WHAT IS 4G? A Closer Look at WiMAX and LTE

WHAT IS 4G?
A Closer Look at WiMAX and LTE
A BRIEF HISTORY OF MOBILE COMMUNICATIONS
 2G
– 2nd generation of mobile telephony
technology; launched in 1991.

Main benefits of 2G:
phone conversations were digitally encrypted;
 2G is significantly more efficient on the spectrum
allowing for greater mobile phone penetration levels;
 2G introduced data services for mobiles, starting with
SMS text messages.
2G technologies can be divided into TDMA-based and CDMAbased standards depending on the type of multiplexing used.
The main 2G standards are GSM, IS-95 (CDMA), iDEN, PDC
(personal digital cellular), IS-136 (aka D-AMPS digitaladvanced mobile phone service which is TDMA).



HISTORY OF TELECOMMUNICATIONS

2.5/2.75 G –are 2G-systems that have implemented a packet-switched
domain in addition to the circuit-switched domain.
 The first major step in the evolution of GSM networks to 3G occurred
with the introduction of General Packet Radio Service (GPRS), and EDGE
Enhanced Data for GSM Evolution which is sometimes referred to as
EGPRS. CDMA2000 networks similarly evolved through the introduction
of 1XRTT.
 EDGE is standardized by 3GPP as part of the GSM family and it is an
upgrade that provides a potential three-fold increase in capacity of
GSM/GPRS networks. The specification achieves higher data-rates (up
to 236.8 kbit/s) by switching to more sophisticated methods of coding
(8PSK), within existing GSM timeslots.
A BRIEF HISTORY OF MOBILE COMMUNICATIONS
 3G – third generation of mobile telephone technology. 3G refers to the
generation of standards as described by (International Mobile
Telecommunications) IMT-2000 by the International Telecommunications
Union (ITU).
 Apps include wide area voice telephone, mobile internet access,
video calls and mobile TV all in a mobile environment.
 The IMT-2000 standards requires a system to provide peak data
rates of at least 200 kBps.
 The main 3G standards are UMTS (Universal Mobile
Telecommunications System) which is the 3G upgrade to the GSM
networks and CDMA2000, the 3G upgrade to the CDMA networks.
UMTS standards are put forth by the 3GPP (Third Generation
Partnership Project); CDMA2000 standards are put forth by 3GPP2,
the standardization group of CDMA2000.
 3GPP is a collaboration between groups of telecommunications
associations, known as the Organizational Partners.
A BRIEF HISTORY OF MOBILE COMMUNICATIONS

GSM/GPRS/EDGE/W-CDMA is the most widespread
wireless standard in the world. A few countries (such as the
USA, India, South Korea and Japan) use both sets of
standards, but most countries use only the GSM family.
A BRIEF HISTORY OF MOBILE COMMUNICATIONS



4G
Not quite yet!
3.5, 3.75G OR 3.9G (transitional)–
 3GPP2 family – CDMA2000 1XEV-DO Rev A,B.
 3GPP family – HSPA, HSPA+, LTE(E-UTRA).
 IEEE family – 802.16e-2005 (mobileWiMAX).
A BRIEF HISTORY OF MOBILE COMMUNICATIONS

CDMA2000 1xEV-DO (Evolution Data Only or Optimized)
Rev A – Enhancement to 1X EV-DO Rev. 0.




EVDO is standardized by (3GPP2) as part of the CDMA2000
family of standards.
EV-DO was designed as an evolution of the CDMA2000
standard that would support high data rates and could be
deployed alongside a wireless carrier's voice services. An
EVDO channel is 1.25Mhz wide.
CDMA 2000 Rev A - can support 3.1MBps in the DL and
1.8MBps in the UL.
CDMA 2000 Rev B – released in 2010.

Can support 4.9X(N) MBps in the DL and 1.8X(N) MBps in
the UL.
A BRIEF HISTORY OF MOBILE COMMUNICATIONS

HSPA – High Speed Packet Access is an combination of two mobile
telephony protocols, High Speed Downlink Packet Access (HSDPA)
and High Speed Uplink Packet Access (HSUDA), These protocols
improve the performance of existing WCDMA protocols.



HSPA supports increased peak data rates of up to 14 Mbit/s in the
downlink and 5.8 Mbit/s in the uplink.
It also reduces latency and provides up to five times more system
capacity in the downlink and up to twice as much system capacity in the
uplink.
HSPA+ - A wireless broadband standard defined in 3GPP release 7
and 8 of the WCDMA specification.

