5G+ is arriving: a connected backhaul is the backbone to future smart cities

Nokia Solutions and Networks Singapore Pte Ltd

Friday, 16 July, 2021

5G+ is arriving: a connected backhaul is the backbone to future smart cities

If government is to leverage the existing public safety backhaul network as a multiservice network for the growth of smart cities, then Nokia claims a high-performance broadband backhaul network is at the heart.

To accomplish smart city goals, governments are upgrading infrastructure by considering private LTE networks. A cost-effective solution is to leverage the existing public safety backhaul network as a multiservice network to carry smart city data.

Smart cities offer the promise of safe, prosperous and sustainable living for all citizens, delivering effective emergency services and providing citizens with better public services. Consequently, governments are already upgrading land mobile radio (LMR) systems and harnessing broadband LTE services, such as in America with the US FirstNet, for a more coordinated emergency response.

To accomplish the smart city goals, governments are planning for other connected city infrastructure deployment that encompasses a wide range of systems such as CCTV, smart lighting and an intelligent transportation system.

Fundamental to a smart city infrastructure is a high-performance broadband connectivity platform connecting its associated assets. Because the infrastructure has a large footprint, to reach all assets economically, a private wireless network is the natural choice. Among the various wireless technologies, open standard-based LTE is the preferred radio technology because of its rich ecosystem, robust security and an evolutionary path to 5G.

In the past, a lack of spectrum has hampered local governments’ efforts to deploy private LTE networks for smart city infrastructure. However, national radio authorities around the world have now started to make suitable spectrum available.

In the US, the FCC has opened up the 3.5 GHz band (also known as band 48 with 3GPP). In Europe, countries such as France have also made the 2.6 GHz band available for vertical industries. These spectrum initiatives have prompted many infrastructure operators, including local governments, to investigate or plan for a private LTE network.

An essential element of a private LTE network is the backhaul network connecting LTE base stations (eNBs) and the LTE core. However, deploying a backhaul network adds significant cost and effort, causing additional time for the project.

Fortunately, there is an alternate option. Many local governments already have backhaul networks dedicated to public safety communications. If they can use those backhaul networks as multiservice networks to transport the private LTE traffic, this will improve the project economics and expedite smart city application deployment.

However, when using a public safety backhaul network as a multiservice network, it is imperative that public safety application performance is never degraded and the communications are never compromised.

Challenges for smart city public safety backhaul

To provide the required performance, a public safety backhaul network transporting smart city private LTE traffic must meet the following challenges:

  • Assured delivery of LMR traffic
  • Cybersecurity
  • Interworking with the cloud
  • Readiness for 5G.
Assured delivery of LMR traffic

Radio communication is a lifeline for first responders. It needs to be up and running 24/7. It is also a real-time application that is sensitive to network delay.

When the backhaul network expands to transport smart city private LTE traffic, there is a diverse set of smart city applications across the smart city infrastructure that run atop the network and compete for network bandwidth. Examples include intelligent traffic management systems, smart lighting and CCTV.

In addition, real-time, mission-critical LMR traffic requires strict delay with the highest possible reliability while smart-city applications have less demanding requirements. It is crucial that the network is application-aware to classify traffic for different quality of service (QoS) so that it always reliably delivers critical LMR traffic, even when there is network congestion, so that first responders can constantly communicate with their radios without disruptions.


A backhaul network provides meshed connectivity so that any device can reach any other device attached to the network. With more application systems such as the LTE system, the attack surface increases.

Furthermore, when the use of the backhaul network is further broadened to connect to city offices and public amenities, the attack surface expands further. And because these facilities are easily physically accessed, there is a concern that network vulnerabilities are increased significantly. When attached devices are compromised, attackers can use them as launching pads to move across the backhaul network and penetrate into the LMR and other critical systems to cause serious disruptions.

Interworking with the cloud

Smart city applications such as video analytics are evolving to a distributed, cloud-based architecture so they can scale up to process a large number of high-definition video streams, improve anomaly detection time and optimise backhaul bandwidth.

This architecture takes advantage of LTE local breakout capability and places the video analytics gateway function on a mobile edge computing (MEC) platform at the edge of the network. The MEC is even colocated with the eNB in some circumstances, with the general operations, administration and maintenance (OAM) functions of the video analytics system remaining in a video analytics cloud server application in the data centre.

With data centres embracing cloud technology, the compute resource hosting the video analytics cloud server application becomes dynamic and mobile. The cloud management system (CMS) can create, delete and migrate compute resources from one server to another and from one data centre to another for server upgrade, optimisation or maintenance.

When this happens, the traditional data centre network fabric connecting all servers does not learn about these events in an automated way, and the connectivity to the applications is disrupted. Consequently, many data centres have transformed their network fabric with software-defined networking (SDN) so that the network fabric can adapt its connectivity to compute resource events in an automated way.

This automation brings two challenges to the communications between the video gateway in the field and the cloud server application:

  • Between the backhaul network and the cloud (referred as network-cloud interworking hereafter): A new network function called a network-cloud interworking gateway is required to seamlessly extend connection from the backhaul network domain across the data centre SDN fabric domain to reach the application.
  • Determining how to make the cross-domain connection adaptive when the application migrates to another data centre.
Readiness for 5G

Because LTE is a 3GPP technology, local governments will benefit from a smooth evolution to 5G when and where needed for more bandwidth-intensive and time-sensitive applications while they continue to use the LTE coverage. Therefore, it is essential that the backhaul network is also ready to provide backhaul for the 5G network.

How IP/MPLS can help overcome challenges

IP/MPLS brings the following capabilities to a public safety backhaul network to help overcome the challenges described:

  • Deterministic QoS for assured LMR traffic delivery
  • IP/MPLS VPN with encryption for cybersecurity
  • Network-cloud interworking
  • Support for 5G transport.
Deterministic QoS for assured LMR traffic delivery

QoS is a set of network capabilities to control delay, jitter and packet loss for data traffic flowing through the network. This is done by controlling and managing bandwidth resources in network equipment.

Although IP and Ethernet platforms do offer QoS, next-generation IP/MPLS routers, with extensive packet classification, queuing and scheduling capabilities, have advanced. A wide range of applications send intensive data with a diverse range of QoS requirements based on a customised QoS policy for each service created for each individual application.

IP/MPLS backhaul routers can classify, buffer, schedule and shape traffic to constantly satisfy the requirements of LMR traffic and various other applications. This capability of constantly meeting the service requirement is called deterministic QoS. See Figure 1.

Figure 1: IP/MPLS backhaul network delivering QoS assurance.

As an example, when the IP/MPLS router is receiving a lot of public Wi-Fi data sent by citizens, as soon as the LMR radio sends critical voice or data traffic, the router recognises the LMR traffic and strictly prioritises it over other data traffic, minimising delay and jitter and avoiding packet discard when link congestion occurs. This is essential to ensure high LMR communications performance.

As more cities are considering a private LTE network as a foundation for a smart city project, those that have already deployed an IP/MPLS backhaul network for their public safety communication infrastructure can leverage this important network asset to simplify and accelerate the deployment of a private wireless network.

IP/MPLS is a technology already chosen by many mobile service providers around the world to backhaul their LTE networks. Due to its deterministic QoS capability, ability to support network segmentation with secure IP/MPLS VPNs and network-cloud interworking as well as its 5G readiness, an IP/MPLS backhaul network delivers the performance and economics needed to support both public safety communications and the future connected smart city services reliably.

Excerpted from Nokia’s Broadening Public Safety Backhaul for Smart Cities white paper.

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