Lecture 5: Evolved Radio Access Networks (LTE-Advanced)jmarty/courses/papers...LTE-Advanced Relaying 2/19/2010 Word template user guide 38 2.1 Relaying principles, need for relaying

Lecture 5: Evolved Radio Access

Networks (LTE-Advanced)

ELEC-E7230 Mobile Communications Systems

Edward Mutafungwa, 2016Department of Communications and Networking

Outline

• Background

– Motivation, requirements, RAN architecture

• Long-Term Evolution (LTE)

– LTE downlink and uplink PHY

– LTE radio protocols and channels

– LTE Radio Resource Management

• LTE-Advanced

– LTE-Advanced carrier aggregation

– LTE-A relaying

– CoMP and extended MIMO

LTE-Advanced Requirements

Background

Realised LTE peak rates and LTE-

Advanced performance requirements

• Realized LTE Rel.8 peak rates:

– In downlink 150 Mbps can be achieved on 20 MHz bandwidth with 2x2 MIMO.

300 Mbps can be achieved on 20MHz band if 4x4 MIMO is used.

– In uplink 75 Mbps can be reached in LTE Rel.8 with single transmit antenna in

UE.

• LTE-Advanced targets

– 1 Gbps with 4x4 MIMO in downlink and 500 Mbps in uplink

– Note the large improvement target in UL spectral efficiency

LTE Rel.8 LTE-A target

Peak data rate DL 150/300 Mbps 1 Gbps

UL 75 Mbps 500 Mbps

Peak spectral efficiency DL 15 bps/Hz 30 bps/Hz

UL 3.75 bps/Hz 15 bps/Hz

LTE-Advanced Requirements

• LTE-Advanced was decided to be an evolution of LTE. – That is, LTE-Advanced is backwards compatible with LTE Release 8:

• LTE Release 8 terminals can work in a LTE‐Advanced network

• LTE‐Advanced terminals can work in a LTE Release 8 network

• More homogeneous distribution of the user experience over the

coverage area.

• Low power consumption aimed in both eNodeB’s and UE’s

– Note that LTE Rel.8/9 was focusing on UE power consumption

KPIs Background

• Signal to Interference and Noise Ratio (SINR)

– Ratio or power of desired signal to total interference and thermal

noise

• Throughput (TP)

– Data transferred (bits per second)

Interference in LTE, illustration

S-72.3216 RC Systems I (5

cr) Lectures 11-12, Autumn

20137

UE

eNodeB

Desired signal from

serving eNodeB

Interfering signal from

other eNodeB

Interfering signal from

adjacent sector

Thermal Noise

• Thermal noise power calculation

– T = Operating temperature in degrees Kelvin (20C or 290K

assumed for room temperature)

– kB = 1.38064852 × 10-23 JK-1 Boltzmann’s constant (W=J/s)

– BW = Effective bandwidth

𝑃𝑡ℎ𝑒𝑟𝑚𝑎𝑙_𝑛𝑜𝑖𝑠𝑒 = 𝑇 ∙ 𝑘𝐵 ∙ 𝐵𝑊

KPIs Background

• KPIs defined in 3GPP standards

– Received Signal Reference Power (RSRP): average power of the

Resource Elements (REs) that carry cell-specific RSs within the

considered bandwidth

– Received Signal Strength Indicator (RSSI): linear average of the

total received power observed only in OFDM symbols carrying

reference symbols by UE from all sources, including co-channel

non-serving and serving cells, adjacent channel interference and

thermal noise, within the measurement bandwidth

– Reference Signal Received Quality (RSRQ): a cell-specific signal

quality metric. Roughly equal to RSRP divided by RSSI

Mapping between SINR and throughput

• SINR determines the Modulation and Coding Scheme (MCS)

that is usable for particular link

Source: Understanding LTE

with Matlab, H. Zarrinkoub

Mapping between SINR and throughput

• Previous spectral efficiency formula provides an approximation for the

Adaptive Modulation and Coding (AMC) schemes (also called as

Modulation and Coding Schemes (MCS)) applied in the system.

