The Latitude E5540 has a better Wi-Fi standard than most medium processor core laptops that were launched around the same time as it. This portable PC has an 802.11a WiFi standard, whereas most medium processor core laptops that came out around the same time as it have an 802.11n WiFi standard. In addition, this notebook PC have 802.11ac and 802.11b and 802.11g WiFi standards.
This portable PC's Wi-Fi standard (802.11a) is in fact the worst Wi-Fi standard across all portable PCs of this spec and age.
The best Wi-Fi standard amongst similar types of portable PC is 802.11n.