CBSD devices using CBRS (Citizens Broadband Radio Service) is defined in the USA for Shared Spectrum Access in 4G Band 48 (5G Band n48) in the 3.5GHz spectrum, 3550 MHz to 3700 MHz.
CBRS can be implemented using 4G, 5G or proprietary technology wireless systems
What is a Citizens Broadband Radio Service Device?
As defined by the FCC, an eNodeB which is capable to support CBRS band is referred as Citizens Broadband Radio Service Device. LTE band B42 and B43 mapped to CBRS frequency spectrum. CBSD devices are categorized into two types:
CBSD-Category A :
Category A shall not be deployed or operated outdoors with antennas exceeding a height of 6 meters above average terrain
If it is deployed or operated outdoors with antennas exceeding 6 meters will be classified as, and subject to, the operational requirements of CBSD Category B
Category A base station is permitted Maximum EIRP of 30 dBm (dBm/10 MHz) or 1 Watt
When registering with a spectrum access system (SAS), Category A devices must transmit with their requested authorization status (Priority Access or General Authorized Access), FCC identification number, call sign, user contact information, air interface technology, unique manufacturer’s serial number, and sensing capabilities if supported
CBSD-Category B :
Category B base station is permitted Maximum EIRP of 47 dBm (dBm/10 MHz) or 50 Watt
Its deployment/operation is limited to outdoor and antenna height is expected more than 6 meter above the terrain
Category B base station must be professionally installed
When registering with an SAS, Category B devices must transmit with their requested authorization status (Priority Access or General Authorized Access), FCC identification number, call sign, user contact information, air interface technology, unique manufacturer’s serial number, sensing capabilities (if supported), plus the following additional information: antenna gain, beam-width, azimuth, down-tilt angle, and antenna height above ground level.
End User Device (EUD):
CBRS EUD permitted to Transmit Maximum Power 23dBm or 200 milliwatt
These Device can operate only if they can positively recieve and decode an authorization signal transmitted by CBSD (CBRS base station)
Management, Orchestration and Charging for 5G networks
Key topics for modern 5G networks include Management, Orchestration and Charging. In December 2017, the 3GPP passed two major milestones for 5G by approving the first set of 5G NR specs and by putting in place the 5G Phase 1 System Architecture. These achievements have brought about the need for new management standards, as 5G adds to the ever-growing size and complexity of telecom systems.
3GPP management standards from working group SA5 are approaching another major milestone for 5G. With our studies on the 5G management architecture, network slicing and charging completed last year, we are now well under way with the normative work for the first phase in 3GPP Release 15, which includes building up a new service-oriented management architecture and all the necessary functionalities for management and charging for 5G networks.
SA5’s current work also includes several other work/study items such as management of QoE measurement collection and new technologies for RESTful management protocols. However, this article will focus on the new 5G Rel-15 architecture and the main functionalities, including charging.
5G networks and network slicing
Management and orchestration of 5G networks and network slicing is a feature that includes the following work items: management concept and architecture, provisioning, network resource model, fault supervision, assurance and performance management, trace management and virtualization management aspects. With the output of these work items, SA5 provides specified management interfaces in support of 5G networks and network slicing. An operator can configure and manage the mobile network to support various types of services enabled by 5G, for example eMBB (enhanced Mobile Broadband) and URLLC (Ultra-Reliable and Low Latency Communications), depending on the different customers’ needs. The management concept, architecture and provisioning are being defined in TS 28.530, 28.531, 28.532 and 28.533.
Network slicing is seen as one of the key features for 5G, allowing vertical industries to take advantage of 5G networks and services. 3GPP SA5 adopts the network slice concept as defined in SA2 and addresses the management aspects. Network slicing is about transforming a PLMN from a single network to a network where logical partitions are created, with appropriate network isolation, resources, optimized topology and specific configuration to serve various service requirements.
As an example, a variety of communication service instances provided by multiple Network Slice Instances (NSIs) are illustrated in the figure below. The different parts of an NSI are grouped as Network Slice Subnets (e.g. RAN, 5GC and Transport) allowing the lifecycle of a Network Slice Subnet Instance (NSSI) to be managed independently from the lifecycle of an NSI.
Provisioning of network slice instances
The management aspects of a network slice instance can be described by the four phases:
1) Preparation: in the preparation phase the network slice instance does not exist. The preparation phase includes network slice template design, network slice capacity planning, on-boarding and evaluation of the network slice requirements, preparing the network environment and other necessary preparations required to be done before the creation of a network slice instance.
2) Commissioning: provisioning in the commissioning phase includes creation of the network slice instance. During network slice instance creation all needed resources are allocated and configured to satisfy the network slice requirements. The creation of a network slice instance can include creation and/or modification of the network slice instance constituents.
3) Operation: includes the activation, supervision, performance reporting (e.g. for KPI monitoring), resource capacity planning, modification, and de-activation of a network slice instance. Provisioning in the operation phase involves activation, modification and de-activation of a network slice instance.
4) Decommissioning: network slice instance provisioning in the decommissioning phase includes decommissioning of non-shared constituents if required and removing the network slice instance specific configuration from the shared constituents. After the decommissioning phase, the network slice instance is terminated and does not exist anymore.
Similarly, provisioning for a network slice subnet instance (NSSI) includes the following operations:
Create an NSSI;
Activate an NSSI;
De-active an NSSI;
Modify an NSSI;
Terminate an NSSI.
Roles related to 5G networks and network slicing
The roles related to 5G networks and network slicing management include: Communication Service Customer, Communication Service Provider (CSP), Network Operator (NOP), Network Equipment Provider (NEP), Virtualization Infrastructure Service Provider (VISP), Data Centre Service Provider (DCSP), NFVI (Network Functions Virtualization Infrastructure) Supplier and Hardware Supplier.
Depending on actual scenarios:
Each role can be played by one or more organizations simultaneously;
An organization can play one or several roles simultaneously (for example, a company can play CSP and NOP roles simultaneously).
Management models for network slicing
Different management models can be used in the context of network slicing.
1) Network Slice as a Service (NSaaS): NSaaS can be offered by a CSP to its CSC in the form of a communication service. This service allows CSC to use and optionally manage the network slice instance. In turn, this CSC can play the role of CSP and offer their own services (e.g. communication services) on top of the network slice instance. The MNSI (Managed Network Slice Instance) in the figure represents a network slice instance and CS represents a communication service.
