Introduction to LTE

Introduction to LTE

B Based d on th the b book k LTE and the Evolution to 4G Wireless

© Agilent Technologies, Inc. 2012

1

LTE = Long g Term Evolution = 4G 1. LTE is now the worldwide standard for cellular systems 2. LTE is a scalable and flexible system y 3. LTE accommodates FDD and TDD architectures 4. LTE is based on a new “all IP” core network backhaul 5. LTE basestations ((eNodeB)) are nodes on an IP network 6. LTE is co-located with existing 2G/3G cell systems 7. LTE can use Diversity, MIMO, Beamforming 8. LTE can deliver ~300 Mbps/cell sector (Release 8) 9. LTE has a broadcast variant 10. LTE core network uses IP Multimedia Subsystem (IMS) 11. LTE supports IPV6 addressing, multiple IP context/UE


2

LTE (4G) in context of new systems • LTE is just one of five major new wireless technology developments • • • • •

3GPP LTE 3GPP HSPA+ 3GPP Edge Evolution 3GPP2 UMB* (similar to 802.20) IEEE WiMAX WiMAX** – (802.16e (802 16e / WiBRO)

• All five systems share very similar goals in terms of spectral efficiency (bits/second/Hz), with the wider systems providing the highest single user data rates • Spectral efficiency is primarily achieved through use of advanced modulation schemes and/or multi-antenna technology, ranging from basic Tx/Rx diversity, MIMO, and beamforming • HSPA+ and Edge Evolution are extensions to existing cellular systems (WCDMA and GSM) • LTE, UMB and WiMAX are new OFDMA systems with no technical precedent other than WiFi and WiBRO * While UMB is still a documented standard, it is no longer under active development ** WiMAX was deployed in several systems worldwide, but is now in rapid decline


3

3GPP UMTS standards evolution (RAN)

1999

2010

Release Functional Freeze

Main feature of Release

Rel-99

March 2000

UMTS 3.84 Mcps (W-CDMA FDD & TDD)

Rel-4

March 2001

1.28 Mcps p TDD ((aka TD-SCDMA))

Rel-5

June 2002

HSDPA

Rel-6

March 2005

HSUPA (E-DCH)

R l7 Rel-7

D 2007 Dec

HSPA+ (64QAM DL DL, MIMO MIMO, 16QAM UL) UL). LTE & SAE Feasibility Study

Rel-8

Dec 2008

LTE Work item – OFDMA air interface SAE Work item,, New IP core network Edge Evolution, more HSPA+

Rel-9

TBD

UMTS and LTE minor changes, LTEAdvanced feasibility study

Rel-10

TBD

LTE-Advanced (4G) work item


4

Wireless evolution 1990 - 2012

Increasing efficiency, bandwidth and da ata rates

2G

IS-95A cdma

IS-136 TDMA

GSM

PDC

802.11b 802.11a

2.5G

IS-95B cdma

3G

IS-95C cdma2000

3.5G

3.9G

1xEV-DO Release 0

HSCSD

GPRS

E-GPRS EDGE 1xEV-DO Release A

UMB

LTE Rel-8 LTEAdvanced Rel-9/10

4G

iMode

W-CDMA FDD

1xEV-DO Release B Edge Ed Evolution

802.11g 802.11h

W-CDMA TDD

TD-SCDMA LCR-TDD

HSDPA FDD & TDD

HSUPA FDD & TDD

802.16d Fixed WiMAXTM

HSPA+

802.16e 802 16e Mobile WiMAXTM

WiBRO

802.11n

802.16m ?


