Hi, allow me to help you with this.
I assume you already have Intel® PROSet Wireless Software version 17.1 as you mentioned above. You may also want to upgrade the router’s firmware.
Try to verify the wireless security encryption being used by the router and the laptop and avoid mixed encryption types if possible.
Intel WiFi Products — Data rate will not exceed 54 Mbps when WEP or TKIP encryption is configured
Disable uAPSD in the adapter properties.
Intel® Wi-Fi Products — TechNote: Access Point interoperability issue with uAPSD