2) Network Slices as NOP internals: network slices are not part of the CSP service offering and hence are not visible to CSCs. However, the NOP, to provide support to communication services, may decide to deploy network slices, e.g. for internal network optimization purposes.
SA5 recognizes the need for automation of management by introducing new management functions such as a communication service management function (CSMF), network slice management function (NSMF) and a network slice subnet management function (NSSMF) to provide an appropriate abstraction level for automation.
The 3GPP SA5 management architecture will adopt a service-oriented management architecture which is described as interaction between management service consumer and management service provider. For example, a management service consumer can request operations from management service providers on fault supervision service, performance management service, provisioning service and notification service, etc.
Network Resource Model (NRM) for 5G networks and network slicing
To support management and orchestration of 5G networks, the Network Resource Model (NRM) representing the manageable aspects of 5G networks needs to be defined, according to 5G network specifications from other 3GPP working groups as well as considering requirements from 5G management architecture and operations.
The 5G NRM specifications family includes 4 specifications: TS 28.540 and TS 28.541 for NRM of NR and NG-RAN, TS 28.542 and TS 28.543 for NRM of 5G core network.
According to content categorization, 5G NRM specifications can be divided into 3 parts:
Requirements, also known as stage 1,
Information Model definitions also known as stage 2, and
Solution Set definitions also known as stage 3.
Identified in the specifications of 5G NRM requirements (TS 28.540 and TS 28.542), the NRM of 5G network comprises NRM for the 5G core network (5GC) and NRM for 5G radio access network (i.e. NR and NG-RAN). The 5GC NRM definitions support management of 5GC Network Functions, respective interfaces as well as AMF Set and AMF Region. The NR and NG-RAN NRM definitions cover various 5G radio networks connectivity options (standalone and non-standalone radio node deployment options) and architectural options (NR nodes with or without functional split).
The 5G Information Model definitions specify the semantics and behavior of information object class attributes and relations visible on the 5G management interfaces, in a protocol and technology neutral way (UML as protocol-neutral language is used). The 5G Information Model is defined according to 5GC, NR and NG-RAN specifications. For example, in 3GPP TS 38.401, the NR node (gNB) is defined to support three functional split options (i.e. non-split option, two split option with CU and DU, three split option with CU-CP, CU-UP and DU), so in the NR NRM Information Model, corresponding Information Object Class (IOC) is defined for each network function of gNB specified, and different UML diagrams show the relationship of each gNB split option respectively. Further, in the 5G Information Model definitions, the existing Generic NRM Information Service specification (TS 28.622) is referenced to inherit the attributes of generic information object classes, and the existing EPC NRM Information Service specification (TS 28.708) is referenced for 5GS / EPS interworking relationships description.
Finally, NRM Solution Set definitions map the Information Model definitions to a specific protocol definition used for implementations. According to recommendation from TR 32.866 (Study on RESTful based Solution Set), JSON is expected to be chosen as data modelling language to describe one 5G NRM Solution Set.
Fault Supervision of 5G networks and network slicing
Fault Supervision is one of the fundamental functions for the management of a 5G network and its communication services. For the fault supervision of 5G networks and network slicing, the following 3GPP TSs are being specified:
1) TS 28.545 “Management and orchestration of networks and network slicing; Fault Supervision (FS); Stage 1”, which includes:
The use cases and requirements for fault supervision of 5G networks and network slicing.
The definitions of fault supervision related management services (e.g. NetworkSliceAlarmAcknowledgement, NetworkSliceAlarmListReading, NetworkSliceAlarmClearance, NetworkSliceAlarmNotification, NetworkSliceAlarmSubscription, etc.)
2) TS 28.546 “Management and orchestration of networks and network slicing; Fault Supervision (FS); Stage 2 and stage 3”, which includes the definition of:
Interfaces of the fault supervision related management services; (Stage 2)
Notifications; (Stage 2)
Alarm related information models (e.g. alarmInformation, alarmList, etc.); (Stage 2)
Solution set(s) (e.g. RESTful HTTP-based solution set for Fault Supervison); (Stage 3)
New event types and probable causes if necessary.
Assurance data and Performance Management for 5G networks and network slicing
The 5G network is designed to accommodate continuously fast increasing data traffic demand, and in addition, to support new services such as IoT, cloud-based services, industrial control, autonomous driving, mission critical communications, etc. Such services may have their own performance criteria, such as massive connectivity, extreme broadband, ultra-low latency and ultra-high reliability.
The performance data of the 5G networks and NFs (Network Functions) are fundamental for network monitoring, assessment, analysis, optimization and assurance. For the services with ultra-low latency and ultra-high reliability requirements, any faults or performance issues in the networks can cause service failure which may result in serious personal and property losses. Therefore, it is necessary to be able to collect the performance data in real-time (e.g., by performance data streaming), so that the analytic applications (e.g., network optimization, SON, etc.) could use the performance data to detect any network performance problems, predict the potential issues and take appropriate actions quickly or even in advance.
For network slicing, the communication services are provided on top of the end-to-end network slice instances, so the performance needs to be monitored from end-to-end point of view.
The end to end performance data of 5G networks (including sub-networks), NSIs (Network Slice Instances) and NSSIs (Network Slice Subnet Instances) are vital for operators to know whether they can meet the communication service requirement.
The performance data may be used by various kinds of consumers, such as network operator, SON applications, network optimization applications, network analytics applications, performance assurance applications, etc. To facilitate various consumers to get their required performance data, the following items are being pursued by this WI:
A service based PM framework and a list of PM services as described in the table below:
Management service name
Management service description
NF measurement job control service
The management service for creating and terminating the measurement job(s) for the NF(s).
NF measurement job information service
The management service for querying the information of the measurement job(s) for the NF(s).
NF performance data file reporting Service
The management service for reporting the NF performance data file.
NF performance data streaming service
The management service for providing streaming of NF performance data.
NSSI measurement job control service
The management service for creating and terminating the measurement job(s) for the NSSI(s).
NSSI measurement job information service
The management service for querying the information of the measurement job(s) for the NSSI(s).
