E RAB (Evolved radio access bearer)

Introduction:

Evolved Radio Access Bearer (E-RAB) is a term used in Long Term Evolution (LTE) technology to define a communication channel between the User Equipment (UE) and the LTE core network. In simple terms, E-RAB is a virtual communication channel that allows the UE to communicate with the LTE core network to access various services like voice calls, video streaming, messaging, and internet browsing. E-RAB is an essential component of LTE technology, which provides high-speed data transmission, low latency, and better network efficiency. In this article, we will discuss in detail the concept of E-RAB, its importance in LTE networks, and the process of its establishment.

The Need for E-RAB:

In a traditional communication network, a dedicated physical connection is established between the UE and the network to provide a service. For example, a dedicated physical connection is established between the UE and the network for voice calls. However, in LTE networks, multiple services can be provided over a single physical connection, which is known as a Radio Access Bearer (RAB). In other words, RAB is a logical connection between the UE and the network, which provides a specific service, like voice, video, or data. RABs are established dynamically as per the user's requirements, which makes the LTE network more efficient and flexible.

The concept of RAB is extended in LTE networks to E-RAB, which provides an enhanced communication channel between the UE and the network. E-RAB is established when the UE requests a service that requires high bandwidth or low latency. For example, video streaming or online gaming requires high bandwidth and low latency, which can be provided by establishing an E-RAB between the UE and the network. E-RABs are also used to support handover between different LTE cells, which ensures a seamless transition of service from one cell to another.

Establishment of E-RAB:

The establishment of E-RAB involves multiple steps, which are discussed below:

Step 1: UE Request for Service The first step in the establishment of E-RAB is the UE's request for a service that requires an E-RAB. For example, the UE requests a video streaming service.

Step 2: E-RAB Setup Request Once the UE requests a service, it sends an E-RAB setup request message to the eNodeB. The eNodeB is the access point of the LTE network, which communicates with the UE and the core network. The E-RAB setup request message contains the UE's requirements for the service, such as the Quality of Service (QoS) parameters, the type of service, and the transport channel requirements.

Step 3: E-RAB Setup Response After receiving the E-RAB setup request message, the eNodeB sends an E-RAB setup response message to the UE. The E-RAB setup response message contains the E-RAB identifier, which is used to identify the E-RAB throughout its lifetime. The eNodeB also sends the QoS parameters and the transport channel requirements to the UE.

Step 4: E-RAB Setup Complete After receiving the E-RAB setup response message, the UE sends an E-RAB setup complete message to the eNodeB, indicating that it has successfully established the E-RAB.

Step 5: RRC Connection Setup Once the E-RAB is established, the UE initiates a Radio Resource Control (RRC) connection setup with the eNodeB. The RRC connection setup is the process of establishing a secure communication channel between the UE and the eNodeB. The RRC connection setup involves multiple steps, which include security authentication, establishment of encryption keys, and configuration of the UE and eNodeB parameters.

Step 6: Data Transmission After the RRC connection setup, data transmission can begin over the established E-RAB. The UE and the eNodeB exchange data packets over the E-RAB, which are then forwarded to the core network for processing. The core network provides various services like voice calls, video streaming, messaging, and internet browsing by processing the data packets received from the UE over the E-RAB.

E-RAB Release:

The E-RAB release process is initiated when the UE no longer requires the service for which the E-RAB was established. The E-RAB can also be released due to various reasons like handover, network congestion, or radio link failure. The E-RAB release process involves multiple steps, which are discussed below:

Step 1: UE Request for E-RAB Release The first step in the E-RAB release process is the UE's request for E-RAB release. The UE sends an E-RAB release request message to the eNodeB, indicating that it no longer requires the service for which the E-RAB was established.

Step 2: E-RAB Release Request Acknowledgement After receiving the E-RAB release request message, the eNodeB sends an E-RAB release request acknowledgement message to the UE, indicating that the E-RAB release request has been received.

Step 3: E-RAB Release Indication After receiving the E-RAB release request acknowledgement message, the eNodeB sends an E-RAB release indication message to the core network, indicating that the E-RAB is being released.

Step 4: E-RAB Release Complete After receiving the E-RAB release indication message, the core network sends an E-RAB release complete message to the eNodeB, indicating that the E-RAB has been released.

Step 5: RRC Connection Release After the E-RAB has been released, the UE initiates an RRC connection release with the eNodeB. The RRC connection release is the process of releasing the secure communication channel between the UE and the eNodeB.

Conclusion:

E-RAB is an essential component of LTE networks, which provides an enhanced communication channel between the UE and the core network. E-RABs are established dynamically as per the user's requirements, which makes the LTE network more efficient and flexible. The establishment of E-RAB involves multiple steps, which include the UE's request for service, E-RAB setup request, E-RAB setup response, E-RAB setup complete, RRC connection setup, and data transmission. The E-RAB release process is initiated when the UE no longer requires the service for which the E-RAB was established, and it involves multiple steps, including the UE's request for E-RAB release, E-RAB release request acknowledgement, E-RAB release indication, E-RAB release complete, and RRC connection release. The E-RAB concept is an important aspect of LTE networks, which provides high-speed data transmission, low latency, and better network efficiency, enabling various services like voice calls, video streaming, messaging, and internet browsing.