On behalf of Bart:
Names are self explanatory. Like the name is telling Access is used to access something, in this case access allows to reach the Core.
Door to your house are access to it, where everything inside is the core.
Someone can tell in context of mme how interconnection between core network and radi access ( 2G, 3G ,4G ) can be done?
What are the major KPIs of LTE/LTEA service at Access and Core side?
Please share any doc or link?