UMTS Architecture (Universal Mobile Telecommunications System)
UMTS is a 3rd Generation (3G) mobile communication system that enhances GSM by offering higher data rates, multimedia services, and improved capacity. It is based on a new radio access technology (W-CDMA) and integrates with the existing GSM core.
Main Components of UMTS Architecture
UMTS architecture consists of three main domains:
1. User Equipment (UE)
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The mobile device used by the subscriber.
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Components:
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ME (Mobile Equipment) – the hardware (phone).
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USIM (Universal Subscriber Identity Module) – stores subscriber identity, authentication keys, etc.
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2. UMTS Terrestrial Radio Access Network (UTRAN)
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Responsible for the radio access part.
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Components:
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Node B: Equivalent to BTS in GSM; handles radio transmission/reception.
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Radio Network Controller (RNC):
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Manages multiple Node Bs.
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Handles handover, radio resource management, encryption, etc.
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3. Core Network (CN)
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Responsible for switching, routing, and service control.
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Divided into two domains:
a) Circuit-Switched Domain
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Handles voice calls.
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Components:
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Mobile Switching Centre (MSC)
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Visitor Location Register (VLR)
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Gateway MSC (GMSC)
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b) Packet-Switched Domain
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Handles data services like internet.
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Components:
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Serving GPRS Support Node (SGSN)
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Gateway GPRS Support Node (GGSN)
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Interfaces
| Interface | Between | Purpose |
|---|---|---|
| Uu | UE ↔ Node B | Radio interface using W-CDMA |
| Iub | Node B ↔ RNC | Controls radio resources, transport bearer info |
| Iur | RNC ↔ RNC | Supports inter-RNC handover |
| Iu-CS | RNC ↔ MSC (CS Domain) | Circuit-switched services |
| Iu-PS | RNC ↔ SGSN (PS Domain) | Packet-switched services |
Key Features of UMTS:
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Supports up to 2 Mbps data rate.
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Uses W-CDMA for radio access.
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Offers global roaming and multimedia services.
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Separates circuit and packet switching, enabling better data/voice integration.