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:: Cellular Technologies Overview

:: 2G Mobile Telephony Cellular Network - GSM

:: 2.5G Mobile Telephony 
 - HSCSD

:: 2.5G  Mobile Telephony
  - GPRS

:: 2.75G Mobile Telephony - EDGE

:: 2.9G Mobile Telephony
  – EDGE Evolution

:: 3G Mobile Telephony 
 – UMTS

:: 3.5G Mobile Telephony
  – High Speed Packet Access (HSPA)

:: 3.75G Mobile Telephony
  - HSPA+

:: Super 3G Mobile Telephony – LTE and SAE

:: Flash OFDM Technology

:: Mobile Broadband Wireless Access (MBWA)

:: 4G Mobile Telephony
  – Future Wireless Cellular Technology

 
  

Wireless Cellular Network Technologies: 3G Mobile Telephony UMTS

 

UMTS
Overview

 

Standards

 

System
Architecture

 

Protocol
Architecture

 

Radio Interface & Modulation

 

Quality of Services (QoS)

 

Security

 
  

3  Protocol Architecture

The UMTS Protocol Architecture for the user plane is shown in Figure umts6 for CSD and in Figure umts7 for PSD. UTRAN RNCs have Asynchronous Transfer Mode (ATM) communication links with 3G-MSCs and 3G-SGSNs. In an ATM link the information to be transmitted is divided into fixed-size cells (53 octets), multiplexed, and transmitted. 

The UMTS Protocol Architecture for CSD uses ATM Adaptation Layer 2 (AAL2). The AAL2 layer is divided into two sublayers, the Convergence Sublayer (CS), shown as ’AAL2’ in Figure umts6, and the Segmentation And Reassembly (SAR) sublayer. AAL2 enables low bitrate and delay sensitive applications, such as Voice over ATM, to share a common ATM Virtual Channel Connection (VCC). Thus the network bandwidth utilization is improved and voice/data call establishment times are reduced. The UMTS Protocol Architecture for PSD uses ATM Adaptation Layer 5 (AAL5), see Figure umts7. This adaptation layer protocol provides support for variable bit rate connection-oriented, or connectionless data and services. 

 

Figure umts6. User Plane UMTS Protocol Architecture in CSD. The Radio Link Control (RLC) protocol is used for the radio interface Uu.

 

In Figure umts7 it can be seen that some layers are the same as GPRS layers. The new layers are

  • Packet Data Convergence Protocol (PDCP), which maps higher-level characteristics onto the characteristics of the underlying radio interface protocols. PDCP supports IPv4, PPP, and IPv6, among other protocols.  
  • GPRS Tunneling Protocol for the User Plane (GTP-U), which tunnels user data between UTRAN and the 3G-SGSN, and between the GSNs in the backbone network. 

 

Figure umts7. UMTS User Plane Protocol Architecture in PSD.

 

The UMTS Control Plane Protocol Architecture for PSD is shown in Figure umts8. SCCP is the SS7 signaling protocol in the GSM protocol architecture for the control plane (see Figure gsm11). New protocols are Radio Resource Control (RRC) and Radio Access Network Application Part (RANAP). Packet switched services of the 3G-SGSN are 

  • GPRS Mobility Management (GMM)
  • Session Management (SM)
  • SMS. 

The UMTS Control Protocol Architecture for CSD is the same as in Figure umts8 but for the services 

  • Mobility Management (MM)
  • UMTS Mobility Management (UMM)
  • Call Control (CC)
  • Signalling Subsystem (SS)

of the 3G-MSC.

 

Figure umts8. UMTS Control Plane Protocol Architecture in PSD.

 

The User Plane Protocol Architecture for GERAN is shown in Figure umts9. The most noticeable differences of the packet switching mode are, that 

  • the packet data convergence protocol (PDCP) is used as a radio link layer protocol for operation over the Iu-ps interface instead of the SNDCP/LLC protocols, which are used for operation over the Gb interface to a GSM/GPRS/EGPRS CN
     
  • a transparent RLC layer has been introduced.

In the circuit switching mode, the Iu-cs interface partly uses the same protocol stack as the Iu-ps interface, but operates with RLC/MAC protocol layers in transparent mode. The protocol stack for the A interface to a GSM/HSCSD/ECSD CN is unchanged.

 

Figure umts9. The User Plane Protocol Architecture for GERAN.

 

The Control Plane Protocol Architecture for GERAN is shown in Figure umts10. The PS and CS channels are handled by the Radio Resource Control (RRC) protocol when the Iu interface is used. The radio resource (RR) protocol of GSM/GPRS is reused for the A/Gb interface. The only exception is for common control channels, such as the Broadcast Control Channel (BCCH). For such channels, the RR protocol is used regardless of service.

 

Figure umts10. The Control Plane Protocol Architecture for GERAN.

 

 

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