4 Introduction

04.073GPPMobile Radio Interface Signalling Layer 3 - General AspectsTS

4.1 General

Three models are defined for Layer 3, one model for non-GPRS services, one for GPRS services supporting Class C MSs only and one model for GPRS-services supporting Class A and Class B MSs. (The third model is a combination of the first two models listed).

The layer 3 for non-GPRS services provides the functions necessary

‑ for Radio Resource (RR) management;

‑ for Mobility Management (MM); and

‑ for the Connection Management (CM) functions, i.e. functions for the control, provision, and support of services offered by the network; among which there are, e.g.:

‑ the functions to establish, maintain and terminate circuit‑switched connections across a GSM PLMN and other networks to which the GSM PLMN is connected;

‑ supporting functions for supplementary services control;

‑ supporting functions for short messages service control.

– supporting functions for location services control.

The layer 3 for non-GPRS services is composed of three sublayers comprising:

‑ the Radio Resource Management (RR) functions;

‑ the Mobility Management (MM) functions; and

‑ the Connection Management (CM) functions.

When CTS services are added to non-GPRS services, the following functions are added:

‑ CTS Radio Resource Management (CTS-RR) functions to RR; and

‑ CTS Mobility Management (CTS-MM) functions to MM.

The layer 3 for GPRS services is composed of four sublayers comprising :

‑ the Radio Resource Management (RR) functions;

‑ the Mobility Management (GMM and GMM-AA);

‑ for the Logical Link Control (LLC);

‑ the Connection Management (CM) functions.

– Session Management (SM) functions to activate, modify and delete the contexts for packet data protocols (PDP)

– supporting functions for short messages service control.

The Connection Management (CM) sublayer is composed of functional blocks for:

‑ Call Control (CC) for non-GPRS services;

‑ Short Message Service Support (SMS) for non-GPRS services;

‑ GPRS Short Message Service Support (GSMS) (for GPRS services supporting Class A, B and C MSs);

– Session Management (SM) (for GPRS services supporting Class A, B and C MSs);

‑ Supplementary Services Support (SS) for non-GPRS services;

‑ Group Call Control for non-GPRS services;

‑ Broadcast Call Control (BCC) for non-GPRS services;

‑ Connection Management of Packet Data on Signalling channels for non-GPRS services.

– Location Services support (LCS) for non-GPRS services;

Within the context of LCS, for GSM LCS, the services defined for an MS are equally applicable to a type A LMU, unless otherwise stated. The following is a list of services essential for a type A LMU.

The layer 3 for non-GPRS services provides the functions necessary

‑ for Radio Resource (RR) management;

  • for Mobility Management (MM); and

– supporting functions for location service control.

The layer 3 for non-GPRS services is composed of three sublayers comprising:

‑ the Radio Resource Management (RR) functions;

  • the Mobility Management (MM) functions; and

‑ the Connection Management (CM) functions.

The Connection Management (CM) sublayer is composed of functional block for:

  • location services support (LCS) for non-GPRS services.

This Technical Specification does not consider the distribution of signalling functions among the different network equipments. The signalling functions are described between two systems which represent the MS side and the network side of the radio interface of layer 3. Only the functions in the network for signalling communication with one MS is considered.

For GPRS services, in addition to the signalling functions also the user data transfer is included in this Technical Specification.

4.2 Applicability of functional blocks

Not for all functional blocks listed in subclause 4.1, support in the MS or in the network is mandatory:

‑ Support of Group Call Control is optional in the MS and in the network.

‑ Support of Broadcast Call Control is optional in the MS and in the network.

‑ Connection Management of Packet Data on Signalling channels. is optional in the MS and in the network.

– Support of GPRS services is optional in the MS and in the network.

– Support of CTS services is optional in the MS. CTS services are not applicable to the network.

– Support of LCS services is optional in the MS and in the network, but not optional in a type A LMU.

Further conditions and constraints are defined in other Technical Specifications.

4.3 Technique of description

Layer 3 and its sub‑layers are specified by:

‑ their service specification, see subclause 4.3.1;

‑ their protocol specification, see subclause 4.3.3;

‑ the specification of functions, see clause 5.

4.3.1 Service description

The services of signalling layer 3 and its sublayers are described in terms of:

‑ services provided to upper (sub‑)layers at the service access points;

‑ services assumed from lower (sub‑)layers at the service access points;

Layer 3 and its supporting lower layers provide the Mobile Network Signalling (MNS) Service and User Data Transfer (UDT) Service (for GPRS services only) to the upper layers.

The service provided/assumed at the service access points are described by means of abstract service primitives and parameters as recommended in CCITT Recommendation X.200.

4.3.2 Abstract service primitives

The abstract service primitives consist of requests, responses, indications and confirmations. The general syntax of a primitive is specified in GSM 04.01.

4.3.3 Protocols and peer‑to‑peer communication

By use of the services provided by lower (sub‑)layers, peer entities in a (sub‑)layer in the MS and the network exchange information. Exchange of information between two peer entities is performed according to the corresponding (sub‑)layer protocols. A protocol is a set of rules and formats by which the information (control information and user data) is exchanged between the two peers. The information is exchanged by use of messages which are defined in the protocol. (Therefore, the messages are also called Protocol Data Units, PDUs).

