Quality of Service in 4G/5G networks

Transcription

1 Quality of Service in 4G/5G networks Prerequisite for Critical Communications Services White Paper 1

2 Contents Executive summary... 3 Mission critical users require high service availability... 3 QoS mechanisms offered by 4G... 4 QoS mechanisms offered by 5G... 6 Considerations when implementing QoS in an MNO environment... 6 QoS when outside 4G/5G coverage... 6 Comprehensive experience of Airbus at your service... 7 Conclusion... 7 Disclaimer The contents of this document are copyright 2017 Airbus Defence and Space. All rights reserved. This is not a contractual document. The content of this document may be downloaded and copied for personal use only. No other rights, license or use of this document or any other intellectual property rights of Airbus Defence and Space is granted herein. Airbus has used best effort to put together this document. The content of this document is provided as is, without warranties of any kind with regards its accuracy or reliability, and specifically excluding all implied warranties, for example of merchantability, fitness for purpose, title and non-infringement. In no event shall Airbus Defence and Space be liable for any special, indirect or consequential damages, or any damages whatsoever resulting from loss of use, data or profits, arising out of or in connection with the use of the document. Airbus Defence and Space reserves the right to revise the document or withdraw it at any time without prior notice. Airbus Defence and Space, Tactilon and Tetrapol are registered trademarks of Airbus Defence and Space. Other product names and company names mentioned herein may be trademarks or trade names of their respective owners. 2

3 Executive summary Today s high-end narrowband PMR technologies (TETRA, Tetrapol, P25) are used widely by mission critical organizations. Communication solutions implemented with these technologies are dedicated systems offering services that match the operational procedures of mission critical users. These solutions offer high service availability and high quality of service. One of the current trends in next generation solutions for mission critical users is the use of commercial 4G, later on 5G networks. Although this will keep investments to a minimum, these networks may not be able to offer the high service availability and high quality of service needed by mission critical users. This document focuses on traffic prioritization, one of the key criteria for high quality of service. Current narrowband systems offer versatile prioritization mechanisms. These need to be available also in commercial mobile network operators (MNO) networks used by mission critical users, but in addition two further prioritization cases must be addressed - consumers vs mission critical users and voice or interactive video vs data applications. Prioritization has always been a complicated question, and is becoming even more so with next generation solutions based on commercial MNO networks. Mission critical users have five main requirements for prioritization. It must be possible to: - Define priorities between mission critical users, consumers and other users - Define priorities between different mission critical users/user organizations - Define priorities based on service type (e.g., voice/signaling/data) and application - Guarantee that emergency calls initiated by a mission critical user are always served - Guarantee service to mission critical users during disasters or other extreme conditions, including cyber-attacks. Mission critical users require high service availability Critical communications solutions are used by governmental public safety authorities, such as police and border guards and other critical users like energy and transportation companies. Common to all these user segments is the need for very reliable communications, very high availability and special operational needs, such as group communication. Public safety users also need uncompromised security and wide geographical coverage, typically much wider than commercial mobile operators offer. These are qualities that current commercial services simply do not come close to offering. In addition, mission critical requirements cannot be met with the QoS features offered by 2G/3G networks. This highlights the need for good 4G/5G coverage and availability, both of which can be improved with national roaming. The value of high availability and reliable communications to public safety users is emphasized when we ask police officers about the most important tool they carry - the answer is a TETRA/Tetrapol/P25 radio. It offers a reliable and secure way to communicate with the control center and with other mission critical users in the field. Occasionally the radio device is literally a police officer s lifeline. And in those situations, when they push the button on their radio, they simply must get an immediate connection. There are many capabilities that make a mobile network compliant with critical communications requirements. They include the following: High availability and resilience The network must be designed, implemented and maintained with the aim of providing high availability and resilience. Measures typically include additional base stations for public safety coverage and improving resilience with rigid single-point-of-failure analysis, including the power supply of radio sites. The analysis must cover all areas of the solution radio access, transmission, core elements, terminals and applications. Also, daily network operations need to be adapted for the 24/7 needs of mission critical users. Prioritization of public safety users The priorities of the network need to be designed to guarantee that mission critical users get radio and other network resources in all situations. In practice, this means assigning them higher priorities than for consumers or enterprise users. There can also be different mission critical user organizations with different priorities. 3