NSSI performance data file reporting Service
The management service for reporting the NSSI performance data file.
NSSI performance data streaming service
The management service for providing streaming of NSSI performance data.
NSI measurement job control service
The management service for creating and terminating the measurement job(s) for the NSI(s).
NSI measurement job information service
The management service for querying the information of the measurement job(s) for the NSI(s).
NSI performance data file reporting Service
The management service for reporting the NSI performance data file.
NSI performance data streaming service
The management service for providing streaming of NSI performance data.
Network measurement job control service
The management service for creating and terminating the measurement job(s) to collect the network performance data that is not specific to network slicing.
Network measurement job information service
The management service for querying the information of the measurement job(s) to collect the network performance data that is not specific to network slicing.
Network performance data file reporting service
The management service for reporting the network performance data file that is not specific to network slicing.
Network performance data streaming service
The management service for providing network performance data streaming that is not specific to network slicing.
Performance measurements (including the data that can be used for performance assurance) for 3GPP NFs;
End to end KPIs, performance measurements (including the data that can be used for performance assurance) for NSIs, NSSIs and networks (where the performance data is not specific to network slicing).
Management and virtualization aspects of 5G networks
For 5G networks, it is expected that most of the network functions will run as software components on operators’ telco-cloud systems rather than using dedicated hardware components. Besides the virtualization for Core Network (including 5GC, EPC and IMS), the NG-RAN architecture is being defined with functional split between central unit and distributed unit, where the central unit can also be virtualized.
SA5 has conducted a study on management aspects of the NG-RAN that includes virtualized network functions, and has concluded in TR 32.864 that the existing specifications (related to management of mobile networks that include virtualized network functions) need some enhancements for 5G. The enhancements are mainly on the interactions between 3GPP management system and external management systems (e.g., ETSI NFV MANO) for the following aspects:
Management requirements and architecture;
Life Cycle Management (e.g., PNF management);
There are gaps identified between 3GPP SA5 requirements and ETSI ISG NFV solutions in terms of the required enhancements, and 3GPP SA5 is in cooperation with ETSI ISG NFV to solve these gaps.
Although the need for enhancements were found in the study for 5G, SA5 has reached the conclusion that they can be the used for 4G as well. So the specifications for management of mobile networks that include virtualized network functions are being made generally applicable to both 4G and 5G networks.
Study on energy efficiency of 5G networks
Following the conclusions of the study on Energy Efficiency (EE) aspects in 3GPP Standards, TSG SA#75 recommended initiating further follow-up studies on a range of energy efficiency control related issues for 5G networks including the following aspects:
Definition and calculation of EE KPIs in 3GPP Systems
Energy Efficiency control in 3GPP Systems
Coordinated energy saving in RAN and other subsystem in 3GPP Systems
Power consumption reduction at the site level
Energy Efficiency in 3GPP systems with NFV
Energy Efficiency in Self-Organizing Networks (SON).
TR 32.972 (Study on system and functional aspects of energy efficiency in 5G networks) aims to:
Identify EE KPI definitions made by ETSI TC EE, ITU-T SG5, ETSI NFV ISG, etc., which are relevant for 5G networks, in addition to definitions made in SA TR 21.866. Such EE KPIs can be defined at various levels, incl. network and equipment levels (potentially, at virtualized network function and virtualized resource level), and per deployment scenario (dense urban, rural, etc.). With 5G, potentially, EE KPIs can be defined at network slice level;
Identify metrics to be defined by 3GPP so as to be able to calculate the above EE KPIs for 5G networks. Such metrics might relate to data volumes, coverage area or energy consumption;
Assess whether existing OA&M mechanisms enable to control and monitor the identified metrics. In particular, check if the IRP for the control and monitoring of Power, Energy and Environmental (PEE) parameters for Radio Access Networks (RAN) (TS 28.304, 28.305, 28.306) can be applied to 5G networks. If not, identify potential new OA&M mechanisms;
Elaborate further on the EE control framework defined in TR 21.866 and identify potential gaps with respect to existing management architectures, incl. SON and NFV based architectures;
Examine whether new energy saving functionalities might enable the 3GPP management system to manage energy more efficiently. In particular, the applicability of ETSI ES 203 237 (Green Abstraction Layer; Power management capabilities of the future energy telecommunication fixed network nodes) to the management of 5G networks is to be evaluated;
Identify potential enhancements in existing standards which could lead to achieving improved 3GPP system-wide energy efficiency.
This study requires interactions with other 3GPP working groups and SDOs working on related topics, including ITU-T SG5, ETSI TC EE, ETSI NFV ISG.
5G Charging system architecture and service based interface
Commercial deployment of the Rel-15 5G System will not be possible without capabilities for Operators to be able to monetize the various set of features and services which are specified in TS 23.501, TS 23.502 and TS 23.503. This is defined under the charging framework, which includes e.g. real-time control of subscriber’s usage of 5G Network resources for charging purpose, or per-UE data collection (e.g. for CDRs generation) which can also be used for other purposes e.g. analytics.
SA5 has investigated, during a study period in 2017, on how charging architecture should evolve, which key features should be specified as part of charging capabilities, and which alternative amongst charging solutions should be selected, to better support the first commercial 5G system deployment. Based on the study results, the charging architecture evolution and selected Rel-15 key functionalities for 5G system are under ongoing normative phase through development of a complete set of specifications (architecture, functionalities and protocols) A brief overview of the charging coverage for the Rel-15 5G system is provided in this article.
Service Based Interface
One key evolution of the charging architecture is the adoption of a service based interface integrated into the overall 5G system service based architecture, enabling deployments of charging functions in virtualized environment and use of new software techniques. The new charging function (CHF) introduced in the 5G system architecture, as shown in the picture below, allows charging services to be offered to authorized network functions. A converged online and offline charging will also be supported.
While offering the service based interface to the 5G system, the overall converged charging system will be able to interface the billing system as for the existing system (e.g. 4G) to allow Operators to preserve their billing environment. These evolutions are incorporated in the TS 32.240 umbrella architecture and principles charging specification. The services, operations and procedures of charging using Service Based Interface will be specified in a new TS 32.290, and TS 32.291 will be the stage 3 for this interface.