Evolved HSPA provides data rates up to 84 Mbit/s in the downlink and
22 Mbit/s in the uplink (per 5 MHz carrier) with multiple input, multiple
output (MIMO) technologies and higher order modulation.
4G

Why do we need 4G?

Did you know there are more mobile phones on the
planet than…
 Automobiles
 PCs
 TVs

COMBINED!!!
Data rates are expected to climb dramatically as
more data-extreme apps are available.
 The mobile industry technology is the most rapidly
adopted technology in the world.

4G

4G is the fourth-generation of mobile telecommunication
technology standards as set by the ITU-R (radio sector), the
standards are the IMT-Advanced set of standards.




IMT-Advanced specifies a 4G network must achieve 1GBps DL speeds
while stationary and 100MBps while mobile.
Based on an all-IP packet switched network.
Peak data rates of up to approximately 100 Mbit/s for high mobility such
as travel on trains or cars, and up to approximately 1 Gbit/s for low
mobility such as nomadic/local wireless access, according to the ITU
requirements.
Dynamically share and use the network resources to support more
simultaneous users per cell.
4G





Scalable channel bandwidth 5–20 MHz, optionally up to 40 MHz.
Peak link spectral efficiency of 15 bit/s/Hz in the downlink, and 6.75
bit/s/Hz in the uplink (meaning that 1 Gbit/s in the downlink should be
possible over less than 67 MHz bandwidth).
System spectral efficiency of up to 3 bit/s/Hz/cell in the downlink and
2.25 bit/s/Hz/cell for indoor usage.
Smooth handovers across heterogeneous networks.
Ability to offer high quality of service for next generation multimedia
support.
4G


Both LTE Advanced and 802.16m (WirelessMAN Advanced
evolution of 802.16e) are considered 4G.
4G is expected to provide a comprehensive and secure all-IP
based mobile broadband solution to laptop computers,
wireless modems, smartphones, and other mobile devices.
4G OR FAUX G??

Are these speeds available now???
Where can I sign up???

Unfortunately, no.



LTE Advanced and 802.16m (WirelessMAN Advanced) are still under
development and are the only two technologies designated by the ITU to
fulfill the IMT-Advanced requirements. They are expected to be finalized
in 2011.
What is available now isn’t Faux G, it is 4G as the ITU announced that
current versions of LTE, WiMax and other evolved 3G technologies that
do not fulfill "IMT-Advanced" requirements could be considered "4G",
provided they represent forerunners to IMT-Advanced and "a substantial
level of improvement in performance and capabilities with respect to the
initial third generation systems now deployed."
WE’LL COVER…
IEEE 802.16
 WiMAX and LTE

 Network
architecture
 Multiplexing technique
 Subcarriers
 Physical channel
 Modulation and coding
 MIMO
WHAT IS 802.16?

IEEE is known for defining LAN standards and
supporting technologies. Over the last few decades,
IEEE 802 group has defined a number of widely
successful LAN technologies.


These included Ethernet and Wireless LAN (a.k.a. Wi-FI).
802.16 is a broadband wireless alternative to wireline
last mile (such as DSL, cable modems, and T1s.


The 802.16 subcommittee has been tasked with defining
Broadband Wireless Access (BWA) technology.
The mandate includes defining BWA for fixed, portable and
mobile applications.
802.16



802.16 has defined both Point-to-Point (PTP) and Point to
Multipoint (PMP) systems.
PMP systems offer both fixed and mobile.
These access technologies are designed as an alternative to
wireline broadband technologies such as DSL, cable
modems and T1s.
IEEE 802 LAN/MAN STANDARDS COMMITTEE






802.3 – Ethernet
802.11 – WLAN
802.15 – WPAN (Wireless Personal Area Network)
802.16 – Fixed, Portable & Mobile BWA
802.20 – Mobile BWA - an IEEE standard to enable
worldwide deployment of multi-vendor interoperable
mobile broadband wireless access networks.
802.21 – MIH Media Independent Handover – handover
and interoperability between both 802.X and non 802.x
networks.
802.16 KEY FEATURES


It is designed to work in both licensed and unlicensed spectrums and
defines features to mitigate interference in the unlicensed spectrum.
It can support different channel bandwidths to accommodate
different spectrum allocations in different countries.



It supports both Time Division Duplex (TDD) and Frequency Division
Duplex (FDD) modes.