5

LTE Major features The motivation behind LTE • Much untapped potential in HSDPA + HSUPA (HSPA+) • But some LTE requirements can’t be met by HSPA+ • LTE goal is to provide further benefits • Spectrum Flexibility (scalable carrier channel bandwidth) • Higher Peak Data Rates with wider 20 MHz channel bandwidth • OFDMA enables less complex implementation of Advanced Antennas/MIMO Technology • OFDMA better suited for Broadcast Services

• But UE terminals will have to carry y the legacy g y of GSM/GPRS,, C2K/EVDO, WCDMA/HSPA+ which increases overall complexity of LTE deployment


6

LTE at a Glance Nov 2004 LTE/SAE High level requirements  Reduced cost per bit  More lower cost services with better user experience  Flexible use of new and existing frequency bands

Spectral Efficiency

1.4

2-3x HSUPA (uplink)

3 5

Latency

10

Idle  active < 100 ms

15 20

Small packets < 5 ms

SPEED!

 Simplified lower cost network with open interfaces  Reduced terminal complexity and reasonable power consumption

MHz

3-4x HSDPA (downlink)

Downlink D li k peak kd data t rates t (64QAM) Antenna config Peak data rate Mbps

SISO

2x2 MIMO

4x4 MIMO

100

172.8

326.4

Uplink peak data rates (Single antenna)

MIMO

Multiple Input Multiple Output

Modulation QPSK

16 QAM

64 QAM

Peak data rate Mbps

57 6 57.6

86 4 86.4

50

Mobility

Optimized: 0–15 km/h High performance: 15120 km/h Functional: 120–350 km/h U d consideration: Under id ti 350–500 km/h


7

UE categories • In order to scale the development of equipment, UE categories have been defined to limit certain parameters • The most significant parameter is the supported data rates: UE Category

Max downlink Number of DL Max uplink Support for uplink data rate Mbps transmit data streams data rate Mbps 64QAM

1

10.296

1

5.18

No

2

51.024

2

25.456

No

3

102.048

2

51.024

No

4

150.752

2

51.024

No

5

302.752

4

75.376

Yes

The UE category must be the same for downlink and uplink


8

LTE vs. HSPA+ Attribute

HSPA+ (Rel-8)

LTE targets

Peak Data Rate / 5 MHz sector in ideal radio conditions

DL – 42 Mbps UL – 10 Mbps

DL – 43.2 Mbps UL – 21.6 Mbps

Peak Data Rate / 20 MHz sector in ideal radio conditions, 2x2 DL

DL – 84 Mbps (10 MHz) UL – 20 Mbps (10 MHz)

DL – 172.8 172 8 Mbps (20 MHz) UL – 86.4 Mbps (20 MHz)

Cell Edge improvement compared to HSPA Release 6 Spectral Efficiency (real world)

Evolved HSPA & LTE - DL – 3x to 4x; UL – 2x to 3x All solutions will benefit from ongoing improvements to the radio interface such as UE RX diversity, equalization, interference cancellation; MIMO, higher order modulation etc.

Latency: End to End Ping Delay

40 ms

L t Latency: Idle Idl to t Active A ti

Currently C tl around d 600 600ms Goal to reduce to 100 ms

200 users @ 5MHz

Spectral efficiency

>400 users for larger BW Essentially on par par, comparisons cited often are based on dissimilar conditions and can be misleading

Access Technology: Downlink (DL) Uplink (UL)

Frequency Band Bit-rate/Site:

MIMO:


10

System Architecture Evolution (SAE) • Today’s core network is a hybrid of elements representing 20+ years evolution of telecommunications • The evolution and availability of the internet is transforming the way people look at the core network • SAE is a project to develop a much flatter, higher performance and cheaper packet-only core network with gateways to legacy networks and non-3GPP technologies • SAE is separate from but closely coupled to LTE • Some of LTE’s LTE s goals - like latency targets - will not be met until the evolved packet core network is implemented

Page 11


11

3GPP Release 5 core network UTRAN – 3G radio

GPRS packet routing

Gm (To P-CSFC) Uu

AMR

Node B

ATM2u/5c

Uu

IP

AMR

Stand alone LMU

RNC BG

Iur ATM5

Iub

associated LMU

Node B

Gp

Gr

Stand alone LMU

Lg

CBE

EIR

CBC

Broadcast services

Lc Lg

from EDGE phones

LCS client

HSS

Sh

MSC

Agprs

Si

PCU

Agprs Abis

HR, FR, EFR

ISUP/BICC

server Mc

Um LMU(b)

