Tips for LTE TTCN Source

Where can I get TTCN and Viewer ?

This is where you can download the TTCN source code from
http://www.3gpp.org/ftp/tsg_ran/WG5_Test_ex-T1/TTCN/Deliveries/LTE_SAE/

You can download free TTCN-3 Viewer from
http://www.eu.anritsu.com/ttcn

Where do I have to start ?

If you open up the TTCN source, it would look extremly complicated and I don't know where to start to look at. Where do I have to start ?

If you want to have overall understanding of test procedure/protocol sequence of each test case, I think it would be better to look at test case description in 3GPP 36.523-1. But when you go over the test procedure over and over, I would start further details of parameters and it's default values of the IE (information elements) for the test cases. I would start with EUTRA_RRC_ASN1_Definitions.asn in CommonEUTRA_Def folder.