About YateUCN, the GSM and LTE Core Network

Unified EPC/IMS core network

The YateUCN is a unified core network solution intended for new LTE networks, for upgrading GSM/GPRS networks to LTE or for extending existing LTE networks.
The YateUCN software-defined core implements all the functions and protocols of the LTE core network in software, and uses commodity hardware (e.g. Dell PowerEdge R430). It integrates the EPC layers – MME, PGW, SGW, and PCEF. The YateUCN also includes the IMS layers for VoLTE – PCSCF, ISCSCF, IWF, and BGW.
It communicates with the LTE eNodeB module over S1AP and GTP protocols and uses a JSON API for configuration and management.

Unified GSM/GPRS core network

The YateUCN also implements the functions and protocols of GSM/GPRS core networks. In GSM/GPRS, the YateUCN acts as a MSC/VLR/SGSN/GGSN/GMSC in a single server. It connects to the YateBTS (GSM module) over GTP and SIP, replacing the costly SS7 MAP-A interface (BSSAP protocol). This leads to a higher return on investment without affecting the reliability of the network or the provided services.
The unified core network solution is based on replacing the eNodeB with the YateENB (LTE) and the base station subsystem with the YateBTS (GSM).
Many areas in the world are not covered by a cellular network due to the cost of existing circuit-switched network technology. YateUCN brings a new solution for deploying GSM/LTE networks at a lower cost.

About YateUCN, the GSM and LTE Core Network 7

Remote access for operations and management

YateUCN is easy to operate and manage remotely using the Yate Mobile Management Interface (MMI). The interface makes it accessible to add a new YateUCN unit, to setup a cluster of YateUCNs, to configure a single YateUCN function (MSC/VLR, GMSC, SGSN, GGSN, SGW or PGW), to configure YateUCN equipment with all its GSM/GPRS/LTE functions and more.

Unified GSM/3G/LTE core network, including GGSN, GMSC, MME, PGW
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YateUCN in a 4G Network

YateUCN is compatible to any 4G mobile network equipment, as seen in the diagram below.

It fulfills all the functions of the following typical SAE components:

About YateUCN, the GSM and LTE Core Network 7

YateUCN Functionalities

As an MME

In its role as an MME, YateUCN performs network access control for UEs trying to connect to the IP network.
It is responsible for subscriber authentication by connecting over the S6a interface (Diameter) to the HSS, the central database containing network subscriber information.
YateUCN also handles mobility management, allowing UEs to have continuous connectivity and active sessions as they move through the network.
Acting as a fully fledged MME, YateUCN keeps track of idle UEs and sends paging messages to all the eNodeBs in the UEs’ tracking area and restores bearers, allowing new data sessions to be established.
As part of its mobility management functions, YateUCN handles roaming management for subscribers to other LTE or 2G/3G networks, also with the HSS. It does also support the MAP v3 protocol to a HLR.
YateUCN is responsible for radio resource management, communicating with both the eNodeBs in the RAN and the HSS to perform this task over the S1-AP and S6a (Diameter) interfaces.

As an SGW

As an SGW, YateUCN connects data sessions over GTPv2 based S5/S8 to a PGW and can also connect over GTPv1 Gn/Gp to a GGSN. It handles handover between eNodeBs over the S1 interface, acting as a data session anchor.

The data forwarding function can be bypassed completely when connected to the built-in PGW.

As a PGW

In its role as a PGW, YateUCN receives GTPv2 control messages, assigns IP addresses and routes IP packets to and from Internet. Once the MME within the YateUCN requests an IP address, the PGW allows the subscriber access to the network and assigns the UE an IP address. Connections and mobility from legacy 2G/3G SGSNs are supported over the GTPv1 based Gn/Gp interface with no performance penalty.

The S5/S8 interface is bypassed and no additional GTP traffic is generated when the built-in PGW is used locally.


Acting as a PCEF YateUCN performs policy enforcement and service data flow detection, allowing data flow through the implemented PGW.


Supported interfaces

YateUCN also supports the following LTE-specific protocol and interfaces:

Roaming in a 4G network with YateUCN

YateUCN in Home Network

As seen in the diagram above, YateUCN is deployed in the home network. It replaces the PGW and establishes the IP session. 

It supports the GTP based S8 interface to connect to the visited SGW and performs signalling and IP traffic, enabling the subscriber access to both the Internet or the IMS network.

unified core network

In a visited network, YateUCN will perform the typical functions of an SGW and an MME.
As a SGW, YateUCN enables signalling and IP traffic tunneling over the S8 interface to the home PGW.
YateUCN also supports the S6a interface to connect to the home HSS and S13 to connect to EIR.


SS7 Connectivity

Voice interconnect



  • MSC <-> AuC messages (authentication)
  • MSC <-> EIR messages (equipment identification, optional)
  • VLR <-> HLR messages (location management, roaming)
  • MSC <-> SMSC messages (SMS)


  • SGSN <-> AuC messages (authentication)
  • SGSN <-> EIR messages (equipment identification, optional)
  • SGSN <-> HLR messages (data mobility management, roaming)
  • SGSN <-> GGSN messages (data sessions)
  • eNodeB <-> MME messages (LTE control and user data)




  • Rotation interval
  • File transfer: FTP

YateUCN architecture

About YateUCN, the GSM and LTE Core Network 9

In the above image you can see YateUCN’s architecture:

  • A Javascript library that eases work with the protocol modules above.
  • Various Js scripts that implement the actual logic of the YateUCN.
    • Example of included scripts: ucn_mme_sgsn.jsc, ucn_msc.jsc, ucn_pgw.jsc, ucn_ssf.jsc, ucn_vlr.jsc, ucn_eap.jsc.
    • The scripts use the Js library to communicate with the protocol modules and the Sqlite database.

Remote access for YateUCN operations and management

 YateUCN is easy to operate and manage remotely using the Yate Mobile Management Interface (MMI).
The interface makes it accessible to add a new YateUCN unit, to setup a cluster of YateUCNs, to configure a single YateUCN function, to configure YateUCN equipment with all its GSM/3G/LTE functions and more. With YateMMI operators can remotely manage their entire network equipment using a single web interface.
Here is a link to a demo of the YateMMI, with a preconfigured YateUCN equipment (both the username and password are admin).

Configuration resources

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