Hi @XinyueZou ,
I recommend that you try the router in a few different locations, restarting at each new location, and visiting fast.com and speedtest.net
When I first joined EE, I found the performance to be less than I had hoped for. I moved the router into a less logical, lower, and covered location and surprisingly found significantly better SINR values of over 10 dBm. You may wish to search online resources and the router management page to see if you can access the LTE parameters, and the SINR value I've found is a good one to find a good location and improve performance.
Customers have found nice locations near windows although I recommend any locations which you can leave the router long-term as it's not easy to judge which materials shield cellular signals more; and line of sight, reflections, and obstructions probably matter more, given the distance to cell towers.
