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ATM Protocols and Signaling

- Fundamentals -

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ATM protocol for signaling

Signaling protocol can be looked at as an important application running on top of the

lower, physical, ATM and AAL layers

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Signaling Protocols Layers

Signaling occurs over a Signaling ATM Adaptation Layer (SAAL) residing between theATM layer and the signaling protocol

The SAAL provides reliable transport of signaling message between two ATM systemsto include the recovery of multiple gaps within the data stream

The SAAL is composed of the sub layers:

Common Part

Based on ALL5

Consists of to additional sub layers Segmentation and Reassembly Sublayer (SAR)

Common Part Convergence Sublayer (CPCS)

Service Specific Part

Service Specific Co-ordination Function (SSCF)

The SSCF maps signaling messages from the upper level into SSCOP

Service Specific Connection oriented protocol (SSCOP)

Provides mechanisms for establishing, releasing and monitoring signaling information exchange between signaling

entities

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Signaling Protocols Layers

There are two types of SAAL:

SAAL-NNI

SAAL-UNI

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AAL Type 2 Signaling

Provides functions to dynamically establish and release AAL type 2 point to pointconnections as requested by AAL2 served users in a network comprised of AAL2endpoint and AAL2 switches

The AAL2 served user in 3G networks is the radio resource management and controlentity which establishes/releases AAL2 connections when new soft handover legs are

established/released

The AAL2 signaling protocol is used by higher layer functionalities for AAL2connection establishment and release of a connection

I can establish an AAL2 connection, release an AAL2 connection and maintenance

functions to align the status of the AAL2 resources within the two peer AAL2 nodes

It offers a reset mechanism which is used to return one or several AAL2 channels toidle condition

Also contains mechanism for blocking and unblocking resources during testprocedures

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AAL2 Signaling protocol architecture

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General Protocol model for UTRAN

terrestrial interfaces

The protocol structures in UTRAN terrestrial interfaces (Iu, Iur, Iub) are designed

according to the same general protocol model as in the figure

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General Protocol model for UTRAN

terrestrial interfaces Horizontal layers

Radio network layer All UTRAN related issues are visible only in the radio network layer

Transport network layer Represents standard transport technology that is selected

Vertical planes

Control Plane Used for all 3G specific control signaling

It includes the application protocol (RANAP in Iu, RNSAP in Iur, NBAP in Iub) and the signaling bearer for transporting theapplication protocol messages

The application protocol is used among other things for setting up bearers to the UE

User plane All information sent and received by the user, such as coded voice in a voice call or the packets in an Internet connection are

transported via the user plane

The user plane includes the data stream and the data bearer Transport network control plane

Is used for all control signaling within the transport network layer

It includes the ALCAP (Access Link Control Application Part) protocol that is needed to set up the transport bearers for theuser plane

Transport network user plane The data bearers in the user plane and the signaling bearers for the application protocol also belong to the transport user

plane

The data bearers in the transport network user plane are directly controlled by the transport network control plane

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Protocol Structure for Iub

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Protocol Structure for Iur

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Protocol Structure for Iu-CS

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Protocol Structure for Iu-PS

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ATM adaptation layer for user plane

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ATM adaptation layer for control plane

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ATM adaptation layer for transport network

control plane

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Protocol stack for circuit switched data

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Protocol stack for packet switched data

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Protocol stack for Iur interface

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Protocol stack for AAL 2 signaling