This white paper gives a comprehensive overview of challenges faced by operators in 4G and an introduction to 5G architecture and its services.
- Over the last decade mobile communication has grown massively. Every new telecommunication generation brought in new changes to the system such as high data-rates and lower latency. But 4G and its evolution brought in substantial enhancements that catered many innovative services, such as services related to Internet-of-Things (IoT), Augmented Reality (AR), Virtual Reality (VR) to name a few. The rate of technological innovation witnessed over the past half a decade has given birth to 5G. “When will it get more faster” is one of the biggest challenges that Telcos are facing today as they begin gauging their options in the fifth-generation wireless technology.
2. Challenges faced by operators with 4G
4G LTE promised significant advantages over older generation technologies such as, lower latency, higher spectral efficiency, low cost data rates are few to name. However, soon the global operators had new challenges to grapple with. So, what are these new challenges?
2.1. Limited availability of spectrum allocated – Many operators have to operate on different frequency bands. This is required because if everyone operated at same frequency there will be interference and because of the same reason it has to be regulated. This is the obvious fact that operators are limited by the availability of the spectrum.
2.2. Building up the network – Another challenge is how operators build their network. Many of the services run on traditionally deployed, dedicated hardware. However, this increases the Operational and Capital expenditures.
2.3. Congestion – 4G enabled quality video streaming and calling on the go. With these features the per subscriber bandwidth requirement increased exponentially which caused congestion in the network. This increased congestion in the network is difficult to address with the present deployment architectures.
2.4. Seamless roaming and seamless transfer of services – 4G supports both inter-RAT (Radio Access Technology) and intra-RAT handovers. During the Inter-RAT handovers, it is difficult to realize the handovers among different wireless communication systems while meeting the various Quality of Service (QoS) requirements. If handover latency is too long, packets may get lost or disconnections may occur during the handover. Therefore, fast and seamless handover is a big challenge for 4G operators who claim to support real-time high-speed applications that require small handover delay and higher quality.
2.5. High density of devices – Number of devices/subscribers within a given area (per sq.km) has increased massively. Operators must be better harnessed to shelter this inflation.
2.6. Building network slices for 4G – Network slicing means creating logical networks overlaid on a common infrastructure. In order to serve different consumers expectation in their area of activity like military, emergency etc. operators had to create private networks for each.This was expensive in terms of operational cost and maintenance.
These are the significant reasons behind the evolution of 5G.
3. 5G Overview
The fifth generation of the mobile communication system will bring huge changes to the industry. The 5G system is designed on new network technologies, such as Network Function Virtualization (NFV), Software-Defined Networking (SDN) and Network Slicing in order to make it more flexible and agile. It supports the Service Based Architecture (SBA) which allows the Network Functions (NF) to discover other network services and communicate, unlike the older technologies where they had predefined interfaces between entities. The service-oriented architecture in the 5G System is more flexible, customizable and scalable. The 5G supports the stateless NFs where the compute resource elements are decoupled from the storage resource elements.
The below Figure-1 depicts services provided by the 5G System and gives a brief overview on the 5G System (5G core + 5G RAN).
Figure-1 : 5G Services
4. 5G Network
A Typical 5G network consists of Access network and Core Network. Below picture depicts the 5G Network.
Figure-2 : 5G network infrastructure
4.1. 5G Access Network
The NG-RAN represents the newly defined Radio Access Network for the 5G.
NG-RAN is comprised of the following elements:
- UE – User Equipment supporting 5G New Radio (NR).
- gNB – Base station supporting New Radio.
- ng-eNB – Existing LTE eNodeB upgraded to support New radio.
Figure-3 : 5G Access network
4.2. 5G Core Network
5G Core introduced Service Based Architecture (SBA) which replaced traditional nodes with individual network functions (NF) Ex: MME was replaced with AMF Network Functions (NF). It is designed to separate Control Plane (CP) and User Plane (UP) functions contradicting the 4G. NF in 5G core is run on a completely virtualized environment.
Figure below explains different 5G core network Functions,
Figure-4 : 5G core Network Functions
Explained below are different network Functions in the 5G Core,
4.2.1. AMF - Access and Mobility Management Function
- Handles Registration, Connection and Mobility Management.
- Establishes and releases NAS signaling connection with the UE.
- Access Authentication and Authorization in conjunction with other NFs.
