What is the future of the 5G cell site router?

In previous blogs, I’ve talked about the advent of 5G and its corresponding impact on the transport network (Why your 5G network needs 5G transport*). As we continue to deploy 5G, we are engaging in even more specific dialogue with Service Providers about how they need to evolve their transport network for 5G. Lots of customers are asking me, “Is a cell site router needed in 5G?”

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Vice President, Strategy and Business Development, Head of Transport

Vice President, Strategy and Business Development, Head of Transport

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Is a cell site router needed in 5G?

When I get this question, I start asking some clarifying questions. Sometimes the conversation leads to discussion about Integrated Access Backhaul (IAB). Other times, the conversation leads to the baseband roadmap, and how routing functionality is being integrated to Ericsson RAN Compute platforms. And in other cases, we discuss Mobile Edge Computing and virtual routing.

But, after clarifications, I usually end up saying, “You’re asking the wrong question.” What you really need to ask is, “How much routing functionality will be needed at a 5G cell site?” This is a completely different question … and my answer is usually unsatisfying for the customer: “It depends.”

So now to the “On what?” It is a combination of three main factors:

  • RAN Architecture
  • RAN Deployment models
  • 5G use case offered

Mix of factors impact routing requirements

The combination of the three factors above lead to different answers on routing requirements. I will explain using some examples.

Example 1:

RAN Architecture: Distributed RAN (DRAN)
Deployment model: hub and spoke
Use Case: enhanced MBB service
In this case, the router functionality is not critical. However, high capacity 5G sites may consist of many basebands that require tight coordination with each other using Elastic RAN. In this situation, the CSR also acts as a local aggregation and baseband interconnect. 

Example 2:

RAN Architecture: Centralized RAN (CRAN)
Deployment model: dozens of co-located basebands
Use Case: range of 5G services from eMBB for capacity augmentation, Fixed Wireless Access (FWA) for residential services, and dedicated network slices for specific enterprise use cases

In this case, routing functionality at the CRAN hub site can become vitally important.

Further considerations

Discussions on routing functionality for 5G sites and where it’s located in the network architecture are just the beginning. I ask the customer to think about some other critical functions necessary for delivering 5G services. Things like:

Traffic prioritization and buffering

Mobile traffic is inherently bursty, and there is no foreseeable end to the of mobile video consumption. Video was 60% of global traffic in 2018 and will be nearly three quarters of traffic by 2024 (read more in the latest Ericsson Mobility Report). Mobile is clearly not about voice and best effort data anymore! Operators must start thinking about how this will impact time sensitive, low latency use cases sharing the transport network. It is critical to be able to classify, schedule, and prioritize traffic from multiple services with various requirements. In addition, buffers must be big enough to guarantee bandwidth for some services, while ensuring streaming content and rich media applications continue with high QoE. On top of this the 5G CSR must be able to handle the new 5G interfaces like eCPRI and F1 and this requires its own prioritization due to its strict latency requirements.  

Timing and synchronization distribution

With 5G, Time Division Duplex (TDD) radios are being deployed alongside and among other TDD and FDD radios. TDD radios are highly dependent on a reliable phase and time synchronization source to operate properly. If you lose the local GPS, you only have an hour before you lose the TDD radios which are driving the vast majority of the capacity at radio sites. Synchronization backup over backhaul is a must.   More about timing and sync in 5G networks in this blog, 5G is all in the timing.

Multi-domain slicing

Network slicing advances have primarily focused on the Core network. What is really needed is multi-domain slicing across the RAN, Transport and Core network.  This can provide E2E traffic control for transport configuration and optimization using domain SDNc (Software defined network controllers) and hierarchical SDN controllers to span multiple transport domains.

Network security

Network security is crucial to delivering on the promise of 5G and the network slice. With network slicing, mobile operators can partition their physical network into multiple virtual networks. Slicing enables service providers to economically scale different types of services for different customer segments. However, service providers must ensure different virtual network slices are adequately isolated from one another. "High security" applications must not be accessible from a "lower security" slice. In some cases, traditional security gateway (SecGW) functionality will suffice. In other cases, due to performance requirements, the SecGW may need to be distributed to the 5G RAN site or CRAN hub. In addition to network slicing, adding in-building networks and smalls cells over untrusted domains also requires new security approaches in the transport layer.

RAN site type

The location of routing functionality is also influenced by the availability and cost of real estate at the RAN site. Sites can range from rail-based to pole-mounted, outdoor cabinets, indoor huts and central offices. With 5G DRAN, CRAN, and VRAN architectures, routing and other critical functions outlined above need to be available to match your RAN site type. Make sure to consider transport network device size, form factors, and hardening as you plan for 5G.

Where should routing functionality reside in a 5G network?

As discussed above, pure routing functionality needs may vary based on 5G RAN architectures, deployment models, and use cases. What about all the additional aspects we have discussed? Where is all this functionality supposed to sit at the RAN site?

  • At the gNB? Nope. Adding all this functionality to an gNB will consume more space and power, limiting deployment options, and end up costing customer’s more
  • At the current cell site router? Nope. Site routers on the market today do not have this functionality. They are not able to support the range of site types and deployment models required for 5G
  • On storage/compute at the MEC location? Maybe, but it will need to be temperature hardened and cost effective to scale to the capacity 5G demands

So, what can be done?

As the leader in 5G, Ericsson has thought about this. Our solution is to bring these critical functions to our customers in the Router 6000 product family. Ericsson Router 6000 is the most robust, efficient, and cost effective 5G service delivery platform on the market today. It provides deep buffers, HQoS, stratum 3E on-board timing source, distributed IPSec Gateway capability, and is available in all RAN form factors giving you consistency across your deployments.

Oh … by the way … it routes too.

Related reading:

Fierce eBrief: Meeting the 5G backhaul challenge

Ericsson 5G transport solutions

Heavy Reading White Paper: Defining the Transport Network for 5G


*Why your 5G network needs 5G transport

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