UMTS Interfaces

The Core Network of UMTS is same as that of GPRS. The air interface is totally different. We therefore only discuss the air interface. The air interfaces in UMTS are listed below:

• Uu: UE to Node B (UTRA, the UMTS W-CDMA air interface
• Iu: RNC to GSM Phase 2+ CN interface (MSC/VLR or SGSN)
  • Iu-CS for circuit-switched data
  • Iu-PS for packet-switched data
• Iub: RNC to Node B interface
• Iur: RNC to RNC interface, not comparable to any interface in GSM

The Iu, Iub, and Iur interfaces are based on ATM transmission principles.