5G Data connectivity charging
The “5G Data connectivity charging”, achieved by SMF invocation of charging service(s) exposed by the charging function (CHF), will be specified in a new TS 32.255, encompassing the various configurations and functionalities supported via the SMF, which are highlighted below.
For 3GPP network deployments using network slicing, by indicating to the charging system which network slice instance is serving the UE during the data connectivity, the Operator will be able to apply business case charging differentiation. Further improvements on flexibility in charging systems deployments for 5G network slicing will be explored in future releases.
The new 5G QoS model introduced to support requirements from various applications in data connectivity, is considered to support QoS based charging for subscriber’s usage. 5G QoS-based charging is also defined to address inter-Operator’s settlements (i.e. between VPLMN and HPLMN) in roaming Home-routed scenario.
All charging aspects for data services in Local breakout roaming scenarios will be further considered.
In continuation with existing principles on Access type traffic charging differentiation, the two Access Networks (i.e. NG-RAN and untrusted WLAN access) supported in Rel-15 are covered.
Charging capabilities encompass the various functionalities introduced in the 5G system to support flexible deployment of application functions (e.g. edge computing), such as the three different Session and Service Continuity (SSC) modes and the Uplink Classifiers and Branching Points.
Charging continuity for interworking and handover between 5G and existing EPC is addressed.
In 5G Multi-Operator Core Network sharing architecture (i.e. shared RAN), identification of the PLMN that the 5G-RAN resources were used for to convey the traffic, allows settlements between Operators.
The stage 3 for “5G data connectivity charging” will be available in TS 32.298 for the CDRs’ ASN.1 definition and in TS 32.291 for the data type definition in the protocol used for the service based interface.
Key challenges for 5G include achieving consistent and uniform speeds to users across all regions of metro, suburban and rural. Otherwise “hot zones” with high speed rapidly drop off in capacity as users move away from base stations.
Small Cells and 5G Deployment
Small cells are integral to new 5G network architectures and 5G deployment. 5G Small Cells may operate in sub-6GHz (FR1) or mmWave (FR2) bands depending on coverage and capacity demands
More distributed baseband processing vs More centralized baseband processing for newer Cloud RAN / VRAN / ORAN type architectures
Some graphic elements reproduced courtesy Ericsson
Private 5G Network Deployments
The rise of industrial & warehouse applications of 5G will necessitate “private 5G” deployments with 5G Core “NextGen Core” installed on the premises, for ultra high availability and low latency.
Virtualised and Disaggregated 5G vRAN Architecture Overview : Futureproof vRAN architecture for Next Generation 5G networks
Now in the 5G era, a wide variety of new technologies and services is being introduced. These include LTE-NR Dual Connectivity (EN-DC), NR-NR Dual Connectivity (NR-DC), millimeter wave (mmWave) spectrum, Network Function Virtualisation (NFV), Containerised Network Functions, massive Machine Type Communications (mMTC), Ultra Reliable Low Latency Communication (URLLC), Multi-Access Edge Computing (MEC), Network Slicing and Vertical Services, just to name a few. Here we consider vRAN:
Conventional access systems provide a static network architecture which suffers from some fairly challenging limitations in terms of supporting many of these technologies and services. Consequently, a new 5G access system architecture, referred to as ‘Disaggregated RAN’, aims to overcome many of these challenges by breaking up monolithic network features into smaller components that can be individually re-located as needed without hindering their ability to work together to provide network services. Virtualisation, on the other hand, transitions each of these functions from dedicated hardware to software components, allowing for flexible scaling, as well as rapid and continuous evolution, so that networks can meet the evolving demands of new and existing services with minimal impact to CAPEX and OPEX. The new 5G access system architecture has four distinct characteristics which will be described in the following section along with the benefits provided in comparison with legacy hardware solutions. I.e., CU (Central Unit) / DU (Distributed Unit) split, CU-CP (Control Plane) / CU-UP (User Plane) split, CU virtualisation and DU virtualisation.
1 CU/DU Split Architecture
The gNB is split into a CU and DU for the scalability and DU offloading
In order to overcome an explosion in traffic usage, 5G largely makes use of higher frequency bands than LTE. Doing so introduces challenges in coverage due to the inverse relationship between frequency and cell coverage. Typically, small coverage cells result in more frequent handovers for mobile users and this risks impacting quality of experience if not appropriately managed. If we can increase the number of cells being managed by each individual base station (gNB), then a greater number of handovers can be handled through intra-gNB mobility which has a significantly smaller impact than inter-gNB mobility since the device’s anchor point remains the same. By separating this functionality from the Digital Unit (DU) and centralizing it towards the Central Unit (CU), we can increase the number of cells being managed by each CU, and thus maximize the ratio of intra- vs inter-gNB handovers. At the same time, higher frequency bands also allow the use of wider bandwidth carriers and thus gNBs need considerably more traffic processing capacity compared to LTE eNBs. Compounding on this, when Dual Connectivity is widely used in 5G networks, devices may connect to two different gNBs, but only one of these (the anchor DU) is responsible for processing the split data streams (via Packet Data Convergence Protocol, or PDCP). Thus the PDCP load is concentrated on the PDCP anchor DU, which creates a load imbalance and inefficient resource usage between the PDCP anchor DU (over-utilised) and the non-anchor DU (under-utilised). To mitigate this load imbalance, PDCP aggregation needs to be off-loaded to the CU in a more central site where pooling /resource sharing can efficiently handle the task. For these reasons, 5G deployments are best served by a separated CU that is more centrally located from the DU.
vRAN CU (Central Unit)
● Non-Real time processing such as RRC, PDCP is off-loaded to the central site and the RRC, PDCP resource pool is shared between multiple DUs. ● CU can accommodate multiple DUs to build a large scale gNB. ● CU is typically virtualised on a COTS server for the scalability and flexibility.
vRAN DU (Distributed Unit)
● Real time processing such as RLC, MAC, PHY, RF need to remain close to the local site. ● DU is also virtualised on a COTS server for business agility.
