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Ⅰ、Protocols are the rules and standards that define how data is connected, transmitted and managed over a network. In the field of communications protocols ensure that hardware and software operate harmoniously across different end-user devices (UEs) and infrastructures, and they control everything from the formation, transmission and reception of packets to the safe and efficient connection and communication of devices.   Ⅱ、Why protocols are needed this is because of the following reasons; Interoperability:Protocols standardize the communication between different systems and devices, ensuring that they can interact with information (signaling) without discrimination. System Efficiency:Optimized protocols make better use of network resources, reduce costs and improve quality of service. System Security: Protocols incorporate security measures to protect the integrity, confidentiality and authenticity of data. Scalability: Standardized protocols support the expansion of network functions without requiring major changes to the core network structure. Ⅲ、The protocol layering in the 5G (NR) network system its protocol structure for layered management, commonly used layer three architecture for the L1, L2 and L3 layers. This structure helps modular organization of network functions, simplifies the design, implementation and troubleshooting; the role of each layer is as follows:   3.1 L1 (Physical Layer) Purpose:The physical layer is responsible for transmitting and receiving raw bit streams over physical media, specifically converting digital bits into signals and vice versa. Physical layer 5G functions mainly include:​ ❶ Waveform Generation:The use of OFDM (Orthogonal Frequency Division Multiplexing) enables efficient and interference-resistant high-speed data transmission. ❷ Modulation and demodulation: Determine the signal formation method and modulation scheme (e.g. QPSK, QAM) according to the network conditions. ❸ Data error correction: techniques such as forward error correction are used to improve data integrity without retransmission.     3.2 L2 (Data Link Layer) Purpose:The data link layer ensures that data is transmitted reliably over the physical network, allows data to be organized into frames and detects/resolves errors that occur at the physical layer. 5G Data Link Sublayer: ❶ MAC (Media Access Control): Manages and maintains control of the radio channel and multiplexes data streams from various sources. ❷ RLC (Radio Link Control): Enhances reliability by segmenting and reorganizing packets, and manages error correction through ARQ (Automatic Repeat Request). ❸ PDCP (Packet Data Convergence Protocol): compresses headers and provides encryption and integrity checking to ensure the security of user data.   3.3 L3 (Network Layer) Purpose: The network layer is responsible for transmitting packets from the source host to the destination host based on the address of the packet. It defines the path taken by the packet from the sender to the receiver. Key Functions in 5G： ❶ IP Routing and Transport: Manages packet forwarding, including addressing, routing, and flow control. ❷ Session Management: Manages the setup and maintenance of network connections. ❸ Mobility Management: Handles the operations required to move devices between sectors or networks while maintaining ongoing sessions.  

As the train enters the high-speed rail era, communication in the railroad private network becomes more and more important; GSM-R and 5G/FRMCS wireless networks are the key to ensure high-speed, continuous and reliable communication for current and next-generation railroad operation and safety. In railroad communication networks including GSM-R and 5G(NR) wireless networks, in addition to coverage and capacity analysis, the environment such as train stations and tunnels has a significant impact on communication and user perception, and modeling of outdoor and indoor areas (including building structures and materials) can accurately predict signal propagation and ensure reliable communication along the railroads.       1、Railway-specific RAN planning refers to the planning of radio access networks to enable communications for railroad operations, such as signaling and railroad mobile communication systems. This is because the railroad industry has unique requirements for security, performance, and reliability that require special consideration in RAN planning. In addition, the railroad wireless communication network must be sufficiently robust, secure and support continuous communication; in the entire railroad track (including tunnels, under bridges and remote or mountainous areas) to achieve uninterrupted coverage is also critical.   2、Continuous coverage railroads often traverse remote and rugged terrain; to ensure that the signal in all areas of the railroad (including tunnels and bridge crossings) to remain strong and uninterrupted, these are critical to maintaining communications security and operational efficiency.     3、In addition to a high degree of reliability, the network must have sufficient redundancy measures to protect against any communications failures, which are essential for safety-critical systems and managing train operations.     4、High mobility support High-speed train mobility is another unique consideration; the RAN must be able to handle high speeds seamlessly and reliably, during which time it is involved in managing switching between cellular sites without dropping lines or data sessions, which are critical for continuous communications.   5、 Capacity Planning, Quality of Service and Interoperability Railway wireless network RAN planning must also take into account the varying load demands, including increased demand during peak hours and significant fluctuations based on passenger train schedules. Quality of Service (QoS) further requires prioritizing critical communications (e.g., emergency service communications) over less important services. Compatibility of technologies and standards for railroad wireless network (RAN) planning is also important as the railroad industry is transitioning from older technologies such as GSM-R (Global System for Mobile Communications in Railroads) to newer technologies such as FRMCS (Future Railroad Mobile Communications System based on 5G).

