
Explanation/Reference:
HSS - Is the concatenation of HLR and AuC
http://www.ciscopress.com/articles/article.asp?p=1681067
MME - Is in charge of all the Control plane functions related to subscriber and session management
https://books.google.co.in/books?id=gXAuo6c72nkC&pg=PA40&lpg=PA40&dq=MME+is+in+charge+of+all
+the+Control+plane+functions+related+to+subscriber+and+session
+management&source=bl&ots=MmEH-
k4pml&sig=u_QAZwOdAFTuHClzOQ4HzChhoS4&hl=en&sa=X&ved=0CB0Q6AEwAGoVChMIsPHs2- vLxwIVSxuOCh1t_AG2#v=onepage&q=MME%20is%20in%20charge%20of%20all%20the%20Control%
20plane%20functions%20related%20to%20subscriber%20and%20session%20management&f=false PCRF Server - Manages the service policy and sends QoS setting information for each user session and accounting rule information
https://books.google.co.in/books?id=9cAblFPGvMkC&pg=PA260&lpg=PA260&dq=PCRF+Server+%E2%
80%93+Manages+the+service+policy+and+sends+QoS+setting+information+for+each+user+session+and
+accounting+rule
+information&source=bl&ots=3rYTYNb7To&sig=QXky7ItQgrs5Y11SXYboPARZJAo&hl=en&sa=X&ved=0 CCEQ6AEwAWoVChMIhOWRmezLxwIVECSOCh2OCAcY#v=onepage&q=PCRF%20Server%20%E2%
80%93%20Manages%20the%20service%20policy%20and%20sends%20QoS%20setting%20information
% 20for%20each%20user%20session%20and%20accounting%20rule%20information&f=false PDN GW - Is the termination point of the packet data interface towards the PDN
https://books.google.co.in/books?id=gXAuo6c72nkC&pg=PA40&lpg=PA40&dq=PDN+GW+is+the
+termination+point+of+the+packet+data+interface+towards+the+PDN&source=bl&ots=MmEH- k4rvo&sig=yI4mXwWKuRM9LiFQweCIHqHCfOc&hl=en&sa=X&ved=0CC4Q6AEwA2oVChMIpaez5- zLxwIVi22OCh3VFwo0#v=onepage&q=PDN%20GW%20is%20the%20termination%20point%20of%20the
%20packet%20data%20interface%20towards%20the%20PDN&f=false
Service GW - Is the termination point of the packet data interface towards E-UTRAN
https://books.google.co.in/books?id=DTsTAAAAQBAJ&pg=PA35&lpg=PA35&dq=Service+GW++Is+the
+termination+point+of+the+packet+data+interface+towards+E-
UTRAN&source=bl&ots=zR3K6DHjkA&sig=Koc5ghWqJgky0qsJo1TQTA3b-
tw&hl=en&sa=X&ved=0CCIQ6AEwAWoVChMIqv30ou3LxwIVw5COCh0w6QCQ#v=onepage&q=Service%
20GW%20%20Is%20the%20termination%20point%20of%20the%20packet%20data%20interface%
20towards%20E-UTRAN&f=false