Passari Cellular routers come from a long tradition in mobile routing, back in the UMTS days…
UMTS/3G was not an full IP technology, having impact on end to end IP services in terms of performance. LTE/4G is a full IP technology which all together was a big step forward, not just in terms of bandwidth. 5G is being introduced. Based on many sources the prediction is that 5G will enable many new services to the market, all of them have to do with optimizing connectivity (beamforming, radio bonding and such) as well as optimizing services (QoS and interconnectivity).
There are a couple of LTE-A and/or 5G modem manufacturers which are being utilized by all cellular router manufacturers. The adaption to the mobile networks globally is being taken care of by these modems. Cellular router manufacturers can only do their tricks with the bitstreams coming and going from these modems. That is where actually the differences between the manufacturers exist.
Single cellular modem routers are meant for low key applications. Always remind that a single cellular connection is vulnerable. The risk of outages is quite high due to network coverage, operator outage (this happens much more often than you might expect, and when these happen can take quite a while), signal quality which impacts bandwidths, etc.
Therefore many cellular router manufacturers offer their routers with a minimum of 2 cellular modems and Load Balancing functionality. This way the best of both worlds is being achieved: 2 cellular modems create more bandwith than one and services can be directed over different cellular connections. An outage at one WAN link doesn’t fully disconnect the router of the internet. A part of the services will continue. Keep in mind that 2 different mobile operators are required to achieve this.
There are a couple of cellular router manufacturers that went another way: Bonding. Bonding is bundling multiple WAN links into one tunnel. All of the services are sent through this tunnel. If a cellular WAN link is broken than still all the services are maintained, there is only less bandwidth available.
Bonding has however a main disadvantage, it is very sensitive for latency variations. Because 2 or more cellular connection always experience different latencies (continuously) the overall bandwidth of bonding is seriously affected. Under ideal situations this will be 80-85% efficient. But in reality this is often seriously lower like 60-70%. In other words you pay for 100% data transfer but get actually 2/3-rd of what you pay for. For that reason many customers decide to go for Load Balancing.