Why does my iBookPro drop its WiFi connection so often?

Question

My question: why does my iBookPro drop it WiFi connection so often, and what can I do to prevent it (or at least extend the duration of active connection)?
I have an iBookPro running OSX 10.9.5, with a 2.4 GHz Intel Core i5 processor and 8 GB 1600 MHz DDR3 RAM.  I think my iBookPro is about 3 or 4 years old.
What seems to happen is that I will use my iBookPro accessing mail & websites for a few minutes, and then when I try to send an e-mail, mail puts up a message that it cannot send mail with the selected server, so I need to either try a different server or try later.  Meanwhile I notice that the WiFi signal indicator shows full service, but when I run diagnostics it shows that the internet is not connected.  Opening the WiFi icon in the top menu bar shows that it is looking for Networks.  After an indeterminate time it finds the network I have had highlighted and logged into (my WiFi -5G router) since I opened my iBook when I arrived at my office.
I often find I have to turn WiFi off, then back on, to get connection with the internet. 
What's going on, and what am I missing?

Answer 1

Hello jBookProAm, 
If you are having issues with your MacBook Pro with maintaining a Wi-Fi connection, then take a look at the articles below to get it sorted out. The first article will talk about using Wireless Diagnostics, which you have already done, but also you look at the additional troubleshooting within the article for assistance. You may want to also create a new location as another troubleshooting option and those steps are in the second article. 
Wi-Fi: How to troubleshoot Wi-Fi connectivity
http://support.apple.com/en-ca/HT4628
Using network locations (Mac OS X v10.6 and later)
http://support.apple.com/en-us/ht5289
Regards,
-Norm G.