The 5G protocol stack is the architecture of protocols within a 5G network that perform specific functions like managing data transmission, error correction, and resource allocation. It exists as two separate elements: the control plane (CP) and the user plane (UP).
It’s more complex than the 4G protocol stack due to the numerous advanced features and technologies added in 5G. Some factors that contribute to the complexity of the 5G protocol stack include (Figure 1):
- Multiple numerology refers to multiple configurations of subcarrier spacing and other parameters in 5G networks. In LTE, 15 kHz is the only subcarrier spacing (numerology). Multiple numerologies allow 5G to meet the needs of a variety of use cases, such as enhanced mobile broadband (eMBB), ultra-reliable low latency communication (URLLC), and massive machine-type communication (mMTC).
- Utilizing millimeter wave frequencies in 5G necessitates more complex signal processing techniques at the physical layer than 4G.
- New features like network slicing, which allows for dedicated network segments for different applications, require additional protocol mechanisms to manage resource allocation and service prioritization.
- Massive MIMO and beamforming add complexity to the protocol stack and are required in 5G to support high data rates and large numbers of simultaneous users.
Figure 1. 5G includes numerous advanced technologies and capabilities not found in LTE that result in a more complex protocol stack implementation. (Image: ShareTechnote)
In a 5G network stack, the user plane is the data pathway, while the control plane manages and directs the data flow. The stack layers that are common to both planes include:
- Physical Layer (PHY) is the lowest layer. It is responsible for converting data into radio signals and vice versa and managing the transmission and reception of control information over the air interface, including tasks like modulation, coding, and beamforming.
- Medium Access Control (MAC) layer manages access to the shared radio resources and schedules data transmission between multiple users. Its tasks include resource allocation, prioritization of traffic, and control signaling.
- Radio Link Control (RLC) layer supports reliable and error-free transmission of data packets over the radio link. Its tasks include segmentation and reassembly of data packets, error detection and correction, and flow control.
- Packet Data Convergence Protocol (PDCP) layer supports compression and decompression of IP packets, encryption and decryption of user data, and header compression to ensure efficient transmission of data packets over the radio interface.
Figure 2. The layers of the 5G protocol stack can be split into the control plane and the user plane. (Image: Keysight)
Additional control plane layers
The Radio Resource Control (RRC) layer supports and manages the establishment, maintenance, and release of the radio connection between the user devices and the base station, including tasks like connection setup, mobility management, and control signaling for handovers.
The non-Access Stratum (NAS) layer supports the signaling and management of non-radio access-related functions, including network registration, authentication, security, and mobility management.
Additional user plane layers
Service Data Adaptation Protocol (SDAP) layer supports Quality of Service (QoS) management. It ensures that different types of traffic, like real-time video vs. background data transfers, receive the required QoS parameters and prioritization. The ability to tailor the QoS to differentiated data streams is a key enhancement in 5G compared to LTE.
The Internet Protocol (IP) layer in 5G is built on top of the IP protocol used in LTE but with enhancements that support optimized data transmission for the much higher speeds and lower latencies of 5G networks. Its interaction with the RRC layer in the control plane differs from LTE to accommodate 5G features like network slicing and enhanced QoS management.
The application layer is where end-user services and applications exist. 5G supports a broader range of applications and use cases, making this layer more complex than LTE.
Summary
The basic layered structure of the 4G and 5G protocol stacks is similar. The differences are found at the implementation level, which enables 5G to support significantly faster speeds and lower latencies than 4G. 5G also supports applications like eMBB, URLLC, mMTC, and high the QoS needed by applications like virtual reality and high-definition streaming. At the same time, 4G was designed for less demanding mobile data applications like email and web surfing.
References
5G NR Protocol Structure Changes – An Overview, Keysight
5G System Overview, 3GPP
5G Toolbox and the 5G NR Protocol Layers, MathWorks
Describe the 5G NR (New Radio) protocol stack and the different layers involved in 5G communication, TELCOMA Global
Key Components of the 4G and 5G Protocol Stack, Apeksha Telecom
The Role of the 5G NR Protocol Stack, 5G Descomplicado
Understanding the difference between 5G Networks and 4G LTE, Cavli
What Is 5G vs 4G?, Cisco
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