LTE General Architecture

LTE General Architecture Overview
http://beyond-3g-wireless.blogspot.com/

Whenever we start discussing about any technology we usually start with Evolution & its Architecture.

So I would like to start my blog with discussion on LTE (Long Term Evolution) which is our next generation wireless

LTE Network Architecture
In this chapter to make it more interesting I tried to compare LTE network elements with existing 2G/3G networks, so that it would be easy for us to understand their functionalities.
In general the LTE Architecture is functionally split into two parts namely

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E-UTRAN -Evolved-UMTS Terrestrial Radio Access Network (eNB)
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EPC-Evolved Packet Core (MME,S-GW,PDN GW,HSS)

Figure2 from 3GPP Spec 36.300
The E-UTRAN consists of eNBs, which provides termination of control plane & user plane towards the UE &EPC network.Currently no need to bother much about what is control/user plane.
eNode B is nothing but combination of both RNC+Node B's in case of a UMTS network or BTS+BSC in case of a GSM network.The eNBs are interconnected with each other by means of the X2 interface. The eNBs are also connected by means of the S1 interface to the EPC (Evolved Packet Core), more specifically to the MME (Mobility Management Entity) by means of the S1-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 eNBs
E-UTRAN typically does Radio Resource Management towards UE, Selection of an MME based on the information provided by UE for routing Control Plane data,Selection of S-GW to route User Plane data, Scheduling etc.
You can refer 3GPP Spec 36.300 for more information on E-UTRAN functionalities.
The EPC provides mobile core functionality that, in previous mobile generations (2G, 3G), has been realized through two separate sub-domains: circuit-switched (CS) for voice and packet-switched (PS) for data.
In LTE, these two distinct core sub-domains, which are used voice and data, are unified as a single IP domain(Packet Switch Domain). Which means in LTE there in no more circuit switched voice call is possible.In LTE voice call is supported through VOIP(Voice Over IP)
With all this features LTE failed to satisfy the operators world wide for not having CS LTE network. So there is a recent development happening in LTE market to support Voice Over LTE via Generic Access Network(VOLGA)
Please follow the below mentioned link to get more info on VoLGA
http://www.volga-forum.com/
LTE will be end-to-end all-IP(ie. from mobile handsets and other terminal devices with embedded IP capabilities, over IP-based Evolved NodeBs).
As discussed earlier EPC consists of four components

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MME (Mobility Management Entity) [similar to SGSN]
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S-GW (Serving Gateway) [similar to GGSN]
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PDN GW (Packet Data Network Gateway)
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PCRF(Policy and Charging Rules Function)

We will discuss each of its functionality later on.
Until then bye from Sridhar.