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Cairo University
Faculty of Engineering
Credit Hour Programs
Senior-2
ELC N406 | Communications-3
LTE (Long Term Evolution)
Prepared by:
Eman Alaa
Christine Onsy
Yasmin Afify
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Table of contents:
Introduction 3
Consumer and industry trends4
LTE proposition... ..4
LTE challenges. ..5
LTE benefits... .6
LTE key features. ..8
LTE Modulation schemes ..12
LTE network architecture ..13
Comparisons between LTE and HSPA+17
Comparisons between LTE and WiMax19
Summary 22
List of figures....23
References.24
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Introduction:
LTE is a standard for wireless communication of high-speed data for mobile phones and
data terminals. It is based on the GSM/EDGE and UMTS/HSPA network technologies,
increasing the capacity and speed using new modulation techniques.
The standard is developed by the 3GPP (3rd Generation Partnership Project).The world's
first publicly available LTE service was launched by Telia Sonera in the Scandinavian
capitals Stockholm and Oslo on 14 December 2009.
LTE is the natural upgrade path for carriers with GSM/UMTS networks, but even
CDMA holdouts such as Verizon in North America and au by KDDI in Japan have
announced that they will migrate to LTE in the future.
LTE is therefore anticipated to become the first truly global mobile phone standard.
Although commonly referred to as a type of 4G wireless service, LTE release 8 currently
in uses does not satisfy the requirements set forth by the ITU-R organization
(International Telecommunication Union Radio Communication).
Future releases of LTE (referred to as LTE Advanced) are expected to satisfy the
requirements to be considered 4G.
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Consumer and industry trends:
End users increase usage of advanced communication services andapplications like media downloads, VOIP, video streaming, online
gaming, social networking, Email and search.
Accelerating the delivery of personal media experience ( broadbandeverywhere, optimized networks)
LTE Makes On-Demand Possible (Entertainmentand productivity, Personal broadband on the go, Fashionable devices
working across technologies.
LTE Proposition:
1. Broadband experience everywhere: faster more responsive
2. Improved business proposition: Lower cost Added capacity Flexible Global
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LTE challenges:
1. The user expectation
Best price Transparent flat rate Full internet Click-bang responsiveness
2. Operators challenges Reduce cost per bit Provide high data rate Provide low latency
Figure (1)
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LTE Benefits:
1. Flexible Spectrum usage possible with LTE
- It supports paired and unpaired frequency spectrum.- The possibility of allocating spectrum bandwidth with variable size
from 1.4 to 20 MHZ. while in WCDMA & HSPA is always 5 MHZand fixed.
- A small channel bandwidth is more beneficial for mobile operators.On the other hand a large bandwidth is required if large peak data
rates to be supported.
2. Higher data rates
- At 20 MHZ it has beenreached to 150 Mbps
using 2x2 MIMO, and
300 Mbps using 4x4
MIMO ( DL) , and 75
Mbps (UL).
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3. Simple Architecture:
- LTE has a much simpler and relatively flat architecture comparedto the legacy UMTS network in HSPA+
4. Lower Cost:- High reuse of existing spectrum assets, which means that(LTE will allow operators to generate fresh sources of value from their
existing network investments while enjoying the significant economies of
scale that flows from the participation in the world's biggest and most
successful family of evolving cellular system)
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5. Ultra low latency:A) Round Trip Times:
LTE enables round trip times (RTT) of less than 20 ms. The round trip
time or user plane latency is the time it takes for information to travel
from the mobile terminal to the destination in the network and back to
the terminal.
B) Control Plane Latency:
Also the control plane latency - the time needed to allocate transport
resources - is important. The requirement for the control plane latency
in LTE is less than 100 ms.
LTE Key features:
1-Evolved NodeB:
- No RNC is provided anymore.- The evolved Node only takes over all radio management functionality.- This will make radio management faster and hopefully simplify Network
architecture
- The eNodeB decides - again on a sub frame-to-sub frame basiswhichmodulation scheme, coding rate, and power level should be applied in
uplink and downlink. Adaptive modulation and coding has already been
implemented in High-Speed Packet Access (HSPA) systems.
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2- IP Transport layer:
- EUTRAN exclusively uses IP as transport layer.
3- UL/ DL resource scheduling:
- In UMTS physical resources are either shared or dedicated
- Evolved Node B handles all physical resource via a scheduler and assigns
them dynamically to users and channels
- This provides greater flexibility than the older system
4-HARQ: Hybrid Automatic repeat Request
- HARQ especially increases the performance (delay and throughput)for cell edge users.
- HARQ simply implements a retransmission protocol on layer 1/2 thatallows sending retransmitted blocks with different coding than the 1st
one.