2 CU-CP/CU-UP Split Architecture
The gNB-CU is split into CP and UP for flexible dimensioning and topology
The new 5G services based around massive Machine Type Communications (mMTC), Ultra Reliable and Low Latency Communications (URLLC), Fixed Wireless Access (FWA), and new industry verticals will generate unique traffic patterns compared to typical mobile data service. The Conventional DUs with fixed Control and User Plane (CU/UP) resources, which are typically designed to accommodate such ‘typical mobile data services’, are not well-suited to support the newer traffic patterns. Instead, a more flexible capability to dimension and scale directly in-line the traffic requirements of new types of services is needed. In particular, as Network Slicing and MEC are introduced, the UP should be divisible into multiple entities and allocated wherever needed for optimization of each specific services.
3 CU/DU Virtualisation
The CU and DU are virtualised for the enhanced scalability, flexibility and resource efficiency Along withthe CU/DU split and CU-CP/CU-UP split, container technology can further enhance scalability, flexibility and resource efficiency.
3-1 CU Virtualisation Each component in the vCU can have its own flavour (size) for flexible dimensioning. Traffic loads for control and user planes are balanced between each plane’s components separately to maximize resource usage efficiency. Each component can be scaled on-demand or automatically based on current load status. 3-2 DU Virtualisation Each component in the vDU can have its own flavour (size) for flexible dimensioning. DU components can be scaled out if additional cells are deployed.
Benefits of Virtualised and Disaggregated RAN Architecture
Network evolution through Software upgrade
In traditional, hardware-oriented network solutions, the deployment of new standards, features and services often requires replacement of hardware, particularly when there are changes to lower layer protocols or when there is a need for increased processing capacity. With Virtualisation of the RAN, in which L1/L2 functions are implemented purely through software, the expensive and time- consuming process of hardware replacement can be avoided. Furthermore, as capacity requirements grow due to increased traffic demand, generic off-the-shelf compute hardware can be added to the resource pool – a much more cost-effective proposition than swapping older proprietary hardware for newer proprietary hardware. The end result is that operators are better able to manage and maximize the lifecycle of their hardware, match forecasted growth to CAPEX and reduce overall costs of ownership.
Adoption of well-developed IT technologies
By implementation of Network Function Virtualisation, operators can deploy and manage their network utilizing well -developed IT principles such as Software-Defined Networking, life-cycle management and CI/CD to minimize CAPEX and OPEX.
Scalable gNB beyond DU boundary
With a CU/DU split, the gNB can be scaled flexibly from small (single DU size) to large (accommodating multiple DUs, up to 2048 cells), agnostic of DU hardware types for various deployment environment (e.g. rural, dense urban, D-RAN, C-RAN, Small Cell, mmWave). This is in contrast to the conventional DU architecture, which presents limitations on gNB scale based on the capacity of individual DU hardware.
Mobility optimised vRAN architecture
In a conventional aggregated RAN, as users move around the boundary of different cells being served by different gNBs, service quality can often be degraded due to frequent inter-gNB handovers and packet forwarding between DUs. On the other hand, each CU in a disaggregated RAN can accommodate a much larger number of cells for each gNB, and itself becomes the mobility anchor point, greatly reducing the number of anchor point handovers that occur as users move between cells. For users, the key benefit is a noticeably improved quality of experience and more reliable mobility as inter-gNB handovers and packet forwarding is reduced within the broader CU coverage footprint. When UE moves to neighbor cell, intra-gNB HO of CU/DU split architecture has no RRC/PDCP anchor change, no traffic forwarding during HO procedure and no HO signaling toward the Core Networks compared to inter-gNB HO of conventional DU architecture.
Flexibility in CU-UP deployment
The user plane of CU can be sliced into multiple CU-UPs to support network slicing and multiple CU-UPs can be deployed in independent locations while single CU-CP is deployed in the central site. For the network slicing and MEC scenarios such as low latency services or local-break out applications, CU-UP can be located close to DU while CU-UP for eMBB service remains in central site for the high capacity.
CP/UP independent dimensioning and scaling
With the CP/UP split along with CU virtualisation, CP/UP separated resource allocation and scaling enables to adapt to the traffic patterns which varies according to the services. (FWA, eMBB, mMTC etc.) For 5G network, traffic pattern will be complicated because new services with different usage will introduced. Conventional dimensioning typically designed for mobile service traffic pattern cannot adapt to these various traffic patterns of the new services. For example, mMTC services have high control traffic load and low user traffic load. FWA services have low control traffic load and high user traffic load. Flexible dimensioning and scaling of virtualised and disaggregated RAN well adapted to various traffic patterns can bring resource efficiency as well.
Resource efficiency via resource pooling
In some networks today, a centralised RAN (C-RAN) architecture has been implemented in order to provide benefits in terms of resource pooling, reduce hardware requirements and footprint at the edge and simplify network operations and management overall. However, conventional DUs create a type of hard-limit in the benefit that can be gained from a C-RAN deployment due to the fixed capacity of each DU and the static boundary between each piece of hardware. Through virtualisation of the DU functionality and separation of the network function from the hardware resources it requires, we gain the ability to flexibly allocate and scale resources independently and in a far more granular manner. For example, a conventional DU can experience severe load imbalance in some situations, such as separate DUs assigned between rural and urban areas, or in the case of anchor versus non-anchor DUs in a Dual Connectivity scenario. If we can instead pool the hardware resources independently of each DU function, we can flexibly assign resources to each DU only as needed, mitigating the potential for load imbalance to occur. Overall, this means that fewer resources are required due to gains in statistical multiplexing, i.e. there is less need to provide emergency overload capacity individually for each DU. The flexible dimensioning and scale in/out features of vRAN which enable efficient resource pooling are described in the following section.
Flexible dimensioning with multiple flavours
The vCU (CU-CP, CU-UP) and vDU consist of several components. Specific components have a flavour set for flexible dimensioning. A flavour defines the amount of resources to support certain capacity or performance. vCU&vDU can be built with various combination of flavours considering required network performance and capacity. This flexible dimensioning based on network virtualisation enables optimization in constructing networks in terms of resources such as CPU core and memory.
Automatic/on-demand scale in/out of vCU
According to the each control/user traffic decreases and increases, CP Component and UP Component can be scaled in/out automatically or on-demand manner. This scale in/out enables dynamic resource adaptation to control/user traffic change respectively. Furthermore, because each components share common resources for scaling, resources can be utilised efficiently.
