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access network and core network

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In telecommunications, especially in the context of mobile networks, the terms "Access Network" and "Core Network" refer to two fundamental components of the overall network architecture. Let's explore these components in detail:

Access Network:

1. Definition:

  • The Access Network, often called the Radio Access Network (RAN) in the context of mobile networks, is the part of the telecommunication system that connects user equipment (UE), such as mobile phones or other devices, to the core network.

2. Key Components:

  • Base Stations (eNodeBs in LTE, gNBs in 5G): These are radio transceiver stations that communicate directly with mobile devices. They manage radio resources, handle handovers, and connect to the core network.
  • Cell Sites: Base stations are distributed across geographical areas known as cells. Each cell site provides coverage to a specific area, and as users move, they may transition between different cells.
  • Backhaul Network: The connection between base stations and the core network is facilitated by the backhaul network. This can be implemented using various technologies like fiber optics, microwave links, or satellite links.

3. Functions:

  • Radio Resource Management (RRM): Allocates and manages radio frequencies, channels, and power levels to optimize network performance and user experience.
  • Mobility Management: Handles the mobility of users as they move between different cells, ensuring seamless handovers.
  • Radio Link Control (RLC): Manages the radio link between the user equipment and the base station, ensuring reliable communication.
  • Connection Establishment and Release: Establishes and terminates connections between mobile devices and the network.

4. Wireless Technologies:

  • Different generations of mobile networks use different technologies in the access network, such as:
    • 2G (GSM): Uses Time Division Multiple Access (TDMA).
    • 3G (UMTS): Uses Code Division Multiple Access (CDMA).
    • 4G (LTE): Uses Orthogonal Frequency Division Multiple Access (OFDMA).
    • 5G: Introduces advanced technologies like Massive MIMO (Multiple Input, Multiple Output) and beamforming.

5. Evolution to 5G:

  • With the evolution to 5G, the access network incorporates technologies like Network Function Virtualization (NFV), Software-Defined Networking (SDN), and dynamic spectrum sharing for enhanced performance and flexibility.

Core Network:

1. Definition:

  • The Core Network is the central part of the telecommunication system responsible for handling communication between different access networks, managing user authentication, and providing services such as voice, data, and messaging.

2. Key Components:

  • Mobile Switching Center (MSC) in 2G/3G, Packet Switched Gateway (PSGW) in LTE, Access and Mobility Management Function (AMF) in 5G: These entities manage circuit-switched and packet-switched connections, respectively.
  • Home Location Register (HLR) and Home Subscriber Server (HSS): Store subscriber information, including user profiles, subscription details, and authentication keys.
  • Serving Gateway (SGW) and Packet Data Network Gateway (PGW) in LTE, User Plane Function (UPF) in 5G: Manage the routing of data traffic between the user equipment and external data networks (e.g., the internet).
  • Authentication Center (AUC) and Authentication and Authorization Function (AAF) in 5G: Handle user authentication and authorization processes.
  • Evolved Packet Core (EPC) in LTE, 5G Core (5GC) in 5G: Comprehensive architecture that includes various elements like SGW, PGW, AMF, SMF (Session Management Function), and others.

3. Functions:

  • Call and Session Management: Establishes, maintains, and terminates voice and data sessions.
  • Handover Management: Manages handovers between different access networks and cells.
  • User Authentication and Authorization: Verifies user identity and authorizes access to network resources.
  • Billing and Charging: Collects information for billing purposes based on the usage of network resources.
  • Policy Enforcement: Implements network policies, including Quality of Service (QoS) and traffic management policies.
  • Lawful Interception: Provides the capability to intercept and monitor communications for legal and regulatory purposes.

4. Evolution to 5G:

  • The evolution to 5G introduces a new core network architecture known as 5GC. It is designed to be more flexible, scalable, and cloud-native, incorporating technologies like Network Slicing, which allows the creation of virtualized, customized networks for different use cases.

Interaction Between Access Network and Core Network:

  • The Access Network and Core Network work collaboratively to enable end-to-end communication. The Access Network handles the wireless communication with user devices and manages the radio resources, while the Core Network handles the overall network management, authentication, and communication with external networks.
  • Handovers between different cells or access technologies involve coordination between the Access Network and the Core Network to ensure a seamless transition for users.
  • User data and signaling traffic flow between the Access Network and Core Network based on the specific protocols and interfaces defined by the respective generations of mobile networks.

In summary, the Access Network and Core Network together form the foundation of mobile telecommunications, providing the infrastructure and services necessary for wireless communication and connectivity. The continuous evolution of these networks contributes to improved performance, enhanced services, and the ability to support new and advanced technologies.