The channel bandwidth may range from 1.25MHz to 20MHz.; i.e.
5/10/20MHz, 3.5/7/14MHz
It operates in the 2.3-GHz, 2.5-GHz, 3.5-GHz, and 5.8-GHz frequency
bands.
TDD appears to be the most popular with operators primarily due to cost
and availability of spectrum.
Speed: Mobile Wimax technology (802.16e)supports DL data rates
up to 63MBps per sector and UL data rates up to 28MBps in a
10MHz channel and 128MBps DL and 56MBps UL in a 20MHz.

These speeds are achieved by the flexible sub-channelization schemes,
adaptive modulation and coding and MIMO antenna techniques.
802.16 A/D (802.16-2004)


IEEE 802.16 defines a series of link layer technologies for
wireless MAN applications.
The standard series is known as 802.16 a/d and defines 5
flavors of access technology, they are:





WirelessMAN – Single Carrier – suitable for PTP and PMP access.
WirelessMAN – Single Carrier Access – Typically used for PTP.
WirelessMAN – OFDM256 – defines fixed PMP operation and
uses licensed bands under 11GHz.
WirelessMAN – OFDMA2048- defines fixed PMP operation as well
and uses licensed bands under 11GHz.
WirelessHUMAN – defined for operation in an unlicensed
spectrum and which could use any of the air interfaces SCa,
OFDM, and Orthogonal Frequency Division Mutliplexing Access
(OFDMA).
802.16E – MOBILE WIMAX

The 802.16e amendment adds the mobility
component to the 802.16 standard. The
802.16e air interface is based on Scalable
OFDMA (SOFDMA), which is designed to
support mobility.
802.16

The 802.16 standard defines Physical (PHY: layer 1) and Medium
Access Control (MAC; layer 2) layers of the OSI (Open Systems
Interconnection) model.

OSI model: The OSI model is a 7 layer model created to standardize the
rules of networking in order for all systems to be able to
communicate. In order for communication to occur on a network using
different device drivers and protocol stacks, the rules for communication
must be explicitly defined. The OSI model deals with the following
issues;





How a device on a network sends its data, and how it knows when and where to
send it
How a device on a network receives its data, and how to know where to look for
it.
How devices using different languages communicate with each other.
How devices on a network are physically connected to each other.
How protocols work with devices on a network to arrange data.
802.16
 OSI
model 7 layers are:
 1.
Physical Layer
 2. Data Link Layer
 3. Network Layer
 4. Transport Layer
 5. Session Layer
 6. Presentation Layer
 7. Application Layer
802.16


Physical layer – this layer is responsible for transmission and
reception of OFDM symbols, power control, modulation and coding.
MAC layer (consists of 3 parts)– this layer is responsible for:




Connection establishment between the subscriber station and network.
It defines messaging for authentication, IP address allocation and
dynamic addition/deletion of services.
Scheduling bandwidth for different users; it performs bandwidth
allocation based on user requirements as well as their Quality of Service
(QoS) profiles.
Performing initial system acquisition when the mobile powers up, and
performs timing synchronization with the network through ranging
procedures.
In 802.16e, this layer also handles radio mobility procedures to provide
full mobility for the mobiles.
802.16

MAC layer continued:




Responsible for mapping Asynchronous Transfer Mode (ATM) and
IP packets to MAC layer Protocol Data Units (PDU), which are then
mapped on top of PHY layer radio channels.
Defines authentication procedures to mutually authenticate the
subscriber and the network.
Defines encryption mechanisms to encrypt user traffic and
control messages.
Defines a key management technique to dynamically update
authentication and encryption keys to enhance the security of the
system .
SO WHAT IS WIMAX?

WiMAX is Worldwide Interoperability for
Microwave Access
 It
is the name of the trade association formed by a
group of network manufacturers, operators and
service integrators that promotes the broadband
wireless technology defined by the 802.16
committee.
 The WiMAX forum is to Wimax as the Wi-Fi Alliance
is to 802.11.
WIMAX FORUM
802.16 defines the BWA radio interface
technology but doesn’t define the end-to-end
network architecture.
 WiMAX Forum performed that task; they defined a
standards-based end-to-end network architecture
which is essential for successful interoperability
among network elements from various vendors
and among networks of various operators.


This network architecture defined by the WiMAX Forum
is an All-IP-based architecture.
WIMAX FORUM

WiMAX Forum also acts as the certification and
verification body for vendor equipment.
 The
Forum must ensure the manufacturers
implement a certain set of features defined by
802.16 standards. To do this, the Forum defines
system profiles that define all of the features that
must be supported by the equipment
manufacturers.

