What are the types of data radio bearer in LTE?
In Long-Term Evolution (LTE) networks, which are a standard for wireless communication, data transmission is organized into various radio bearers to efficiently manage different types of data and services. LTE defines several types of radio bearers to cater to the diverse requirements of applications and services. Let’s explore these types of radio bearers in detail:
Traffic Radio Bearers (DTCH – Data Traffic Channel):
AMBR (Allocation and Retention Priority): This is a type of Traffic Radio Bearer that is used for the transfer of user data. AMBR is associated with a specific user and represents the aggregate maximum allowed uplink and downlink bit rates for that user. These rates can be adjusted based on the user’s subscription and network conditions.
Signaling Radio Bearers (DCCH – Dedicated Control Channel):
SRB (Signaling Radio Bearer): SRBs are used for the transmission of control plane signaling messages between the User Equipment (UE) and the Evolved Node B (eNodeB), which is part of the LTE infrastructure. There are two types of SRBs:
- SRB1: It is used for initial access and connection establishment, including the exchange of security-related information during the attachment process.
- SRB2: This is used for the exchange of radio resource control (RRC) messages, which are essential for maintaining the connection and managing various procedures in the LTE network.
Bearer Types Based on QoS (Quality of Service):
GBR (Guaranteed Bit Rate): GBR bearers are used for services that require a guaranteed, constant bit rate, such as voice or video calls. These bearers ensure that the specified bit rate is always available, providing a stable connection for real-time services.
Non-GBR (Non-Guaranteed Bit Rate): Non-GBR bearers are used for services that do not require a guaranteed constant bit rate, such as web browsing or email. They provide more flexibility in terms of resource allocation, allowing for efficient use of network resources.
Bearer Types Based on QCI (QoS Class Identifier):
QCI 1-4: These QCIs are used for GBR bearers and are associated with services like voice and video calling, which require low latency and high reliability.
QCI 5-9: These QCIs are used for Non-GBR bearers and cover various services like web browsing, email, and file transfer. They may have different requirements in terms of latency and reliability, allowing for flexibility in resource allocation.
Default Bearer and Dedicated Bearer:
Default Bearer: When a UE initially attaches to the LTE network, a default bearer is established. This bearer is used for initial communication and is typically associated with lower QoS parameters.
Dedicated Bearer: Dedicated bearers are established after the default bearer and are associated with higher QoS parameters. They are used for specific services or applications, such as multimedia streaming or online gaming.
Emergency Bearer:
Emergency Bearer: LTE networks support emergency services, and an emergency bearer is dedicated to handling emergency calls. It ensures that emergency calls receive the highest priority and quality of service in times of network congestion.
IMS Bearer (IP Multimedia Subsystem):
IMS Bearer: These bearers are used for IP multimedia services such as voice over LTE (VoLTE) and video calling. IMS bearers ensure efficient handling of multimedia traffic over the LTE network.
In summary, LTE networks utilize various types of radio bearers to accommodate different types of data and services. These bearers are differentiated based on their characteristics, including their purpose (traffic or signaling), QoS requirements, bit rate guarantees, and QCI assignments. This diversity in bearers allows LTE networks to efficiently handle a wide range of applications and services while optimizing resource utilization and ensuring a good user experience.