사설망은 기존 공용망과는 다르게 특정 산업체 또는 기업의 특정 요구사항을 충족하도록 설계된 이동 통신망입니다. 사설망의 주요 특징은 다음과 같습니다. 첫째, 저지연 통신, 신뢰할 수 있는 전송 등을 비롯한 산업체의 특정 요구사항을 충족합니다. 둘째, 특정 기업이 모든 망 자원을 독점으로 사용하고 망 전반을 관리할 수 있습니다. 셋째, 사설망은 공용망과 물리적으로 분리되어 기업의 중요 정보가 외부로 유출되는 것을 막을 수 있습니다. 마지막으로, 기업이 도심과 멀리 위치한 경우(예: 광산업체, 발전소 등), 사설망을 이용하여 안정적인 통신 서비스를 보장받을 수 있습니다.

사설 5G망 이전에, 기업들은 Wi-Fi 또는 LTE망을 이용하여 사설망을 구축하여 이용했습니다. Wi-Fi 기반의 사설망은 장비 및 망 설치 비용이 저렴하면서도 전송 속도가 빠르다는(Wi-Fi 6 기준 9.6Gbps) 장점이 있어 많은 기업이 사설망으로 이용해왔습니다. 하지만 비면허 대역 무선 자원을 이용하기 때문에 망의 용량과 커버리지가 매우 제한적이고 QoS(Quality of Service)를 지원하지 않습니다. 이러한 단점은 여러 산업체의 요구사항을 충족할 수 없어 산업체 내에서 사설망으로 사용하기에는 한계가 있습니다. 또 다른 선택지로는 LTE 기반의 사설망이 있습니다. LTE 기반 사설망은 면허 대역 무선 자원을 사용하기 때문에 무선 자원을 독점하여 사용할 수 있고, Wi-Fi와 비교해 상대적으로 넓은 커버리지와 QoS 지원이라는 장점을 가집니다. 하지만 사설 LTE망은 표준화가 되지 않아 장비가 비싸고 타사 제품과의 호환성에도 문제가 있으며, 산업체를 위한 사설망으로써 특별한 지원이 없다는 단점이 있습니다.

3GPP는 Release 16부터 NPN(Non-Public Networks)이라는 사설망을 대상으로 표준화를 시작했습니다. 사설 5G망은 크게 SNPN(Standalone NPN)과 PNI-NPN(Public Network Integrated NPN), 이렇게 두 가지의 전개 형태(Deployment)를 가집니다. SNPN망은 기존 공용망(PLMN: Public Land Mobile Network)과 독립적으로 전개되는 망이고, PNI-NPN망은 기존 공용망을 이용하여 전개되는 망입니다. 사설 5G망은 산업체 내에서의 이용을 목적으로 초고신뢰 저지연 통신(URLLC: Ultra Reliable and Low Latency Communication) , 대규모 연결(Massive Connections), 네트워크 슬라이싱(Network Slicing), 모바일 에지 컴퓨팅(Mobile Edge Computing) 등의 기능을 지원합니다. 또한, 기존 사설 LTE망의 한계였던 표준화 문제가 해결되어 여러 회사의 장비가 완벽하게 호환되어 장비 및 망 설치 비용이 저렴합니다.

현재 3GPP는 2024년 6월까지 Release 18을 완성하는 것으로 목표하고 있습니다. Release 18은 사설 5G망을 위한 새로운 기능들을 추가로 보강하여 더 많은 산업체와 기업이 내부에서 사설망을 설치할 수 있도록 할 예정입니다. 5G 통신 상용화로 개인 소비자로부터 큰 수익을 올리지 못한 이동 통신사들은 새로운 수입처로 사설 5G망에 주목하고 있습니다.

With increasing 5G deployments around the world, I am sure many of us have upgraded to 5G over last few years. We are in the middle of 5th Generation of mobile revolution currently, and even if the upgrade experience may not have been noticeable, 5G is changing the way we live and is penetrating into our life gradually and incrementally.

