OK, now I'm really confused and would greatly appreciate any insights. First, my setup: I'm on 4G wireless RBI, Huawei gateway device upstairs with laptop in next room connected at the moment via Ethernet cable about three metres long. Another 30 metre cable runs through the house to feed a TP Link router. At this end we use wi-fi. The cables are cat 5 something, I think cat 5e.  

Although I have a fair bit of general computer knowledge, I don't have much network experience and don't know much about it. When I run Speedtest, I consistently get a ping of around 56 - 60, download 30 mb/s, upload around 20 mb/s. 

Having recently heard that some people can get up to 70 mb/s with 4G, I became curious as to whether our setup was doing everything it might be capable of so I decided to run a quick comparison test. I took a new laptop and ran Speedtest via wi-fi while sitting next to the downstairs router. I got 39 down and 20+ up, slightly better than usual. I then took the same laptop upstairs and ran several tests using a LAN connection. On one of the tests I connected the laptop directly to the Huawei with a new cable about two metres long. All of the LAN tests, including a later one on a different cable, gave the same result: similar ping but around 5mb/s down and nearly the same up. WTF?

After those tests I immediately went back to my first location (downstairs next to the TP Link router) and did the test again via wi-fi. I got the same result as earlier, 39 mb/s down and over 20 mb/s up. So apparently the wi-fi fed by LAN is significantly faster than a direct LAN connection. This doesn't seem to make sense, at least not to me. Can anyone with more knowledge explain this? What am I actually measuring with those tests? Can it be that my laptop just has a slow LAN port? I can't make sense of these findings.