Converging cellular and non-cellular capillary networks

In previous blogs, we looked at the structure of the power grid and how LTE plays a major role in interconnecting power generation with distribution through substations. We then moved on to the last mile of electricity supply, where it is increasingly essential to protect people and community assets. This blog is about the last hop in the last mile, where wireless connectivity is often provided through a legacy non-3GPP wireless network. These capillary networks in the last hop power the reliability of LTE private wide area networks in the last mile.

The power grid today contains many purpose-built capillary networks, each optimized for a unique use case. Capillary networks consist of a capillary gateway (CGW) and many devices served by that gateway. Performance, reliability and consolidation require versatile networks in the last hop. The next logical step is to merge these access networks by leveraging the common backbone infrastructure provided by private LTE through converged cellular capillary networks.

Figure 1: Converged cellular capillary networks combine 3GPP and non-3GPP devices into a single multipurpose network.

Connectivity today

To address the last mile and the last hop, cellular technologies such as LTE have evolved with new categories of devices and networks that include wideband LTE, narrowband IoT, and Category M. These categories enable simpler and cheaper LTE modems for connected devices that can increase LTE coverage by 15 to 20 dB. Ericsson’s deployments across the vast expanses of Australia have taken advantage of this improved coverage to enable very wide connectivity. This extended network can also allow utilities to access devices in remote or difficult locations, such as a smart meter in a basement. With the falling price of LTE modules, these “chip-under-glass” devices are the components of cellular access.

Capillary networks and local short-range communication technologies that allow them to provide connectivity to millions of devices with many individual use cases. Examples of technologies include Bluetooth Low Energy (BLE), IEEE 802.15.4 and IEEE 802.11ah. These mesh networks provide efficient connectivity to devices in a specific local area. Typically, capillary networks connect at the edge of a communications infrastructure to, for example, reach head-end systems hosted on the Internet or in a cloud.

Connecting a capillary network to the global communications infrastructure can be accomplished through a cellular network, which can be a wide area network or an indoor cellular solution. The gateway between the cellular network and a capillary mesh network acts like any other user equipment when this gateway is activated with a SIM card.

The converged cellular capillary network

A capillary network consists of the following elements (see Figure 1):

  • Devices which may not be end-to-end 3GPP security compliant but have a well-established trust relationship with their gateway. These can run on license-exempt short-range, low-power technologies such as Wi-Fi, Zigbee or BLE.
  • Capillary Gateway (CGW) serve these devices and provide a connection to the Internet.
  • Cellular Connectivity Domain which connects these gateways to the Internet or to the device’s headend systems. These are often served by consumer best-effort networks today and can be enhanced with dedicated private LTE networks.

One of the benefits of integrating capillary gateways into a common LTE core is the ability to move some headend and meter data management processing to the edge. This allows earlier preprocessing of capillary network data at the community level to optimize processing at existing headends.

Here are three other benefits of consolidating between single-purpose capillary gateways and the common LTE core, with more details below:

  • Consolidation, priority, and preemption can be applied on both 3GPP and non-3GPP networks, with each of the CGW use cases being mapped to QoS in the LTE packet core. Consolidation of use cases at the head end is now possible because the LTE packet core can classify traffic based on CGW.
  • Scalable management of devices across all use cases is now possible on a common management infrastructure. Delegated device configuration reduces network planning and provides centralized security and the reliability of a common private LTE core.
  • Multi-use case smart devices can scale to re-select the correct CGW based on the use case, as the converged architecture allows the device to be assigned an updated priority without affecting CGW functionality.

Consolidation, priority and preemption

To provide end-to-end QoS, a bridge is needed between the QoS domains of the capillary and cellular networks. This bridge specifies how traffic from one domain (via domain-specific QoS processing) is mapped to a specific QoS level in the other. The specifics of the QoS bridge are determined in a Service Level Agreement (SLA) established between the providers in the capillary network domain and the cellular connectivity domain, or between the service owner (in the data domain) and the providers in the connectivity domain. Consolidation can be extended on the common LTE core to include centralized IP pools that are shared across capillary networks. Such consolidation allows for more seamless use case transitions in a general-purpose scenario and better predictability in converged cellular capillary network design. Many of the concepts used in Ericsson networks to manage competing priorities in traffic flows are easily applicable to dealing with the complexities of a capillary network.

Scalable management

A series of tasks are now performed by network management. An example is to provide automatic configuration and connectivity for devices connected through a capillary network. Additionally, network management establishes access control restrictions and data processing rules for QoS based on SLAs, subscriptions, and security policies. Additionally, a utility provider can use the management feature to adjust service policies and add or remove devices.

Network management of connected devices in capillary networks poses new challenges, especially in relation to the management of cellular networks. This is partly due to the large number of connected devices, far greater than the number managed by current network management systems. Instead of managing devices as individual nodes, economies of scale can be achieved by managing devices in groups that use managed policies and settings that are more abstract and also fewer in number.

A significant challenge for network management is providing complete end-to-end reach, an issue that is particularly evident when different areas of the end-to-end chain are provided by different business entities. The best way to overcome this limitation is to interconnect the network management systems in the different domains. The resulting cross-domain management provides end-to-end management opportunities. For example, the quality of service in the capillary and 3GPP domains can be adapted, and the alarms of the two domains can be correlated to point faults. Business support systems with the added intelligence of AI/ML algorithms enable efficient mixed network management

Multipurpose smart devices

As devices evolve to do multiple things (your electric meter reports the weather?), single-use-case gateways must either evolve or devices must become intelligent by selecting the right gateway. The gateway selection process by the device is a feature that can be leveraged from the common LTE backbone infrastructure. Some of the criteria involved in this selection would include collecting connectivity and policy constraints per gateway, applying those constraints when choosing a gateway, informing gateways of this decision, and forwarding traffic from the device based on the new use case enabled by the versatile device. . Design considerations may lead to this intelligence being co-located within the core network, or individually within gateways.


The network modernization journey toward last mile consolidation with the last hop requires many considerations. Convergence of 3GPP (cellular) and non-3GPP (non-cellular) networks is possible with a converged cellular capillary network that enables the following:

  • Consolidates SIM, eSIM, and non-SIM solutions into a single wireless network.
  • Aligns IP planning and address preservation and predictability across multiple connectivity domains to set the stage for those domains to evolve to LTE.
  • Work and plan LTE solutions on capillary gateways to balance performance, load, and use cases.
  • Manages devices and network elements in a common architecture.
  • Extends security relationships between domains to establish better control over the flow of information.

With over 145 years of experience in wired and wireless technologies, we are excited to be part of the digital transformation in the utility space as well. I look forward to diving deep in my next blog on how the hairnets featured in this blog will integrate with 5G and other wireless technologies, bringing it all together!

Read the full blog post series where we unpack the state of the digital power grid and show how private networks enable utilities to achieve their goals.

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