Introduction
The first commercial 5G networks are launched everywhere, Europe USA, and Korea. Recently many operators announced the commercial start of 5G networks. Some of them, like Swisscom in Switzerland, even promised to deliver countrywide coverage till the end of 2019. Things are happening, but what about 5G SA?
Based on these announcements I asked myself the question. Does it mean 5G technology is fully capable, does it delivers all that was promised by standards?
To be first, to deliver the first base station, cover some city, deliver first modem, first phone, is it just marketing? To show who is defining the leaderboard or the real winner in the race?
To find the answers to my questions, we shall understand what are services building a 5G network. We need also to understand how it differs from 4G or 3G networks.
ITU-R and ETSI/3GPP shall help to understand it better.
ITU-R’s definition of 5G mobile network use cases
Mobile data consumption of the internet is growing year to year.
The main drivers are
- streaming services,
- an increase in the penetration of smartphones, and
- an increasing number of parallel connections. At home, we have more devices requiring internet connections. Mobiles, broadband modes, refrigerators, washing machines, heating systems, security systems, etc.
The new 5G mobile technology assumes that it shall extend usability and quality for new use cases and applications. They can not be delivered today over 4G/LTE technology.
ITU-R has defined three main usage scenarios [ITU-R M.2083]:
- Enhanced Mobile Broadband (eMBB) to deal with hugely increased data rates, high user density, and very high traffic capacity. It will be used in hotspot scenarios, seamless coverage, and high mobility scenarios with still improved used data rates
- Massive Machine-type Communications (mMTC) for the IoT, requiring low power consumption. These devices have alow data rates for very large numbers of connected devices
- Ultra-reliable and Low Latency Communications (URLLC) to cater to safety-critical and mission-critical applications
which requires different key capabilities as shown in Figure 1.:
5G network use scenarios
1. eMBB (enhanced Mobile BroadBand) offers broadband services, and live media. It requires a high data peak ratio, wide area coverage, and high efficiency in spectrum utilization (capacity per km2). It promises a good user experience data rate and of course low energy consumption on the end-user terminal. Typical solutions: video streaming services, online gaming (EDGE computing), Augmented Reality/Virtual Reality, and broadband services. Latency for that segment shall be 10 ms for the User Plane and 5-10 ms for Control Plane. It is in practice, improved service of already existing 4G/LTE broadband access.
2. mMTC (massive Machine Type Communication) usage scenario, designed for IoT solution. It supports millions of devices communicating in parallel with small data peak rates, low energy consumption, and limited mobility. Smart city and smart Home are typical use scenarios for that case. Latency for that segment shall be 10 ms for the User Plane and 5-10 ms for the Control Plane.
3. URLLC (Ultra-reliable Low Latency Communication) use cases, are very specific for safety-critical scenarios. It requires extremely low latency and very high reliability and mobility. The typical customers will be self-driving cars, and industry/production automation (Industry 4.0). Latency for that segment shall fulfill the requirement of below 5 ms, best 1 ms for User Plane!
Looking especially at low latency demand, we can see, that both 5G System elements must support it. 5G NR and 5G NGC. 3rd critical element is the ISP provider performance. To deliver all these services, the challenge is in the design and delivery of New Radio technology. New frequencies, new modulation techniques, multi-array antennas, MIMO, etc. Also, the design and implementation of 5G New Generation Core architecture 5G (NGC) shall support it. Especially URLLC and mMTC low latency use cases require changes in the Core architecture.
3GPP in Q1 2019 closed standards Release 15, of new core network architecture. Let’s see what are the changes and challenges.
3GPP approach to new 5G core network architecture (5G NSA and 5G SA)
It is gonna happen for the first time in the mobile industry, that the core network and ISP connectivity will become a bottleneck in the network latency case when the new 5G NG radio solution will be very efficient in latency delivery. Based on IUT-R assumptions, clearly, we can see it requires a change in the Core network architecture to support case mMTC and URLCC.
3GPP, following network operators’ suggestions, defined the 5G core network standard based on three different phases:
- “early Rel-15 drop” so-called Non-standalone NR (NSA NR) which allows the connection of NR base station (called gNB) to existing Evolved Packet Core network (EPC).
- “regular Rel-15 freeze” so-called standalone NR (SA NR), competently new core network architecture with new functions and interfaces, intended to support connection only of gNBs.
- “late Rel-15 drop” where the LTE base station will be connected to NR SA via gNB (Control plane and user plane – architecture in option 4 or User plane directly to NGC and control plane over gNB – architecture in option 4a) or vice versa (option 7 and 7a) [3GPP TS38.801]. This version was added on the last stage of standardization, to let utilize the LTE network as well in the SA case (multi-access).
The first phase, “early Rel-15 drop” was designed to help launch the first 5G networks already in 2019-2020, based on existing core network nodes. It requires mainly software modifications into existing core network elements. This drop was in that case answer to the first part of the question. It is an early-phase solution, not ready to support all the ITU-R cases.
