There are lots of identifiers in LTE to identify cells, tracking areas, users, tunnel endpoints, etc. etc. Most are similar to what already exists in GPRS and UMTS but most of them have new names and lengths. While I know some of them that I use regularly, there are quite a number of them that I have to look up every now and then. Here's a good resource that has them all, including a description of how they are related and sometimes part of each other. Enjoy.