Lecture 10 LTE

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12 Δεκ 2013 (πριν από 4 χρόνια και 7 μήνες)

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Lecture 10 LTE

Two potential candidates for 4G networks



This lecture will look at 3G LTE technology and
the future development into 4G LTE Advance

3G LTE is an upgrade to 3G, i.e. a change of
protocols / software but with the existing
network. (4G will require a new network ?)

Currently the BEST 3G is HSPA (High Speed
Packet Access) signed as 3.5G

Many operator are running the basic 3G and
3G LTE is seen as a significant leap forward for

Reduced cost per bit

Increased service provision

more services at a
lower cost and better user experience.

Flexibility of use of existing and new bands

Simplified architecture based on open standard

Reasonable battery consumption

100mbps download (50mbps upload) for
20MHz of bandwidth

200 active phone calls in ever 5MHz cell

Under 10ms latency for small IP packets

3G LTE is an evolution for 3G

FDMA instead of CDMA

All IP based supporting IP4 and IP6.

No basic voice provision

VoIP is the


Orthogonal Frequency Division

Uses a large number of closely spaced carriers,
modulated with low data rate

Usually will have interference but signals
orthogonal to neighbours so no interference.

Use of error correction to re
create data where
it is lost.

Low data rate can overcome reflections and
interference. (Main reason for choice)

MIMO Multiple Input Multiple Output

Another technology used to improve

Adds complexity and added antennas

Uses multiple path propagation to send data;
uses a disadvantage as an advantage.

MIMO employs multiple antennas on receiver
/ transmitter to utilise multi
path effects that
always exist, to transmit additional data rather
than cause interference.

LTE works with both paired (LTE FDD) and
unpaired (LTE TDD) communication.

LTE FDD will be used as the migration path for
current paired frequencies currently in

LTE TDD seen as providing an upgrade path
and gaining importance.

LTE TDD especially important in China due to
the way they have split their spectrum.


System Architecture Evolution.

With high data rates and low latency need to
evolve system architecture to enable this

Cut some “core” functions (move to periphery)
to give faster throughput the network.

Connected to NodeB is an “Evolved packet

Mobility Management Entity (MME)

the main
control node within the system

Server gateway (SGW)

main border between the
Radio Access Network and the core network

PDN Gateway (PGW)

provides connectivity to
external packet networks

Policy and Charging Rules Function (PCRF)
provides the charging mechanism and policing the
devices on the network.

Improved data capacity.

All IP architecture

Reduced Latency

Reduce capital and operational expenditure

So 4G could be:

A new network built from scratch based on LTE

Packet switched , data not voice

Based on OFDM (OFDMA downlink SC

MIMO taking advantage of multiple routes

Do operators want to invest in another network
or use LTE with 3G

When new frequencies are released do we want
unpaired TDD or paired FDD

Perhaps 4G LTE will be a 3G network using the
LTE System Architecture, OFDM, MIMO on
unpaired frequencies. This is the best we can
do now but is it 4G

is it a new network