Section: 4.4.9 HeNB subsystem
Content: A HeNB subsystem consists of a HeNB, optionally a HeNB GW and optionally a Local GW. The Local IP Access and SIPTO at the Local Network with L-GW function collocated with the HeNB functions are achieved using a Local GW (L-GW) collocated with the HeNB. Figure 4.4.9-1 illustrates the architecture for LIPA and/or SIPTO at the Local Network with L-GW function collocated with the HeNB. Figure 4.4.9-1: Architecture for LIPA or SIPTO at the Local Network with L-GW collocated with the HeNB NOTE 1: The optional HeNB GW is not shown in the figure for simplicity. The HeNB subsystem is connected by means of the standard S1 interface to the EPC (Evolved Packet Core), more specifically to the MME (Mobility Management Entity) by means of the S1-MME interface and to the Serving Gateway (S-GW) by means of the S1-U interface. When LIPA or SIPTO at the Local Network with L-GW function collocated with the HeNB is activated, the L-GW has a S5 interface with the S-GW. NOTE 2: In this specification and for simplification the term eNodeB refers to the HeNB subsystem if the UE accesses the network via a HeNB unless stated otherwise. NOTE 3: Detailed functions of HeNB and HeNB GW are described in TS 36.300[ Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 ]  [5]. NOTE 4: An L-GW collocated with a HeNB may support LIPA, or SIPTO@LN, or both. The Local GW is the gateway towards the IP networks (e.g. residential/enterprise networks, Internet) associated with the HeNB. The Local GW has the following PDN GW functions: - UE IP address allocation; - DHCPv4 (server and client) and DHCPv6 (client and server) functions; - Packet screening; - Functionality as defined in RFC 4861 [32]. Additionally, the Local GW has the following functions: - ECM-IDLE mode downlink packet buffering; - ECM-CONNECTED mode direct tunnelling towards the HeNB. NOTE 5: The architecture for SIPTO at the Local Network with L-GW function collocated with a HeNB depicted in Figure 4.4.9-1 also applies to SIPTO at the Local Network with L-GW function collocated with an eNodeB.