Describe the basic LTE network architecture.

LTE (Long Term Evolution) architecture consists of two main parts: E-UTRAN (Evolved UMTS Terrestrial Radio Access Network) contains eNodeB (evolved Node B) base stations that handle all radio functions and connect directly to the core network, eliminating the RNC layer of 3G. EPC (Evolved Packet Core) includes: MME (Mobility Management Entity) for signaling and mobility; S-GW (Serving Gateway) for user data routing; P-GW (PDN Gateway) for connection to external networks; HSS (Home Subscriber Server) for user authentication. LTE is all-IP with no circuit-switched voice natively (VoLTE uses IMS). The flat architecture reduces latency to ~10-20ms.