My iPhone 4s isn't receiving iMessages?

Does anyone else have this problem? I've been thinking that my friends were ignoring me but I found out that I haven't been receiving me all along after I installed iOS 7.It's definitely not the signal.

Added (1). I already checked… I'm not that dumb like most of the people around me. I wouldn't be asking this question if that worked out well.

The problem could just be the upgrade. I have a 4S and did the upgrade, but haven't had a problem with iMessage. I've seen some sites saying 4, 4S or older shouldn't do the upgrade, but I took a chance. I even did it without syncing, which was kind of foolish, but luckily I didn't lose anything.

Here's something that might be worth reading that addresses the iMessage issue:

http://arstechnica.com/apple/2013/10/apple-imessage-problems-to-be-fixed-in-upcoming-ios-7-update/

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