The WiMAX Forum also provides technical
leadership.
WIMAX
 802.16 defines layer 1 and layer 2 only. It also defines radio mobility aspects
that enable Mobile Stations (MS) to change a radio link from one transmitter
to the another transmitter and it defines system profiles that detail lists of
mandatory and optional features required in the radio interface.
 WiMAX Forum defines a standardized network architecture beyond the air
link aspect of the base station and defines mobility across different
networks.
WIMAX NETWORK

Between the MS and internet, the WiMAX
Network Architecture is basically defined as two
networks:
 The
Access Services Network (ASN)
 The Connectivity Services Network (CSN)
WIMAX NETWORK

ASN – includes the base station (BS) and an ASNGateway (ASN-GW).
The BS controls radio access, handover control and
resource scheduling.
 The ASN-GW provides functions in support of managing
and maintaining data paths for services, and performs
the role of a context server and paging controller for
MSs that are in “idle”mode.
 The ASN-GW is connected to a number of BSs.
 The ASN-GW performs roles similar to the BSC in 2G
networks and RNC in 3G networks.

WIMAX NETWORK


CSN – this includes a Domain Name Server (DNS), an
authentication, authorization and accounting server
(AAA), a mobile IP Home Agent (HA), which provides
allocation of dynamic IP address and a Dynamic Host
Configuration Protocol (DHCP) server. The DHCP
provides address configuration.
The CSN provides most of the backend functions such
as authentication, IP address management, billing and
mobility to the ASN and tunneling support.


The HA works with a Foreign Agent (FA) at the ASN-GW and
is responsible for forwarding user traffic to the FA serving
the MS.
The FA is router serving as a mobility agent for an MS.
WIMAX NETWORK
A single ASN may connect to the multiple CSNs
and vice versa. The ASN and CSN can be
owned by different business entities.
 The ASN provider is known as the Network
Access Provider (NAP) and the CSN is known as
a Network Service Provider (NSP).

WIMAX NETWORK
Figure 1. WiMAX Network (Award Solutions, Exploring WiMAX, 2009)
QOS MODEL


802.16 is designed to support a wide range of applications that
require different levels of Quality of Service (QoS). To accommodate
these apps, the 802.16 standard has defined five service classes.
WiMAX is QoS driven.

UGS – Unsolicited Grant Service



RT-VR – Real Time-Variable Rate



Needs guaranteed QoS, minimum delay and jitter.
Commercial IP/TV, T1.
Guaranteed average data rate, can tolerate small variable delays between
packets.
Steaming Music.
ERT-VR – Extended Real Time-Variable Rate


Variable Rate with minimum delay between packets.
VOIP with silence suppression.
QOS MODEL
 NRT-VR
– Non-Real-Time Variable Rate
 Variable
rate, can tolerate longer delay between packets.
 FTP, Web browsing.
 BE
– Best Effort
 Just
that, best effort.
 Non-real-time apps with very low delay sensitivity.
 Email retrieval.
OFDM





WiMAX air interface is based on OFDM/OFDMA.
OFDM uses multiple sub-carriers, the sub-carriers are closely spaced to
each other without causing interference, this allows the removal of guard
bands between adjacent sub-carriers. This is possible because the
frequencies (sub-carriers) are orthogonal, meaning the peak of one subcarrier coincides with the null of an adjacent sub-carrier.
In an OFDM system, a very high rate data stream is divided into multiple
parallel low rate data streams. Each smaller data stream is then mapped to
individual data sub-carrier and modulated using some sorts of PSK (Phase
Shift Keying) or QAM (Quadrature Amplitude Modulation). i.e. BPSK, QPSK,
16-QAM, 64-QAM.
OFDM needs less bandwidth than FDM to carry the same amount of
information which translates to higher spectral efficiency and it is more
resilient in a NLOS environment.
OFDM can efficiently overcome interference and frequency-selective fading
caused by multipath because equalizing is done on a subset of sub-carriers
instead of a single broader carrier. The effect of ISI (Inter Symbol
Interference) is suppressed by virtue of a longer symbol period of the
parallel OFDM sub-carriers than a single carrier system and the use of a
cyclic prefix (CP).
OFDMA



Whereas OFDM is a modulation technique, OFDMA is a multiple
access technique used primarily in mobileWiMAX and allows
different users to have access to the available channel at the
same time.
OFDMA is a multi-user version of the OFDM digital modulation
scheme. Multiple access is achieved in OFDMA by assigning
subsets of subcarriers to individual users
In an OFDM based system, entire subcarriers are allocated to
only one user, while in OFDMA subcarriers are divided into
different groups of subcarriers and each group has a number of
subcarriers, known as sub-channels.
OFDMA

OFDM-TDMA
OFDMA includes OFDM-TDMA as one of the possible
modes of operation.
 Users are allocated capacity only on the basis of time.
 Each user is given a time slice periodically; the time
slices are allocated in terms of number of OFDM
symbols.

 i.e.
If each time slice is two OFDM symbols, a user is allocated
all the subcarriers for two OFDM symbols.