Mapping between SINR and throughput• Modified Shannon formula for mapping SINR to throughput (TP)

– BW = Bandwidth allocated to UE (in Hz)

– SINR (in linear scale, not dB) and TP in bps

– BWeff = Effective bandwith to account for overheads of cyclic prefix, reference signals, practicalfilter implementations

– SINReff = adjusts SINR for implementation efficiency etc.

– Correction factors BWeff and SINReff are obtained from link-level simulations

– BWPRB = Bandwidth of one PRB (180 KHz)

– NPRB = Number of PRBs allocated to UE (scheduling)

– SE = spectral efficiency (bps/Hz)

𝑇𝑃 = 𝐵𝑊 ∙ 𝐵𝑊𝑒𝑓𝑓 ∙ log2 1 +𝑆𝐼𝑁𝑅

𝑆𝐼𝑁𝑅𝑒𝑓𝑓

𝑇𝑃 = 𝑁𝑃𝑅𝐵 ∙ 𝐵𝑊𝑃𝑅𝐵 ∙ 𝐵𝑊𝑒𝑓𝑓 ∙ log2 1 +𝑆𝐼𝑁𝑅


𝑇𝑃 = 𝑁𝑃𝑅𝐵 ∙ 𝐵𝑊𝑃𝑅𝐵 ∙ 𝑆𝐸

1- LTE-Advanced Carrier Aggregation

(Rel.10/11)

1.1 Principles of Carrier Aggregation

Principle

– The LTE-Advanced target peak data rate of 1 Gbps in downlink and 500 Mbps in uplink can be achieved with bandwidth extension from 20 MHz up to 100 MHz.

– In LTE-Advanced this extension is achieved through carrier aggregation

– By combining N LTE Release 8 Component Carriers (CC), together to form N x LTE bandwidth, up to 5 x 20 MHz = 100 MHz operation bandwidth could be obtained

Frequency

LTE-Advanced maximum configuration

RF band

R8

20 MHz

R8

20 MHz

R8

20 MHz

R8

20 MHz

R8

20 MHz

Component

carrier (CC)

Principle

Frequency

LTE-Advanced maximum configuration

RF band

R8

20 MHz

R8

20 MHz

R8

20 MHz

R8

20 MHz

R8

20 MHz

Component

carrier (CC)

Bandwidth (B) 1.4MHz 3 MHz 5MHz 10MHz 15MHz 20MHz

Resource Blocks (𝑁𝑟𝑏) 6 15 25 50 75 100



Backward compatibility with Rel.8/9

• LTE Rel.8/9 terminals can receive/transmit only one

component carrier

• LTE-Advanced terminals may receive/transmit on multiple

component carriers (CCs) simultaneously to reach higher data

rates.

FrequencyR8/9 UE R8/9 UE R8/9 UE

LTE-A UE

1.4MHz 20MHz

R8/9 UE

…

Example LTE Rel. 8/9 frequency bands

Band Uplink (MHz) Downlink (MHz) Region

1 1920 - 1980 2110 - 2170 Europe, Asia

3 1710 - 1785 1805 - 1880 Europe, Asia, Americas

5 824 - 849 869 - 894 Americas, Korea,

7 2500 - 2570 2620 - 2690 Europe, Asia, Canada, Korea

8 880 - 915 925 - 960 Europe. Japan, Latin America

13 777 - 787 746 - 756 Americas, Verizon

http://www.etsi.org/deliver/etsi_ts/136100_136199/136104/11.02.00_60/ts_136104v110200p.pdf

For more, see:

http://www.etsi.org/deliver/etsi_ts/136100_136199/136104/11.02.00_60/ts_136104v110200p.pdf

Example band allocation (Finland)

http://www.spectrummonitoring.com/frequencies/#Finland

Carrier Aggregation types

Frequency

Inter-band, non-contiguous CA

Band 1 Band 2

Frequency

Intra-band, non-contiguous CA

Band 1 Band 2

Frequency

Intra-band, contiguous CA

Band 1 Band 2

Contiguous vs non-contiguous CA

• In practice it seems that in the low frequency band (< 4 GHz)

it will be difficult to allocate continuous 100 MHz bandwidth

for a mobile network.

