggering is essential to test time division duplex (TDD) radios. In TDD, the uplink and downlink are on the same frequency band and separated in time. Test coordination is necessary between the O-DU emulator and the rest of the test equipment used in the test. The O-DU emulator captures the uplink U-plane messages to extract the frequency domain I/Q data from those messages. It will analyze the I/Q data with a software-based vector signal analyzer to assess the data contained in the resource blocks to determine whether they match the ask from the C-plane messages.