LTE Test Terminologies

This topic Includes LTE test terminologies and definitions.

NOTE: This topic is constantly evolving and will be populated with test terminologies and definitions as and when they become available.

Default Bearer and Dedicated Bearer
Circuit Switched Fallback (CSFB)
SRVCC from E-UTRAN to UTRAN/GERAN
eMBMS

Evolved Radio Access Network (eRAN)

Consists of the eNodeB (eNB)
Offers Radio Resource Control (RRC) functionality
Radio Resource Management, admission control, scheduling, ciphering/deciphering of user and control plane data, and compression/decompression in DL/UL user plane packet headersServing Gateway (SGW)
Routes and forwards user data packets
Acts as the mobility anchor for the user plane

During inter-eNBhandovers Between LTE and other 3GPP technologies

Pages idle state UE when DL data arrives for the UEPacket Data Network Gateway (PDN GW)
Provides connectivity to the UE to external packet data networks
A UE may have simultaneous connectivity with more than one PDN GW
Performs policy enforcement, packet filtering, and charge support
Acts as mobility anchor between 3GPP and no-3GPP technologies

Mobility Management Entity (MME)

Manages and stores UE contexts
UE/user identities, UE mobility state, user security parameters
Paging message distribution

The Mobility Management Entity (MME) is the key control-node for the LTE access-network. It is responsible for Idle mode UE tracking and paging procedure including re-transmissions. It is involved in the bearer activation/deactivation process and is also responsible for choosing the Security Gateway (SGW) for a UE at the initial attach . MME is also responsible for authenticating the user (by interacting with the HSS.

The Non-Access Stratum (NAS) signaling terminates at the MME and it is also responsible for generation and allocation of temporary identities to UEs. The MME is the termination point in the network for ciphering/integrity protection for NAS signaling and handles the security key management.

SGW Emulation

When emulating an SGW in a MME Nodal test case, Landslide supports the following functionality:

Connects to the MME using the S11 interface
Sends session information to the MME as necessary (such as at MS session establishment) to emulate a flow
Responds to requests from the MME
Tears down the emulated flow

eNodeB Emulation

The eNodeBs are connected by means of the S1-MME interface to the MME and to the Serving Gateway (S-GW) by means of the S1-U. The S1 interface supports a many-to-many relation between MMEs/Serving Gateways and eNodeBs. When emulating eNodeB in a MME Nodal test case, Landslide supports the following functionality:

Connects to the MME using the S1-MME interface
Sends session information to the MME as necessary (such as at MN session establishment) to emulate an MN session/flow
Performs session/flow modification updates to the MME
Responds to requests from the MME
supports the S1U interface in the end-to-end mode.
Tears down the emulated flow

Default and Dedicated Bearer

EPS Bearer

For E-UTRAN access to the EPC the PDN connectivity service is provided by an EPS bearer for GTP-based S5/S8, and by an EPS bearer concatenated with IP connectivity between Serving GW and PDN GW for PMIP-based S5/S8.

An EPS bearer uniquely identifies traffic flows that receive a common QoS treatment between a UE and a PDN GW for GTP-based S5/S8, and between UE and Serving GW for PMIP-based S5/S8.

EPS Bearer is a virutal connection between UE and PGW which identifies a data send and received between these two end points with specific QoS attributes.

The procedure used to establish an EPS Bearer is called “EPS Bearer Activation” procedure. Either endpoint can trigger this procedure. For example, the PDN-GW may trigger this procedure when it determines that a new VoIP call is requested and a new EPS Bearer should be established to support this call.

Default Bearer

One EPS bearer is established when the UE connects to a PDN, and that remains established throughout the lifetime of the PDN connection to provide the UE with always-on IP connectivity to that PDN. That bearer is referred to as the default bearer.

Dedicated Bearer

Any additional EPS bearer that is established for the same PDN connection is referred to as a dedicated bearer.

NOTE: Default bearers are created on a per PDN basis. So if a UE is connecting to two PDNs it will need to establish two default bearers. The first default bearer will be established during the Attach process when the UE first powers up and the second will be done using Activate default EPS bearer context request procedure. When the second default bearer is established it will be dependent on the service and the UE.

Circuit Switched Fallback (CSFB)

The CSFB in EPS supports provisioning of voice and other CS-domain services (e.g. CS UDI video/ LCS/ USSD) by reuse of CS infrastructure when the UE is served by E UTRAN. A CS fallback enabled terminal, connected to E UTRAN uses GERAN or UTRAN to connect to the CS domain. This function is only available in case E UTRAN coverage is overlapped by either GERAN coverage or UTRAN coverage.