4 Prioritization of traffic classes Mission critical users have different applications, for example Push-ToTalk (PTT) services, video and data queries. These make different demands on traffic handling and so users can have different prioritization levels for different applications. Management of extreme conditions In extreme conditions, networks may experience exceptionally high levels of traffic, far beyond the day-to-day norm. These situations can be due, for example, to terror attacks, major accidents or disas- Critical Communications QoS needs Management of extreme conditions Prioritization of traffic classes ters. Exceptional circumstances by their nature are unpredictable and difficult to plan for. Hence the networks must be able to adapt very quickly to exceptional mission critical load. There can be a very large number of first responders in a small geographical area creating heavy traffic, with many thousands of users served by the same base station. The command structure can also be very different to everyday operations. This calls for exceptional communications arrangements, not only at the incident scene, but across a wider area as well. Prioritization of Public Safety users High availability and resilience QoS mechanisms offered by 4G Mobile broadband IP communication for mission critical users may be provided by 4G (LTE) technology as standardized by 3GPP and implemented by telecom vendors. The technology offers Quality of Service (QoS) features capable of prioritiz- ing certain users and traffic flows. Today, 3GPP is starting work on the 5G standard. It is expected to take a few years to develop, but the initial high-level architecture concepts are already taking shape. 4G Architecture UTRAN SGSN GERAN HSS S3 S6a MME S1-MME S4 S10 LTE-Uu 4 Gx S11 E-UTRAN UE S1-U Serving gateway PCRF S12 S5 PDN gateway Rx SGi IP Services The 4G high level architecture includes user equipment (UE), radio access, E-UTRAN and core network elements. It also supports interworking with 2G (GERAN) and 3G (UTRAN) accesses. The concept of QoS in LTE is based on bearers. An LTE bearer is a transmission path through the infrastructure and radio interface with a defined capacity, latency and packet loss. Based on the requirements, a proper bearer can be allocated either dynamically or statically (subscription-based). When a terminal attaches to the network it always gets a subscription-based default bearer. Additional, dedicated bearers can also be set up based on the subscription or can be added later when

