More networks, more possibilities: roaming from private to public

On 02-10-2023
Reading time : 3 minutes

Private LTE and 5G mobile networks are on the rise. As more use cases for them emerge, the ability to roam from private networks to public networks becomes more important. How can telcos service this new and growing need? A number of different approaches are possible.

The number of private LTE/5G networks in the public domain continues to grow. According to Analysys Mason’s Private LTE/5G networks tracker, the number of private networks reached 448 in Q1 2023, up from 338 a year earlier – and of those 50% use 5G. Why the rapid growth? Much of it is because new use cases continue to emerge that leverage private networks. 

Increased Internet of Things (IoT) adoption is a factor, driving uptake of private networks in manufacturing and industrial environments. Mission-critical life and health support devices, security requirements, and high occupancy are all seeing increased demand for private networks in healthcare. Offices and corporate campuses are another area of potential as Wi-Fi isn’t always available. So are stadiums and arenas, where high levels of users create congestion on public cellular networks. 

According to IDC, the private LTE and 5G infrastructure market will reach a value of $8.3 billion by 2026 as businesses see the growing value of this connectivity.

Pros and cons of private networks 

Private networks offer a range of benefits that attract both organizations and users. First, you are able to customize features like coverage, security, reliability, speed, SLAs, all specifically to your requirements. Second, private networks can deliver optimum quality of service (QoS), because traffic remains local. This works particularly well for use cases that require very low latency. Third, private networks offer good indoor or local coverage and QoS, ideal for office sites and business campuses with many end-users performing business-critical tasks.

Forrester has highlighted manufacturing as a particular success for private networks, where private 5G has enabled factory-floor automation as well as augmented reality and virtual reality (AR/VR) and HD video applications. It is being used for remote inspection and surveillance, quality assurance, remote monitoring, predictive maintenance, employee safety solutions, and more.

Private networks can be set up at a company level, or even site level, such as in the use case of enabling remote maintenance or robots at an industrial site. 

But there are some drawbacks to private networks. Depending on the host country’s domestic regulations, you may need to acquire dedicated licensed spectrum. In addition, private 5G networks are complicated, and require the skills to manage them in-house – and not all companies have that. So some may need to invest in training programs or outsourcing. Private networks also need an increase in capital and operational expenditures for spectrum and equipment acquisition, implementation, operations and maintenance.

However, there are plenty of companies offering private network solutions to the market, including traditional telcos and telecom equipment providers, as well as smaller, new entrants that are proposing their own solutions.

The roaming factor: private to public networks 

Users of private networks, which can be either people or objects, have been defined, identified, and set up to use a specific private network. As such, they are not by default defined as users of any public networks. But these users or devices may need to move outside of their private network boundaries, potentially nationally or even internationally. And that requires a type of roaming.

Consider an airline that has set up a private network in its home airport to capture data from its aircraft to increase efficiencies or improve passenger experience. This airline may obviously want to keep collecting data wherever its planes travel to in the world. And they would need a mechanism that enables them to do that.

Today, there are a few ways that private network users can roam between private and public networks, and make calls or send data over public networks. They include: 

1. Private network users/connected objects have another identity on the public network 

In practice, this means having a second SIM installed in the smartphone or connected object, or an e-SIM card, dedicated to the public network. In this case, the private network user/device will have two mobile country codes (MCC) and mobile network codes (MNC) plus also two telephone numbers.

This approach has pluses and minuses to it. On the plus side, it is easy to implement, since the public network provider does not have to open its network to other users or identities. And for the private network operator, it only needs to manage one relationship with one public network provider. The private network benefits from all the roaming agreements that the public network provider has in place.

On the minus side, terminating SMS or voice calls to the user or object is not possible. This is because the location of the device at any given time is unknown, and therefore which identity, private or public, it is using. So the calling party does not know which number to call. In the case of IoT, traffic is largely data, which lessens the problem, and all that is required is internet access. 

Furthermore, the user must be registered into two home location register/home subscriber service/unified data management (HLR/HSS/UDM) databases, plus also the database of the public network and that of the private network, and two encryption keys. It’s a complicated exercise.

2. A unique identity with a dual international mobile subscriber identity (IMSI)  

Here the private network device requests a new temporary public identity when it connects to the public network. The private network operates effectively as an MVNO of the public network. And the connected device only needs to have one SIM or e-SIM that carries two IMSI, one for the private network and one for the public network.

If the device is “roaming” at a local or national level, and attempting to travel from a private network to a public one, a roaming agreement with one or more national public operators will suffice. However, if roaming needs to happen at international level and potentially in multiple countries, it becomes more complicated. This is because the private network operator will need to negotiate, set up, test and then manage all the roaming agreements. 

This complexity means it can be in the private network operator’s interests to outsource some of the process to its public network partner. With a hub solution, such as Orange Wholesale International’ Open Roaming Hub, the public network operator can have access to numerous roaming partners with one connection, while also retaining the flexibility to negotiate its own roaming tariffs with those it is interested in.

There’s another option for private network operators since they often don’t have the time or in-house expertise for this. They can use a solution like Orange Wholesale International Roaming Sponsor, which lets them benefit from all the roaming agreements, including the tariffs, of their chosen partner.

3. Use 5G slicing to create a VPN built on a public network  

According to analyst TBR Insights, “The private 5G network market is expected to scale in the middle of this decade as key 3GPP standards are completed and the device ecosystem broadens.”

This presents the possibility for using slicing. Public networks could propose 5G private networks to customers via a “slice” that is dedicated to the private network and its users. This gives customers the opportunity to customize functionalities, security or QoS, without the need to invest heavily in dedicated private infrastructure. Although a private radio network may still be required, many other network components would be offered by the public network provider. Under this approach, the private network would use the MCC/MNC of the public operator. 

The main benefit of this approach is that private network users can automatically use the public network even if the private network is not available, because the user is outside the private network’s boundaries or because 5G SA is not available at their location.

Early days but big potential 

As it stands, there is no real perfect solution for roaming between private and public networks, but in time there will need to be one. For now, much depends on the private network operator’s needs, budget, resources and skills, to set up and manage the solution. Local regulatory rules can also limit what can be done. So, depending on needs, several of these solutions can be combined to enable roaming between private and public networks. 

And as private networks continue to find new use cases and grow rapidly in number, it’s only a matter of time until this type of roaming becomes a more pressing issue.

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