The primary goal of previous generations of mobile networks has been to simply offer fast, reliable mobile data services to network users. 5G has broadened this scope to offer a broad range of wireless services delivered to the end user across multiple access platforms and multi-layer networks.
5G is effectively a dynamic, coherent and flexible framework of multiple advanced technologies supporting a variety of applications. 5G utilizes a more intelligent architecture, with Radio Access Networks (RANs) no longer constrained by base station proximity or complex infrastructure. 5G leads the way towards disaggregated, flexible and virtual RAN with new interfaces creating additional data access points.
5G Architecture 3GPP
Services are provided via a common framework to network functions that are permitted to make use of these services. Modularity, reusability and self-containment of network functions are additional design considerations for a 5G network architecture described by the 3GPP specifications.
5G Spectrum and Frequency
Multiple frequency ranges are now being dedicated to 5G new radio (NR). The portion of the radio spectrum with frequencies between 30 GHz and 300 GHz is known as the millimeter wave, since wavelengths range from 1-10 mm. Frequencies between 24 GHz and 100 GHz are now being allocated to 5G in multiple regions worldwide.
In addition to the millimeter wave, underutilized UHF frequencies between 300 MHz and 3 GHz are also being repurposed for 5G. The diversity of frequencies employed can be tailored to the unique applications considering the higher frequencies are characterized by higher bandwidth, albeit shorter range. The millimeter wave frequencies are ideal for densely populated areas, but ineffective for long distance communication. Within these high and lower frequency bands dedicated to 5G, each carrier has begun to carve out their own discrete individual portions of the 5G spectrum.
Multi-Access Edge Computing (MEC) is an important element of 5G architecture. MEC is an evolution in cloud computing that brings the applications from centralized data centers to the network edge, and therefore closer to the end users and their devices. This essentially creates a shortcut in content delivery between the user and host, and the long network path that once separated them.
This technology is not exclusive to 5G but is certainly integral to its efficiency. Characteristics of the MEC include the low latency, high bandwidth and real time access to RAN information that distinguish 5G architecture from its predecessors. This convergence of the RAN and core networks will require operators to leverage new approaches to network testing and validation.
5G networks based on the 3GPP 5G specifications are an ideal environment for MEC deployment. The 5G specifications define the enablers for edge computing, allowing MEC and 5G to collaboratively route traffic. In addition to the latency and bandwidth benefits of the MEC architecture, the distribution of computing power will better enable the high volume of connected devices inherent to 5G deployment and the rise of the Internet of Things (IoT).
NFV and 5G
Network function virtualization (NFV) decouples software from hardware by replacing various network functions such as firewalls, load balancers and routers with virtualized instances running as software. This eliminates the need to invest in many expensive hardware elements and can also accelerate installation times, thereby providing revenue generating services to the customer faster.
NFV enables the 5G infrastructure by virtualizing appliances within the 5G network. This includes the network slicing technology that enables multiple virtual networks to run simultaneously. NFV can address other 5G challenges through virtualized computing, storage, and network resources that are customized based on the applications and customer segments.
5G RAN Architecture
The concept of NFV extends to the radio access network (RAN) through for example network dis-aggregation promoted by alliances such as O-RAN. This enables flexibility and creates new opportunities for competition, provides open interfaces and open source development, ultimately to ease the deployment of new features and technology with scale. The O-RAN alliance objective is to allow multi-vendor deployment with off-the shelf hardware for the purposes of easier and faster inter-operability. Network dis-aggregation also allows components of the network to be virtualized, providing a means to scale and improve user experience as capacity grows. The benefits of virtualizing components of the RAN provide a means to be more cost effective from a hardware and software viewpoint especially for IoT applications where the number of devices is in the millions.
Network dis-aggregation with the functional split also brings other cost benefits particularly with the introduction of new interfaces such as eCPRI. RF interfaces are not cost effective when testing large numbers of 5G carriers as the RF costs rapidly increase. The introduction of eCPRI interfaces presents a more cost-effective solution as fewer interfaces can be used to test multiple 5G carriers. eCPRI is aimed to be a standardized interface for 5G used for instance in the O-RAN front haul interface such as the DU. CPRI in contrast to eCPRI was developed for 4G, however in many cases was vendor specific making it problematic for operators.
Perhaps the key ingredient enabling the full potential of 5G architecture to be realized is network slicing. This technology adds an extra dimension to the NFV domain by allowing multiple logical networks to simultaneously run on top of a shared physical network infrastructure. This becomes integral to 5G architecture by creating end-to-end virtual networks that include both networking and storage functions.
Operators can effectively manage diverse 5G use cases with differing throughput, latency and availability demands by partitioning network resources to multiple users or “tenants”.
Network slicing becomes extremely useful for applications like the IoT where the number of users may be extremely high, but the overall bandwidth demand is low. Each 5G vertical will have its own requirements, so network slicing becomes an important design consideration for 5G network architecture. Costs, resource management and flexibility of network configurations can all be optimized with this level of customization now possible. In addition, network slicing enables expedited trials for potential new 5G services and quicker time-to-market.