• The non-contiguous CA technique provides a practical

approach to enable mobile network operators to fully utilize

their current spectrum resources

– Thus, to use also currently unused scattered frequency bands and those

already allocated for some legacy systems, such as GSM and 3G

systems.

Contiguous vs non-contiguous CA• In terms of UE complexity, cost, capability, and power consumption,

it is easier to implement contiguous CA with minimal changes to the

physical layer structure of Rel.8-9 LTE.

– In non-contiguous CA advanced RF components are needed in receiver in

order to receive non-adjacent carriers.

– Compared to non-contiguous CA, it is easier to implement resource allocation

and management algorithms for contiguous CA.

UE categories for CA

UE Category Carrier Aggregation MIMO DL Peak

Rate

Commercial

Availability

Category 4 10 + 10 MHz DL

10 MHz UL

2 x 2 150 Mbps 2013

Category 6 20 + 20 MHz DL

20 MHz UL

2 x 2 300 Mbps 2014

Category 9 20 + 20 +20 MHz DL

20 MHz UL

2 x 2 250 Mbps 2015

Category 11/12 4 × 20 MHz DL

20 + 20 MHz UL

2 x 2 600 Mbps 2016

… 5 × 20 MHz DL 4 x 4 1+ Gbps ??

• 3GPP specifies UE categories for placing devices into specific

segments according to combined DL and UL capabilities

(MIMO, modulation level, CA etc.)

Current CA status: Cat. 6 networks

Current CA status: devices

Example Cat. 9 device

Example Cat. 6 devices

1.2 Practical configurations and

deployment issues

Practical CA combinations and naming

conventions• The following terms and definitions for CA combinations are applied:

– Aggregated Transmission Bandwidth Configuration (ATBC): This

refers to the number of aggregated resource blocks.

– CA bandwidth class (A, B and C): Refer to the combination of ATBC

and number of CCs. In Rel.10 and Rel.11 classes are:

• Class A: ATBC ≤ 100, maximum number of CC = 1

• Class B: ATBC ≤ 100, maximum number of CC = 2

• Class C: 100 < ATBC ≤ 200, maximum number of CC = 2

– CA configuration: This defines the combination of operating bands

and CA bandwidth class, for examples configurations, see the next slide

Bandwidth (B) 1.4MHz 3 MHz 5MHz 10MHz 15MHz 20MHz

Resource Blocks (𝑁𝑟𝑏) 6 15 25 50 75 100

CA configuration examples (FDD)

Source: 4G Americas, 2014

• Example: Configuration CA_1C means

that CA operate on Band 1, with two

continuous components carriers, with a

maximum of 200 RBs.

Interesting CA deployment scenarios• The coverage areas of component carriers (CCs) can be

different

• Example 1: Large frequency separation between CCs– Interesting CA scenario occurs when operator uses e.g. 2GHz and

800MHz bands for LTE (CA_1A_5A)– Load balancing between CCs will not be trivial due to traffic variations

within coverage areas of different CCs

– CA not utilised in areas where CC bands coverage do not overlap

eNodeB

800MHz + 2GHz

CA

800MHz

No CA

Interesting CA deployment scenarios

• Example 3: Antenna directions are not the same for all CCs

• Example 4: CA possible if the same eNodeB is controlling

main antenna unit and remote radio head (RRH)

eNodeB

eNodeBRRH

1.3 Primary and secondary Component

Carriers

Primary and secondary CC

• When UE first establishes RRC connection with eNodeB,

only one CC is attached for downlink and uplink directions.

Corresponding CCs are called as primary CCs (PCCs) for

both downlink and uplink, and the related cell is the primary

serving cell (PCell).

• Based on the traffic load and QoS requirements, UE can be

attached with additional one (or more) CC, called as

secondary CC (SCC) which correspond to the secondary

serving cell (SCell).