“regular Rl-15 drop” defining new architecture SA NR standards was approved by 3GPP Release 15 just in Q1 2019. This standard is delivering a completely new solution into the operator’s garage, but not the final one, as 3GPP Release 16 will be defining new elements of service function to support URLLC products.
When is the best moment to invest in 5G SA architecture?
Now, in 2019 we have a dilemma. Connect 5G NR to the existing core network, or wait and change the core network into NGC SA? What makes sense?
In my opinion, the support to the answer is in the definition of use cases from ITU-R mentioned previously. If we think only about the implementation of eMBB, at least in the very basic scenario, we could “refresh” the existing core network and it would be enough to start.
However, if the ambition is to implement also mMTC and URLLC use cases, it will demand to step into a new 5G SA solution, and in my opinion, it makes sense for various reasons, as soon as possible to do it.
The new low latency requirement, demand from mobile operators for new architecture, not to forget about better ISP providers. Both elements of the communication chain become crucial.
What are the changes to the architecture and technology basics of the new core network?
5G SA – new generation of Core Network
I will describe the benefits of the new SA NR architecture as well as new technological assumptions using the 3GPP standard.
General assumptions of 5G SA are described in the document [3GPP TS23.501]:
The 5G System architecture is defined to support data connectivity and services enabling deployments to use techniques such as e.g. Network Function Virtualization and Software Defined Networking. The 5G System architecture shall leverage service-based interactions between Control Plane (CP) Network Functions. Some key principles and concepts are:
- Separate the User Plane (UP) functions from the Control Plane (CP) functions, allowing independent scalability, evolution, and flexible deployments e.g. centralized location or distributed (remote) location.
- Modularize the function design, e.g. to enable flexible and efficient network slicing.
- Wherever applicable, define procedures (i.e. the set of interactions between network functions) as services, so that their re-use is possible.
- Enable each Network Function to interact with other NF directly if required. The architecture does not preclude the use of an intermediate function to help route Control Plane messages (e.g. a DRA).
- Minimize dependencies between the Access Network (AN) and the Core Network (CN). The architecture is defined with a converged core network with a common AN – CN interface which integrates different Access Types e.g. 3GPP access and non-3GPP access.
- Support a unified authentication framework.
- Support “stateless” NFs, where the “compute” resource is decoupled from the “storage” resource.
- Support capability exposure.
- Support concurrent access to local and centralized services. To support low latency services and access to local data networks, UP functions can be deployed close to the Access Network.
- Support roaming with both Home routed traffic as well as Local breakout traffic in the visited PLMN.
Other benefits of 5G SBA architecture
We can add also, that the 3GPP decided to change the standard of signaling for the control plane into HTTP/2 over TCP/IP and exchange of information composed of JSON payload (11). It is another BIG fundamental change, giving telecom vendors and operators access to wisely used for years. Tools, software libraries, and programming solutions from the IT software development market.
It is a revolutionary change from “closed, strictly defined core network nodes/elements architecture” towards modern software-defined architecture utilizing service-based applications communicating with each other (not always, however) over RESTfull interfaces. It allows building multi-layer clouds typically dividing it into central, regional to local cloud systems (EDGE computing in 3GPP called Multi-access Edge Computing – MEC).
Benefits of SBA architecture
What are the practical arguments for each of the assumptions (numbers refer to the previous counting):
UP and CP separation
1. Separation of UP and CP let the operator implement multi-layer infrastructure, which will be critical to delivering low latency solutions for mMTC and URLLC cases. As I already mentioned, the core network must be much faster than today delivered solutions from mobile operators and ISP providers. It will be possible only in case of pushing the Network Functions and applications into the EDGE of the network, working locally, and delivering locally. It does not mean only access to the internet, as eMBB is a separate issue. If we understand that URLLC cases like Industry 4.0 or V2X between vehicle communication require control over fast-responding applications, we need to put the applications as close to the geographical location of the customer, as possible. Examples: City infrastructure (V2I) to aim to communicate with all vehicles (V2V) and pedestrians (V2P) will require more than one local MEC system, due to its size.
We can imagine a few concentrated Virtual RAN systems covering parts of the city, each requiring separate MEC support. The movement of the vehicle in the city, and changing the Virtual RAN zones requires inter-MEC communication, and here the separation of UP and CP delivers support.
Network slicing
2. Network slicing is a concept, which allows separating “physical” resources of radio and core network for separate service delivery applications. As long as the mobile network operator will delivers locally enough radio capacity, we will be able to give a higher warranty of service to separate slices, with different QoS conditions, specific for end-user needs – V2X vehicles control, control of production line, etc.. Network slicing will let operators give different priorities for other services (Standardized SST values: eMBB -1, URLLC – 2, MIoT -3). Another interesting feature of slicing is the possibility to implement it regionally, e.g. deliver low latency service locally to the industrial zone, and stadium. It simplifies the launch strategy and minimizes associated costs for the operator. Slicing, 5G SA based, is crucial for mMTC and URLCC use cases.
Functions/applications will have an impact on the New Radio parameters including QoS. It means it would be possible to influence the Quality of Experience (QoE) for some of the users from external applications, like the MEC system.