Wireless parameters are the settings and configurations that characterize a wireless network (RAN) and play a critical role in determining network performance, coverage and overall functionality. These parameters are critical to delivering the desired user experience, meeting service demands, and ensuring efficient network operation; and the basic wireless parameters in 5G(NR) include the following:   1、 Frequency bands (Sub 6GHz and mmWave):5G can operate in Sub6 GHz and mmWave (millimeter wave) frequency bands, where Sub 6GHz provides wider coverage, while mmWave provides higher data rates but shorter coverage.   2、Parameter Set:It defines parameters such as subcarrier spacing and symbol duration in 5G, which allows flexibility to accommodate a variety of use cases with different latency and throughput requirements.   3、Modulation and Coding:Higher-order modulation schemes such as 256QAM can be used in 5G systems to increase data rates. Adaptive modulation and coding can be dynamically adjusted according to channel conditions to optimize data rates while maintaining reliability.   4、Duplexing Scheme:5G supports full-duplex TDD and FDD communications, which means that it allows simultaneous transmission and reception on the same frequency, and also supports half-duplex configurations for communications in one direction at a time.   5、 Structure Frame: 5G is flexible in time slot and symbol configuration, where flexibility is provided in the time slot and symbol configuration of the frame structure to accommodate a variety of use cases, including low latency and high throughput scenarios.   6、Channel Coding and Error Correction: 5G employs advanced channel coding techniques to enhance error correction and ensure reliable communications even under challenging radio conditions.   7、Multiple Antenna Technologies: 5G networks utilize Mass MIMO (Multiple Input Multiple Output) and Beam Forming to enhance coverage, capacity and overall network efficiency.   8、TimeSlot Format: 5G introduces a variety of time slot formats, including normal time slots, short time slots, and mini time slots, to accommodate different traffic characteristics and delay requirements.   9、Frequency Guidance and Reference Signals: 5G combines frequency guidance and probe reference signals to assist in channel estimation for efficient beamforming and network optimization.   10、TTI (Transmission Time Interval): Defines the time interval between transmissions in the air interface. Configurable TTI allows optimization for different services and use cases.   11、Beam Management: 5G includes parameters related to beamforming that enable efficient beam management, concentrating signals in specific directions to improve signal strength and overall network coverage.   12、Switching Thresholds and Triggers: Defines thresholds and triggers for initiating switching between different cells or base stations to ensure seamless mobility of connected devices.   13、Slicing Configuration Parameters: 5G parameters in the context of network slicing include the configuration of different network slices, each of which is customized according to specific service requirements and characteristics.   14、Authentication and Encryption: Settings Security parameters include settings related to user authentication, encryption, and integrity protection to ensure confidentiality and integrity of communications.   15、SBA Architecture: With the transition to a service-based architecture, parameters related to service provisioning, orchestration, and management play a vital role in providing flexible and efficient services.   16、Quality of Service QoS parameters: include settings used to prioritize different types of traffic, ensuring that critical applications receive the necessary resources and meet specific performance criteria.   17、Carrier Aggregation :defines how multiple frequency bands are aggregated to increase overall network capacity and data rates.   18、Interference Management: Parameters related to interference management include configurations to mitigate interference from adjacent cells or frequency bands and optimize overall network performance.   19、Power Saving and Sleep Mode: 5G parameters include settings for sleep mode and power saving features to optimize the energy consumption of connected devices and network infrastructure.   20、Network Interoperability Parameters: Parameters related to the coexistence of 5G with previous generations, such as LTE (Long Term Evolution), to ensure smooth transition and interoperability.   5G parameters cover a wide range of settings and configurations, from frequency bands and modulation schemes to security, QoS, and network slicing; optimizing these parameters is critical to delivering the desired user experience, supporting different use cases, and ensuring efficiency.  

