How the Cellular System Works
Cellular/IP uses local cellular service to relay the fire alarm signal wirelessly from the building to the nearest cellular tower. From there the signal is relayed to an internet gateway either via point-to-point microwave or over fiber optic cable. Once on the internet, the signal gets routed to the central monitoring station via IP protocol.
How Mesh Network System Works
In wireless mesh networks, a collection of wireless routers is used to provide network access to wireless clients deployed in commercial buildings. Multiple mesh routers within the network serve as gateways to the central monitoring station.
Mesh networks work similarly to the way the internet works, in which internet routers use multiple hops to send information from one point to another. The only difference with mesh networks is that the signals are routed wirelessly, rather than over fiber optic cables.
Just like internet routers, wireless mesh routers have multiple paths to choose from to get the information to the end destination. They dynamically adapt to changing environments and essentially self-heal in case of a node or link failure. If one mesh router becomes obstructed or otherwise unavailable, traffic is automatically redirected via an alternative path.
Reliability of Cellular
When it comes to system reliability, cellular/IP suffers from one vulnerability: a single point of failure. In the cellular/IP system, if any part of the communication chain (cellular base station, backhaul link, gateway or internet service provider) goes down, the communication link is broken and there is no workaround.
It is not at all uncommon for a backhoe to accidentally cut a buried fiber cable.
Reliability of Mesh Network
When it comes to reliability, wireless mesh networks have a benefit that unmatched by either of the other communications technologies: path redundancy plus gateway redundancy.
With path redundancy, wireless mesh networks can survive a mesh router going down. The system simply reroutes the signal around the downed unit. The real unmatched benefit of wireless mesh networks though is gateway redundancy. Within the mesh network, there are multiple gateways connected to the central monitoring station. In the event that one of the gateways goes down, the system reroutes the signal to another gateway.
There is no single point of failure anywhere in a wireless mesh network.