I won't tell much story but go straight to the point.
OTA means Over The Air I. e upgrading your android using your phone and network.
Many of us experience this boot loop (phone doesn't boot beyond logo) after upgrading our phones using OTA. The reasons are your phone is rooted and the upgrade file is not completely downloaded the first time it says 100% and asks you to continue. First unroot your phone before the download. If you get100% first time of download, stop or cancel then re-download the upgrade file. It won't take your mb (if you are scared) because the file is already in your memoryCard... If you get 100% second time continue with your upgrade. It should work perfectly.
I used these on Gionee M2 and it works perfectly after bricking the first time.
So happy un-boot loop upgrade.