Another breakthrough technology integral to the success of 5G is beamforming. Conventional base stations have transmitted signals in multiple directions without regard to the position of targeted users or devices. Through the use of multiple-input, multiple-output (MIMO) arrays featuring dozens of small antennas combined in a single formation, signal processing algorithms can be used to determine the most efficient transmission path to each user while individual packets can be sent in multiple directions then choreographed to reach the end user in a predetermined sequence.
With 5G data transmission occupying the millimeter wave, free space propagation loss, proportional to the smaller antenna size, and diffraction loss, inherent to higher frequencies and lack of wall penetration, are significantly greater. On the other hand, the smaller antenna size also enables much larger arrays to occupy the same physical space. With each of these smaller antennas potentially reassigning beam direction several times per millisecond, massive beamforming to support the challenges of 5G bandwidth becomes more feasible. With a larger antenna density in the same physical space, narrower beams can be achieved with massive MIMO, thereby providing a means to achieve high throughput with more effective user tracking.
5G Core Architecture
The 5G core network architecture is at the heart of the new 5G specification and enables the increased throughput demand that 5G must support. The new 5G core, as defined by 3GPP, utilizes cloud-aligned, service-based architecture (SBA) that spans across all 5G functions and interactions including authentication, security, session management and aggregation of traffic from end devices. The 5G core further emphasizes NFV as an integral design concept with virtualized software functions capable of being deployed using the MEC infrastructure that is central to 5G architectural principles.
Differences from 4G Architecture
Changes at the core level are among the myriad of architectural changes that accompany the shift from 4G to 5G, including the migration to millimeter wave, massive MIMO, network slicing and essentially every other discrete element of the diverse 5G ecosystem. The 4G Evolved Packet Core (EPC) is significantly different from the 5G core, with the 5G core leveraging virtualization and cloud native software design at unprecedented levels.
Among the other changes that differentiate the 5G core from its 4G predecessor are user plane function (UPF) to decouple packet gateway control and user plane functions, and access and mobility management function (AMF) to segregate session management functions from connection and mobility management tasks.
5G Architecture Options
Bridging the gap between 4G and 5G will require incremental steps and a well-orchestrated game plan. Emblematic of this shift will be the gradual transition from stand-alone mode to non-standalone mode 5G architecture options. The 5G non-standalone standard was finalized in late 2017 and utilizes existing LTE radio access and core networks as an anchor, with the addition of a 5G component carrier. Despite the reliance on existing architecture, non-standalone mode will increase bandwidth by tapping into millimeter wave frequencies.
5G standalone mode is essentially 5G deployment from the ground up with the new core architecture and full deployment of all 5G hardware, features and functionality. As non-standalone mode gradually gives way to new 5G mobile network architecture deployments, careful planning and implementation will make this transition seamless for the user base.
5G Geographical Architecture Adoption
The infrastructure inherent to standalone 5G deployment will necessitate a worldwide step function in 5G integration for various geographical regions. Technology leading regions such as North America, Asia and Europe are already beginning limited deployment while other nations around the globe follow closely behind. A total of 55 live networks are expected to be in service by the end of 2019. Proximity of neighboring countries and a vast proliferation of carriers will make the rollout particularly challenging in Europe. To address this challenge, the European Commission has created a 5G for Europe action plan to jump start progress and create a roadmap for deployment in all EU states by the end of 2020.
Industrial nations such as China, Japan and India are heavily invested in the practical as well as the financial implications of the 5G conversion. New antenna, infrastructure hardware and software technologies create a bonanza for electronics and software design and manufacturing industries around the world, so speedy deployment has been emphasized. One of the largest telecom providers in India has already upgraded their entire network for 5G compatibility, and China Mobile is expected to create 10,000 5G base stations by 2020.
Security in 5G Architecture
5G implementation will engender tremendous performance benefits and diversity of applications through extensive use of cloud-based resources, virtualization, network slicing and other emerging technologies. With these changes come new security risks and additional “attack surfaces” exposed within the 5G security architecture.
5G is building on the security practices of past mobile technology generations, yet the trust model has become much more expansive with more players involved in the service delivery process. The IoT and user propagation create an exponentially higher number of endpoints with many of these traffic inputs no longer supervised by human hands.
Among the improved 5G security features detailed by the 3GPP standards are unified authentication to decouple authentication from access points, extensible authentication protocols to accommodate secure transactions, flexible security policies to address more use cases and subscriber permanent identifiers (SUPI) to ensure privacy on the network.
As 5G deployment continues and critical performance nodes become increasingly virtualized, operators will need to continually monitor and assess security performance. Adherence to best practices means end-to-end network security monitoring throughout the system architecture, devices and apps.
Undoubtedly, 5G will deliver the exponential speed enhancement users have grown accustomed to with each new generation of mobile networks, but speed is just the beginning. The expected changes to industries ranging from personal transportation to manufacturing and farming will be so significant that many have dubbed 5G the next Industrial Revolution. At the heart of this paradigm shift is the multi-faceted 5G architecture, with MEC, NFV massive MIMO and a cloud-aligned, service-based core architecture working in concert to deliver the new wave of services. 5G test solutions designed to accommodate this architectural seed change will be the true enablers of the forthcoming 5G transition.
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