5G tutorial : 5G NR system basics, architecture, Frame, Channels and more

5G New Radio (NR) is the latest cellular network standard developed by the 3rd Generation Partnership Project (3GPP) to meet the evolving requirements of modern wireless communication systems. It represents a significant leap forward from its predecessor, 4G LTE, in terms of speed, latency, capacity, and efficiency. The primary objectives of 5G NR are to provide enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC) to support a wide range of applications, from mobile devices to industrial automation and Internet of Things (IoT). This 5G tutorial covers 5G technology basics, architecture, frame, channels, protocol stack (PHY, MAC, RLC, PDCP), comparison with 4G, advantages and disadvantages.

Evolution of 5G NR :
1G - First generation (1G) analog systems in the 1980s
2G - Second generation (2G) GSM networks, which introduced digital voice communication
3G - Third generation UMTS networks, Mobile data services
4G - Fourth generation LTE, introduced high-speed data transmission and all-IP architecture.
5G - Fifth generation 5G NR (New Radio) specifications, introduced in 3GPP Release 15

5G technology features

The 5G technology makes use of all the existing cellular wireless technologies(2G, 3G and 4G). Apart from high throughput it provides following featutes.
• Better revenue for the service providers.
• Interoperability will become feasible and easier.
• Low battery power consumption.
• Better coverage and high data rates at the edge of cell.
• Multiple data transfer paths concurrently.
• More secure
• Flexible architecture based on SDR(Software Defined Radio).
• Higher system spectral efficiency
• Harmless to human health
• Cheaper fees due to lower costs of deployment infrastructure
• Better QoS(Quality of Service)
• Ultimate download and upload speed provides user great experience like broadband cable internet
• Most of the devices such as 5G dongle works on USB power and hence better in developing countries where electric power cuts are very common.

5G Specifications

5G architecture

The 5G NR network architecture consists of three main components viz. the User Equipment (UE), the Radio Access Network (RAN) and the Core Network (5GC).
• User Equipment (UE): The devices used by end-users to access the 5G network, such as smartphones, tablets, IoT devices and laptops.
• Radio Access Network (RAN): The 5G RAN includes the gNB (Next-Generation Node B), which handles radio communications with the UE and connects to the core network. The RAN supports features like beamforming and Massive MIMO for improved coverage and capacity.
• 5G Core Network (5GC): The 5GC is responsible for managing the overall network, including mobility management, session management, and authentication. It adopts a service-based architecture, allowing network functions to be deployed and scaled independently.

5G NR overall architecture is shown in the following figure-2. This is as defined in the 3GPP TS 38.300 specification. Refer 5G network architecture >>

5G Network Elements and Interfaces

1. gNB (Next-Generation Node B): The base station in 5G NR that manages radio resources and communicates with the UE.
2. AMF (Access and Mobility Management Function): Manages UE registration, mobility, and connection setup.
3. SMF (Session Management Function): Handles session establishment, modification, and release.
4. UPF (User Plane Function): Manages data transfer between the RAN and external networks.
5. PCF (Policy Control Function): Enforces policy decisions regarding QoS and charging.
6. NRf Interface: The interface between the gNB and the 5G core network.
7. N1 and N2 Interfaces: N1 is used for signaling between the UE and the AMF, while N2 is used for signaling between the gNB and the AMF.

Refer 5G NR network interfaces which include Xn interface, NG interface, E1 interface, F1 interface and F2 interface. Refer 5G NR interfaces >>.

5G Channel Types

5G NR defines several channel types to facilitate communication between different network elements.
1. Logical Channels: Define the type of information transmitted, such as control or data channels. Examples include the Dedicated Control Channel (DCCH) and Dedicated Traffic Channel (DTCH).
2. Transport Channels: Define how and with what characteristics data is transmitted over the air interface. Examples include the Physical Uplink Shared Channel (PUSCH) and Physical Downlink Shared Channel (PDSCH).
3. Physical Channels: Define the exact format of data on the physical medium. Examples include the Physical Random Access Channel (PRACH) and Physical Broadcast Channel (PBCH).

5G channel types cover logical channels and transport channels used in uplink and downlink with mapping between them. The 5G logical channels include xBCCH, xCCCH, xDCCH, xDTCH etc. The 5G transport channels include xBCH, xDL-SCH, xRACH, xUL-SCH etc. Refer 5G Channel Types >>.

