Symptom:

The wireless connection data rate reported by the software utility or other WiFi monitor cannot connect for more than 150 Mbps, even though the router, access point, and/or adapter are advertised as being capable of more than 150 Mbps.

Cause:

Wi-Fi-certified N routers and access points are required to comply with the "Coexistence Requirement" set forth by Wi-Fi Alliance.  The Coexistence Requirement ensures that the N devices operating in the 2.4 GHz frequency band default to 20 MHz operation when operating in close proximity to other Wi-Fi networks.

Devices operating in the 5 GHz frequency band are not prone to interference and are not subject to the Coexistence Requirement.

Resolution:

If your router or access point operates on the 2.4 GHz frequency band, your device is functioning as intended.

Related Information: 

For general information on the Wi-Fi Alliance, please visit http://www.wi-fi.org/
You may also be interested in reading the "40 MHz channel operation" details available from the Wi-Fi Alliance.

Note:  Clicking the above links will exit the NETGEAR Support Website.