Hi.
So cat 12 has a max of 603 Mbps download and 102 Mbps upload with carrier aggregation across 2 or 4 channels. Cat 18 is 1174Gbps download with CA across 2,4 or 8 channels (typically paired with a cat13 module for ~150Mbps upload.
Cat12 modem modules are available and good value. I understand that Cat 18 modems are also available (just not as available as Cat 12 and of course more expensive).
Knowing Peplink as well as I do - I’m confident that if you wanted a HD4-MBX with Cat 18 modems they’d make you one (or 100 or 1000), but I think they have ,made the right mass market decision to go with CAT12 straight out of the gate.
Don’t know about you, but I live in a part of the world where 4G coverage is not guaranteed and even when it is available is often heavily contended. Yes in theory the operators are rolling out new massive mimo 5G ready tower equipment that can support Gbps+ speeds, but in practice those are few and far between - a least for the moment.
That said, I follow an epic guy called Peter Clarke on twitter who spends and extraordinary amount of time looking for and testing towers and he has found some great ones:
https://twitter.com/PedroClarke1/status/1111246788948869121
Of course headline LTE speeds are important - yes you want to be future proof, but at these kinds of speeds the typical cellular data contracts don’t fit any more ( a couple of mins into the month on a 20Gb contract and you’ll have run out of data…).
Even ignoring the fibre rollout that has to happen to get Gbps of bandwidth to all the towers in the UK which then need upgraded equipment, I still think the gating factor on actually using massive speeds on LTE is finding an end user application that actually needs that amount of data in the first place and then the commercial costs of buying large amounts of cellular bandwidth. We can happily provide you with Terrabits of data a month on any UK network but the cost of that amount of data is not acceptable for most internet users - unless your application demands it and your business model can support it.
Its these commercial restrictions around data costs - combined with a lack of mass market demand for silly levels of bandwidth currently that’s driven the initial choice of the CAT12 modems I would imagine.