On-demand scale in/out of vDU
As the vDU support on-demand scaling for the DU Component, it does not have to be allocated HW resource of maximum vDU capacity for further network growth at initial deployment stage. Instead, it can start with a number of DU Components only required for the initial deployment. When more cells are required, vDU can increase its cell capacity by scaling-out the DU Component.
L1/L2 acceleration on x86 server
The physical layer and MAC layer of a RAN consist of a set of functions with very high computational complexity: channel estimation and detection, Successive Interference Cancellation (SIC) for MIMO, Forward Error Correction (FEC), scheduling algorithms that handle resource allocation between users with different QoS requirements and channel conditions, and so on. Intel’s Advanced Vector Extension (AVX) instruction set can be applied to many of these functions – especially those related to signal processing that involve vector operations. To further increase the capacity of the vDU, some computation-intensive task with repetitive structures, such as FEC, may be off-loaded to an FPGA, which can be optionally installed into a COTS server via a PCIe interface.
Real time processing technique
User data received from the vCU (i.e. the downlink PDCP packets) passes through a chain of processes in the vDU to become physical layer packets. For successful transmission of these packets over the air, all processing must be completed before the designated time slot begins. Similarly in the uplink, the vDU recovers the information bit stream from the received uplink signals through channel estimation, demodulation and channel decoding, and sends a HARQ feedback to the corresponding user device within the given time budget. In order to meet this timing-stringent operation requirement, L1/L2 tasks in the vDU are carefully designed to be scheduled and completed. IT application software in general show unpredictable response times with a large deviation from the average. The figure below shows how such jittery processing times can affect vDU operation. In the case of conventional task scheduling, generated packets can frequently end up being discarded due to such unexpected delay, degrading link performance due to high packet loss rates.
Performance and capacity optimization
The efficient use of compute resources, as well as accelerated packet processing and networking, are crucial for a competitive vRAN design considering the large amount of data that vRAN must handle. One simple way to see this is to compare the fronthaul bandwidth to the user traffic rate. For example, in 16-QAM, just four bits of user data turns into a pair of I/Q samples composed of about 20 bits to ensure reasonable performance in a noisy, fading channel. In essence, vRAN needs a much higher packet handling capability for the radio-side interface than its backhaul interface. To get the best performance and capacity from x86-based COTS servers, our vRAN adopts various virtualisation techniques, including core pooling and pinning, DPDK and SR-IOV.
Telco grade reliability and availability
We note that in modern societies, it is easy to identify a growing reliance on communications across a variety of sectors, including business, finance and public safety. If a mobile communication service becomes unavailable for even a short period of time, serious collateral damage can result in terms of social disorder and monetary losses. To avoid such chaotic outcomes, each component of a network must maintain a high standard of telco-grade service availability and reliability – and the vRAN is no exception to this. Basic fault recovery and redundancy features commonly available in the IT domain are no sufficient. Our vRAN applies enhanced or newly designed health checks, fault recovery and geo-redundancy techniques to minimize service outages.
Introduction of Virtualised DU in 5G Networks
Virtualised DU for Network Slicing
Through network slicing, 5G networks can effectively and efficiently provide a wide variety of different service types (e.g., eMBB, URLLC, mMTC, etc.) in a given cell. Each network slice has its own service and performance requirement profile. For example, URLLC requires very low millisecond-scale latency and very high reliability in comparison to eMBB, where latency and reliability requirements or more relaxed but bandwidth is a key concern. In the case of mMTC on the other hand, individual traffic volumes are much lower, but reliable device density is of prime importance. 5G networks must be capable of efficiently allocating hardware and radio resources for each of these separate services on a per-slice basis. While a traditional DU may be effective in the deployment of a large number of high-bandwidth, wideband NR cells thanks to the high performance of dedicated hardware technologies such as application-specific integrated circuits (ASICs), as networks begin to target more diverse service types virtualised DUs capable of flexibly adapting to customised traffic profiles will prove to be a valuable and cost-efficient approach.
DU Separation for Secure Network Slice
Some network slice could need dedicated DUs separated from existing DUs to serve services like eMBB. For example, a security service could need extremely high security level to need separate DU not to eavesdrop traffic packets. In the following diagram, on top of existing NR network, Virtualised DU is deployed for secure service slice. You can notice that RU is shared between two DUs through common layer.
The widely deployed distributed RAN was designed nearly 20 years ago in the pre-smartphone 3G era, when few would have foreseen the incredible volume and variety of traffic, devices, and applications that mobile networks carry today. While this outdated architecture has evolved to more centralised models, current solutions do not go far enough to address CSP challenges. CSPs are under pressure to keep up with surging traffic demand and the influx of new devices and applications, while at the same time finding additional service revenue to stabilise ARPU and cut costs to protect profit margins. By extending the benefits of NFV from the core network to the RAN, virtualised RAN is the optimal solution for cost-efficiently increasing capacity, reducing costs, and creating new services. Various vendors have joined forces to create a pre-integrated solution that CSPs can deploy today to start reaping the benefits. The solution delivers carrier grade reliability and predictable performance, low-latency, unrivaled manageability and orchestration, massive scalability, optimised resource utilisation, and flexible deployment options as well as the ability to quickly launch new services through network slicing and service chaining. The pre-integrated vRAN solution and comprehensive professional services mitigate deployment risk and accelerate time-to-market.
Functional Split Options for gNodeB 5G-NR Base Stations
A major benefit of 5G for Mobile Network Operators (MNOs) is the prospect of migrating from custom network nodes to a far more flexible approach that enables network nodes to be implemented in software running on generic hardware platforms. In the core network, this process is in an advanced state, with virtualisation and orchestration techniques from the IT world now being used to deploy network functions automatically at a large scale. The functional “split” is key to achieving efficiency gains.
The process is significantly more difficult in the RAN and backhaul network, and the prize for MNOs is greater here as these functions typically account for 70-80% of Capex. In Release 15, the 3GPP identified various functional splits in the 5G NR RAN gNodeB (base station) that would facilitate this process, identifying eight possible places where the gNodeB function could be split into separate functional units. The most popular of these “split” options are:
Split 0 – gNodeB Integrated Small Cell
Split 2 – 3GPP F1
Split 6 – Small Cell Forum (SCF) nFAPI
Split 7.2 – O-RAN Open Fronthaul
Industry Body Backed Split Option Definitions
3GPP specified the higher layer F1 interface, but additional interfaces at lower layer splits have also been specified by other industry bodies, and offer different relative advantages and disadvantages.
