Long Term Evolution (LTE): A Technical Overview

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Introduction
The recent increase of mobile data usage and emergence of new applications such as MMOG (Multimedia
Online Gaming), mobile TV, Web 2.0, streaming contents have motivated the 3rd Generation
Partnership Project (3GPP) to work on the Long-Term Evolution (LTE). LTE is the latest standard in
the mobile network technology tree that previously realized the GSM/EDGE and UMTS/HSxPA network
technologies that now account for over 85% of all mobile subscribers. LTE will ensure 3GPP’s
competitive edge over other cellular technologies.



PERFORMANCE GOALS FOR LTE
E-UTRA is expected to support different types of services including web browsing, FTP, video
streaming, VoIP, online gaming, real time video, push-to-talk and push-to-view. Therefore, LTE is
being designed to be a high data rate and low latency system as indicated by the key performance
criteria shown in Table 1. The bandwidth capability of a UE is expected to be 20MHz for both transmission
and reception. The service provider can however deploy cells with any of the bandwidths
listed in the table. This gives flexibility to the service providers’ to tailor their offering dependent
on the amount of available spectrum or the ability to start with limited spectrum for lower upfront
cost and grow the spectrum for extra capacity.


Packet Data Network Gateway (PDN GW)
The PDN GW provides connectivity to the UE to
external packet data networks by being the point of
exit and entry of traffic for the UE. A UE may have
simultaneous connectivity with more than one
PDN GW for accessing multiple PDNs. The PDN
GW performs policy enforcement, packet filtering
for each user, charging support, lawful Interception
and packet screening. Another key role of the PDN
GW is to act as the anchor for mobility between
3GPP and non-3GPP technologies such as WiMAX
and 3GPP2 (CDMA 1X and EvDO).


S1-flex Mechanism
The S1-flex concept provides support for network
redundancy and load sharing of traffic across network
elements in the CN, the MME and the SGW,
by creating pools of MMEs and SGWs and allowing
each eNB to be connected to multiple MMEs and
SGWs in a pool.