good morning, I have a Mikrotik LHG LTE18, I have a problem with the aggregation of the b38 band which does not happen in any way. If I set the router to use the single b38 it works, but if I set it to aggregate the b38 with 1,2 or 3 other “b1-b3-b7-b20” bands it doesn’t work.
example
does anyone know why?
ask first your service provider if they have it configured in their cellular network.
In a wider perspective: not every band combination is standardized for CA. And even if it’s standardized, not every user device supports all of combinations … and, as @dinosgb noted, not every MNO supports every combination.
Additional problem is the combination of B7 (FDD band in 2.6GHz region with part between 2570MHz and 2620MHz serving as duplex gap) and B38 (TDD operating in duplex gap of B7). Duplex gap exists because band filters are not ideal and can only supress emission in adjacent frequency band by certain degree. Duplex gap gives space for band filters (both on Tx and Rx chain) to do their job. And device, operating in both B7 and B38 at the same time might self destruct its own receivers (B7 transmitter might “bleed” into B38 while it switches to receive mode and B38 transmitter might “bleed” into B7 receiver … in FDD mode, receivers and transmitters may work 100% of time).