Lecture 10 LTE

bottlelewdMobile - Wireless

Dec 12, 2013 (4 years and 20 days ago)

97 views

Lecture 10 LTE


Two potential candidates for 4G networks


LTE


WiMax


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
them.


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


Uses OFDMA / SC
-
FDMA instead of CDMA


All IP based supporting IP4 and IP6.


No basic voice provision


VoIP is the
standard.


OFDM


Orthogonal Frequency Division
Multiplex


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
performance.


Adds complexity and added antennas
required.


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
existence.


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.


SAE


System Architecture Evolution.


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


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


Connected to NodeB is an “Evolved packet
Core”


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
-
FDMA
uplink)


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
technology?