5- QOS Awareness:
- The scheduler must handle and distinguish different quality of service- Otherwise real time services would not be possible via EUTRAN.- The system provides the possibility for differentiated service.
6-Self Configuration:
- Possibility to let Evolved Node configure themselves.- But it will not completely substitute the manual configuration and
optimization.
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7-Packet Switched Domain Only:
- No circuit switched domain is provided.- If CS applications are required, they must be implemented via IP.
8-Non 3GPP Access:
- The EPC will be prepared also to be used by non3GPP accessnetworks (e.g. LAN, WLAN, Wi-MAX, etc.)
- This will provide true convergence of different packet radio accesssystem.
9-MIMO (Multiple Input Multiple Output):
- LTE will support MIMO as an option- It describes the possibility to have multiple transmitter and receiver
antennas in a system.
- Up to four antennas can be used by a single LTE cell (gain:Spatial multiplexing)
- MIMO is considered to be the core technology to increase Spectralefficiency.
The LTE radio interface initially supports 2x2 (and later 4x4) MultipleInput Multiple Output (MIMO) transmission in the downlink. 2x2
MIMO employs two transmit antennas at the eNodeB side and two
receive antennas at the mobile terminal side of the transmission link.
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There are actually two kinds of MIMO techniques:
Multi stream transmission (also known as spatial multiplexing)MIMO
Diversity (or space-time coding) MIMO.Multi stream Diversity
Each transmit antenna transmits a
different data stream
Each transmit antenna transmits the
same data stream
Although the data streams are
transmitted simultaneously at the
same frequency, the receiver can
nevertheless detect the different
streams received via different
antennas - hence the name spatial
multiplexing
In the special case of beam forming,
the same data stream is transmitted,
but with a different phase shift in
each transmit antenna, thus
effectively sending the transmit
signal in a certain direction
Increases the peak data rate over
the radio link. For instance, 4x4
MIMO effectively increases thepeak data rate by a factor of four
Does not increase the peak data rate
over the radio link, but is beneficial
in low SNIR conditions
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LTE Modulation Schemes:
1. OFDM- LTE uses OFDM for the DLthat is, from the base station to the
terminal.
- OFDM meets the LTE requirement for spectrum flexibility andenables costefficient solutions for very wide carriers with high peak
rates
- The basic LTE downlink physical resource can be seen as atimefrequency grid. In the frequency domain, the spacing between
the subcarriers, f, is 15kHz.
- In OFDMA, each subcarrier only carries information related to onespecific symbol.
- The Signals are orthogonal to each other at their peaks to guaranteethe maximum power and least interference.
2. SC-FDMA- Each subcarrier contains information of ALL transmitted symbols.- Uplink multiplexing-
Lower Peak to Average Power Ratio (PARR)Less Power Consumption
Less expensive RF amplifiers in the terminal
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LTE Network Architecture:
- In contrast to the circuit-switched model of previous cellular systems,Long Term Evolution (LTE) has been designed to support only packet-
switched services.
- It aims to provide seamless Internet Protocol (IP) connectivity betweenuser equipment (UE) and the packet data network (PDN),
Without any disruption to the end users applications during mobility.
- While the term LTE encompasses the evolution of the UniversalMobile Telecommunications System (UMTS) radio access through the
Evolved UTRAN (E-UTRAN), it is accompanied by an evolution of the
non-radio aspects under the term System Architecture Evolution
(SAE), which includes the Evolved Packet Core (EPC) network.
Together LTE and SAE comprise the Evolved Packet System (EPS).
- EPS uses the concept of EPS bearers to route IP traffic from a gateway inthe PDN to the UE.
- A bearer is an IP packet flow with a defined quality of service (QoS)between the gateway and the UE.
- The E-UTRAN and EPC together set up and release bearers as requiredby applications.
- EPS provides the user with IP connectivity to a PDN for accessing theInternet, as well as for running services such as Voice over IP (VoIP). An
EPS bearer is typically associated with a QoS. Multiple bearers can beestablished for a user in order to provide different QoS streams or
connectivity to different PDNs. For example, a user might be engaged in
a voice (VoIP) call while at the same time performing web browsing or
FTP download. A VoIP bearer would provide the necessary QoS for the
voice call, while a best-effort bearer would be suitable for the web
browsing or FTP session.
- The network must also provide sufficient security and privacy for theuser and protection for the network against fraudulent use.
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Figure (2)
The core network:
The core network (called EPC in SAE) is responsible for the overall control
of the UE and establishment of the bearers. The main logical nodes of theEPC are:
PDN Gateway (P-GW)
Serving Gateway (S-GW)
Mobility Management Entity (MME)
In addition to these nodes, EPC also includes other logical nodes and
functions such as the Home Subscriber Server (HSS) and the Policy Control
and Charging Rules Function (PCRF). Since the EPS only provides a bearer
path of a certain QoS, control of multimedia applications such as VoIP is
provided by the IP Multimedia Subsystem (IMS), which is considered to be
outside the EPS itself.