I. AMF and NW Slicing Selection The AMF is selected when CN-RAN and NG RAN interact information according to Table 16.3.2.1-1 Terminal (UE) provides Temp ID or NSSAI through RRC.   II.Radio Interface Support When a service is triggered by the upper layer the terminal (UE) transmits the NSSAI via RRC in a format explicitly indicated by the upper layer.   III.Wireless Resource Isolation and Management Resource isolation can be implemented specifically tailored to avoid one slice affecting another. Whereas hardware/software resource isolation depends on the implementation, where each slice can be allocated shared, prioritized or dedicated wireless resources; depending on the RRM implementation and SLAs (as described in TS 28.541 [49]); in order to be able to differentiate traffic with different SLAs for network slices, the NG-RAN will:     NG-RAN configure a different set of configurations for different network slices via OAM; Select the appropriate configuration for each network slice of traffic, and the NG-RAN receives relevant information indicating which configurations apply to this particular network slice. Slice-based RACH configurations for RA isolation and prioritization can be included in SIB1 messages. The slice-based RACH configuration is associated with a specific NSAG, and if the UE does not provide the NSAG used for selecting the RACH configuration, the UE does not consider the NSAG used for selecting the slice-based RACH configuration.The UE determines the NSAG to be considered during the RA as specified in TS 23.501 [3].The UE will not apply the slice-based RACH configuration when the UE AS does not receive any of the information used for the random access NSAG from the NAS. information, the UE does not apply the slice-based RACH configuration.   IV Slicing Resource Handling NG-RAN nodes can use multicarrier resource sharing or resource reclassification to allocate resources to slices to support slice service continuity in case of slice resource shortage.     In multicarrier resource sharing, RAN nodes can set up dual connections or carrier aggregations with different frequencies and overlapping coverage where the same slices are available. Resource reallocation allows a slice to use resources in a shared or/and prioritized pool when its own dedicated or prioritized resources are unavailable, and the use of unused resources in the prioritized pool is as described in TS 28.541 [49]. The slicing RRM policy/limit associated with resource reallocation is configured by O&M. Measurements of RRM policy utilization based on resource types defined in TS 28.541 [49] are reported by the RAN node to the O&M and may result in the O&M updating the configuration of the sliced RRM policies/restrictions. V. Slice-based Cell Reselection Its information may be included in the SIB16 and RRCRelease messages delivered. The slice-based cell reselection information may include: a reselection priority per frequency per NSAG and a corresponding list of cells that support or do not support slicing of NSAGs. the UE determines that the NSAGs and their priorities are to be taken into account during cell reselection (see described in TS 23.501 [3] and TS 38.304 [10]).   When slice-based cell reselection is supported and slice-based cell reselection information is provided to the UE, the UE will use the slice-based cell reselection information.Valid cell reselection information provided in the RRCRelease always takes precedence over the cell reselection information provided in the SIB message. When no slice-based cell reselection information is provided for determining any NSAG to be considered during cell reselection (as described in TS 23.501 [3]), the UE will use the general cell reselection information i.e. without considering the NSAG and its priority.

As the information exchange interface between the 5G core network (5GC) and the radio access network (RAN), the NG, interacts with various information through the NGAP protocol, in which signaling is divided into two main categories;   I. Interactive signaling (response required) Main messages include; Initial Context Setting:Establishes an initial connection between the terminal (UE) and the network to allow service access. PDUSession Resource Setup/Modification/Release:Manages data connections for specific services (e.g. Internet, video calls). Switchover preparation/resource allocation/cancellation:Ensures seamless switchover between different gNBs during mobility. NG Reset:Resets the UE context on the network side, typically used for network maintenance or troubleshooting. NG Setup:Establishes the initial connection between the gNB and the core network. Path Switching Request:Switches the UE data path between different gNBs to optimize performance. UE Context Modification:Updates UE information on the network side, such as location or service access rights. UE Context Release:Releases the UE context indicating that the UE is no