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Quick Notes
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Quick Notes
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The E-UTRAN (The access network)
The E-UTRAN handles the radio communications between the mobile and
the evolved packet core and just has one component, the evolved base
stations, called eNodeB or eNB. Each eNB is a base station
that controls the mobiles in one or more cells. The base station that
is communicating with a mobile is known as its serving eNB.
LTE
Mobile communicates with just one base station and one cell at a time
and there are following two main functions supported by eNB:
- The eBN sends and receives radio transmissions to all the mobiles using the analogue and digital signal processing functions of the LTE air interface.
- The eNB controls the low-level operation of all its mobiles, by sending them signalling messages such as handover commands.
Each
eBN connects with the EPC by means of the S1 interface and it can also
be connected to nearby base stations by the X2 interface, which is
mainly used for signalling and packet forwarding during handover.
A
home eNB (HeNB) is a base station that has been purchased by a user to
provide femtocell coverage within the home. A home eNB belongs to a
closed subscriber group (CSG) and can only be accessed by mobiles with a
USIM that also belongs to the closed subscriber group.
Summary
• The Access Network (Access Stratum)Summary
• Optimised for Packet Switched services only
• Support for non-real-time (data services) and real-time services (constant data rate and delay)
• eNodeBs linked by X2 interface for transfer of user data packets during handover (no RNC)
Unlike, 3G where several NodeB stations are linked to an RNC, here the eNodeBs communicate with each other to forward unacknowledged data packets during handover. The eNodeBs then connect directly to the Core Network (EPC).
Since there is no support for Circuit Switched services, the PS domain must be able to support real time services by ensuring that it provide a constant data rate and delay for speech or video telephony calls.
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