5G Protocol Stack

The 5G NR protocol stack consists of several layers, each responsible for different functions. The main layers include the Physical (PHY) Layer, Medium Access Control (MAC) Layer, Radio Link Control (RLC) Layer, and Packet Data Convergence Protocol (PDCP) Layer.

The 5G layer-1 is PHYSICAL Layer. The 5G layer-2 include MAC, RLC and PDCP.The 5G layer-3 is RRC layer as shown in 5G protocol stack. Refer 5G protocol layer functions >>.

5G NR Physical layer processing for PDSCH and PUSCH

Function : Responsible for the transmission and reception of data over the air interface. Functions also include modulation, coding, and beamforming.

➨Refer 5G NR PHY >> for understanding step by step guide to physical layer processing for 5G NR PDSCH channel and 5G NR PUSCH channel.

5G NR MAC Layer Overview

Function : Manages access to the shared physical medium and controls scheduling, priority handling, and HARQ (Hybrid Automatic Repeat Request).

➨Refer 5G NR MAC Layer >> to understand 5G NR MAC architecture, 5G NR MAC channel mapping, 5G NR MAC procedures and format of 5G NR MAC header and subheaders.

5G NR RLC Layer

Function : Provides error correction and retransmission handling. It operates in three modes viz. Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM).

➨Refer 5G NR RLC Layer >> for understanding 5G NR RLC modes (TM mode,UM mode, AM mode), data structures (TMD, UMD, AMD), RLC PDUs (TMD PDU, UMD PDU, AMD PDU), data transfers (TM, UM and AM) and RRC parameters which defines RLC layer.

5G NR PDCP Layer Overview

Function : Handles data compression, header compression, and security through encryption and integrity protection.

➨Refer 5G NR PDCP Layer >> for basics of PDCP architecture (structure, entities), PDCP procedures for data transfer during transmit/receive operation, Data PDU and Control PDU formats of PDCP layer etc.

Advantages of 5G NR

Following are the benefits of 5G NR system.
1. Supports data rates up to 20 times faster than 4G LTE, enabling faster downloads and seamless streaming.
2. Latency as low as 1 ms facilitates real-time applications like remote surgery and autonomous vehicles.
3. Supports up to one million devices per square kilometer, making it ideal for IoT deployments.
4. Reduces energy consumption with features like advanced sleep modes.
5. Provides seamless connectivity even at high speeds, such as in high-speed trains.

Disadvantages of 5G NR

Following are the drawbacks or limitations of 5G NR system.
1. The need for new infrastructure and spectrum licenses increases deployment costs.
2. mmWave frequencies used in 5G NR have limited coverage and are prone to signal loss due to obstacles.
3. Older devices are not compatible with 5G NR, requiring users to upgrade to new devices.
4. The introduction of new features and network functions adds to the overall system complexity.

Future research and developments in 5G technology

Various projects based on 5G are in progress and are administered and managed by 5G-PPP. The projects include 5G-NORMA, 5G-ENSURE, CHARISMA, COGNET, XHAUL, mmMAGIC, SPEED-5G, Flex5Gware, FANTASTIC 5G etc.

5G-PPP is the short form of 5G Infrastructure Public Private Partnership. It has been initiated by EU commission, manufacturers, operators, researchers and SMEs. The 5G-PPP will provide next generation solutions, technologies, standards, architectures to be used for telecommunications.

Future research in 5G NR is focusing on enhancements such as integrated access and backhaul (IAB), non-terrestrial networks (NTNs), and further optimization of network slicing. Additionally, research is being conducted on extending 5G capabilities to support use cases like holographic communications, AI-based network management, and seamless integration with 6G technologies.

Comparison between 4G LTE and 5G NR

Following table compares 5G NR (New Radio) with its predecessor 4G LTE.

Conclusion

5G NR represents a transformative shift in mobile communication, offering unprecedented speed, low latency, and massive connectivity. Its flexible architecture, advanced features, and diverse use cases position it as a critical enabler of the digital future. While there are challenges to overcome, the ongoing research and development will ensure that 5G NR continues to evolve and support the growing demands of a connected world. This 5G tutorial is very useful for beginners who would like to start learning 5G basic fundamentals.

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