5G offers much faster speeds than 4G, but operators knew that just “faster speeds” is not going to be the money-spinner for them this time. LTE networks were able to manage HD/4K video streaming services moderately well; it is questionable if applications offering ultimate Metaverse/XR experiences (that are still some time away) will run on 5G, and there isn’t a pressing need of 8K streaming yet. Still all the operators wished to launch 5G networks as soon as possible. Why?

5G promised a new money-spinner – the enterprise networking market, aka Private-5G. It offers the opportunity to explore a new market, and a rich one. Network infrastructure vendors are excited too, they too have an opportunity to explore this rich new market for their products, and offer their solutions to the enterprise/vertical customers.

Unlike traditional public networks that services general consumers, a private network is intended for the sole use of a private entity, fully customized for its specific needs. There are several reasons why an enterprise or vertical customer deploys private networks. First, it can provide an optimized and tailored functionalities and services to meet the requirements of each industrial application (e.g. low-latency, reliable transmission and so on). Second, network can be fully and exclusively used, easily deployed, and independently managed by the enterprise. Third, the network is isolated from the public network, so, there is less possibility for sensitive data being leaked outside of the enterprise. Last, it guarantees coverage, especially for mines, agricultural lands, factories, or power plants, which are usually located far from urban area. Since it can be deployed at their facilities or location, they can have reliable network connectivity.

Figure 1. Private Network Ecosystem

Wi-Fi has been the preferred choice for enterprise wireless networks for a long time. Relatively cheap to deploy and maintain, it can provide speeds as high as 9.6 Gbps (with Wi-Fi 6). In addition, Wi-Fi networking products have matured with so many customizations over the years that it will take long before an alternate can match their might.

There are use-cases though in which Wi-Fi may not be suitable. Limited coverage and capacity, and lack of QoS assurance are some of the factors that make it not-so-suitable for many enterprises and verticals involved in mission-critical, public safety, defence and manufacturing space, and those requiring e.g. drones and AR/VR/XR based applications, where performance assurance is key.

LTE is another alternative which has gained traction in this space in last few years. It offers QoS centric design, superior coverage and higher level of reliability. With LTE, the throughput capacity of a cell also improved significantly and wide range of sectors started looking more positively at the proposition of private cellular networks for their factories.

A private LTE network can use licensed or shared spectrum and can cater to a wide variety of devices and applications. It can serve devices that require, say, 4K streaming services, and the devices that require low power and low data-rate, simultaneously; it can even be customized to provide different reliability and QoS to different services.

However, there are still some key requirements that the private LTE network cannot meet for enterprises. For example, the concept of private LTE network is not fully standardized one, which means the cost of deployment of the private LTE network can be relatively expensive due to lack of interoperable ecosystem. Additionally, LTE network does not provide specific features (e.g. reliable and low-latency transmission and management of millions of devices and connections) for various applications, such as mission critical services, factory automation services, etc.

3GPP introduced support of "Non-Public Networks (NPN)" in its Release-16 version of specifications, more commonly known as Private 5G. The technology supports URLLC (Ultra Reliable and Low Latency Communication), superior throughput capacity and higher device density as compared to the previous generation which makes it attractive for a number of new use-cases. To add to that, Network Slicing, Edge Computing and Control-User Plane Separation coupled with Network Function Virtualization offer a flexible, extensible and an agile approach to network design, which makes it far more interesting proposition to enterprises.

More importantly, Private 5G introduces native support of NPNs into its architecture and protocols thus avoiding fundamental problems with Private LTE (where support of NPNs was more of an afterthought), while also allowing co-existence with the public networks (PLMNs).

