4 General aspects

37.4703GPPGeneral aspects and principlesRelease 17TSW1 interface

4.0 General

This clause captures the W1 interface principles and characteristics.

The general principles for the specification of the W1 interface are as follows:

– An ng-eNB may consist of an ng-eNB-CU and ng-eNB-DUs. An ng-eNB-CU and an ng-eNB-DU is connected via W1 logical interface.

– One ng-eNB-CU controls one or more ng-eNB-DUs.

– One ng-eNB-DU supports one or multiple cells. One cell is supported by only one ng-eNB-DU.

– ng-eNB-DU ID is used to identify ng-eNB-DU only over W1AP procedures, ng-eNB-DU ID is not connected to cell identifier.

– The ng-eNB-CU terminates W1 interface connected with the ng-eNB-DU.

– The ng-eNB-DU terminates W1 interface connected with the ng-eNB-CU.

– The W1 interface shall separate Radio Network Layer and Transport Network Layer.

– The W1 interface shall enable exchange of UE associated information and non-UE associated information.

– The W1 interface is open;

– From a logical standpoint, the W1 is a point-to-point interface between an ng-eNB-CU and an ng-eNB-DU.

NOTE: A point-to-point logical interface should be feasible even in the absence of a physical direct connection between the endpoints.

– The W1 interface supports control plane and user plane separation;

– The W1 interface enables exchange of UE associated information and non-UE associated information;

– The standard should not prevent to separated CP and UP.

The W1 interface specifications facilitate the following:

– inter-connection of an ng-eNB-CU and an ng-eNB-DU supplied by different manufacturers.

The W1 interface supports:

– procedures to establish, maintain and release radio bearers for the NG-RAN part of PDU sessions and for E-UTRAN Radio Access Bearers;

– the separation of each UE on the protocol level for user specific signalling management;

– the transfer of RRC signalling messages between the UE and the ng-eNB-CU.