Frequency

Band 1 Band 2

PCCPCC

SCC

SCC

CC1 CC2 CC3

PCC

• The use of downlink/uplink SCC is decided by the eNodeB.

The PCC/SCC configuration is UE-specific and can be

different for different UEs served by the same eNodeB.


• The PCC serves as an anchor CC for the user and it is used for basic connectivity functionalities

• The SCCs carry only user data and dedicated signaling information

– PDSCH (physical DL shared channel), PUSCH (physical UL shared channel), and PDCCH (physical DL control channel)

• Since user connection greatly depends on PCC, it should be robust in both downlink and uplink

– PCC should be selected such that it provides ubiquitous coverage and/or best overall signal quality

• When UE is moving within the eNodeB service area the PCC may be changed

– CC with best signal quality

– Load balancing carried out between CCs

1.4 Radio Resource Management

principles for Carrier Aggregation

Radio Resource Management in CA• Based on user QoS requirements and traffic load, the eNodeB assign a set

of CCs for user and physical layer scheduling is carried out over multiple users on each CC.

• Cross-carrier scheduling is also possible

– In cross-carrier scheduling PDCCH is transmitted from a particular CC and may contain the scheduling information on other CCs as well as its own CC.

CA Impact on LTE Radio Protocols

Source: 3GPP

2. LTE-Advanced Relaying

2/19/2010Word template user guide

38

2.1 Relaying principles, need for relaying

and use cases


39

Wireless relay: Principle

I listen,

modify and

retell

I have a

message

I am only

listening

Base Station (BS) Relay Station (RS) Mobile Station (MS)

Repeaters (amplify and forward relays) are

well known and used in 2-3G networks.

The rest of this lectures considers mainly relays that

detect, encode and retransmit (decode and forward)

a signal between base station and terminal

Why relays for LTE?

Some key requirements for LTE-Advanced

• 1 Gbps on the downlink and 500 Mbps on the uplink.

• Higher peak and average spectral efficiencies than in LTE Rel’8.

• More homogeneous distribution of the user experience over the coverage area.

Expected properties of LTE-Advanced relays

• Enhanced capacity in hotspots.

• Enhanced cell coverage.

• Overcome extensive shadowing.

• Enable more homogenous user experience.

• Low total cost of operation (TCO).

Proposed benefits from relaying

• Cell edge users have low received signal strength

eNB 1

UE 1

UE 2UE 1 in cell center

• Strong signal from serving BS

(eNB1)

UE 2 at cell edge

• Weak signal from serving BS

(eNB1)



Proposed benefits from relaying

Extend coverage

Overcome excessive shadowing

d-eNB

RNIncreasethroughput in hotspots

Relay link

Access link

UE

Direct link

UE

UE

UE

RN

RN

But are relays really needed?

• Claim is that relays will provide an easy and cost effective way

to increase macrocell range, fill coverage holes in macrocells

and improve indoor coverage.

– Counter argument: There are other efficient solutions like small cells

(micro, pico cells etc.)

– Value proposition: Relays are self-backhauled wireless nodes (no

wired or dedicated fixed wireless backhaul) and thus flexible to deploy

• Self-backhauling implies that backhaul is provided my the macro

base station directly

Conventional small cells

Source: Small Cell Forum

Use cases for LTE-Advanced relays

Relay use case

Fixed Infrastructure

Usage

Outdoor Relay for

Indoor Coverage

Enhancement

In-Building Relay

for Coverage

Enhancement

Temporary Usage

Coverage in case

of emergency

/disaster

Coverage in case

of events

Mobile UsageCoverage in trains,

busses, ferries

This has not realized in Rel.10/11

2.2 LTE-Advanced relaying principles

LTE-Advanced relaying principles• In 3GPP Technical Report [TR 36.814] the following has been

stated:

• Relaying is considered for LTE-Advanced as a tool to improve e.g.

the coverage of high data rates, group mobility, temporary network

deployment, the cell-edge throughput and/or to provide coverage in

new areas.

