Nexus 5 - LGD821 - Over the Air Upgrade :
Nexus 5 supports software upgrade over the air. This is generally called G-OTA
This can be done as per the below process
After one upgrade, a user can click again on the "Check Now" option to see if some other upgrade
is available.
When the prompt "Your System is upto date" appears, it means the handset has the latest available
versionf rom google.