There are several protocols of the RR sublayer, one protocol of the LLC sublayer, three protocols of the MM sublayer, and several protocols of the CM sublayer. For each functional block of the CM sublayer as defined in subclause 4.1 there is one protocol. The CM protocols are specified in the Technical Specifications identified in subclause 4.3.4.

In the model used in this ETS, there is:

1) for non-GPRS services:

‑ one RR sub‑layer entity in the MS and one RR sub‑layer entity in the network;

‑ one MM sub‑layer entity in the MS and one MM sub‑layer entity in the network;

for each functional block of the CM sublayer as defined in subclause 4.1 which is supported in the MS (in the network), there are, depending on the protocol, one or more entities in the MS (in the network). Two different entities of the same functional block in the MS (in the network) are called parallel entities. The entities of the same functional block in the MS correspond in a one‑to‑one relation to the entities of the functional block in the network. The corresponding entities are called peer entities.

2) for CTS services (in addition to non-GPRS services)

‑ one RR sub-layer entity in the MS and one in the CTS fixed part. These RR sub-layers include one CTS-RR sub-entity on each side.

‑ one MM sub-layer entity in the MS and one in the CTS fixed part These MM sub-layers include one CTS-MM sub-entity on each side.

‑ for each functional block of the CM sublayer as defined in subclause 4.1 which is supported in the MS (in the fixed part), there are, depending on the protocol, one or more entities in the MS (in the fixed part). Two different entities of the same functional block in the MS (in the fixed part) are called parallel entities. The entities of the same functional block in the MS correspond in a one‑to‑one relation to the entities of the functional block in the fixed part. The corresponding entities are called peer entities.

3) for GPRS services supporting Class C MSs :

‑ one RR sublayer entity (RR) in the MS and one RR sublayer entity in the network;

‑ six LLC sublayer entities (QoS1-QoS4, signalling, SMS) in the MS and six LLC sublayer entities in the network;

‑ one or more MM sublayer entities (GMM and/or 1-n GMM-AA) in the MS and one MM sublayer entity in the network (GMM or GMM-AA, i.e. the network don’t know if several MM sublayer entities belong to the same MS or not);

– one SM entity in the MS’s CM sublayer and one SM sublayer entity in the network’s CM sublayer;

– one or more GSMS functional blocks in the CM sublayer if supported.:

4) for non-GPRS and GPRS services supporting Class A and Class B MSs :

‑ two RR sublayer entities (RR) in the MS and two RR sublayer entities in the network;

‑ six LLC sublayer entities (QoS1-QoS4, signalling, SMS) in the MS and six LLC sublayer entities in the network;

‑ two or more MM sublayer entities (GMM + MM or 1-n GMM-AA + MM or GMM + 1-n GMM-AA + MM) in the MS and one or two MM sublayer entity in the network (GMM + MM or GMM-AA);

– one SM entity in the MS’s CM sublayer and one SM entity in the network’s CM sublayer;

– for each functional block of the CM sublayer as defined in subclause 4.1 which is supported in the MS (in the network), there are, depending on the protocol, one or more entities in the MS (in the network). Two different entities of the same functional block in the MS (in the network) are called parallel entities. The entities of the same functional block in the MS correspond in a one‑to‑one relation to the entities of the functional block in the network. The corresponding entities are called peer entities.

As each sub‑layer entity is specified by one and only one protocol, it is also called a protocol entity or protocol control entity.

For GPRS-services supporting Class A and Class B MSs, the MM entities of the MM-sublayer are able to exchange information by means of GMM PDUs as well as MM PDU’s. This means if a mobile is GPRS attached, non-GPRS mobility management procedures may make use of GRPS mobility management messages.

When two peer protocol entities exchange PDUs, a transaction is said to be established (or: to be active; or: to exist). It depends from the protocol when exactly a protocol entity considers the transaction to be active, normally this is the case.

‑ from the moment when it has passed the first suitable message to lower (sub‑) layers or received the first suitable message from its peer entity.

up to the moment when it has released the transaction.

4.3.4 Contents of layer 3 related Technical Specifications

The Radio Resource (RR) management protocol is defined in GSM 04.08:

‑ the Mobility Management (MM) protocol is defined in GSM 04.08;

– the Session Management (SM) protocol is defined in GSM 04.08;

‑ the Call Control (CC) protocol is defined in GSM 04.08;

‑ the Supplementary Services (SS) protocol is defined in GSM 04.10, GSM 04.8x and GSM 04.9x;

‑ the Short Message Service (SMS) protocol is defined in GSM 04.11;

‑ the Group Call Control (GCC) protocol is defined in GSM 04.68;

‑ the protocols for Packet Data on Signalling channels (PDS), PDSS1 and PDSS2, are defined in GSM 04.63;

– the Logical Link Control (LLC) protocol is defined in GSM 04.64;

– the GPRS Radio Resource (GRR) protocol is defined in GSM 04.60 and GSM 04.08.

– the CTS Radio Resource (CTS‑RR) sub-protocol is defined in GSM 04.56;

– the CTS Mobility Management (CTS‑MM) sub-protocol is defined in GSM 04.56;

– the CTS additions to the Call Control (CC) protocol are defined in GSM 04.56.

– the Location Services (LCS) protocol is defined in GSM 03.71 and GSM 04.71.