Nc

BSC Lb

GERAN – 2G/3G radio

SMLC

A (Ater) MGW G HR, FR, EFR

Nb

Dx

voice mail

SIP server

ISC

OSA SCS OSA API OSA app server

ISC

Mb

Mw

MRFC

Mr

Mp

? Mr

S-CSCF call server

Mg

Mi

Mb

MRFC

ISC

Mn

Other PSTN network

IM-SSF

IMS - IP Multimedia Services

IP

HR, FR, EFR or AMR or PCM over ATM or QoSIP

SIP server

Sh

HSS

Sh

IP

Enterprise PSTN

MGW

ISC

home network IMS

Si Sig GW

server

BGCF

Cx Cx

OSA app server

BGCF

Mk

SLF

OSA API

MGW

Mj

Dx

S-CSCF call server

OSA SCS

MGCF

GMSC

Mc

I-CSCF call server

Mp

MRFP

I-CSCF call server

ISC

C

B VLR

Abis

SLF

Sh

Enterprise

Mw

P-CSCF call server

Cx Cx

SMSC

BTS

BTS

Go

(from handset)

D

Gm (To P-CSFC)

DHCP

PDN

Gm

Gc

IP SCP (gsm (gsm SCF) SRF)

LMU(b)

RADIUS

GGSN

F

Um

LMU(a)

Le

Application & Content Providers

content

IP

Lh

GMLC

DNS

Gi

MMSC

Gs

IuBC

LMU(a)

AAA

Call Control IP & operator specific services

Node B

ISP

BG

Gf

associated LMU

apps

Gp

IP

Gn GTP

Gb

e-mail

GTP

GTP

SGSN IuCS

Iub

GGSN

Gp

IuPS

SMLC

RNC

ATM2u/5c

Gm (To P-CSFC) Uu

GTP

ATM2u5c

Gm (To P-CSFC)

Other GPRS PLMN

SMLC

Iub

associated LMU

Stand alone LMU

Operator ISP

OLO

PCM

Packet-switched voice

The point here is the complexity!

Roaming partners


12

Simplified LTE network elements and interfaces

MME = Mobile Management M entity S1

S1 S1

S1

X2

X2

SAE = System Architecture Evolution

3GPP TS 36.300 Figure 4: Overall Architecture


13

LTE uses an asymetric DL/UL physical layer • OFDM – Orthogonal Frequency Division Modulation for the downlink. • SC-FDMA – Single Carrier Frequency Division Multiple Access for the uplink. • Asymetric physical layer is common in many cellular systems, due to bounds of basestations being stationary and multiuser, while mobiles can be moving and disassociated from other mobiles.


14

Orthogonal Frequency Division Multiplexing • OFDM already widely used in non-cellular technologies only recently usable in cellular due to improved processing power • OFDM advantages • The use of multiple subcarriers means the channel bandwidth is scalable as well as supporting frequency selective scheduling within the channel • Wide channels are possible which support higher data rates • Almost Al t completely l t l resistant i t t tto multi-path lti th due d tto very long l symbols b l • The frequency domain representation of the signal make equalizer design and MIMO implementation easier then in CDMA systems

• OFDM disadvantages • • • •

Sensitive to frequency errors and phase noise due to close subcarrier spacing Sensitive to Doppler shift which creates interference between subcarriers Pure OFDM creates high PAR which is why SC-FDMA is used on UL More complex than CDMA for handling inter-cell interference at cell edge


15

OFDM – Review of Basic Concepts • Slower symbol rate x multiple carriers = similar bits/sec/Hz p to: •Less susceptible - single freq. interference - multipath dropouts - impulse noise

...

...