The Split 6 interface protocol is the Network FAPI (nFAPI), specified by the Small Cell Forum, where the MAC and PHY functions are physically separate.
The Split 7 interface has been specified by the O-RAN Alliance, which has adopted the eCPRI interface as its basis. Whereas CPRI passes digitised RF signals to the antenna using a proprietary serial protocol, eCPRI uses Ethernet. Moreover, in O-RAN fronthaul, it is frequency domain samples that are transported between the upper PHY and lower PHY, which leads to advantages.
The Split 8 interface is mainly being considered where there are legacy systems and existing hardware and cabling/fibre can be reused.
5G with Dynamic Spectrum Sharing (DSS) is a game-changer
Wireless Service Providers can tap spectrum currently used for 4G to launch nationwide 5G coverage with a simple network software upgrade, and deploy a “5G Ready” network to operate on 4G today, with easy upgrade to 5G without disruption.
What is Dynamic Spectrum Sharing (DSS)?
Dynamic Spectrum Sharing (DSS) is emerging as a key part of mobile service providers’ 5G strategy. Using cellular base stations with DSS offers the lowest total cost of ownership (TCO) to launch 5G in bands currently used for 4G – enabling nationwide 5G coverage in short time after launch. Dynamic Spectrum Sharing allows an existing LTE carrier to operate 5G New Radio (NR) and LTE simultaneously – with a simple software upgrade. The solution is based on innovative intelligent scheduler algorithms that enable optimal performance as the mix of 4G and 5G devices in the network changes over time.
From the early stages of research into 5G NR, when developers began to map 5G transmissions to time-frequency resources, the developers created the possibility for holes in the 5G transmission grid which could be used for 4G LTE transmissions. This means that, by simultaneously sharing frequency bands which are already available today, service providers can fire up 5G on existing LTE bands without actually shutting off LTE. This means that, as well as having the option to roll out 5G on existing DSS-compatible 4G hardware, operators can keep the LTE network up and running while starting 5G. This can make it far easier for operators to transition to 5G in the coming years.
How does DSS work?
The 5G physical layer is designed to be so similar to 4G in 3GPP that DSS becomes feasible with the same subcarrier spacing and similar time domain structure. DSS is designed to be backwards compatible with all existing LTE devices. communication service providers (CSPs) therefore need to maintain LTE cell reference signal (CRS) transmission. 5G transmission is designed around LTE CRS in an approach called CRS rate matching.
DSS with 5G carrier aggregation (CA) releases the full potential of the technology, especially when combined with standalone (SA) architecture. CA provides the highest data rates while SA maximizes low-band coverage and access to 5G services. DSS will be supported by a growing number of 5G devices from 2020 onwards, with widespread support for devices with DSS, SA and CA available during the course of 2021. The introduction of DSS capability therefore aligns with the growing availability of devices
One option is for DSS to use a single shared baseband card for 4G and for 5G, which obviously precludes a multi-vendor solution for 4G and 5G. The other option is to keep the existing 4G baseband and add a new 5G baseband. The scheduling between the two baseband functions is then based on a fast Xp interface between 4G and 5G. This interface is not open and works only for a single vendor, so CSPs must use the same vendor in 4G and 5G if they use DSS
DSS is a great solution for flexibly refarming spectrum to 5G. Operators can build a “5G ready” network today, operating in 4G, and switch over partially – or fully – to 5G at any later date, without losing back-compatibility for 4G device users
Do the new security and privacy features of 5G require a new SIM card? Simple answer is no. However, the complete answer is more complex.
SIM cards are Smart Cards with data
In this article, we refer to these newer smart cards as Rel 99+ USIM which are compatible with 3GPP Release 1999 (first 3G specifications) and afterwards. These Rel 99+ USIMs can be used to access every generation of mobile networks, including 5G. Such backward and forward compatibility is achieved by the carefully-designed offloading of some computations and storage to mobile phones.
While accessing the 5G system is one thing, the question we have is whether using the “new” security and privacy features of 5G requires a new kind of USIM other than Rel 99+ USIMs which could be used for 4G security. This is a valid question and something which we address below. For the sake of brevity, in this post, we do not touch upon other new features in 5G that do not concern USIM.
SIM Identity and access management (IdaM)
In 5G, subscription permanent identifier (SUPI) could be in two formats, one is the legacy format called international mobile subscriber identity (IMSI) and another is the format newly adopted in 5G called network access identifier (NAI). Furthermore, 5G provides at least two methods of authentication and key agreement (AKA) for accessing the network. One such method, 5G AKA, is an evolution of the authentication method in 4G. Another, called EAP-AKA’, is a method now widely adopted in 5G for broader use of the Extensible Authentication Protocol (EAP) framework.
In any case, from the IdaM viewpoint, the Rel 99+ USIMs that could be used in 4G are still compatible with 5G, in that they can be used to authenticate and gain access to the 5G system. The main reason for this forward compatibility is the fact that there is no need for a new permanent security key shared between USIMs and the network. Another reason is that newer storage and computations required for new security features can be offloaded to mobile phones, like the calculation of a new type of AKA response and new session keys.
The adoption of the EAP framework in 5G means that it is possible for other methods than EAP-AKA’, such as Extensible Authentication Protocol-Transport Layer Security (EAP-TLS), to be used for isolated deployments. In those cases, it could be such that the USIM’s role is skipped. It is also worth noting that, just as with 4G networks, any smart cards older than Rel 99+ USIM (which may be called Rel 98- SIM) cannot be used to access 5G.
5G SIM Privacy
5G has introduced significant privacy enhancements in terms of how permanent and temporary identifiers are used.
An important topic which is use of subscription concealed identifier (SUCI). The SUCI, which basically hides the SUPI over-the-air, can be calculated using standardized schemes like so-called Profile A and Profile B. It also requires some new parameters like public key of the home network, scheme identifier, and routing indicator. While SUCI calculations using Profile A/B can be offloaded to mobile phones, the standards only permit the storage of the new parameters in the USIM. For brevity, in this post we will not discuss the proprietary option where SUCI calculation can be done in USIMs using non-standardized schemes.