– LTE-A specifications support fixed relaying and nomadic relaying is

possible but relay (group) mobility is not yet part of the standards.

• The relay node is wirelessly connected to the radio-access network

via a donor eNode B.

Donor eNBRelay Node (RN)

Donor cell border

Relay-eNB link

Inband operation/outband operation

Note: In outband operation RN-UE link do not need to be LTE

Rel’8 compatible if Rel’8 terminals are not operating on this

frequency carrier.


Donor cell border

RN-eNB

(relay) link

UEUE

Inband operation

(RN-UE and eNB-RN

links on same carrier

frequency)


Donor cell border

RN-eNB link

UEUE

UE-eNB link

UE-eNB

(direct) link

Outband operation

(RN-UE and eNB-RN

links on different carrier

frequency)

RN-UE

(access) link

RN-UE link

3GPP relay nodes

• 3GPP “Type 1” relay nodes are an inband RNs

– Assigned a unique physical-layer cell identity (PCI)

– Implements same Radio Resource Management mechanisms

(scheduling, admission etc.) like a eNode B

– Backward compatibility: support also LTE Rel-8 UEs (to UE RN

appears just like any other Rel. 8 eNode B)

– To LTE-Advanced UEs, it is possible for a relay node to appear

differently than Rel-8 eNodeB to allow for further performance

enhancement

Donor eNB Type 1 RN

Donor eNB control

resources in eNB – relay link

UE

Access Link

3GPP relay nodes• “Type 1a” relays:

– Type 1a relays characterised by the same set of features as the “Type 1” relay

node, except that “Type 1a” operates outband

• “Type 1b” relays:

– Type 1b are in same featues and inband like Type 1 but transmission in relay

(DeNB-RN) and access (RN-UE) link occur at same time => high antenna

isolation required (expensive)

– Type 1 transmissions in relay and access links are time-division multiplexed

Source: O. Bulakci, NSN, 2011

2.3 LTE-Advanced Type 1 relaying: The

Backhaul problem

Inband Type 1 relaying: the resource

sharing needed between links

• In order to allow inband relaying, resources in the LTE

time-frequency space needs to be shared between

backhaul and access links

– Backhaul link between RN and Donor eNodeB: The name of this

logical interface is Un (defined in LTE Rel.10)

– Backhaul resources cannot be used for the access link. The

name of this logical interface is Uu (as in LTE Rel. 8).

Donor eNB Relay Node (RN) UE

Un Uu

Resource sharing should be compatible with LTE Rel’8

Resource sharing: General principle

• General principle for resource partitioning at the LTE-

Advanced Type 1 relay:

– eNB → RN and RN → UE links are time division multiplexed in

a single carrier frequency

– RN → eNB and UE → RN links are time division multiplexed in

a single carrier frequency

(Donor) eNodeB RN RN UE

UE RN RN (Donor) eNodeB

DL

UL

Sounds simple but is it really straightforward?

BH backward compatibility: A problem

• Backward compatibility requirement with LTE Rel.8

creates a problem:

– Rel.8 UE expects continuous pilot/control transmission in DL

from eNodeB. In case of Type 1 relay, RN represents the

eNodeB for Rel.8 terminal.

– RN should be able to receive backhaul (Un) transmissions on

the same frequency.

– Problem: Reception and transmission on the same frequency

carrier is possible only for Type 1b relay that requires physical

separation (strong isolation) between RX and TX antennas. Yet,

this is costly solution.

Type 1 relaying is the most attractive relaying option. Yet, due to

above problem there was a threat in the beginning of the LTE-

Advanced standardization that relaying will be dropped out.

BH backward compatibility: The solution

• Recall: LTE Frame consists of 10 subframes of 1 ms each.

• Actually part of the LTE DL subframes can be configured as

MBSFN subframes– MBSFN refers to term ’Multi-Media Broadcast over a Single Frequency

Network’.