longer connected. The specific transfer interaction information is shown in Table 8.1-1 of the (lower) table; II. Signaling (no response required) mainly consists of;   AMF Configuration Updates:Notifies the gNB about AMF configuration changes that affect service delivery. Broadcast Session Setup/Modification/Release:Manage broadcast sessions for group communication services. Message Distribution Setup/Release:Establish/terminate distribution of messages to multiple UEs simultaneously. RAN Configuration Update:Updates the gNB configuration with new parameters or settings. uEContextSuspend/Resume:Temporarily suspend or resume the UE context without terminating the connection. uERadioCapabilityIDMapping:Associates a UE's radio capability with its identifier. The specific information to be passed (no answer required) in the NGAP is shown in table 8.1-2 of table (below);

Ⅰ、NGAP stands for NG Application Protocol, which is an application protocol between the 5G core network (5GC) and the radio access network (NG-RAN) to ensure efficient and secure messaging in the network.   Ⅱ、NGAP Architecture As shown in Figure 1 NGAP is built on the N2 interface; this interface connects the gNB (RAN) and the AMF (core network) to help accomplish the transmission and exchange of control plane signaling messages.   Ⅲ、The interface protocol layer is included： Application Layer:This layer contains the NGAP protocol entities and is responsible for generating and processing NGAP messages. Transport Layer: This layer is responsible for reliably delivering NGAP messages between the gNB and the AMF, and it usually uses the SCTP (Stream Control Transmission Protocol) protocol. Security Layer: This layer is responsible for providing security services for NGAP messages, such as authentication, integrity protection and confidentiality. It typically uses the TLS (Transport Layer Security) protocol. Ⅳ、IMPORTANCE 5G can be visualized as a high-speed train through which packets are transported; NGAP ensures smooth boarding, seamless switching between sites (units), and efficient resource allocation while keeping everything safe and smooth. Without it 5G's promise of ultra-high speeds, ultra-low latency and diverse services would be just a dream. Ⅴ、 How it works NGAP operates on a dedicated line N2 interface, connecting the radio access (gNB) to the core network (AMF). This is the dedicated communications channel for important updates and instructions to transmit a range of programs and messages, while the NGAP manages everything from subscriber authentication to mobility and service activation.   Ⅵ、Included in the related entities： gNB:5G network base station, which is responsible for providing wireless access to UEs (user equipment)； AMF(Access and Mobility Management):responsible for managing UE mobility and providing access to network services； UPF(User Plane Functions): responsible for forwarding user-plane data between the gNB and the core network Ⅶ、Features and Functions   ① NAS signaling:NGAP facilitates NAS (Non-Access Layer) signaling for user authentication, mobility and bearer service management; ensuring secure access and a seamless service experience across different wireless access technologies.  ② Separation of the control plane: This can be thought of as a dedicated traffic channel. the NGAP maintains a clear separation between the control plane (signaling) and the user plane (data). This allows for efficient resource management and scalability, processing information flows without interfering with data traffic. ③ Security mechanisms:NGAP employs strong security measures such as mutual authentication and integrity protection. This guards against network threats and ensures secure communications, protecting network integrity and user data. ④ Flexibility and Scalability:NGAP is designed to be flexible and adaptable to emerging needs. Its modular architecture allows for easy integration of future enhancements and new services, paving the way for B5G evolution and unforeseen advancements. ⑤ User Equipment (UE) Management: NGAP establishes and manages the UE context that handles user authentication, registration and mobility procedures. It ensures smooth onboarding, seamless switching and continuous connectivity as users move through the network. ⑥ Wireless Resource Management:NGAP helps to allocate and manage radio resources for UEs, optimizing network performance and ensuring fair and optimal resource utilization for each connected device. ⑦ Service Management:NGAP can establish and manage a variety of services for UEs, seamlessly facilitating cutting-edge applications such as data, voice, video, IoT connectivity, and even AR/VR. ⑧ Mobility Management:NGAP facilitates seamless switching between different RATs (Radio Access Technologies) and gNBs (Base Stations), thus guaranteeing uninterrupted connectivity for mobile users and ensuring that there are no dropouts or service interruptions.

