The present document specifies the E-UTRAN radio network layer signalling protocol for the S1 interface. The S1 Application Protocol (S1AP) supports the functions of S1 interface by signalling procedures defined in this document. S1AP is developed in accordance to the general principles stated in TS 36.401 and TS 36.410.
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
For a specific reference, subsequent revisions do not apply.
For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TS 37.320: "Universal Terrestrial Radio Access (UTRA) and Evolved Universal Terrestrial Radio Access (E-UTRA); Radio measurement collection for Minimization of Drive Tests (MDT);Overall description; Stage 2".
For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply.
A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.
A functionality controlling the access to network nodes. In case of Access Control Lists (ACL) functionality is applied in a network node the network node may only accept connections from other peer network nodes once the source addresses of the sending network node is already known in the target node.
an E-UTRAN cell broadcasting a CSG indicator set to true and a CSG identity. This cell operates in Closed Access Mode as defined in TS 22.220.
S1AP consists of Elementary Procedures (EPs). An Elementary Procedure is a unit of interaction between eNBs and the EPC. These Elementary Procedures are defined separately and are intended to be used to build up complete sequences in a flexible manner. If the independence between some EPs is restricted, it is described under the relevant EP description. Unless otherwise stated by the restrictions, the EPs may be invoked independently of each other as standalone procedures, which can be active in parallel. The usage of several S1AP EPs together or together with EPs from other interfaces is specified in stage 2 specifications (e.g., TS 23.401 and TS 36.300).
An EP consists of an initiating message and possibly a response message. Two kinds of EPs are used:
Class 1: Elementary Procedures with response (success and/or failure).
Class 2: Elementary Procedures without response.
For Class 1 EPs, the types of responses can be as follows:
A signalling message explicitly indicates that the elementary procedure successfully completed with the receipt of the response.
A signalling message explicitly indicates that the EP failed.
On time supervision expiry (i.e., absence of expected response).
Successful and Unsuccessful:
One signalling message reports both successful and unsuccessful outcome for the different included requests. The response message used is the one defined for successful outcome.
When S1-AP messages associated to one UE uses the UE-associated logical S1-connection for association of the message to the UE in eNB and EPC.
UE-associated logical S1-connection:
The UE-associated logical S1-connection uses the identities MME UE S1AP ID and eNB UE S1AP ID according to definition in TS 23.401. For a received UE associated S1-AP message the MME identifies the associated UE based on the MME UE S1AP ID IE and the eNB identifies the associated UE based on the eNB UE S1AP ID IE. The UE-associated logical S1-connection may exist before the S1 UE context is setup in eNB.
For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply.
An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
Access Control List
Additional RRM Policy Index
Cell Change Order
Code Division Multiple Access
Cell-ID (positioning method)
Cellular Internet of Things
Closed Subscriber Group
Dual Active Protocol Stacks
Dedicated Core Network
evolved Access Network
E-UTRAN Cell Global Identifier
Enhanced Cell-ID (positioning method)
evolved High Rate Packet Data
E-UTRA-NR Dual Connectivity
Evolved Packet Core
Evolved Packet System
E-UTRAN Radio Access Bearer
Evolved Serving Mobile Location Centre
Guaranteed Bit Rate
Global Navigation Satellite System
Globally Unique MME Identifier
GPRS Tunnelling Protocol
Hyper Frame Number
High Rate Packet Data
Integrated Access and Backhaul
International Mobile station Equipment Identity and Software Version number
Internet of Things
Local Home Network
Local Home Network ID
Local IP Access
LTE Positioning Protocol Annex
LTE WLAN Radio Level Integration with IPsec Tunnel
Multimedia Broadcast multicast service Single Frequency Network