According to the HCIA-5G V2.0 Exam Outline, the 3.5 GHz+2.1 GHz uplink and downlink decoupling/super uplink architecture uses spectrum sharing technologies such as Dynamic Spectrum Sharing (DSS) and Spectrum Sharing (SS) to enable 3.5 GHz NR and 2.1 GHz LTE to share only the uplink spectrums, while the downlink spectrums are used exclusively by each technology.

According to the 5G SA Cell Search & Network Entry Matrix, the first step for a UE to perform a cell search in SA networking is to synchronize frames and obtain PCI group number. This step involves the following sub-steps:

• The UE scans the available frequency range to detect the presence of Synchronization Signal Blocks (SSBs) from different base stations. SSBs are periodic signals that contain essential synchronization and system information for cell search and initial access.
• The UE selects an SSB with the strongest signal strength and decodes its Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS). The PSS and SSS are part of the SSB and provide coarse timing synchronization and cell identity information.
• The UE uses the PSS and SSS information to synchronize its internal clock with that of the base station and obtain the Physical Cell Identity (PCI) group number. The PCI group number is a 9-bit value that identifies a group of 8 cells that share the same PSS and SSS sequences. The PCI group number ranges from 0 to 1007.

The other steps for a UE to perform a cell search in SA networking are:

• Synchronize half-frames and obtain the ID within a PCI group: The UE further synchronizes its timing with the base station by decoding its Narrowband Synchronization Signal (NSSS), which is also part of the SSB. The NSSS provides more precise timing information and the ID within a PCI group, which is a 3-bit value that identifies a specific cell within a PCI group. The ID within a PCI group ranges from 0 to 7. By combining the PCI group number and the ID within a PCI group, the UE can obtain the full PCI, which is a 10-bit value that uniquely identifies a cell.
• Obtain other cell information: The UE decodes other signals and channels in the SSB to acquire other cell information, such as system bandwidth, subcarrier spacing, frame structure, etc. These signals and channels include Demodulation Reference Signals (DMRS), Master Information Block (MIB), System Information Block (SIB), etc.
• Obtain the cell signal quality: The UE measures the cell signal quality based on various indicators, such as Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal-to-Interference-plus-Noise Ratio (SINR), etc. These indicators reflect the strength, quality, and interference level of the received signal.

Massive MIMO is a technology that uses a large number of antennas at the base station to serve multiple users simultaneously, thereby increasing the spectral efficiency and capacity of the wireless system 1. Massive MIMO is especially suitable for application scenarios where there is high user density and high traffic demand, such as large venues, high-rise buildings, and densely populated urban areas 2. Suburban areas with light traffic do not have such high requirements for spectral efficiency and capacity, and therefore are not a typical application scenario of massive MIMO.

According to the Uplink Power Control, PDCCH is the channel that is used to send uplink power control commands, also known as TPC commands. These commands indicate how much power should be increased or decreased by the UE for PUSCH or PUCCH transmissions.

According to the 5G NR Physical Layer Specifications, demodulation reference signals (DMRSs) are required for the following channels/signals in the downlink and uplink:

• Downlink Physical Broadcast Channel (DPBCH)
• Downlink Physical Downlink Control Channel (DPDCCH)
• Downlink Physical Shared Channel (DPOSCH)
• Uplink Physical Random Access Channel (PRACH)
• Uplink Physical Uplink Control Channel (PUCCH)
• Uplink Physical Uplink Shared Channel (PUSCH)

According to the HCIA-5G V2.0 Exam Outline, handover execution failures can use the counters to collect failure reasons in SA networking, which corresponds to option A. The counters include N.HO.Exec.Fail.RadioResFail, N.HO.Exec.Fail.TAExceed, N.HO.Exec.Fail.NoRespFromUE, and N.HO.Exec.Fail.Other.

According to the 5G EN-DC Architecture and Interfaces, there are two methods that can be used to support X2 interconnection between an eNodeB and a gNodeB in NSA networking:

• Interconnection through CI interfaces on the UMPT boards in different subracks: The UMPT is a universal main processing and transmission unit that provides main processing and transmission functions for a subrack. The UMPT has two CI interfaces that can be used for X2 interconnection with other base stations. The CI interfaces support CPRI, OBSAI, and eCPRI protocols and can use optical fibers or electrical cables for transmission. The CI interfaces can be configured as master or slave interfaces depending on the network topology.
• IPRAN interconnection between subracks: IPRAN is an IP-based radio access network that uses IP transport technologies to carry base station traffic over Ethernet or MPLS networks. IPRAN can support X2 interconnection betweendifferent base stations by using IP routers or switches. IPRAN can provide flexible networking, high bandwidth, low latency, and high reliability for X2 interconnection.

The other two methods are not valid for X2 interconnection between an eNodeB and a gNodeB:

• Interconnection via backplane in a subrack: This method is only applicable for X2 interconnection between two eNodeBs or two gNodeBs that are installed in the same subrack. The backplane is the internal bus that connects different boards within a subrack. The backplane supports CPRI, OBSAI, and eCPRI protocols and can provide high-speed data transmission between boards.
• Interconnection through HEI interfaces on the UBBP boards in different subracks: This method is not supported by Huawei base stations. The HEI interface is a high-speed Ethernet interface that is used for data transmission between base stations and core networks or transport networks. The HEI interface supports S1, Xn, F1, E1, and N2 protocols and can use optical fibers or electrical cables for transmission. The HEI interface cannot be used for X2 interconnection between base stations.

Therefore, the correct answer is A and D.