No granularity in the frequency domain is provided
because all subcarriers are allocated to the same
server.
OFDMA
In OFDMA allocation is possible in both time
and frequency dimensions. In theory, every
intersection of symbol time and subcarrier
frequency is uniquely assignable.
 This allows any given frame to support many
simultaneous subscribers and their respective
sessions.

OFDMA
The two primary variables in an OFDM system
are the symbol time and the subcarrier
spacing.
 Symbol time and subcarrier spacing are related
by the following:

 Subcarrier

spacing=1/T, T is the Symbol Time
The subcarrier spacing is fixed, this allows the
bandwidth scalability.
SCALABLE OFDMA (SOFDMA)

SOFDMA is the scalable form of the OFDMA,
which is employed by mobileWiMAXnetworks.
 In
this scheme, the number of the subcarriers
which is equal to the size of FFT, scales with the
bandwidth, while maintaining each sub-channel’s
bandwidth constant; which means the subcarrier
spacing and the number of the subcarriers are
independent of the bandwidth.
SCALABLE OFDMA (SOFDMA)




For a given channel bandwidth, the subcarrier spacing is
inversely proportional to the number of subcarriers and,
therefore, the FFT size.
The time duration of the OFDMA symbol is set by the inverse
of the subcarrier spacing. Therefore by fixing the subcarrier
spacing, the symbol time is automatically specified.
The inverse relationship between subcarrier spacing and
symbol duration is a necessary and sufficient condition to
ensure that the subcarriers are orthogonal.
By fixing the subcarrier spacing and symbol time, this
ensures channel/hardware conditions are the same at vary
bandwidths.
SOFDMA
Figure 2 – Subcarrier spacing
SOFDMA
Same subcarrier spacing is maintained for
different channel bandwidths.
 OFDMA symbol duration and cyclic prefix is the
same, resulting in the same effects due to
multipath.
 With the subcarrier spacing the same, this then
implies the same sensitivity to frequency offset,
phase noise and Doppler Shift (the effects due to
the various channel/hardware conditions are the
same at varying bandwidths).

SCALABLE OFDMA PARAMETERS

For frequencies, 1.25, 5, 10 and 20MHz, these
are the parameter values:
 Subcarrier
frequency spacing (Delta f)=
10.9375kHz
 Useful symbol time (Tb=1/Delta f) = 91.43us
 Guard time or cyclic prefix (Tg=Tb/8) = 11.43us
 Could
be ¼, 1/8, 1/16 and 1/32 and is chosen based
on certain assumptions about the wireless channel.
 Total
OFDM symbol time (Ts=Tb+Tg) = 102.86us
SCALABLE OFDMA – FRAMES & SUBCHANNELS







Symbols and subcarriers are organized into frames.
The OFDMA frame consists of a DL sub-frame and an UL sub-frame. The
flexible frame structure of the TDD signal consists of a movable boundary
between the DL and UL sub-frames.
Each TDD frame includes a DL subframe, followed by a Transmit/Receive
Transition Gap (TTG), followed by the uplink subframe, finally followed by a
Receive/Transmit Transition Gap (RTG).
In MobileWiMAX 47 total symbols are used in the DL and UL subframes for 5
and 10MHz channels. The remaining time is used for the TTG and RTG.
Recall a total OFDMA symbol is 103us.
This DL subframe begins with a Preamble which is one symbol time and is
used for BS identification, timing synchronization, and channel estimation at
the MS.
The preamble consists of a Pseudo Number (PN) sequence used to acquire
and synchronize with the system.
The data in the preamble is mapped to every third subcarrier, using BPSK,
giving a modest peak-to-average power level compared to the data
subchannels.
OFDM-TDD PHY LAYER FRAME
Figure 3 TDD PHY Layer Frame (Award Solutions, Exploring WiMAX, 2009)
SCALABLE OFDMA – FRAMES & SUBCHANNELS