– In LTE Rel.8 MBSFN subframes are designed to carry MBMS (Multimedia

Broadcast Multicast System) information.

– MBMS service area typically covers multiple cells. Example application is Mobile

TV.

– The set of MBSFN subframes is semi-statically assigned; a maximum of 6

subframes can be configured out of the subframes 1, 2, 3, 6, 7, and 8 [*].

How could this be leveraged?

# 0 # 1 # 2 # 9

10 ms frame with 10 × 1ms subframes

BH backward compatibility: The solution

• MBSFN subframes used for the DeNB-RN link (Un interface)

– Non-MBSFN subframes from DeNB used for UE directly connected to

DeNB

– MBSFN subframes not used in RN-UE link (they are subframes)

– RN uses its non-MBSFN subframes for UEs it serves

# 0 # 1 # 2 # 9

Donor eNBRN UE

Un Uu

DeNB subframes

# 0 # 1 # 2 # 9

RN subframes

3. Coordinated Multipoint (CoMP)

Transmission and Receiption


58

3.1 CoMP: Idea and benefits


59

Idea of CoMP

• Coordinated Multi-Point Transmission is one of the most

important technical improvements of LTE Rel.11

• CoMP improves to some extent macrocell network

performance

– Through reduced interference (increased signal to interference

and noise ratio, SINR)



Idea of CoMP• In all network deployment strategies (macrocell only and HetNet)

cell edge users are experiencing the inter-cell interference. – Downlink: Inter-cell interference occurs due to parallel transmissions from

adjacent base stations

– Uplink: Intercell interference occurs due to simultaneous transmission (on the same time-frequency resources) by users in adjacent cells.

• The goal of the CoMP is to further minimize inter-cell interference for cells that are operating on the same frequency

eNB 1

eNB 2

UE 1

UE 2UE 1 in cell center

• Strong signal from serving BS

(eNB1), weak interferer (eNB2)

UE 2 at cell edge

• Weak signal from serving BS

(eNB1), strong interferer (eNB2)

3.2 CoMP categories and schemes


62

CoMP terminology

• CoMP Cooperating Set

– The CoMP Cooperating Set is is a set of geographically

separated TX/RX points that are directly or indirectly involved in

data transmission to a device in a time-frequency resource

– The CoMP cooperating set defines the coordination area

• CoMP Measurement Set

– The CoMP Measurement Set is a set of points, in which channel

state information (CSI) or statistical data related to their link to

the mobile device is measured and/or reported


63

Downlink CoMP


64

DL CoMP

Joint Processing Coordinated

scheduling/beamforming

Joint Transmission Dynamic Point

Selection

Joint Transmission (JT): Transmission executed from multiple points at a time (within CoMP cooperating set)Dynamic Point Selection (DPS): Transmission executed from one point at a time (within CoMPcooperating set). Also known as dynamic cell selection

Coordinated scheduling/beamforming: Data to a UE is transmitted from one transmission point. The scheduling decisions as well as transmission beams are coordinated to control the interference

Downlink CoMP• Joint processing schemes for transmitting in the downlink:

Improve the received signal quality and strength.

Actively cancel the interference from transmissions that are intended for other UEs.

This form of CoMP places a high demand onto the backhaul network because the copies of same data need to be sent to each transmission point that will be transmitting it to the UE.

• Coordinated scheduling and or beamforming : Backhaul requirements are reduced since only scheduling decisions and

details of beams needs to be coordinated between multiple transmission points

Relatively lower SINR gains compared to joint processing schemes (particularly on cell edge)

Uplink CoMP


66

UL CoMP

Joint ReceptionCoordinated scheduling

Receiver processing in

centralized reception point

Joint Reception:

• Antennas at different reception points are utilized.

• Coordinating between the different reception points it

is possible to form a virtual antenna array.

• The signals received by the reception points are then

combined and processed to produce the final output

signal.

The main disadvantage with this technique is that

large amounts of data needs to be transferred between

the reception points

Coordinated scheduling: • This scheme coordinates the scheduling

decisions amongst the reception points to minimize interference

This scheme provides a reduced load in the backhaul because only the scheduling data needs to be transferred between the different reception points that are coordinating with each other.

