Smart backhaul meets multiple goals
There are lots of definitions around, but I think of a smart city as a connected community where data feeds intelligent processes that adapt services to the needs of citizens. Connectivity is crucial to this vision. It should be available everywhere, carrying everything from sensor traffic to high bandwidth video. And, it needs to be very secure.
Wireless technologies such as 4.9G (advanced LTE) and, soon, 5G meet all these requirements. High performing and reliable, 4.9/5G wireless is able to support massive IoT sensor and camera deployments, as well as ultra-low latency applications needed for autonomous processes. With spectrum becoming available (e.g., CBRS in the US and the 2.6 GHz band in France), this makes it the best choice for many of the most advanced smart city applications.
Despite the magic of wireless, the reality is that there are “wires” connecting all the 4.9/5G base stations. This wired infrastructure “backhauls” the traffic from the wireless network, connecting mobile users, sensors and equipment to municipal data centers, the internet and the cloud.
It is important for cities to do as much with their backhaul network as possible. Putting up antennas to provide seamless wireless coverage for citizens is no small task for a city, but it pales in comparison to digging up the streets for a second or third wired backhaul network.
Fortunately, there is no need to duplicate a wired network infrastructure. Many cities, for instance, already have a wired backhaul network in place for public safety communications. Converting to multiservice IP/MPLS can broaden its use for smart city private wireless traffic, with no degradation of public safety application performance.
The most important part of any public safety network is radio communications using land mobile radio (LMR). LMR traffic on the network is classified as “real-time” traffic, meaning that it cannot be buffered or delayed. Because it is used 24x7 by first responders, it has to be delivered with the highest reliability and very securely. The network has to be capable of meeting these performance criteria for any LMR traffic.
Smart city traffic will have different performance criteria. CCTV video, for instance, requires higher bandwidth than LMR, but is not as mission-critical and delay-sensitive. Public Wi-Fi does not require high levels of reliability but is quite bandwidth intensive. Thus, the network has to be capable of prioritizing LMR traffic over these other types.
Cyber-security issues arise when you have different applications running across a single network. Essentially, the attack surface grows with each application. Adding public Wi-Fi and municipal office traffic expands the possibility for attackers to get inside the network. If using cloud services, whether Office 365 or specialized XaaS offerings for municipal applications, this again opens up the network to security issues.
Speaking of cloud services, it is also important for the network to interwork with both centralized and local edge clouds. As an example, a video analytics application might perform the local analysis of video footage on the edge of the network —co-located at a cell site with the base station, for example — but the OAM application is still run in a central cloud.
This interworking with the cloud data center (DC) software-defined network (SDN) requires that there be a network-cloud gateway to interconnect the DC with the backhaul network. There also needs to be some way to adapt the connection if part of the application processing moves to another DC or to an edge cloud.
All of these requirements can be met with an IP/MPLS network: from QoS assurance for different traffic types (e.g., LMR, CCTV), encryption of traffic streams for security, network-cloud interworking, as well as the various kinds of support required by for 4.9/5G backhaul. IP/MPLS expands IP with new capabilities — advanced traffic engineering, a deterministic QoS mechanism and segregated network services — make it an ideal technology for multiservice networks.
As an example, if the IP/MPLS router is carrying a lot of public Wi-Fi data and the public safety LMR radio starts to transmit critical voice or data traffic, the router recognizes the LMR traffic and strictly prioritizes it over the Wi-Fi data traffic, minimizing delay and jitter and avoiding packet discard when link congestion occurs. This is essential to constantly ensure high LMR communications performance.
On the cyber security front, IP/MPLS segments the network into segregated virtual domains called virtual private networks (VPNs) This enables the backhaul network to carry many kinds of application traffic with no possibility of intruders moving laterally between applications. Thus, in the case of LMR, a malware-infected computer in the city Wi-Fi domain could not communicate or interfere with the LMR system.
For network-cloud internetworking, the key ingredient is an IP/MPLS router that supports SDN technology on which the cloud is founded. This is called a datacenter gateway. It seamlessly extends VPNs in the backhaul network into the cloud, enabling field devices attached to the backhaul network (or 4.9/5G wireless network) to follow application processes (or “workloads” in cloud speak) that move within the DC, or to another DC.
As 5G connectivity services are added in the future to an existing 4G or LTE network, additional VPN services can be provisioned over a bigger “trunk” (e.g. 10 Gbps or even 100 Gbps Ethernet) to transport the 5G traffic, just as with any other application.
Along with 4.9/5G private wireless, an IP/MPLS backhaul network is an essential part of the smart city communications platform. The good news is that many cities have already installed IP/MPLS backhaul for other applications, especially public safety networks. For those that haven’t, the operational and CAPEX advantages of consolidating all smart city applications on a single network make it a crucial piece of any smart city’s infrastructure.
For more information on using a public safety backhaul network to backhaul other data traffic, such as smart city and 4.9/5G, download and read our application note.
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