WiMAX groups symbols into frames and subcarriers into subchannels.
 A user is allocated one or more subchannels for all or part of a frame.
Subchannel allocation schemes:
 PUSC, FUSC and Band AMC (Adaptive Modulation and Coding) are
schemes for assigning subcarriers to subchannels. There are more,
these are the most often used.
Modulation:




There are three modulation types available for modulating the data onto the subcarriers:
QPSK, 16QAM, and 64QAM.
Binary phase shift keying (BPSK) modulation is used during the preamble, on the pilots,
and when modulating subcarriers in the ranging channel.
In the UL, the transmit power is automatically adjusted when the modulation coding
sequence (MCS) changes to maintain the required nominal carrier-to-noise ratio at the BS
receiver.
64QAM is not mandatory for the UL.
ADAPTIVE MODULATION & CODING

Adaptive Modulation refers to the selection of different modulation
and coding schemes by the transmitter and allows for the scheme to
change on a burst-by-burst basis per link, based on the state of the
channel.


A transmitter has to transmit the data in as high as possible data rate if
the channel has a good condition. However, if the condition of the
channel is weak, the data rate must be as low as possible. The condition
of the channel is mostly determined through the (Signal to Interference
Noise Ratio) SINR measurement.
Channel Coding: There are various combinations of modulations and
code rates available in the OFDMA burst. Channel coding is the
randomization of data, forward error correction (FEC) encoding,
interleaving, and modulation.

In some cases, transmitted data may also be repeated on an adjacent
subcarrier.
SCALABLE OFDMA – FRAMES & SUBCHANNELS

Differences between the DL and UL signal:
 In the UL there isn’t a preamble, but there are an increased
number of pilots.




Pilots are the control and synchronization signal.
Pilots in the UL are never transmitted without data
subcarriers.
UL uses special CDMA ranging bursts during the network
entry process.
Data is transmitted in bursts that are as long as the uplink
sub-frame zone allows, and wrapped to further subchannels as required.
WIMAX SUMMARY
All IP network, heavily QoS driven, uses smart
antenna technology to increase data speeds.
 Network architecture consists of ASN and CSN.

ASN is BS and ASN-GW.
 CSN is typical of a ISPs backend network.


SOFDMA
Uses SOFDMA on radio access link.
 Subcarrier spacing is fixed.
 Subchannel allocation schemes are: PUSC, FUSC,
Adaptive Modulation and Coding.

SMART ANTENNA TECHNOLOGY

Multiple antenna techniques:

TX/RX Diversity
 Frequency
Diversity.
 Delay diversity.
 STC Space Time Coding.

MIMO
 Spatial

Multiplexing (True MIMO).
Beamforming
 Switched
Beam Systems.
 Adaptive Beamforming.
 SDMA Space Division Multiple Access.
MIMO

MIMO:


MIMO is the use of multiple antennas at both the transmitter and
receiver to improve communication performance.
offers significant increases in data throughput and link range
without additional bandwidth or transmit power.


It achieves this by higher spectral efficiency (more bits per second per
hertz of bandwidth) and link reliability or diversity (reduced fading).
This method transmits one data bit from the first antenna, and
another bit from the second antenna simultaneously, per symbol.
As long as the receiver has more than one antenna and the signal
is of sufficient quality, the receiver can separate the signals. This
method involves added complexity and expense at both the
transmitter and receiver. However, with two transmit antennas
and two receive antennas, data can be transmitted twice as fast
as compared to systems using Space Time Codes with only one
receive antenna.
LTE
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3GPP Long Term Evolution (LTE), is the latest standard in the mobile network
technology tree that produced the GSM/EDGE and UMTS/HSPA network
technologies.
It is a project of the (3GPP), operating under a name trademarked by one of the
associations within the partnership, the European Telecommunications Standards
Institute.
LTE may also be referred more formally as Evolved UMTS Terrestrial Radio Access (EUTRA) and Evolved UMTS Terrestrial Radio Access Network (E-UTRAN).
e-UTRA or eUTRAN is the air interface of 3GPP’s LTE upgrade path for mobile
networks.
E-UTRAN is a radio access network standard meant to be a replacement of the
UMTS, HSDPA and HSUPA technologies specified in 3GPP releases 5 and beyond.
Unlike HSPA, LTE's E-UTRA is an entirely new air interface system, unrelated to and
incompatible with W-CDMA. It provides higher data rates, lower latency and is
optimized for packet data. It uses OFDMA radio-access for the downlink and SCFDMA on the uplink.
LTE