S3 — In CSFB, S3 supports ISR for CS fallback/SMS over SGs. It also enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state.
SGs — The reference point between the MME and MSC server. The SGs reference point is used for the mobility management and paging procedures between EPS and CS domain, and is based on the Gs interface procedures. The SGs reference point is also used for the delivery of both mobile originating and mobile terminating SMS. Additional procedures for alignment with the Gs reference point are not precluded.

Test Terminology in MME Testing with CSFB

UE	The CSFB capable UE supports access to E-UTRAN/EPC as well as additional access to the CS domain over GERAN and/or UTRAN. The SMS over SGs capable UE supports access to E-UTRAN/EPC. A UE that supports CSFB also supports SMS over SGs (however, a UE that supports SMS over SGs does not necessarily support CSFB.)
MME	The CSFB and/or SMS over SGs enabled MME supports the following additional functions: Deriving a VLR number and LAI from the GUTI received from the UE or from a default LAI. Maintaining of SGs association towards MSC/VLR for EPS/IMSI attached UE. Initiating IMSI detach at EPS detach. Initiating paging procedure specified in this document towards eNodeB when MSC pages the UE for CS services. Supporting SMS procedures defined in this document. Rejecting CS Fallback call request (e.g. due to O&M reasons)
MSC	The CSFB and/or SMS over SGs enabled MSC supports the following additional functions: Maintaining SGs association towards MME for EPS/IMSI attached UE. Supporting SMS procedures.
E-UTRAN	The CSFB enabled E-UTRAN supports the following additional functions: Forwarding paging request for CS domain to the UE. Directing the UE to the target CS capable cell.
BSS	If the network supports ISR, the CSFB enabled BSS forwards Gb interface paging messages to the radio interface.

E-UTRAN and 3GPP UTRAN/GERAN SRVCC

SRVCC (Single Radio Voice Call Continuity) is an LTE functionality that allows a VoIP/IMS call in the LTE packet domain to be moved to a legacy voice domain (GSM/UMTS or CDMA 1x). SRVCC provides the ability to transition a voice call from the VoIP/IMS packet domain to the legacy circuit domain.

SRVCC offers VoIP subscribers with coverage over a much larger area than would typically be available during the rollout of a new network (during deployment of IMS/VoIP-based voice services in conjunction with the rollout of an LTE network for a legacy cellular network).

High Level Concept of SRVCC from E-UTRAN to UTRAN/GERAN

For SRVCC from E-UTRAN to UTRAN/GERAN, MME first receives the handover request from E-UTRAN with the indication that this is for SRVCC handling, and then triggers the SRVCC procedure with the MSC Server (with SRVCC via the Sv reference point, where MME requires SRVCC STN-SR information for the UE). MSC Server then initiates the session transfer procedure to IMS and coordinates it with the CS handover procedure to the target cell. MSC Server (for SRVCC) then sends PS-CS handover Response to MME, which includes the necessary CS HO command information for the UE to access the UTRAN/GERAN.

Handling of any non-voice PS bearer is done by the PS bearer splitting function in the MME. MME starts the handover of non-voice PS bearer during SRVCC procedure based on the information received from E-UTRAN. The handover of non-voice PS bearer(s), if performed, is done as according to Inter RAT handover procedure.

The MME is responsible for coordinating the Forward Relocation Response from PS-PS handover procedure and the SRVCC PS to CS Response.

eMBMS

The MBMS (multimedia broadcast multicast service) feature includes the MBMS Bearer Service and the MBMS User Service, which are defined over both UTRAN (i.e. WCDMA, TD-CDMA and TD-SCDMA) and LTE (referred to as eMBMS). The eMBMS (evolved multimedia broadcast multicast service), also referred as LTE Broadcast, is an advanced mobile data delivery technology that enables mobile operators to significantly reduce the cost of delivery.

NOTES:

· In addition to MBMS Bearers (over SGmb/SGi-mb), the BM-SC may use EPS Bearers (over SGi) to realize an MBMS User Service.

· MBMS service over Gn-SGSN is supported when the MBMS-GW is co-located with the PDN GW and this PDN GW has the necessary GGSN functions to control the MBMS Bearer Service over Gn.