January 9th, 2020 - Telecom, Roaming
By Nina Le-Richardson, Director of Product Management
With commercial 5G service popping up in markets on six continents, how will 5G roaming work? 5G will provide users with global services based on the ability to roam and access local infrastructure in visited countries.
Enhanced global roaming is a big advantage for 5G and its ability to balance user control with convenience can’t be understated. The continuity of global services and a consistency of experience for users, when they aren’t in their home network or country, is a big differentiator for 5G roaming. However, you should expect 5GC roaming to be a five-to-10 year roll out.
Why so long you might ask?
Standalone (SA) 5GC roaming is not anticipated in the near term due to complexity of network slicing, massive capital investment involved, business models and the charging principles are not fully defined. As a result, the incentive to replace 3G/4G technology could be small and it is expected that the technology will co-exist alongside 5G for some time. However, when operators implement the 5G core network protocol stack they can utilize all of the options which are deployed in a network simultaneously.
When more 5GC networks are deployed, roaming between these 5GC networks will also be introduced. The signaling between 5GC networks needs to be secure or even encrypted. This will be discussed in more detail in an upcoming blog post.
The reality is that most existing operators will deploy Non-Standalone (NSA) Option 3. 5G NSA Option 3 will not introduce any changes to the existing roaming architecture and procedures. It is up to the visiting mobile operator to allow inbound roamers to use 5G NSA Option 3 and is backwards compatible to 4G.
Option 3 is defined as E-UTRA New Radio-Dual Connectivity (EN-DC) and is a 3GPP feature introduced to support New Radio 5G data speeds with existing LTE core and radio networks without introducing 5G core network elements. EN–DC Option 3 can be a useful feature for heterogeneous networks to offer increased data throughput at 5G speeds while offering existing reliable 4G roaming coverage.
The term “dual connectivity” therefore actually refers to dual RAN connectivity. 5G NSA Option 3 will not introduce any changes to the existing LTE international roaming footprint or roaming business standards and processes. Once the VPMN (Visited Public Mobile Network) has deployed Option 3, the VPMN must configure their EN-DC deployment to allow inbound roamers to leverage 5G speeds. EN-DC is backwards compatible to 4G; therefore Option 3 will enable less service interruption for roaming as SA 5GC rollouts are underway.
EN-DC also ensures better system reliability by reducing service interruptions due to higher propagation loss in millimeter wave or non-line of sight situations in Massive MIMO. Over time, more spectrum will be moved from 4G LTE to 5G NR as the number of 5G capable devices grows.
What will happen to 4G and 3G?
Despite the continued growth and deployment of 3G Universal Mobile Telecommunications System (UMTS) in many countries beyond 2020, a global 3G turndown is anticipated as soon as 2023. The influencing factors of 3G turndown include:
Existing 4G users can currently travel globally and seamlessly using their mobile device due to a litany of legacy technology neutral roaming agreements between mobile operators. Most of these mobile roamers will access 4G LTE with Circuit Switched FallBack (CSFB) to 3G voice, due to VoLTE launch delays.
In summary, roaming support is currently not specified when home network is EPC only and the visited network is 5GC only; see chart below from GSM Intelligence.
As stated earlier in this blog, more operators are focusing on 3G turndown and VoLTE roaming launches. The estimated timeframe for SA 5GC roaming could be as far out as a five-to-10 year roll out.
Coming Soon – Blog #5 5G Network Virtualization, Network Slicing, and Orchestration