Figure 2(a). SNPNs / Figure 2(b). PNI-NPN(s)

Figure 2(a). shows two simplified architectures of Private 5G networks as proposed by 3GPP in its Release-16 and Release-17 versions of specifications. There are two flavours in which private networks can be deployed: Standalone Non-Public Networks (SNPNs) as shown in Figure 2(a). and Public Network Integrated Non-Public Networks (PNI-NPNs) as shown in Figure 2(b).

SNPNs do not rely on network functions provided by a PLMN, and can be deployed and operated by enterprises themselves. The key features of SNPNs are:

• The combination of a PLMN ID and Network Identifier (NID) uniquely identifies an SNPN.
• For network selection, one or multiple PLMN IDs and list of NIDs per PLMN ID are broadcasted by NG-RAN.
• SNPN-enabled User Equipment (UE) is configured with PLMN ID and NID, Subscription identifier (SUPI) and credentials for the subscribed SNPN.
• SNPN-enabled UE supports the SNPN access mode for network selection.
• UE in SNPN access mode can access PLMN services via SNPN network as depicted in Figure 3.

Figure 3. Access to PLMN services via SNPN networks

PNI-NPNs, on the other hand, are integrated with a PLMN networks. The key features of PNI-NPNs are:

• PNI-NPNs can be deployed on a dedicated network-slice or the dedicated DNN within the PLMN network, while re-using the same frequency band as the public networks.
• PNI-NPNs can be identified by a PLMN ID and a Closed Access Group (CAG) Identifier.
• UE is configured with list of allowed CAG Identifiers, and optionally with time validity information.
• CAG cell broadcasts information so that only UEs supporting CAGs can access the cell.
• Emergency Services can be supported in CAG cells.

SNPNs are typically useful when enterprises need a fully isolated network, preferably with its own IT teams managing the infrastructure. PNI-NPNs, on the other hand, are useful when operators lease (part-of) their own infrastructure for exclusive use by a factory site.

With specialized Private 5G features, it can provide the enterprises with many useful services. In enterprises, what is the most important service? It might be various types of communication among employees. Thanks to large coverage, high data rate, and QoS of Private 5G, employees can use a normal phone call service and even a high-quality multilateral video call service. They can work anytime and anywhere with their handheld devices using the mobile office connected to company’s cloud.

Private 5G also introduces an easy and convenient on-line instant user subscription feature called UE on-boarding and remote provisioning service. Consider a large number of sensors are to be deployed in the oil refinery company for measuring the amount of oil in every tank. As soon as sensors are deployed, with this feature, they are subscribed to company’s private network automatically.

Another useful feature is the remote user authentication and authorization service. Usually, many enterprises have several branch offices or factories located all over the country. Employees, therefore, may frequently visit another branch office or factory for meeting, cooperative work etc. With the remote user authentication and authorization service using their subscription data and credential in home private network, they can use the visited private network located in other sites like their home network.

Private 5G also provides localized services. When users are in some popular places, such as music concerts, stadiums or exhibition venue, they can use the services which are only provided in those area and at some specific time (e.g. live video streaming service of music concerts). Users without subscription to this network can enjoy this high quality service using this private network.

With all these capabilities, Private 5G offers a complete standards-based architecture, and therefore, can cater to various enterprises such as manufacturing, defence installations, public-safety organizations, stadiums and arenas, mission critical services and hospitals, all requiring different level of security and QoS; seamlessly.

3GPP Rel-18 (aka 5G-Advanced) standards are set to complete by June 2024 with further enhancements, and will be an important milestone enabling a number of new use-cases for wider adoption of this technology. These include, hosting of 3rd party enterprise-grade services on an infrastructure owned by a venue operator (e.g. stadiums, airport) to enable a diverse set of use-cases ranging from temporary data connectivity, temporary events and application based network selection.

Samsung has been committed to the development of standards for Private 5G in 3GPP since initial phases and is an active contributor to support for localized services, security aspects and public-network integrated non-public networks. We firmly believe that Private 5G can be an important alternate revenue source for Mobile Network Operators (MNOs) as well as the Infrastructure Vendors.