When the 3GPP (the cellular world’s standardisation body) started working on 5G, it promised to address use cases that may sound contradictory: Massive IoT, mission-critical control, and enhanced mobile broadband. These objectives may seem incompatible, as massive IoT would require a solution (network and devices) that consumes very low power for devices running on battery to operate for more than ten years. In contrast, enhanced mobile broadband requires offering very high bandwidth.
The first focus of 5G standardisation and deployment was to address one of the three pillars, the one that mobile network operators are comfortable with and the most profitable segment at the time: enhanced mobile broadband. This fully aligns with the mobile broadband evolution from 2G to 3G to 4G — offering more throughput and better network reactivity. This leaves the other two pillars needing to be better addressed to fulfil the 5G promise: Massive IoT (such as smart meters) and mission-critical control (such as public safety networks).
In addition to the 5G evolution to address massive IoT and mission-critical control, network virtualisation is another trend in the IT industry that is becoming a reality. In the past, a specific hardware was designed for a specific network function and linked to its dedicated software. Today, there is a need to virtualise these network functions with software that can run on commercial off-the-shelf hardware or even in the cloud. This brings more cost efficiency, higher reliability, and more flexibility in the network design.
Network slicing
In the past, cellular networks were split into two network types: the Circuit Switch (CS) network managing voice and SMS and the Packet Switch (PS) network dedicated to data. The rationale at the time was that voice could not wait, and data did not have the same constraints (jitter, delay and so forth). This was the case with 3G networks. With 4G came the unification of the two worlds (voice and data) on a data network with Voice over IMS over IP. Of course, this merge of networks has been transparent for the end user, who is still able to make phone calls over IP and more data services.
The two trends mentioned above (contradictory network requirements and network virtualisation) have created new challenges in the current context. To cope with contradictory constraints, the network can be split again, but virtually, with slices dedicated to one use case.
A common infrastructure can be virtually split to dedicate resources for a specific use case. A network slice can be seen as a virtual network that is dedicated to a certain type of service or application (e.g., automotive, IoT, or classic mobile broadband) with specific requirements: on functionality (e.g., priority, policy control), in performance (e.g., latency, mobility and data rates), for specific types of users (e.g., public safety, corporate customers, roamers).
For instance, let us imagine a common infrastructure split into three virtual networks: one network slice could be dedicated to the massive IoT use case — requiring support for a massive number of devices with low power consumption, but with very limited throughput. This could be the case for smart meters, for example. Another network slice could be dedicated to critical communication — use case examples include monitoring factory robots or for firefighters. This network slice would have an extremely low latency service with very high reliability. While the final network slice could be dedicated to mobile broadband to serve smartphones requiring very high throughput.
This opens up additional possibilities for mobile network operators, for example, to offer a slice of their network and allocate it to a specific factory. Essentially, this allows MNOs to provide network services to a company that operates a factory which requires dedicated network resources for its robots and equipment to ensure the high reliability of its machines’ connections.
The role of the SIM
The SIM — whether in its traditional, embedded or integrated form — plays a key role in the evolution of network slicing. For the sake of brevity, when referring to the SIM throughout this paper, we are using the umbrella term to cover the SIM in its plastic form factor and soldered form factor as well as the reprogrammable SIM (eUICC) —where the mobile subscription can be changed, and the iUICC — where the SIM functionality is integrated within the baseband of the cellular device.
The basic functionality of the SIM is to authenticate the user subscription to the mobile network operator’s network, but it can also do much more. It can pre-configure the device with preferred configurations loaded by the mobile operator into the SIM. This is the case for the network slicing configuration. The mobile operator can configure the SIM with rules to indicate which network slice the traffic of the device application will be directed to and to which a particular charging policy may apply. This is the URSP (UE Route Selection Policy).
The URSP is used by the connected devices to determine how to route application traffic to the network slicing. This configuration (file) has been introduced with the 3GPP Release 16. The 3GPP R16 is the second 5G release, after 3GPP R15 where 5G was first specified by this standard.
This URSP file with the SIM requires a specific memory format called BER-TLV. In simpler terms, this means that the SIM’s operating system (OS) needs to support this specific memory management method in order to load the format required for this configuration file.
The SIM and its evolution need to support the right format of memory management for the mobile operator to be able to configure the appropriate routing of the user equipment for policy and charging control.
Conclusion
Network slicing is a way for mobile network operators to address specific use cases and potentially private network use cases. The SIM plays a key role by hosting the device and application routing policy to one or the other slice. The SIM’s operating system needs to be able to cope with a specific memory management format called BER-TLV. Mobile network operators shall then consider this feature in their SIM that has been introduced in 3GPP R16 to be able to cope with Network Slicing.
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