Defined procedures
3. Defined procedures as a service will let operators faster and easier develop new functionalities based on already set-up communication procedures between functions and applications.
Network Function interactions
4. Direct interaction between network functions (NF) is a revolution in mobile telecommunication standards. In the new concept, relevant NFs will be able to communicate directly with other NF. There is no need to communicate over one central point (today it is a case of SS7 signaling nature). The exception is defined for Non-3GPP (LAN-based) systems which must be interconnected over the N3IWF function. So, there won’t be network elements/nodes, but only network functions, which may be elastically realized on different virtual systems. The next benefit is a simplification of the communication interface between NFs. It will be realized over a service-based interface bus. The communication with the external world will utilize API based on OpenAPI 3.0.
Standard communication Interface
5. Interface communication between Access Network (AN) or none-3GPP access and Core Network (NGC) is going to be standardized.
Unified authentication
6. Unified authentication framework, allows the development of new services using simplified service procedures (OAuth 2.0).
Stateless Network Functions
7. Stateless NFs, is another technology required to support low latency solutions, but also to adapt to modern REST-based coding. This is one of the most fundamental changes. Any synchronization between Control Plane (CP) and User Plane (UP) was negatively influencing latency.
Capability exposure
8. Capability exposure will simplify the development of new services. Thanks to this capability, Application Functions will be providing information to each other via the NEF function or directly.
UPF controlling connectivity
9. UP functions deployed close to the Access Network in parallel to a central location. It is another benefit of spiting User Plane system (UPF). It let influences lower latency and speed of delivery of the internet.
Home Route roaming and LBO support
10. Support for Home Route roaming as well as LBO connection, are crucial for fast and world-wise solutions. Looking at the difficulties of roaming VoLTE rollout not being standardized from the beginning between operators, we can see low penetration of that technology today. 5G roaming scenario from the beginning is standardized and hopefully will be seriously implemented by all the industry.
HTTP/2 support
11. Last, but not least is the development of future communication protocol. In 3GPP Rel 15 standard, it was decided to change it to HTTP/2 over TCP/IP. TLS delivers a security layer. It is not an optimal solution, as TCP/IP is not supporting asynchronous communication. It has many bottlenecks in terms of supporting fast communication from the first seconds (start-up Window). ETSI and 3GPP are very aware of these problems. The next change followed in 3GPP Rel. 16 is going to change the communication protocol into HTTP/2 over QUIC and UDP/IP. The benefits of QUIC are 0ms latency for known connection (perfect for 5G network). It has inbuilt security, which does not require TLS, again impacting positively on decreasing latency and increasing speed.
ETSI is working also on New Generation Protocol for the future (NGP protocol), with the results expected beyond 2025. My prediction is that change to HTTP/2 in CP will happen as soon as the first 5G SA will appear. Today User Plane (UP) connections are dominated by TCP/IP and IPv4. Let’s hope it is not going to follow a very bad history of IPv6 protocol. Hopefully, UP connections will smoothly transfer into QUIC/UDP and IPv6 technology.
Ease of implementation – “Beauty and the Beast”
Merging two worlds, DevOps methods on cloud base systems with telecom regime shall give very interesting results. Many software developers, ready-to-use microservices based on containers, can deliver NFs in a relatively short time. Standardization of communication and definition of NFs functions is a good receipt for product delivery.
The new 5G SA architecture, controversially is just as easy for development for IT software houses as for “BIG” vendors. Affirmed Networks, Ericsson, Huawei, Nokia, ZTE, will deliver it too. We can also recognize the development of small firms, announcing the first versions of virtual Radio. Open Radio Access Network (O-RAN Alliance) or virtual EPC (OMEC Open Mobile Evolved Core, from Open Networking Foundation (ONF). Soon we shall recognize more and more competition in that field.
Concluding
Thinking out loud, the 5G NGC architecture is a must, but. Any new 5G network soon commercializing will be based mainly on 5G NSA architecture. It is simpler and faster to deliver the eMBB case. Implementation of additional 5G radio units (RRU) in existing locations is simple. It let delivering a simple broadband solution with higher speed and relatively lower latency. The operational effort for the operator and vendor.
The 5G SA implementation today may look difficult due to a lack of terminal support. Qualcomm’s modem “X50” do not support yet 5G SA core network protocols. Qualcomm “X55” supports higher speed and 5G SA is planned for the end of the year 2019. Huawei’s “Balong 5000” modem is supporting SA according to the specification from the beginning. It will be launched in the second half of the year 2019. Analyzing that aspect from a time perspective, the implementation of 5G SA architecture will take about a year. The massive deliveries of 5G SA-based terminals will meet this time frame, too.
The business case shows that it would be good to start now in parallel to 5G NSA, study and implement of first 5G SA systems.
References:
- ITU-R M.2083
- 3GPP – TS23.501
- ETSI – NGP principles
- O-RAN Alliance
- ONF (Open Networking Foundation)
- Qualcomm
