Chapter9 Gay part

Question 1

explain enB

Answer 1

Evolved node B

1. Only network element defined as EUTRAN
2. Terminates the complete radio interface including physical layer and provides all radio management functions
3. Can handle several cells
4. inter-enB interface x2 specified for efficient inter-cell radio management for cells not attached to the same enB. It will allow coordination to enB handovers without direct involvement of EPC

Question 2

MME mobility management entity

Answer 2

It is a pure signaling entity inside the EPC.

SAE uses tracking areas to track the position of idle UEs. The basic principle is identical to location or routing areas from 2G/3G.

MME handles attaches and detaches to the SAE system, as well as tracking area updates
Therefore it possesses an interface towards the HSS (home subscriber server) which stores the subscription relevant information and the currently assigned MME in its permanent data base.

A second functionality of the MME is the signaling coordination to setup transport bearers (SAE bearers) through the EPC for a UE.

MMEs can be interconnected via the S10 interface. It generates and allocates temporary ids for UEs.

Question 3

Serving Gateway (SGW)

Answer 3

*Manage User IP tunnel between eNode B and PDN gateeway
* Manage user plane Mobility
* Termination point of PDN toward e-UTRAN
* Local Mobility anchor

Question 4

Packet Data Network (PDN) Gateway

Answer 4

• The PDN gateway provides the connection between EPC and a number of external
  data networks.

*A major functionality provided by a PDN gateway is the QoS coordination between t
he external PDN and EPC.

• Therefore the PDN gateway can be connected via S7 to a PCRF (Policy and Charging
  Rule Function).
• If a UE is connected simultaneously to several PDNs this may involved connections
  to more than one PDN-GW

Question 5

Policy and Charging Rule Function (PCRF)

Answer 5

Function
QoS policy negotiation with PDN
Charging Policy: determines how
packets should be accounted

• The PCRF major functionality is the Quality of Service (QoS) coordination between the
  external PDN and EPC.
• Therefore the PCRF is connected via Rx+ interface to the external Data network (PDN)
• This function can be used to check and modify the QoS associated with a SAE bearer
  setup from SAE or to request the setup of a SAE bearer from the PDN.

Question 6

Home Subscriber Server (HSS)

Answer 6

Functions:
Permanent and central subscriber
database
Stores mobility and service data for
every subscriber
Contains the Authentication Center
(AuC) functionality.

The HSS is already introduced by UMTS release 5.
* With LTE/SAE the HSS will get additionally data per subscriber
for SAE mobility and service handling.
*Some changes in the database as well as in the HSS protocol
(DIAMETER) will be necessary to enable HSS for LTE/SAE.
*The HSS can be accessed by the MME via S6a interface.