AMF is mainly responsible for access and mobility management in 5G system; it is a core network component in 5G, in addition to being responsible for managing the access and mobility of 5G devices, it also interacts with other network function units (such as UPF, SMF, and AUSF) to complete the identity authentication of the terminal equipment (UE), service application, and billing, etc. The main functions of AMF itself are as follows:   ⒈、Device registration:AMF is responsible for registering 5G devices with the network and assigning unique identifiers to them, allowing the network to track the devices and their locations.   ⒉、Access Management:The AMF performs access management functions such as authentication, authorization and accounting (AAA) for 5G devices. It verifies the identity of the device and determines whether it is authorized to access the network.   ⒊、Mobility management:The AMF tracks the location of the device and manages switching between cells and base stations. It ensures that the device stays connected as it moves through different areas of the network.   ⒋、Policy enforcement:AMF enforces network policies. For example, quality of service (QoS) and charging policies, it ensures that network resources are appropriately allocated and devices are correctly charged for the services they use.   ⒌、Session Management:The AMF manages the creation, modification, and termination of 5G sessions for devices. It coordinates with other network functions such as the Session Management Function (SMF) to ensure that sessions are set up correctly and resources are allocated appropriately.   ⒍、User-Plane Function Unit (UPF) Selection: The AMF selects the appropriate UPF based on network policy and device location, and is responsible for forwarding user data between the device and the network.   ⒎、Subscriber data management: AMF stores and manages subscriber data, such as device profiles, subscription data and service data, to allow the network to provide personalized services for the device.   ⒏、Security Management:The AMF is responsible for ensuring the security of 5G devices and networks; handling security functions such as key management, authentication and encryption.   ⒐、Network Slicing:The AMF plays a key role in network slicing, allowing the network to create virtualized network segments with dedicated resources and services for different use cases.The AMF is responsible for managing access and mobility of devices within each network slice.   ⒑、Network Integration:The AMF is responsible for integrating the 5G core network with external networks (e.g., 4G LTE networks or Wi-Fi networks). It is responsible for coordinating with other network functions to ensure seamless switching between different networks.   ⒒、Control Plane Management: The AMF manages the control plane of the 5G network, which is responsible for signaling and network management. This plane is responsible for signaling and network management. It ensures that signaling messages are correctly transmitted between network functions and that network resources are effectively managed.   ⒓、Fault Management: The AMF is responsible for detecting and managing faults within the 5G core network; monitoring network anomalies and alerting the network operator when faults are detected.   ⒔、Policy Control:AMF is responsible for enforcing policies related to network resource allocation, quality of service (QoS) and billing. To ensure that the correct application of policy and appropriate charges to the device based on the services used by the device.   ⒕、Location Management:The AMF is responsible for tracking the location of 5G devices and managing their mobility to ensure that they remain connected as they move through different areas of the network.   ⒖、Network Optimization:The AMF plays a key role in optimizing the performance and efficiency of the 5G network. It monitors network usage and adjusts network resources to meet device demands.    

AMF  as a core network component in 5G, is responsible for managing 5G terminal equipment (UE) access and mobility management and interacting with other network functional units (e.g., UPFs, SMFs, and AUSFs); during this time, multiple secure encryption and key interaction processes are performed, and its security number is abbreviated as ASN.   I. Definition and Function In 5G(NR) mobile communication system ASN (Access and Mobility Management Function Security Number) is the security number of AMF (Access and Mobility Management Function).The AMF security number-ASN is an important part of the security architecture of 5G(NR) network. Especially, it plays a crucial role in 5G core (5GC) network; its specific applications and characteristics are as follows;   The AMF security number is a unique identifier assigned to the access and mobility management functions; it plays a crucial role in protecting the communication between the user (UE) and the 5G (NR) network, due to the fact that the AMF is specifically responsible for access management, mobility management, and security in 5G networks. The ASN is used as a security parameter used in the authentication and key negotiation process between the terminal (UE) and the AMF. These procedures are essential for establishing secure connections and ensuring the confidentiality and integrity of communications between the terminal (UE) and the 5G (NR) network. II.ASN application during the initial establishment of the connection the terminal (UE) and the AMF authenticate each other; the ASNs are involved in this process to verify each other's identities in order to contribute to the generation and exchange of security keys; and these keys will be used to encrypt and decrypt the data exchanged between the terminal (UE) and the network.   III.ASN Characteristics AMF Security Numbering is used to enhance the overall security posture of a 5G network by providing a unique identifier for each AMF. This ensures that authentication and key negotiation procedures are performed securely, preventing unauthorized access and protecting user data.   ASN in 5G (NR) is a key security parameter associated with access and mobility management functions. It helps to ensure communication between user devices and the 5G core network, contributing to strong and secure connectivity in 5G deployments.

Network Slicing is one of the key features introduced by 3GPP for 5G (NR) and can also be seen as a dynamically created logical end-to-end network. Multiple slices can be used by a terminal (UE) over the same gNB, and each slice provides services for a specific service type based on an agreed service level agreement (SLA). While Network Slicing in 5G system is just a logical network can fulfill user (UE) specific service requirements such as low latency, high bandwidth or other service related parameters. And NSSAI uses are as follows;   I. NSSAI is Network Slice Selection Assistance Information (NSSAI) in 5G (NR) systems, which is a key factor in the definition of specific network slice functions and characteristics.   II.NSSAI Functions It allows distinguishing and selecting network slices based on a variety of factors, which contain information about the slice's functionality, and services to fulfill specific requirements. This information is essential for the 5G core network to make informed decisions when selecting the appropriate network slice for a given user or application.   III. The NSSAI structure includes key elements about slices, such as SD-slice distinguisher (which helps to uniquely identify a specific slice) and SST-service type (which specifies the type of service provided by a slice); in addition the NSSAI contains information about the coverage area to ensure that the network slices are applicable within the defined geographic area.   In short ,NSSAI in 5G(NR) plays a key role in enabling the effective selection and management of network slices, ensuring that each slice meets specific service requirements, ultimately contributing to a more versatile and dynamic 5G network architecture.    

