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. LTE-WLAN Aggregation: LWA bearer: LWIP bearer: LWIP Operation: Xw: WLAN Termination:

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. eNB LWA LWIP WT

The transport layer for data streams over Xw is an IP based Transport. The following Figure shows the transport protocol stacks over Xw.

The GTP-U (TS 29.281) protocol over UDP over IP shall be supported as the transport for data streams on the Xw interface. The data link layer is as specified in clause 4. For LWA bearers, there may be one UL data stream and there may be one DL data stream per E-RAB at the Xw interface. For LWIP bearers, there may be one UL data stream and there may be one DL data stream per UE at the Xw interface.

• The DL data stream is used for DL user data forwarding from the eNB to the WT.
• The UL data stream is used for carrying the UL flow control feedback (if flow control is supported) and for UL user data forwarding from the WT to the eNB.

Each data stream is carried on a dedicated transport bearer. If supported, the WT may use the DRB Identifier in the LWA PDU header of the UL data stream to identify the dedicated UL transport bearer. The identity of a transport bearer signalled in the RNL control plane consists of the IP address and the TEID of the corresponding GTP tunnel, allocated by the target node (see TS 29.281).

The GTP-U (TS 29.281) protocol shall be used over the Xw interface between eNB and WT.

The path protocol used shall be UDP (RFC 768). The UDP port number for GTP-U shall be as defined in TS 29.281. The eNB and the WT over the Xw interface shall support fragmentation and assembly of GTP packets at the IP layer. The eNB and the WT shall support IPv6 (RFC 2460) and/or Ipv4 (RFC 791). LWA: There may be one or several IP addresses in both the eNB and the WT. The packet processing function in the source eNB shall send downstream packets corresponding toa given E-RAB to the target WT IP address (received in XwAP) associated to the DL transport bearer of that particular E-RAB. The packet processing function in the source WT shall send upstream packets corresponding to a given E-RAB to the target eNB IP address (received in XwAP) associated to the UL transport bearer of that particular E-RAB or the E-RAB with the lowest E-RAB ID. LWIP: There may be one or several IP addresses in both the eNB and the LWIP-SeGW. The packet processing function in the source eNB shall send downstream packets corresponding to a given LWIP bearer to the target LWIP-SeGW IP address (received in XwAP) associated to the DL transport bearer of that particular GTP-U TEID. The packet processing function in the source LWIP-SeGW shall send upstream packets corresponding to a given UE to the target eNB IP address (received in XwAP) associated to the UL transport bearer of that particular GTP-U TEID. The Transport Layer Address signalled in XwAP messages is a bit string of either

1. 32 bits in case of Ipv4 address according to RFC 791; or
2. 128 bits in case of Ipv6 address according to RFC 2460.

IP Differentiated Services code point marking (RFC 2474) shall be supported. The mapping between traffic categories and Diffserv code points shall be configurable by O&M for based on QoS Class Identifier (QCI)/ Label Characteristics and others E-UTRAN traffic parameters. Traffic categories are implementation-specific and may be determined from the application parameters.

For the LWA bearer option

• the GTP-U (TS 29.281) protocol over UDP over IP shall be supported as the transport for the downlink and uplink user data streams of LWA PDUs and the uplink flow control feedback stream on the Xw interface. The GTP-U PDU may include a Xw RAN Container with flow control information as specified in TS 36.465 which is carried in the GTP-U extension header. The transport bearer is identified by the GTP-U TEID (TS 29.281) and the IP address of the eNB and WT respectively. There is one UL data stream and there is one DL data stream per E-RAB at the Xw interface:
  • The DL data stream is used for DL user data transmission from the eNB to the WT.
  • The UL data stream is used for UL user data transmission and UL flow control feedback transmission from the WT to the eNB.
• the packet processing function in the eNB shall send downstream packets corresponding to a given E-RAB to the WT IP address (received in XwAP) associated to the DL transport bearer of that particular E-RAB. The packet processing function in the WT shall send upstream packets corresponding to a given E-RAB to the eNB IP address (received in XwAP) associated to the UL transport bearer of that particular E-RAB or the E-RAB with the lowest E-RAB ID.
• in addition, user data forwarding (from WT to eNB ) may be performed by eNB providing another GTP-U TEID to receive the DL data forwarded by the WT.

For the LWIP bearer option

• the GTP-U (TS 29.281) protocol over UDP over IP shall be supported as the transport for the downlink and uplink user data streams of LWIP PDUs and the uplink flow control feedback stream on the Xw interface. The GTP-U PDU includes a Xw RAN Container with flow control information as specified in TS 36.465 which is carried in the GTP-U extension header. The transport bearer is identified by the GTP-U TEID (TS 29.281) and the IP address of the eNB and LWIP-SeGW respectively. There is one UL data stream and there is one DL data stream per UE at the Xw interface:
  • The DL data stream is used for DL user data transmission from the eNB to the LWIP-SeGW.
  • The UL data stream is used for UL user data transmission and UL flow control feedback transmission from the LWIP-SeGW to the eNB.
• the packet processing function in the eNB shall send downstream packets corresponding to all LWIP bearers to the LWIP-SeGW IP address (received in XwAP) associated to the DL transport bearer of that particular GTP-U TEID. The packet processing function in the LWIP-SeGW shall send upstream packets corresponding to all LWIP bearers to the eNB IP address (received in XwAP) associated to the UL transport bearer of that particular GTP-U TEID.