• Carrier spacing creates orthogonality. • Phase noise, timing and frequency offsets decrease orthogonality. orthogonality


16

Orthogonal Basis Functions • Can C U Use C Codes d or S Subcarriers b i • Both are Orthogonal (Separable) Over A Time Interval y • Similar In Theory • Different in RF Behavior, Design Optimization • Very Different in RF Analysis

CDMA: CDMA Dividing Capacity by Code

OFDM: OFDM Dividing Capacity by Carrier


17

Orthogonal Frequency Division Multiplexing 5 MHz Bandwidth

FFT

gem vlu44L G 41

.eu4in scTG 4w uh 1 gafm yh 1

… Frequency

… nLr 25.892 Figure 1: Frequency-Time Representation of an OFDM Signal

OFDM is a digital multi-carrier modulation scheme, which uses a large number of closely-spaced orthogonal sub-carriers. Each sub-carrier is modulated with a conventional modulation scheme (such as QPSK, 16QAM, 64QAM) at a low symbol rate similar to conventional single-carrier modulation schemes in the same bandwidth. © Agilent Technologies, Inc. 2012

18

Orthogonal Multiplexing •Multiple Multiple carriers may be spaced at multiples of FP and be mutually orthogonal, i.e. they do not interfere with one another. The zeros of one pulse occurs exactly on the peaks of the other carriers.

1

0.8

0.6

0.4

0.2

0

-0.2

-0.4

0

2

4

6 Freqeuncy (f/Fp)

8

10

12


19

Orthogonal Multiplexing •Using U i aL Large N Number b off S Such hC Carriers i Yi Yields ld an OFDM Si Signall

x t  

K

j 2 n

K

 x t    a

n  K

n

n  K

n

e

t TP

0  t  Tp

1 0.8 06 0.6 0.4 0.2 0 -0.2 -0.4

-15

-10

-5

0 Freqeuncy (f/Fp)

5

10

15

OFDM Operates as a Number of Orthogonal (Non-Interfering) Narrowband Systems © Agilent Technologies, Inc. 2012

20

OFDMA How do I add Access (user channels) to this system? 1 0.8 0.6 0.4 02 0.2 0 -0.2 -0.4

-15

-10

-5

0 Freqeuncy (f/Fp)

5

10

15

Assigned sub-carriers for user 1 Assigned sub-carriers for user 2 © Agilent Technologies, Inc. 2012

21

LTE Downlink Mapping P-SS - Primary Synchronization Signal S-SS - Secondary Synchronization Signal PBCH - Physical Broadcast Channel PDCCH -Physical Downlink Control Channel PDSCH - Physical Downlink Shared Channel

16QAM

64QAM

QPSK

Reference Signal – (Pilot)


22

Pilot Carriers – the Needed Reference for Both Amplitude and Phase •A Portion of the Carriers are Not Modulated and Provide Amplitude and Phase References for the Nearby Modulated Channels. These must be spaced close enough for interpolation to provide valid references to the active sub-carriers.

1 0.8 0.6 0.4 0.2 0 -0.2 -0 4 -0.4

-15

-10

-5

0 Freqeuncy (f/Fp)

5

10

15


23

Single Carrier FDMA: The new LTE uplink transmission scheme • SC-FDMA is a new concept in transmission and it is important to understand how it works • When a new concept comes along no single explanation will work for everyone • To help put SC-FDMA in context we will use six i diff differentt ways off explaining l i i what h t SCFDMA is all about • In summary: SC-FDMA is a hybrid transmission scheme combining the low peak to average (PAR) of single carrier schemes with the frequency allocation flexibility and multipath protection provided by OFDMA


24

Comparing OFDMA and SC-FDMA p using g M=4 subcarriers QPSK example Q

-1,1

1, 1

1,1

-1,-1

1, -1

-1,-1

1, 1

1, -1

-1, 1

Sequence of QPSK data symbols to be transmitted

I -1,-1

-1, 1

1,-1

QPSK modulating data symbols V

V

CP

fc

Frequency

CP

60 kHz

Frequency

15 kHz

OFDMA

SC-FDMA

Data symbols occupy 15 kHz for one OFDMA symbol period

Data symbols occupy M*15 kHz for 1/M SC-FDMA symbol periods


25

Comparing OFDMA and SC-FDMA PAR and constellation analysis at different BW

V

V

CP

fc

CP

Frequency

60 kHz

Frequency 15 kHz

Transmission scheme Analysis bandwidth

OFDMA 15 kHz

Peak to average power Same as data symbol ratio (PAR) Observable IQ Same as data symbol at 66.7 μs rate constellation