EUTRAN has the following features:
 Peak download rates of 292 Mbit/s for 4x4 antennas, 143 Mbit/s for
2x2 antennas with 20 MHz of spectrum.
 Peak upload rates of 71 Mbit/s for every 20 MHz of spectrum.
 Low data transfer latencies (sub-5ms latency for small IP packets in
optimal conditions), lower latencies for handover and connection
setup time.
 Support for terminals moving at up to 350 km/h or 500 km/h
depending on the frequency band.
 Support for both FDD and TDD duplexes as well as half-duplex FDD
with the same radio access technology.
 Market preferences dictate that the majority of deployed systems
will be FDD.
 Support for all frequency bands currently used by IMT systems by
ITU-R.
LTE

EUTRAN features:
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Flexible bandwidth: 1.4 MHz, 3 MHz, 5 MHz 15 MHz and
20 MHz are standardized. By comparison, W-CDMA uses
fixed size 5 MHz chunks of spectrum.
Increased spectral efficiency at 2-5 times more than in
3GPP release 6 (HSPA).
Support of cell sizes from tens of meters of radius (femto
and picocells) up to over 100 km radius macrocells.
Simplified architecture: The network side of EUTRAN is
composed only by the eNodeBs.
Support for inter-operation with other systems (e.g.
GSM/EDGE, UMTS, CDMA2000, WiMAX.)
Packet switched radio interface.
LTE NETWORK ARCHITECTURE
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LTE has only one network element, the eNB (evolved
Node B). The eNB is similar to a base station in 2G/3G
systems.
eNBs support all Layer 1 and Layer 2 features
associated to the E-UTRAN OFDM physical interface, and
they are directly connected to network routers.
The 3G RNC (Radio Network Controller) inherited from
the 2G BSC (Base Station Controller) has disappeared
from E-UTRAN and the eNB is directly connected to the
Core Network using the S1 interface.

The features supported by the RNC have been distributed
between the eNB, the Core Network MME and the Serving
Gateway entities.
LTE NETWORK ARCHITECTURE
Figure 4 – LTE Network Architecture
LTE NETWORK ARCHITECTURE

eNB – Evolved Node B – WLAN access point.

eNB performs the following tasks:
 Radio
bearer control.
 Radio admission control.
 Connection mobility management.
 Dynamic resource allocation.
 Inter cell interference coordination.
 Load balancing.

The eNB is connected to the EPC by SI interface, and
connected to other eNBs by X2 interface, this
minimizes packet loss.
LTE NETWORK ARCHITECTURE

EPC (Evolved Packet Core) – consists of the following
entities:

MME – Mobility Management Entity
This is the key control node for the LTE access network.
 Security procedures - end-user authentication
 Terminal-to-network session handling - signaling procedures used to
set up Packet Data context and negotiate associated parameters like
the Quality of Service.
 Idle-terminal location management - this relates to the tracking area
update process. (idle)


S-GW – Serving-GateWay

Serves as a local mobility anchor. Packets are routed through this
point for intra E-UTRAN mobility and mobility with other 3GPP
technologies.
LTE NETWORK ARCHITECTURE

PDN-GW – Packet Data Network- GateWay
This is the termination point of the packet data interface towards the
Packet Data Network.
 It provides connectivity to the subscriber to external packet data
networks by being the point of exit and entry of traffic for the
subscriber.
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PCRF – Policy and Charging Rules Function Server
This server manages the service policy and sends QoS setting
information for each user session and accounting rule information.
 It also combines functionalities for the two UMTS nodes: The Policy
Decision Function (PDF) and the Charging Rules Function (CRF).


HSS – Home Subscriber Server

This is a concatenation of the HLR (Home Location Register) and
AuC (Authentication Center).
LTE – PHYSICAL LAYER
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E-UTRA uses OFDM and MIMO antenna technology depending on the
terminal category for the downlink and for the UL it uses both OFDM and
Single Carrier FDMA (SC-FDMA) depending on the physical channel.
LTE Frames: The generic radio frame for FDD and TDD has a duration of
10ms and consists of 20 slots with a slot duration of 0.5ms. Two adjacent
slots form one sub-frame of length 1ms. A resource block spans either 12
sub-carriers with a sub-carrier bandwidth of 15kHz or 24 sub-carriers with a
sub-carrier bandwidth of 7.5kHz each over a slot duration of 0.5ms.
With the subcarrier spacing at 15 kHz apart from each other, to maintain
orthogonality, this gives a symbol rate of 1 / 15 kHz = of 66.7 µs.
LTE – PHYSICAL LAYER

