http://www.ee.columbia.edu/pages/academics/course_info/course_descriptions.html  

Basic Telecommunication Theory

Vector representation of signals

http://www.infosyssec.org/infosyssec/security/teletut1.htm

http://www.telecomspace.com/

Books

http://williamstallings.com/DCC/DCC8e.html

Wireless Sensor Networks: Ian Akyildiz and Mehmet Can Varun

http://www.bestwebbuys.com/Telecommunications-books.html

http://www.crcpress.com/product/isbn/9780849318054

http://www.mitsot.com/

http://mitsloan.mit.edu/corporate/british-telecom.php

http://www.mit-comms.co.uk/intellirad.asp

http://www.telecommunications-tutorials.com/  

http://www.slideshare.net/dpd/tutorial-2-basic-communication-on-the-internet-email-presentation