SC-FDMA Signal BW (M x 15 kHz)

15 kHz

Signal BW (M x 15 kHz)

High PAR (Gaussian)

< data symbol (not meaningful)

Same as data symbol

Not meaningful (Gaussian)

< data symbol (not meaningful)

. Same as data symbol at M X 66.7 µs rate


26

Multi-antenna Technologies

• Overview of Multi-antenna techniques q • LTE Terminology • How MIMO works in LTE


27

Multi-Antenna Techniques in LTE • Just because there is more than one antenna, doesn’t mean it’s MIMO • Diversity can usefully be combined with MIMO Spatial Multiplexing to improve performance • A focus on the need to provide an increased DL data rate leads to an asymmetric y system y in LTE


28

System & Antenna Configurations, Terms “Input” and “Output” Refer to the Channel

SISO

MISO Tx0

Tx

Rx

Rx Tx1

Tx Diversity, Diversity Beamforming SIMO T Tx

Rx Diversity

MIMO R 0 Rx0

Tx0

R 0 Rx0

Rx1

Tx1

Rx1

Spatial Multiplexing


29

Terminology I Spatial Multiplexing

The process of transmitting data from multiple antennas on the same frequency at the same time

Transmit Diversity

Transmission of common data, but modified in some y, on more than one antenna way,

Channel

The entire route, from transmission to reception, including all the analog & RF circuits & antennas, that could introduce unwanted coupling or distortion

(Channel) Rank

The number of useable data stream (layers) in a multi-antenna radio system

Correlation

A measure of the similarity between different signals (after the receiver antennas)

Condition Number

A short term measure of the increase in SNR needed to recover a spatially multiplexed signal


30

MIMO Spatial Multiplexing and Diversity Both Important, Different Objectives Multiple Antennas can be used in a variety of ways: • Beamforming B f i • Transmit Diversity • Receive Diversity

Diversity techniques protect against fading, and improve coverage


31

Double Diversity does not make MIMO Transmit Diversity + Receive Diversity = Spatial Multiplexing MISO plus MRC Tx0 Tx1 Data modified and repeated on second symbol (or subcarrier)

Tx0

Rx0

Tx1

Rx1

MIMO Tx0 Tx1 Data only transmitted once


32

MIMO Operation in LTE In the Downlink Downlink, it’s normally like WLAN, the MIMO transmission is sent to a single mobile. Known as Single User MIMO

•In the Uplink, two mobiles are used together to create the MIMO signal. signal •Known as Multi-User MIMO


33

Diversity and Spatial Multiplexing Processes in LTE

The diagram allows for several techniques. To distinguish between SM and others, ask: “How many receive antennas do I need?”


34

Terminology II Codeword

The input data after basic adaptation from the payload

(Transmission) Layer

With spatial multiplexing, it is synonymous with a stream

Precoding

process of cross coupling p g the signals g before The p transmission (used in closed loop operation) to equalize the demodulated performance of the layers

Codebook

The look-up table of cross coupling factors used for precoding; shared by the mobile and base-station base station

Closed Loop MIMO

A mechanism used to continuously adapt the transmitted signal to suit the channel characteristics, using the precoder

Beamforming

The process of cross coupling the signals at transmitter (or receiver) to adapt to the channel. LTE precoding is one example of doing this

Beamsteering

When beamforming with phased array array, it is the process of tracking the movement of the mobile


35

From Codewords to Layers

SISO SU-MIMO(4 antennas) or Diversity (with Alamouti) May/may not be

Diversity

Single User ((or MU)) MIMO


36

2 (or 4) Layer Transmit Diversity Paired symbols, frequency based Alamouti technique Space Frequency Block Coding


37

Combined Spatial Multiplexing & Diversity The specification allows for this:


38

So Tell (or Remind) Me - How does MIMO work? 1: Consider a moment in time time, at a single frequency, frequency and model the channel as a box with fixed components inside: A

If we add two completely different signals at A and B, they’ll get mixed together, but in a precisely defined way, dependant on the values of Z1- Z4

B

MIMO is used uncouple signals on twisted p pairs

2: Send a training signal first, that’s unique to A and to B. Measure what comes out and therefore how they got coupled. [If you know how yg get coupled, p yyou can work out how to uncouple p them]] they 3: Everything going into the box will be coupled the same way, so you apply what you found to the real data you want to sent


39

… and when does it not work? Noise & interference always y limit the modulation we use. With MIMO,, there is an ADDITIONAL factor – how well can you uncouple the signals – measured by the Condition Number of the channel matrix A

Extreme example: If all the Z’s Z s are the same same, both outputs are the same. This is a “keyhole” channel, which does not support spatial multiplexing (rank =1) B

For every dB increase in condition diti number, b you may need a dB increase in the SNR


40

The Famous Hand-waving Demo Matrix Condition Number – shows the higher g SNR needed for MIMO Condition Number vs Cross Coupling

PER vs MIMO Condition Number 25

100 Condition Number (0dB)

20

PER %

15

10

10

1

5

0.1 0 -25

-20

-15

-10

-5

0

0

5

10

15

Condition Number (dB)

In Phas e Cros s Coupling (dB)

Page 41

As condition number increases, higher SNR for the same performance (EVM)

Agilent is required Restricted

Condition Number as a function of symmetric, in-phase coupling

PER vs. Condition Number (example)

How to get a real feel for it! UE eNB

•10 MHz Freq ref. •Time sync •Option phase lock

•10 MHz Freq ref. •Time sync y

• Frame Trigger


41

Performance Changes with Frequency and Time Condition number & Frequency q y response p 10 MHz [[Pedestrian A]]

0 dB


42

LTE Channel Training Signals • The Reference Signals are what allow the receiver to calculate the channel h l coefficients. ffi i t They Th NEVER overlap l b before f th they are ttransmitted itt d

R0

R0

R0

R0

R0

R0

R0

R0

l0

l6 l0

l6

Resource element (k,l)

R0

R0

R0

R0

R1

R0

R0

R0

R0

R0

l0

R0

odd-numbered slots

Antenna port 0

l0

R2

R1

R3

R2

R1 l6 l0

even-numbered slots

R3

R2 l6

odd-numbered slots

Antenna port 1

R3

R2

R1

R1 l6

l6

R1

R1

R0 l6 l0

even-numbered slots

l6 l0

R1

R0

Reference symbols on this antenna port

R1

R1

R0

R0

l0

l6

Not used for transmission on this antenna port

R1

R1

l6 l0

R0

R1

R1

R0

l0

R1

R1

l 0

R3 l6 l0

even-numbered slots

l6

odd-numbered slots

Antenna port 2

l0

l6 l0

even-numbered slots

l6

odd-numbered slots

Antenna port 3


43

What makes a good channel for MIMO? • A perfect MIMO channel:

T0 T1

Channel H

h00

h11

R0

1

0

R1

0

1

• By simple observation it follows that R0 = T0 and R1 = T1 • This is a case that creates double the capacity

But suppose we create a simple static channel like this:

Channel H 0.8 0.2

How do we know if it will provide capacity gain?

0.3 -0.9


44

The MIMO challenge: Recovering the signal • If all four paths are the same the original signal cannot be recovered since R0 = R1 h00 T0

R0

R0 = T0 + T1 and R1 = T0 + T1 T1

h11

R1

Channel H 1

1

1

1

• But put in a phase inversion e.g. on ch3 we get: Channel H

R0 = T0 + T1 and R1 = T1 – T0 thus T0 = (R0 - R1)/2 and T1 = (R0 + R1)/2

1

1

-1

1

• The original signal is completely recovered even though the apparently unwanted ch2 and ch3 exist


45

The MIMO challenge: Recovering the signal • So S iis th the earlier li example l good d or b bad d ffor MIMO? R0 = 0.8 T0 + 0.3 T1

Channel H

R1 = 0.2 0 2 T0 - 0.9 0 9 T1

0.8 0.2

Giving:

0.3 -0.9

T0 = 1.15 R0 + 0.39 R1 T1 = 0.26 R0 - 1.03 R1 • We can recover the original signal • In fact any H matrix other than the unity matrix can be resolved PROVIDED there is no external or internal noise!