5 the need arises. Dynamic control of QoS can be triggered by application servers using a 3GPP Rx interface. For mission critical communica tions, it is essential to ensure that the communication service is also pro vided if the network or parts of it are congested. The 4G standard provides a good tool set for managing QoS and prioritization of certain subscribers and traffic flows. These include: 4G Quality of Service Applications / Services Radio Bearer UE S1 Bearer enodeb S5/S8 Bearer Serving GW PDN GW 1. Access Class Barring (ACB): Prioritization of terminal classes in the radio interface when attaching to the network uses the ACB feature. When the radio interface is massively overloaded, a terminal may not even be able to tell the network its identity or the prioritized status of its request due to the unmanaged co-channel interference caused by other terminals. When such a state is detected, a base station can bar certain terminal classes. There are Access Class (AC) values 0 to 15. All terminals have an Access Class from AC0 to AC9. Public safety terminals can also have AC14 (Emergency Services) or AC12 (Security Services). Consumer terminals making an emergency call can also have AC10. If a congested base station bars AC0-AC9 terminals or a subset of them, only public safety terminals with AC12/AC14 and terminals attempting an emergency call with AC10 will gain access to the network. The rest are either barred for a set time or with a particular probability, which the terminal must adhere to. 2. Allocation and Retention Priority (ARP): Prioritization in bearer admission control for attached terminals using ARP has three components: a. ARP priority (1-15) where 1 is the highest value. Public safety may use values 1-8 b. Pre-emption capability indicator (PCI) is a one-bit flag c. Pre-emption vulnerability indicator (PVI) is a one-bit flag. ARP is part of a subscribed QoS profile in the Home Subscriber Server (HSS) for the default bearer. ARP is allocated by the Policy and Charging Rules Function (PCRF) and set by the Packet Gateway (PGW) for dynamic QoS of dedicated or modified default bearers. ARP values are used for deciding whether a bearer can be admitted or pre-empted if there is insufficient capacity available. ARP is not used by schedulers or packet queue management. 3. QoS Class Identifier (QCI): Prioritization in scheduling and queuing of admitted flows uses QCI which can have values Each value is associated with three attributes: a. Priority b. Packet delay budget c. Packet error loss. QCI values are used for selecting scheduling weights, queue thresholds, link-layer configuration and IP transport Differentiated Services Code Point (DSCP) mapping. QCI values are reserved for standardization and 3GPP has already standardized some of these. QCI 9 is used for the best effort traffic and most of the current commercial subscriber flows are classified for QCI 9. QCI 1 and QCI 5 can be used for commercial voice (e.g. VoLTE) flows and signaling. QCI values for public safety have been standardized in 3GPP rel.12. They are QCI 65 for Guaranteed Bit Rate (GBR) bearers used for the mission critical user plane (e.g. MCPTT voice), QCI 69 for Non-guaranteed Bit Rate (NGBR) bearers used for mission critical signaling and QCI 70 for NGBR bearers used for mission critical data. QCI values are operator-specific and their attributes must be provisioned into the network elements as there is no standard way of propagating such information with control signaling. As we will see, 5G s QoS concept addresses this issue. As we have seen, there is a QoS toolbox that can be used for prioritizing mission critical users and flows in LTE networks. It is not as comprehensive as the toolbox in the current PMR systems but the capabilities are good enough to cover most practical uses, if supported by the implementations end-to-end, i.e. terminals, infrastructure, transmission, applications, etc. 5

6 QoS mechanisms offered by 5G QoS when outside 4G/5G coverage 3GPP is working on 5G and the high-level system architecture is already formulated in the normative standard draft and includes the QoS concept for 5G. The QoS concept will be flow-based. Packets are classified and marked with QoS Flow Identifier (QFI). There will be two types of flows: One with standardized QoS profiles and the other with operator-specific QoS profiles. For the first one, only the QFI value is used in the network. For the latter one, QoS attributes are also signaled between the network elements. The 5G QoS flows are mapped in the Access Network to Data Radio Bearers (DRBs), unlike 4G where the mapping is 1:1 between EPC and radio bearers. The 3GPP work on the 5G standard is expected to refine and enrich the QoS concept over the next few years. In most commercial networks the coverage of 2G/3G radio access is better than 4G (and possibly 5G one day). 2G/3G coverage is typically better deep indoors but also in rural areas or offshore. The implemented and deployed QoS capabilities in 2G/3G networks and terminals are not matching those of 4G/5G. However, if some of them are available, e.g. Access Class Barring, they should be used to alleviate the congestion in the 2G/3G coverage area. Part of the public safety needs when out of coverage is device-to-device communication. This is being addressed by 3GPP with ProSe (Proximity Services) feature but the expected performance is not at the level required by mission critical users. Considerations when implementing QoS in an MNO environment A network implementation suitable for mission critical users in an MNO environment shall include two layers - the LTE network and a Critical Communications Service Layer (see the figure below). The LTE network includes all components needed to offer services for consumers. The Critical Communications Service Layer adds services and functionalities specifically required by mission critical users. One of these functionalities is a traffic prioritization management for applications. LTE networks require many different network elements to provide services for users. Typically, MNO network elements are provided by several vendors. Furthermore, different MNO networks operate at different 3GPP release levels. Of course, all relevant features must also be supported by the terminal vendor and used by application clients and servers. The equipment, both infrastructure and terminals, must be verified for compliance. LTE networks, as well as 5G networks, offer several different kinds of parameter classes and parameters which are used as tools to implement traffic prioritization. These need to be implemented according to 3GPP specifications. However, it is expected Critical Communications Services Layer for Mission Critical services Control Centers Applications Critical Communications Service Layer 4G/5G Network User Devices 6 that traffic prioritization for mission critical users will use related parameters in a new way or at least assign new values to these parameters. Furthermore, traffic prioritization for mission critical users is a new area for MNOs, with consumer networks so far providing mostly non-prioritized services for their subscribers. All this means that specific verification is needed for each MNO network to guarantee that traffic prioritization works correctly both for consumers, enterprises and mission critical users, in the infrastructure and in the terminals. For an MNO, there is a recommended step-by-step process for implementing QoS for mission critical use, one that introduces the concept gradually learning in stages and minimizing risks. The first step is to start with data rather than jumping straight to mission critical voice, which is the most challenging service from QoS point of view. It should be remembered that all organizations and countries have different starting points and different targets, so it is not possible to produce one universally applicable plan for all circumstances.

