Downlink data split over the NR air interface in the NSA Option 3x architecture is implemented at the medium access control (MAC) layer. The MAC layer is responsible for the management of data transmission over the air interface, including segmentation and reassembly of data packets, scheduling of transmission resources, and error correction. The other layers (RLC, PDCP, and physical) are not involved in the implementation of downlink data split.
https://ec.europa.eu/research/participants/documents/downloadPublic?documentIds=080166e5a964aa85&appId=PPGMS Preliminary results for multi-service support in link solution adaptation
https://ec.europa.eu/research/participants/documents/downloadPublic?documentIds=080166e5a964aa85&appId=PPGMS
https://ieeexplore.ieee.org/iel7/6287639/8948470/08998153.pdf
3GPP NR Sidelink Transmissions Toward 5G V2X
https://ieeexplore.ieee.org/iel7/6287639/8948470/08998153.pdf
https://www.3gpp.org/ftp/Inbox/Marcoms/ICT_6_1-2.pdf
journal of ict standardization - 3gpp
https://www.3gpp.org/ftp/Inbox/Marcoms/ICT_6_1-2.pdf
In the Non-Stand-Alone (NSA) Option 3x architecture, the control plane functions are handled by the 4G LTE network (EPC), while the user plane functions are handled by the 5G NR network. Data split is a technique that allows to split the user plane data between the 4G LTE and 5G NR networks.
The MAC (Medium Access Control) layer is responsible for controlling the access to the shared wireless medium, and it is where the downlink data split is implemented. In this architecture, the MAC layer in the 5G NR network receives the downlink data from the 4G LTE network and sends it to the physical layer for transmission.

According to the official Huawei documentation, the possible causes for a 4G cell not delivering B1 measurement configurations during a 5G service test are that the UE does not support EN-DC, the NSA switch is not turned on, or neighboring LTE cells and SCGs are not configured.

https://www.5gworldpro.com/blog/2020/11/11/what-is-difference-between-pci-in-4g-lte-and-pci-in-5g-nr/
The maximum number of PCIs (Physical Cell Identifiers) supported by a 5G network is 1008.
This is specified in 3GPP 5G standard TS 38.211, which states that the maximum number of PCIs that a 5G network can support is 1008.
In 5G, each cell is assigned a unique identifier called the PCI (Physical Cell Identity).
The PCI is used to identify the cell and its system information, and it is used for various purposes such as cell selection, handover, and interference management.
According to 3GPP specifications, the maximum number of PCIs that can be supported by a 5G network is 1008, which allows for a large number of cells to be deployed in a network. However, the actual number of PCIs used in a network will depend on the specific deployment scenario, the network architecture, and the capacity requirements of the network.

The correct answers are A. DMRS of the uplink PUSCH of the UE and B. Downlink DMRS signal. According to the official Huawei documentation, gNodeBs can use downlink DMRS signals or the DMRS of the uplink PUSCH of the UE to obtain downlink channel characteristics. The downlink DMRS signals contain information about the downlink channel characteristics, and the DMRS of the uplink PUSCH of the UE can be used to measure the uplink channel characteristics. The uplink SRS and PMI signals reported by the UE are used to determine the uplink channel characteristics. For more information, please see this link: https://www.huawei.com/en/doc/NR-BBU-Design-V1.1/18104301/bbuf-cqi-report.html

According to Huawei's official documentation, the purpose of replaying logfiles is to reproduce the test process, and the GENEX Probe can work without a license in this case. This allows users to test the results of previous tests and compare them with new test results, which is useful for troubleshooting and network optimization.