3.2 CoMP scenarios


67

3GPP Rel.11 CoMP scenarios

eNB

Coordination area

High Tx

power RRH

Assume high Tx power RRH

as same as eNB

Optical fiber

Low Tx power

RRH

(Omni-antenna)

eNB

Optical fiber

Scenario 1: Homogeneous network

with intra-site CoMP

Scenario 2: Homogeneous network inter-site

CoMP with high Tx power (sectored) RRHs

Scenario 3/4: Network with low power RRHs or

small cells within the macrocell coverage (in

scenario 3 macro and smalls employ different cell

IDs, while they are same for scenario 4)

• 3GPP Rel.11 standardization is based on four different CoMPscenarios.

• All scenarios assume Ideal Backhaul

– Non-ideal backhaul scenarios considered only in Release 12

– Rel. 12 also considers inter-site CoMP scenarios

3.4 LTE-Advanced extended Multiple

Input Multiple Output (MIMO)


69

Benefits of multi-antenna techniques

• The availability of multiple antennas at the transmitter and/or the receiver may achieve different aims:– Provide additional diversity against fading on the radio channel– Can be used to “shape” the antenna beam (beamforming) in a

certain way e.g. to maximize the overall antenna gain in the direction of the target receiver or transmitter

– Spatial multiplexing by enabling transport multiple data streamsthat within the same limited channel bandwidth

Source: M. Sauter, From GSM to LTE : an introduction

to mobile networks and mobile broadband, 2011

Downlink MIMO

• Downlink MIMO schemes are extended/enhanced from Rel.8 LTE– Operation is extended to support 8 TX antennas, (instead of 4TX

supported by Release 8 LTE).

LTE Rel.8 LTE-A target

Peak data rate DL 300 Mbps (4x4 MIMO,

20 MHz)

1 Gbps (8x8 MIMO,

20 + 20 MHz)

Peak spectral efficiency DL 15 bps/Hz 30 bps/Hz

Performance Improvements

• BWeff and SINReff are factors that are selected such that SE

approximates the LTE link spectral efficiency.

• Factors BWeff and SINReff depend on the number of antennas and

physical layer performance.

• M = number of data streams

MIMO M BWeff SINReff

SIMO 1x2 1 0.62 1.8

MIMO 2x2 2 0.42 0.85

MIMO 4x4 4 0.40 1.1

MIMO 8x8 8 0.33 1.4

𝑇𝑃 = 𝑀 ∙ 𝑁𝑃𝑅𝐵 ∙ 𝐵𝑊𝑃𝑅𝐵 ∙ 𝐵𝑊𝑒𝑓𝑓 ∙ log2 1 +𝑆𝐼𝑁𝑅


Spectral efficiency improved by MIMO

0

5

10

15

20

25

30

-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

Sp

ectr

al

eff

icie

nc

y [

bit

s/s

/Hz]

SINR [dB]

SIMO (1x2)

MIMO (2x2)

MIMO (4x4)

MIMO (8x8)

Max SE

Max SE

Uplink MIMO

• Uplink single-user MIMO is being introduced in order to increase average user throughput and, in particular, user throughput at the cell edge

• UL SU-MIMO was considered already for Rel.8 LTE, but compared to the added benefit, it was found too expensive for the terminals due to need of multiple power amplifiers.

• Up to 4 TX antenna transmission can be used in LTE-Advanced uplink.

CoMP is actually a MIMO variant….

• In CoMP transmitters are not necessarily co-located

– But linked by a high speed connection and can share user data

– In CoMP transmission if coherent combining used it also known

as cooperative or network MIMO

Ref: Agilent

Thank You!


76

Lecture 5: Evolved Radio Access Networks (LTE-Advanced)jmarty/courses/papers...LTE-Advanced Relaying 2/19/2010 Word template user guide 38 2.1 Relaying principles, need for relaying

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