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The logical CN nodes:
PCRFThe Policy Control and Charging Rules Function is responsiblefor policy control decision-making, as well as for controlling the flow-based
charging functionalities in the Policy Control Enforcement Function (PCEF),
which resides in the P-GW. The PCRF provides the QoS authorization (QoS
class identifier [QCI] and bit rates) that decides how a certain data flow will
be treated in the PCEF and ensures that this is in accordance with the users
subscription profile.
HSSThe Home Subscriber Server contains users SAE subscription datasuch as the EPS-subscribed QoS profile and any access restrictions for
roaming. It also holds information about the PDNs to which the user can
connect. This could be in the form of an access point name (APN) (which is
a label according to DNS naming conventions describing the access point tothe PDN) or a PDN address (indicating subscribed IP address (es)). In
addition the HSS holds dynamic information such as the identity of the
MME to which the user is currently attached or registered. The HSS may
also integrate the authentication center (AUC), which generates the vectors
for authentication and security keys.
P-GWThe PDN Gateway is responsible for IP address allocation for theUE, as well as QoS enforcement and flow-based charging according to rules
from the PCRF. It is responsible for the filtering of downlink user IP packets
into the different QoS-based bearers. This is performed based on Traffic
Flow Templates (TFTs). The P-GW performs QoS enforcement for
guaranteed bit rate (GBR) bearers. It also serves as the mobility anchor for
interworking with non-3GPP technologies such as CDMA2000 and WiMAX
networks.
S-GWAll user IP packets are transferred through the Serving Gateway,
which serves as the local mobility anchor for the data bearers when the UE
moves between eNodeBs. It also retains the information about the bearers
when the UE is in the idle state (known as EPS Connection ManagementIDLE [ECM-IDLE]) and temporarily buffers downlink data while theMME initiates paging of the UE to reestablish the bearers. In addition, the S-
GW performs some administrative functions in the visited network such as
collecting information for charging (for example, the volume of data sent to
or received from the user) and lawful interception. It also serves as the
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mobility anchor for interworking with other 3GPP technologies such as
general packet radio service (GPRS) and UMTS.
MMEThe Mobility Management Entity (MME) is the control node thatprocesses the signaling between the UE and the CN. The protocols running
between the UE and the CN are known as the Non Access Stratum (NAS)
protocols.
The main functions supported by the MME can be classified as:
Functions related to bearer management This includes theestablishment, maintenance and release of the bearers and is handled by the
session management layer in the NAS protocol.
Functions related to connection managementThis includes theestablishment of the connection and security between the network and UE
and is handled by the connection or mobility management layer in the NAS
protocol layer.
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Comparison between LTE and HSPA+:
Advantages of LTE over HSPA+:
Flexible Spectrum usage possible with LTE: LTE will be the same
whether the bandwidth available is 5MHz or 20MHz. Of course the
data rate will increase when the BW is increased. With HSPA+ only
5MHz bandwidths is possible. Similarly with HSPA+ only FDD mode
of operation is possible whereas with LTE FDD or TDD mode is
possible.
Spectrum Efficiency: Better spectrum efficiency, by a factor of 2 atleast over HSPA+
Simpler Architecture: LTE has a much simpler and relatively flat
architecture compared to the legacy UMTS network in HSPA+
Higher Data Rates: LTE gives DL data rates of 144Mbps and UL of57Mbps. HSPA+ gives 42Mbps in DL and 11Mbps in UL
Ultra Low Latency: 10ms instead of 50ms for HSPA+
Short TTI: 0.5ms instead of 2ms for HSPA+
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Advantages of HSPA+ over LTE
Will be ready much before LTE: HSPA+ technology should be
available in Q1 2009 whereas the earliest with LTE would be
sometime in 2010.
Much less investment in infrastructure: Since HSPA+ is evolution of
HSPA which is already being deployed; it would be easier and less
costly to upgrade. With LTE since its based on OFDM a lot of newcomponents will be required. Also in case of LTE the number of
components is reduced but since they work in a different way, new
components will be required.
Figure (3)
Figure (4)
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Comparison between LTE and WiMAX:
WiMax is in the market while Long Term Evolution is still inthe labs...So, in this point, WiMax has a clear time
advantage over LTE: WiMax is present nowadays in
numerous countries around the world.
Figure (5)
There is a good difference in the latency of WiMax andLTE, and some "real time" multimedia services will get
benefit of this.