4.2.2. SMF - Session Management Function
- Establishment, modification and Termination of the PDU session between the UE and Data Network.
- Interacts with PCF to check if a particular data session is allowed or not.
- UE IP address allocation.
- Selection of UPF to handle the UE traffic.
- Handles traffic steering at UPF, to route traffic to chosen DN.
4.2.3. UPF - User Plane Function
- External PDU session Point of Interconnect to DN.
- Execute the traffic steering rules.
- Enforces QoS and Policy Enforcement.
4.2.4. NEF - Network Exposure Function
- Expose the capabilities and services offered by the core network to the external world. (Not trusted by the operator to have direct access to core)
- Secure provision of information from external application to 3GPP network.
- Translation of internal-external information. In particular, NEF handles masking of network and user sensitive information to external AF‘s according to the network policy.
4.2.5. AF - Application Function
- These are the Network Functions that are external to 5G core and use the services offered by the 5G core.
- AF trusted by operators interact with the 5G core NF directly and others not trusted by operators interact via NEF.
4.2.6. PCF - Policy Control Function
- Supports unified policy framework to govern network behavior.
- Provides Policy rules to control plane functions to enforce them.
- Accesses subscription information relevant for policy decisions in a Unified Data Repository (UDR).
4.2.7. NRF - Network Repository Function
- Supports Service discovery Function.
- Supports P-CSCF discovery (specialized case of AF discovery by SMF).
- Maintains the NF profile of available NF instances and their supported services.
- Notifies about newly registered/updated/deregistered NF instances along with its NF services to the subscribed NF service consumer.
4.2.8. UDM - Unified Data Management
- Generation of 3GPP AKA prime & 5G AKA Authentication Credentials.
- User Identification Handling (e.g. storage and management of Subscribers permanent Identifier (SUPI) for each subscriber in the 5G system).
- Support of de-concealment of privacy-protected subscription identifier (SUCI – Subscriber Concealed identifier).
4.2.9. AUSF - Authentication Server Function
- Supports the authentication and Authorization for 3GPP and Non-3GPP access.
- Access authorization based on subscription data.
4.2.10. UDR - Unified Data Repository
- Storage of subscription data.
- Storage of policy data by the PCF.
- Storage and retrieval of structured data for exposure.
4.2.11. NSSF - Network Slice Selection Function
- Selecting the set of Network Slice instances serving the UE.
- Determining the Allowed NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs.
- Determining the Configured NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs.
- Determining the AMF Set to be used to serve the UE, or, based on configuration, a list of candidate AMF(s), possibly by querying the NRF.
5. 5G Services
The 5G system will respond to the widest range of services and applications that will have different characteristics and performance requirements. These are categorized in,
5.1. Enhanced mobile broadband (eMBB)
The services focused on eMBB are data driven and provides greater bandwidth with moderate latency. This will address scenario like, high Data rates, higher density of traffic, scenarios related to coverage, larger user mobility. For Example,
- Office scenarios where productivity is dependent on system response time. Users are using video conferencing or frequently uploading data to the servers.
- Users uploading or sharing Multimedia traffic in a populated shopping mall or in an event or stadium.
- In an education scenario where a remote student will require 360-degree video communication with their tutors and require 100% geographic coverage.
- Enhanced broadband in fast moving trains and airplanes.
5.2. Ultra-reliable and low latency communications (URLLC)
These mission critical services focus on providing extremely low latency and high reliability. For Example:
- In a Power Plant where high reliability and low latency is the key.
- In Military services
- Remote surgeries
- Industry automation, where the next action is dependent on the completion of previous action. High reliability is the key here.
- Tactile Internet where low latency is expectation.
- Disaster and emergency responses require very low latency and higher accuracy.
5.3. Massive machine type communications (mMTC)
These services need to support a very large number of devices within a small area, which may send data sporadically. For Example:
- Use cases related to Internet-of-things. Smart Metering, Street video recording.
What does this mean to the operator? How can the operator provide these services to the customers and end users? For instance, the eMBB services can be provided by leveraging the services from existing LTE network (Explained in Reference Deployment option 3) or operators can choose to deploy a new 5G core and New Radio (NR) (Explained in Reference Deployment option2).
Refer 5G Reference Deployment options whitepaper which explains each deployment option in detail.