Luci-Proto-3G increase bandwidth

Per trial 3G protocol is quite stable and reconnection by itself is quick. However the bandwidth is limited to 45 mbps max. Is there anyway to increase it to infinite? I tried using RM520N which is supposed to exceed.

I know that actual 3G is only max to 45 mbps but it would have been nice to see it exceed when paired with faster modems

Enhanced 3G HSPA Plus has a theoretical limit of 42Mbits per second it is a limit of the standard and protocol.

To go faster you need to switch to a newer protocol such as 4G, LTE or 5G.

In New Zealand they are killing off 3G networks over the next few years because of the much better 4G network and better band use I'd expect the same for the rest of the world in time to follow the same path.

Don't use it with newer modems.
If automatic reconnect is desired switch the modem into ECM mode and configure OpenWrt as shown here:
https://openwrt.org/docs/guide-user/network/wan/wwan/ethernetoverusb_cdc

ECM mode it assigns you a fake Eithernet interface between your modem and router because of this you get presented with a local gateway and the modem hides you behind a NAT and firewall and gives you a web page to configure the modem and port forwarding firewall and nat.

QMI mode you get a public IP (or cgnat depending on the ISP) address on your wan interface so you are directly exposed to the internet (no double Nat on your site)

That happens quite often but not always. The actual implementation is modern specific.

My $0.02: why not use ModemManager? It might be an overkill but it works with a lot of devices, including Serial AT + Ethernet, MBIM, QMI and others.