46

Why Precode (cross couple) the SM signal?

No precoding – the layer performance is unbalanced

Precoded with 1,1,-1,1 – similar performance for both layers


47

Precoding Matrix Index definition 3GPP TS 36.211 Table 6.3.4.2.3-1 Deals with FDD case Only 3 choices for spatial multiplexing (16 for the 4 layer case) For single data stream t transmission, i i th precoding the di produces beamsteering (with 4 antennas) Subband PMI reporting can be configured down to the resource block level


48

Why Apply Cyclic Delay Diversity? Top: No CDD Bottom: Large CDD Test signal with cross coupled static channel 500ns delay, -2dB in one path Condition Number shows this, and the impact on EVM Spectrum


49

Cyclic Delay Diversity, CDD • Works out to be a very long delay (~33us) ( 33us) • There are only two choices, Off or “Large”


50

Antenna influence on performance • The dynamic condition number example did not isolate effects from different components, including the antenna • In real life life, the instantaneous channel matrix H is made up from the interaction of three components: • The static 3D antenna pattern of the transmitter • The dynamic multipath and Doppler characteristics of the radio channel • The static 3D antenna pattern of the receiver

• The overall antenna contribution is the product of the transmit and receive antennas known as the channel correlation matrix


51

Computing the instantaneous channel The complex instantaneous channel coefficients are obtained by applying each path of the desired fading profile to each channel of the correlation matrix h00

T0 T1

h01

h11 h00

h00

R0 h11

h10

R1

h10 h01 h11

The received signals and condition number are dynamic in both the time and frequency domains according to the chosen h ffading di profile fil © Agilent Technologies, Inc. 2012

52

Real life performance

Variation due to instantaneous correlation Variation in the frequency domain not shown Most macrocell activity takes place in this region Variation due to fading and variable interference


53

Multi-antenna operation in the Uplink • Multi-User – two UEs controlled by the eNB to act like a combined transmitter • Currently more theoretical than practical – of research interest

This demonstration with g g generators allows signal the introduction of the kinds of timing and power errors that the receiver will have to cope with


54

Summary MIMO Spatial Multiplexing is a powerful additional transmission scheme in the right conditions The list of 7 modes for DL transmission highlights how the ENB and UE will have to work together to choose which multi-antenna technique to use:

LTE has seven different downlink transmission modes: 1.Single-antenna 1 Single antenna port; port 0 2.Transmit diversity 3.Open-loop spatial multiplexing 4.Closed-loop 4.Closed loop spatial multiplexing 5.Multi-user MIMO 6.Closed-loop Rank=1 precoding 7.Single-antenna port; port 5

SISO MISO MIMO - no precoding MIMO - with precoding MIMO - separate UE (for UL) MISO - beamsteering MISO - beamsteering


55

The End


56

Introduction to LTE

Introduction to LTE

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[Read] From GSM to LTE-Advanced: An Introduction to ... - Google Sites

LTE and LTE-Advanced TecnoEconomic Modelling Budapest

Editorial 3GPP LTE and LTE-Advanced

Long Term Evolution (LTE): An Introduction, rev A - MForum.ru

LTE Release 9 Technology Introduction White ... - Rohde & Schwarz

Editorial 3GPP LTE and LTE-Advanced

Application to Mobility in 3G LTE Networks

Using Carrier Ethernet to Backhaul LTE

Vulnerability of LTE to Hostile Interference

Device-to-Device Communications in LTE-Advanced

LTE and the Evolution to 4G Wireless

Mobile Access Evolution to LTE-4G.pdf

LTE Network

Network Transition from WiMAX to LTE