Figure (6)
LTE provides FULL mobility. While WiMax needs amobile target with a speed lower than 120 km/h, LTE stilloperates with a target up to 350 km/h.
LTE supports handover and roaming with the3GGP mobile networks. However, these services are not
easy to achieve with WiMax.
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It seems that Intel will integrate WIMAX in its newdevices...It ensures a good number of WiMax devices in the
market by default, which is very good to expand
the potential market of WiMax.
LTE, like GSM, needs a SIM card to operate. The use of aSIM card has its advantages and also its disadvantages.
On the one hand, with LTE, the use of a SIM card ismandatory for the users and that is a requirement for them,
which is not good because the users want things easy, so
the fewer requirements needed the better.
On the other hand, the use of SIM card makes easier toprovide some services like roaming, which is a key service
nowadays. Identifying subscribers with a SIM makes thingseasier to the carrier.
There are plenty of telecom carriers around the world thatare going to LTE instead of WiMax. Most of them have a
GSM infrastructure already deployed, so LTE is a logic
step in their evolution to the next 4G (or 3,9G)
Some examples of this are: Biggest carriers in USA: AT&T, Verizon.
Vodafone China Mobile
DoCoMo (2010-2011).
Others: KDDI, Telstra, Telecom Italia, China Telecom, Orange,
and T-Mobile.
The initial costs of WiMax are lower when the operators donot have any 2G3G equipment, so WiMax could be agood option because the CAPEX of WiMax are lower than
the CAPEX of LTE, and the initial investment is a keypoint in developing countries.
LTE needs lower power consumption than WiMax. One ofthe reasons of this is the use of SC-FDMA modulation in
uplink channels.
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WiMax Architecture vs. LTE Architecture:
Figure (7)
Figure (8)
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Summary:
LTE is well positioned to meet the requirements of next generationmobile networks.
UMTS LTE was designed to simultaneously provide a mix ofservices ranging from real time voice to high-speed Internet browsing.
The use of a single IP type of interconnection simplifiesdeployment, maintenance, and reduces equipment cost.
Base stations (eNBs) can directly connect to each other witheliminates the need for a switching system.
The radio structure is flexible (bandwidth, duplex types) whichallows UMTS LTE to be deployed in different spectrums.
IP Multimedia Subsystem - IMS - is used to setup and managemultimedia sessions with devices in and outside of the UMTS LTE
system.
Multiple types of location based services are integrated intothe UMTS LTE system.
UMTS LTE is a great evolution ofGSM, GPRS, and WCDMA. LTE infrastructure is designed to be as simple as possible. LTE offers scalable bandwidths, from 1.4 MHz up to 20MHz.
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List of figures:
Figure 1 chart representing price per megabyte Vs. different wireless
communication services
Figure 2 LTE architecture
Figure 3 comparison between 3G and LTE networks
Figure 4 comparison between uplink and downlink in LTE ,Wimax ,
HSPA
Figure 5 Evolution of Wimax and LTE
Figure 6 chart representing latency time of LTE Vs. Wimax
Figure 7 Wimax network architecture
Figure 8 simplified LTE architecture
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References:
www.nokiasiemensnetworks.com
www.slideshare.net
CPG0599090904_LTE_Network_Architecture_EN_StraWhitePaper
http://4gwirelessjobs.com/articles/article-detail.php?Analysis-WiMax-&-LTE&Arid=MTA5&Auid=OTU=
www.gsacom.com
http://www.nokiasiemensnetworks.com/http://www.nokiasiemensnetworks.com/http://www.slideshare.net/http://www.slideshare.net/http://4gwirelessjobs.com/articles/article-detail.php?Analysis-WiMax-&-LTE&Arid=MTA5&Auid=OTU=http://4gwirelessjobs.com/articles/article-detail.php?Analysis-WiMax-&-LTE&Arid=MTA5&Auid=OTU=http://4gwirelessjobs.com/articles/article-detail.php?Analysis-WiMax-&-LTE&Arid=MTA5&Auid=OTU=http://4gwirelessjobs.com/articles/article-detail.php?Analysis-WiMax-&-LTE&Arid=MTA5&Auid=OTU=http://4gwirelessjobs.com/articles/article-detail.php?Analysis-WiMax-&-LTE&Arid=MTA5&Auid=OTU=http://www.gsacom.com/http://www.gsacom.com/http://www.gsacom.com/http://4gwirelessjobs.com/articles/article-detail.php?Analysis-WiMax-&-LTE&Arid=MTA5&Auid=OTU=http://4gwirelessjobs.com/articles/article-detail.php?Analysis-WiMax-&-LTE&Arid=MTA5&Auid=OTU=http://www.slideshare.net/http://www.nokiasiemensnetworks.com/