Core Network Functionality for LTE Access

OpenEPC includes the core network functionality related to the LTE access through its MME and eNodeB emulation components and through the extension of the Serving GW and HSS to support the required interfaces. The functionality for the core network related to the LTE access follows the 3GPP standard specified in 3GPP TS 23.401, enabling the showcasing of LTE specific connectivity features for various service platforms and applications.

It includes, the S1-MME reference point between the eNodeB emulation and the MME based on S1-AP protocol, the S11 reference point between the MME and the S-GW, the S1-U reference point between the eNodeB and the S-GW all based on the OpenEPC implementation of the GTPv2 protocol stack. It also includes the S6a reference point between the MME and the HSS based on the Fraunhofer FOKUS C Diameter stack implementation.

OpenEPC Rel. 3 includes the X2 interface implementation based on the X2-AP protocol which enables the direct communication between the eNodeBs enabling the deployment of more complex testbeds for self-organizing and flat network communication.

Additionally, OpenEPC Rel.3 includes an overhaul of the NAS and GTP stacks for providing full standard support as well as functionality and performance enhancements for the eNodeB, MME and S-GW.

The OpenEPC Core Network Support for LTE Access includes the functionality for the attachment and the detachment of UEs from the LTE access correspondent to the eNodeB emulation as well as the reservation of default and dedicated bearers. An aggressive timeline is considered for the development of the other features addressing the LTE access integration and especially for the integration with 3rd party LTE radio components.

eNodeB Emulation Supported Features:

• support for attachment and detachment procedures (based on the procedures from  3GPP TS 23.401 Section 5.3.2.1 and Section 5.3.8.2)
• support for default and dedicated bearer establishment, modification and termination (based on the procedures from  3GPP TS 23.401 Section 5.3.2.1, Section 5.4.1 and Section 5.4.4)
• X2 interface implementation based on the principles of TS 36.420 and inspired as signaling transport of TS 36.422 and as data transport from TS 36.424.
• X2-AP protocol based on the TS 36.423 specification
• support for the security association through the MME through S6a reference point
• communication with a modified ISC-DHCP server serving IPv4/IPv6 addresses
• communication with the Fraunhofer FOKUS eDHCP serving IPv4/IPv6 addresses
• dual IPv4/IPv6 supported for GTP signaling
• ability to use various types of tunnels (ipip RFC2003, sit RFC4213, ipip6 RFC 2473, ip6ip6 RFC 2473), covering all possible IPv4/IPv6 connectivity combinations
• modular architecture, enabling the replacement of key components (tunnel control module) with custom implementations
• binding cache and context state saved in persistent MySQL database

MME Supported Features:

• support for attachment and detachment procedures (based on the procedures from  3GPP TS 23.401 Section 5.3.2.1 and Section 5.3.8.2)
• support for default and dedicated bearer establishment, modification and termination (based on the procedures from  3GPP TS 23.401 Section 5.3.2.1, Section 5.4.1 and Section 5.4.4)
• support for the security association through the MME through S6a reference point
• dual IPv4/IPv6 supported for GTP signaling
• modular architecture, enabling the replacement of key components (tunnel control module) with custom implementations
• binding cache and context state saved in persistent MySQL database

Serving GW Supported Features:

• support for attachment and detachment procedures (based on the procedures from 3GPP TS 23.401 Section 5.3.2.1 and Section 5.3.8.2)
• support for default and dedicated bearer establishment, modification and termination (based on the procedures from 3GPP TS 23.401 Section 5.3.2.1, Section 5.4.1 and Section 5.4.4)
• dual IPv4/IPv6 supported for GTP signaling
• modular architecture, enabling the replacement of key components (tunnel control module) with custom implementations
• binding cache and context state saved in persistent MySQL database

Limitations:

• support for Seamless IP Traffic Offload (SIPTO), for Local IP Access (LIPA) and for Machine Type Communication (MTC) can be added upon request based on common R&D research projects
• IDLE mode and location management features can be added based on firm requests from OpenEPC partners
• network triggered detachments are not supported for now.
• congestion control supported only through flexible entities selection
• no support for E-UTRAN sharing or for emergency bearers
• no support for the relaying functionality
• radio technology functionality is not in the scope of the OpenEPC toolkit including header compression, bearer enforcement and admission control over the radio link.
• Transport Level packet marking in the uplink e.g. setting the DiffServ Code Point based on QCI;
• SGSN selection for handovers to 2G or 3G 3GPP access networks;
• Roaming (S6a towards home HSS);
• Currently traffic detection and lawful interception are not included;
• no intra-3GPP handover support