7 Comprehensive experience of Airbus at your service Conclusion Airbus Defence and Space has long experience in mission critical communications. Over several decades in the critical communications business, we have seen many generations of technology and today we are a market leader in large nationwide public safety networks. Although the technologies have been evolving, the basis of customers needs have remained unchanged. Special operational models, very high service availability and uncompromised security are the essential requirements of critical communications customers. The customers of Airbus Defence and Space can be confident that whatever the technological solution, these needs are driving the development of new products and solutions. Airbus Defence and Space is experienced in 4G/LTE technologies and how to apply them in critical communications. Airbus has a solution portfolio called Tactilon Suite which implements the Critical Communications Service Layer. With Tactilon Suite the capabilities of TETRA/Tetrapol networks and broadband communication can be combined, including smart devices and apps. Airbus is experienced in integrating Tactilon Suite solutions with LTE networks, as well as with commercial mobile operators. The comprehensive expertise and experience of Airbus is at your service when you need to learn more about the QoS functionalities of mobile broadband technologies and how to apply them with critical communications. Meeting the needs of public safety organizations is challenging. The way they operate and what they are expected to achieve means they must have excellent communications, continuously available. With careful design, in the future these requirements can be met by 4G and 5G networks, which offer a good set of mechanisms to provide public safety users with the priority they need. It is also important that the design balances the needs of consumers and public safety users sharing an MNO network. Conversely, public safety requirements cannot be met with the QoS features offered by 2G/3G networks. This highlights the need for good 4G/5G coverage and availability, both of which can be improved with national roaming. The Critical Communications Service Layer adds services and functionalities needed by mission critical users. Among these functionalities is a traffic prioritization management. With its extensive expertise and experience of the QoS solutions needed for public safety, Airbus Defence and Space is ready for 4G/5G technologies. We are the right partner to work with MNOs and public safety service providers to achieve demanding, mission critical QoS requirements. Learn more Find out more about how Airbus solutions are bringing more value to TETRA/Tetrapol users by complementing existing services with new broadband capabilities and smart devices. More information is available about Tactilon Suite solutions: If you would like to discuss the requirements of mission critical communications and how they affect the use of LTE technology or mobile operators networks, please contact us: marketing@securelandcommunications.com 7

8 04/2017 Copyright 2017 Airbus Defence and Space. All rights reserved. This document is not contractual. Subject to change without notice. For more information please contact Airbus Defence and Space Hiomotie Helsinki Finland T: Airbus Defence and Space Wörthstraße Ulm Germany T: +49 (0) Airbus Defence and Space MetaPole 1, bld Jean Moulin CS Elancourt Cedex France T: +33 (0)