Therefore, Rel 99+ USIMs can be used to store the parameters required for SUCI calculation with Profile A/B given that they support creating the necessary files (DF5GS/EFSUCI_Calc_Info/EFRouting_Indicator). This is also true for Rel 99+ USIMs already in the field i.e. if they support some mechanisms like remote file management over-the-air (OTA), then they could be used for storing the parameters required for SUCI calculation with Profile A/B. Otherwise, SUCI will be calculated by mobile phones using the so-called “null-scheme” which is a dummy scheme and does not hide SUPI. In other words, Rel 99+ USIMs that cannot store new parameters required for SUCI calculation could still be used to get access to the 5G system but without the ability to hide the SUPI over-the-air.
Note that there are also other privacy enhancements in 5G like the strict refreshment of temporary identifiers, decoupling of permanent identifiers from paging procedures, and partial confidentiality protection of initial messages. For these features, the USIM’s role is not required in the standards.
Steering of roaming (SoR) and UE parameter update (UPU)
SoR and UPU are two new procedures in 5G between mobile phones and the home network. These new procedures enable the home network to update configuration parameters in mobile phones and/or USIM using control plane signaling. It means that, in 5G, the home network has an alternative to existing mechanisms like over-the-air (OTA) updates that use SMS as transport.
As well as handling of the so-called “secured packet” that mobile phones can basically relay to the USIM, the scope of SoR and UPU procedures include parameters like operator controlled PLMN selector with access technology, default configured network slice selection assistance information (NSSAI), and routing indicator.
Handling of new control plane signaling including security, like calculation and verification of new security tokens, are offloaded to mobile phones. Furthermore, in some cases, storage of parameters is also offloaded to mobile phones like default configured NSSAI and mobile phone’s copy of operator controlled PLMN selector with access technology. Therefore, in such cases, special support from the USIM is not required for SoR and UPU in 5G, which means that Rel 99+ USIMs can be used.
There are other cases when the storage of the new/updated parameters is still done in USIM, like routing indicator (EFRouting_Indicator), USIM’s copy of operator controlled PLMN selector with access technology (EFOPLMNwACT), and any file handling done by the “secured packet”. Even then, Rel 99+ USIMs are still compatible with SoR and UPU in 5G given that they support the necessary file management operations.
5G SIM card Summary
To summarize, impacts on USIMs by relevant security and privacy features that are new in 5G.
from IdaM viewpoint, Rel 99+ USIMs which could be used for 4G are still compatible to get access in 5G.
Regarding SUPI privacy, Rel 99+ USIMs can be used to enable SUCI calculation with Profile A/B as long as they support necessary file management operations. Regarding other privacy features, Rel 99+ USIMs are fully compatible in their current form.
From a perspective of SoR/UPU procedures, Rel 99+ USIMs are compatible in their current form only in some cases, while in other cases compatibility will depend on them supporting necessary file management operations.
Whether/how to use the above mentioned new security and privacy features is in the remit of the network operator and therefore, even in worst case, they will not prohibit access to the plethora of other basic 5G features.
IdaM part – The formats of SUPI (IMSI and NAI) are defined in 3GPP TS 23.003, see clauses 2.2A, 2.2, and 28.7.2. The new type of AKA response is called RES* and new session keys are called KAUSF and KSEAF. See clauses 6.1 in 3GPP TS 33.501 for details. In Annex B of that TS, you will also find details of using EAP-TLS
Privacy part – The formats of SUCI are defined in clauses 2.2B and 28.7.3 in 3GPP TS 23.003. Clause 6.12 and Annex C in 3GPP TS 33.501 contain main details of subscription identifier privacy. Clause 4.4.11 in 3GPP TS 31.102 specifies USIM files specific to 5G
SoR/UPU part – The new security tokens are called SoR-MAC-IAUSF, UPU-MAC-IAUSF, SoR-MAC-IUE, and UPU-MAC-IUE. See the main details of SoR and UPU can be found in clauses 6.14 and 6.15 in 3GPP TS 33.501, Annex C in TS 23.112, and Clause 4.20 in TS 23.502
RadioMobile: Popular software for 5G Network Coverage planning
RadioMobile is a widely-available software package which can be used for 5G Network Coverage planning, including path profiling and clearance criteria, power budgets, choosing antenna sizes and tower heights.
For website for RadioMobile, please see this link here:
For 5G Coverage Planning, the software package can be configured with the characteristics of your required radio network.
CPE types and locations
Link Budget & Fade Margins
The software enables quick and rapid calculation of link budget and fade margins for any frequency band.
The software uses the freely available SRTM terrain data which can download “on demand” for calculation of terrain heights. Combined with LandCover, this enables estimation of trees/forests also.
Line of Sight
The software uses the terrain database to allows quick establishment of available Line of Sight and “what if” adjustment of antenna/tower heights in a 5G radio network design
Radio Fresnel Zone
RadioMobile automatically calculates the Fresnel Zone for any required link, with graphical display enabling quick feasibility and identification of any obstacles to be noted.
Radio Parameters & Network Properties
Any new user to Radio Mobile will have to enter link parameters for the chosen equipment. This includes transmit power, receive sensitivity and antenna gains. Some vendors such as CableFree include this data as a planning service with their products
Radio Mobile: Free to Use
The Radio Mobile software is free to use including for commercial use. Radio Mobile software is a copyright of Roger Coudé. The author notes:
Although commercial use is not prohibited, the author cannot be held responsible for its usage. The outputs resulting from the program are under the entire responsibility of the user, and the user should conform to restrictions from external data sources.
For Further information
For More Information about Microwave Link Planning, we will be delighted to answer your questions. Please Contact Us
Frequency bands for 5G are divided into “sub 6GHz” and “mmWave” bands. “Sub 6” is generally for longer range coverage, with in-building penetration. “mmWave” bands use higher frequencies which offer short range, and no or little penetration of building structures.
This list of 5G frequency bands is taken from the latest published version of the 3GPP TS 38.101,the following tables list the specified frequency bands and the channel bandwidths of the 5G NR standard.
Note that the NR bands are defined with prefix of “n”. When the NR band is overlapping with the 4G LTE band, they share the same band number.