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In the UL LTE uses both OFDMA and Single Carrier Frequency Division
Multiple Access (SC-FDMA) depending on the channel.
 This is to compensate for a drawback with normal OFDM, which has a
very high peak to average power ratio (PAPR). High PAPR requires more
expensive and inefficient power amplifiers with high requirements on
linearity, which increases the cost of the terminal and drains the battery
faster.
The modulation schemes supported in the downlink are QPSK, 16QAM and
64QAM, and in the uplink QPSK, 16QAM and 64QAM. The Broadcast
channel uses only QPSK. The modulation scheme is dependent on the
channel condition, mainly SINR.
Coding: The channel coding scheme for transport blocks in LTE is Turbo
Coding with a coding rate of R=1/3, two 8-state constituent encoders and a
contention-free quadratic permutation polynomial (QPP) turbo code internal
interleaver.
WIMAX VS. LTE

Similarities:
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They have similar network architecture.
All-IP network.
The two standards both define layer 1 and layer 2 of the OSI
model.
use OFDMA in the DL.
use OFDM.
support TDD and FDD.
Support different bandwidths.
QoS driven.
Both use smart antenna technology (MIMO, STC)
Modulation: QPSK, 16QAM, 64QAM in the DL; and BPSK, QPSK,
8PSK and 16QAM in the UL
WIMAX VS. LTE

Differences:




LTE doesn’t require a new network build, an incumbent
advantage.
Their networks differ in that the eNB is the only network element
for LTE, whereas WiMAX has 2, the BS and the ASN.
LTE uses single-carrier frequency division multiple access (SCFDMA) for uplink signaling, while WiMax sticks with OFDMA for UL.
Frequency bands:


WiMAX operates in the 2.3-GHz, 2.5-GHz, 3.5-GHz, and 5.8-GHz
frequency bands.
LTE operates in 700 & 1700 in NA, 900, 1800, 2600 MHz in Europe;
1800 and 2600 MHz in Asia; 1800 MHz in Australia.


An inherent advantage as the lower frequencies offer better penetration.
LTE supports seamless passing to cell towers with older network
technology such as GSM, CDMAOne, UMTS, and CDMA2000.
CONCLUSION

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LTE and WiMAX are cousins that are developed by two separate
entities.
LTE-Advanced and 802.16m both fulfill IMT-Advanced requirements.
LTE has the incumbent advantage in that a new network doesn’t
need to be built out and operates at lower frequencies for better
penetration.
4G - The main advantages with 4G are high throughput, low latency,
plug and play, FDD and TDD in the same platform, an improved enduser experience and a simple architecture resulting in low operating
costs.
Main benefit of all IP based network is seamless mobility, which has
been the goal of wireless networks for a long time. Seamless
mobility describes the ability to move among various radio networks
such as WLANS, cellular networks and enterprise networks with no
impact to subscriber’s perception of service.
REFERENCES
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Key features of the LTE radio interface, by Erik Dahlman, Anders Furuskär, Ylva Jading, Magnus
Lindström and Stefan Parkvall, November 2008
http://www.3gpp.org/LTE
Planning of WiMAX and LTE Networks, by Mehrnoush Masihpour and Johnson I Agbinya
http://business.motorola.com/experiencelte/pdf/LTEAirInterfaceWhitePaper.pdf
http://www.wimax.com/lte/why-the-wimax-vs-lte-battle-isnt-a-battle
Exploring Wimax, Award Solutions, Figures 1, 2, 3. 2009.
http://blogs.broughturner.com/2010/03/lte-and-spectrum-stupidity.html
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr200811sf5.html
http://blogger.xs4all.nl/jurjen1/archive/2008/07/06/400647.aspx
http://gigaom.com/2008/03/05/a-little-4g-sibling-rivalry/
http://www.telecomcircle.com/2009/09/what-is-the-difference-between-wimax-and-lte
http://www.networkworld.com/news/2010/060710-tech-argument-lte-wimax.html
http://www.slideshare.net/marioeguiluz/analysis-wimax-vs-lte
http://technologizer.com/2009/05/20/lte-vs-wimax-the-4g-wireless-war/
http://en.wikipedia.org/wiki/4G#Data_rate_comparison
http://en.wikipedia.org/wiki/3GPP_Long_Term_Evolution