Osmocom Home NodeB Gateway, for attaching femtocells to the 3G CN (OsmoMSC, OsmoSGSN) https://osmocom.org/projects/osmohnbgw
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osmo-hnbgw/doc/manuals/chapters/overview.adoc

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[[overview]]
== Overview
[[intro_overview]]
=== About OsmoHNBGW
OsmoHNBGW implements the Home NodeB Gateway function in the 3G network architecture. It serves
as a gateway between the classic 3G core network (CN) domain with its IuCS and IuPS interface
and the femtocell based RAN.
A typical 3G network consisting of Osmocom components will look as illustrated in the following
diagram:
[[fig-3g]]
.Typical 3G network architecture used with OsmoHNBGW
----
+------------+ +--------+ +----------+ +---------+
UE <-->| hNodeB |<--Iuh---->| HNB-GW |<--IuCS-->| OsmoMSC |<--GSUP-->| OsmoHLR |
UE <-->| femto cell | ...-->| | ...-->| | | |
| | | | +----------+ +---------|
+------------+<--GTP-U | |
\ | | +------+ +------+
| | |<--IuPS-->| SGSN |<--GTP-C-->| GGSN |
| +--------+ ...-->| | GTP-U-->| |
| +------+ / +------+
\_______________________________/
----
The HNB-GW performs a translation interface between the IuCS/IuPS interfaces on the one hand
side, and the Iuh interface on the or ther hand:
----
Iuh IuCS/IuPS
NAS +----+----+ +----+----+
Non-Access Stratum | CC | MM | | CC | MM |
- - - - - - - - - - - +----+----+-------+ +----+----+
| RANAP | | H | RANAP |
Access Stratum +---------+ HNBAP | N +---------+ - - SCCP USER SAP
| RUA | | B | SUA | \
+---------+-------+ - +---------+ |
| SCTP | G | SCTP | } SIGTRAN
+-----------------+ W +---------+ |
| IP | | IP | /
+-----------------+ +---------+
----
On the femtocell (Home NodeB) side, OsmoHNBGW implements the Iuh interface as specified by 3GPP.
=== The Iuh interface
Iuh consists of the following sub-layers:
- HNBAP (Home NodeB Application Part)
- RUA (RANAP User Adaptation, between RANAP and SCTP