In order to enable passengers to access the Internet in the cabin of an aircraft through the use of a wireless LAN, in December 2020 3GPP RAN4 discusses the following definitions in R17 regarding ATG (Air-to-ground) network technology;   I. Application Scenario ATG (Air to Ground) network refers to in-flight connectivity technology, where signals are sent to the aircraft antenna of the airborne ATG terminal through the use of a ground base station. When the aircraft flies into different airspace, the airborne ATG terminal will automatically connect to the base station with the strongest received signal power; this is just like a cell phone on the ground. Figure 1. Schematic diagram of the ATG communication system   II.3GPP discussion The new WID (RP-193234) solution for 5G (NR) to support NTN (Non-Terrestrial Networks) was approved at RAN#86.The NTN work item specifies enhancements identified for NR NTN (Non-Terrestrial Networks) based on the following principles, in particular LEO and GEO with implicit compatibility to support HAPS (High Altitude Platform Station) and ATG (Air to Ground) scenarios; among others. Station) and ATG (Air to Ground) scenarios;    * NR-NTN core specification working assumptions for FDD.   * Assumption that the Earth Fixed Tracking Area (EFTA) has both Earth Fixed and Mobile units   * UEs are assumed to have GNSS capability.     III.ATG characteristics Base stations and terminals (UEs) are unique types, and ATG will operate in existing frequency bands without the need to identify new frequency bands and band attributes.   IV. Some characteristics of ATG deployment scenarios can be considered   * Extremely large Inter-Site Distance (ISD) and large coverage area:In order to control the network deployment cost and considering the limited number of flights, it is preferable to use a large ISD, e.g., about 100 km to 200 km. The distance between the aircraft and the nearest base station may be more than 200 km or even up to 300 km when the aircraft is over the sea. Therefore the ATG network should be able to provide cell coverage of up to 300 km.   * Deploying ATG and terrestrial networks using non-separated operators' proprietary frequencies:Operators want to deploy ATG and terrestrial networks using the same frequencies in order to save the cost of frequency resources, while the interference between ATG and terrestrial networks becomes non-negligible and should be addressed. From China Mobile's point of view, 4.8GHz is an optimal frequency for deploying ATG and terrestrial NR networks.   * More Powerful Airborne ATG Terminal Capacity:Airborne ATG terminals are more powerful than normal terrestrial UEs, e.g., higher EIRP through higher transmission power and/or larger onboard antenna gain.   V. Challenges to ATG Deployment Considering the network deployment specificities, the following issues will be addressed in the ATG project:   * Extremely large cell coverage (up to 300 km) and flight speed (up to 1200 km/h);   * Coexistence requirements between ATG and terrestrial networks;   * ATG BS/UE core and performance requirements.   VI. ATG Objectives RAN4 discusses RF requirements for coexistence between ATG and IMT terrestrial networks Core specification designation functions include.   * Determine the absolute need to differentiate ATG BS and UE from terrestrial BS and UE key characteristics - Reuse existing BS and UE requirements wherever possible.   * Study and specify the framework for defining the ATG core requirements.   6.1 Determine if these requirements are included in existing specifications or if new specifications are created; Determine if both BS and UE require conduction, OTA, or both types of requirements; In addition   * Determine the potential FR1 frequency bands to be used as ATG examples   * Perform FR1 coexistence assessment for ATG networks (e.g. ACLR, ACS)   * Assign new UE/BS types for ATG networks if necessary   6.2 Consider identified differences between ATG and terrestrial systems   - Specify RF requirements for the ATG UE/BS   6.3 Consider the impact of coexistence simulation results on transmit and RX requirements, cell size and link budgets, technical capabilities, possible BS and UE architectures, and other relevant aspects.   * Specify test procedures for ATG BS conformance testing   6.4 Determine at an early stage whether conduction, OTA or both types of testing are required