AIRCOM LTE Webinar 4 - LTE Coverage

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AIRCOM LTE Webinar Series:

Basic overview of LTE radio Coverage
© 2013 AIRCOM International Ltd

AIRCOM LTE Webinar Series:

Basic overview of LTE radio Coverage

About the Presenters
Graham Whyley – Lead Technical Trainer

AIRCOM Technical Master Trainer since 2005

Currently responsible for all LTE training
course creation and delivery

Over 20 years of training experience at
companies including British Telecom and
Fujitsu

Adam Moore – Learning & Development
Manager

With AIRCOM since 2006

Member of CIPD

Contact us at training@aircominternational.com
3


About AIRCOM
AIRCOM is the leading provider of mobile network planning,
optimisation and management software and consultancy services.
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Founded in 1995
14 offices worldwide
Over 150 LTE customers
Acquired Symena in 2012
Products deployed in 159 countries
Comprehensive Tool and technology
training portfolio

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TEOCO offer very complimentary assurance an optimisation solutions as
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Find out more at www.aircominternational.com

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LTE Planning and
Optimisation Engineer
(5 days inc exam)

5


Agenda- Basic overview of LTE radio
coverage
 So you want to support VoIP
What do you need?
 So you want to support Circuit Switched
Voice
 What effects coverage

6


VoIP over LTE coverage
LTE network operator wants to move voice services to
VoIP over IMS.
What happens if we
VoIP over LTE
(without header compression)

move into GSM/UMTS
cell

IP Multimedia Subsystem
Packet switched

Speech

RTP

12 Bytes Header

UDP

8 Bytes Header

IPv4

20 Bytes Header

PDCP

1 Byte Header

RLC

100% LTE coverage

1 Byte Header

MAC

PSTN
Gateway

1 Byte Header

PSTN
circuit switched

600 bits every 20 ms
L1

30 kbps

LTE supporting
Cell

This would require 100% LTE coverage from day 1 to
have a competitive VoIP
7


Early stages LTE
In the early stages of rolling out the technology, LTE will only be available in large
cities and in isolated hotspots.
I am using VoIP via IMS
and I am moving outside
LTE coverage?

GSM/UMTS

I want to
make
circuitswitched call?

LTE supporting
Cell
Not supporting
LTE –GSM/UMTS

8

LTE is a packet-based all-IP network that cannot support circuit-switched calls. So
what about coverage for circuit switched


Single radio voice call continuity
SRVCC is an LTE functionality that allows a VoIP/IMS call in the LTE packet domain to be
moved to a legacy voice domain (GSM/UMTS or CDMA)
If a mobile moves outside the coverage area of LTE, then the network can use this
technique to transfer the mobile from VoIP communications over the IMS, to traditional
circuit switched communications over GSM, UMTS
circuit switched

VoIP
IP Multimedia Subsystem
Packet switched

Packet switched

PSTN
Gateway

PSTN
circuit switched

circuit switched

GSM/UMTS
circuit switched

moves outside the coverage area of LTE
9


If operators look to limit LTE deployments to high traffic areas
and at the same time wish to transition voice service in those
areas to VoIP, then SRVCC is exactly what they need.

High traffic
areas + Voice
Services to VoIP
You need SRVCC

VoIP over LTE
(without header compression)
Speech

RTP
UDP

8 Bytes Header

IPv4

20 Bytes Header

Not supporting
LTE –GSM/UMTS
10

1 Byte Header

RLC

LTE supporting
Cell

PDCP

1 Byte Header

MAC

1 Byte Header
600 bits every 20 ms

L1

30 kbps


Operator does NOT plan to migrate to VoIP

High traffic areas

NO Voice
Services to VoIP
LTE supporting
Cell
Not supporting
LTE –GSM/UMTS
11

SRVCC NOT
REQUIRED

Circuit switched fall-back
Paging Response
MSC/VLR

Paging

Paging CS
Service Request extended

GSM/
UMTS

MME

HO Command
SWITCH

LTE NETWORK

CSFB is often seen as an interim solution for LTE operators.
Voice over LTE (VoLTE) is considered to be the long-term goal for the delivery of voice
services on LTE networks
LTE
VoIP
PSTN

12

IMS


Circuit switched fallback
UE does
not support
VoIP
OR/AND
network
operator
not
supporting
IMS

circuit switched

UE can only use the technique if it is
simultaneously in the coverage area of LTE and
a 2G or 3G cell

Packet switched

LTE COVERAGE

UMTS/GSM
COVERAGE

circuit switched

Circuit switched fallback

inter-system handovers have traditionally been one of the least reliable aspects
of a mobile telecommunication system
13


Types of cell
Each cell has a limited size, which is determined by the maximum range
at which the receiver can successfully hear the transmitter.
Ref Sens = KTB + NF + SINR + IM

Ref Sens
SINR

QPSK
2bits/Hz

16QAM
4bits/Hz

SINR SINR SINR

SINR

SINR

64QAM
6bits/Hz
SINR SINR

transmit power

SINR

modulation and coding scheme

Macrocells -provide wide-area coverage.

Evolved
Node B
(eNB)

You may want to limit
the cell size?

• Does not have an upper limit for its transmit power capability
• Above roof-top antenna deployment
• Relatively large cell areas

Microcells

14

• Can be deployed using a ‘wide area’ BTS with reduced transmit power
• Below roof-top antenna deployment
• Relatively small cell areas


Picocells
Picocells are used in large indoor environments such as offices or shopping centres and are a
few tens of metres across. Hotspot type deployment.

PDN
Gateway

Evolved
Packet Core
Serving
Gateway

Macrocells

MME

Macrocells
Internet

Repeater

Picocells
15

Microcells

Home eNodeB

Closed Subscriber Group Selection
Base station is associated with a closed subscriber group
and a home eNB name, which it advertises in SIB 1 and
SIB 9 respectively.
Home eNodeB
USIM
contains any
closed
subscriber
groups,

SIB 1
CSG indication: To indicate whether this cell is
CSG cell or not. If it is CSG cell, then CSG
identity stored in the UE should match with
CSG id of the cell

Only those users included in the femtocell's
access control list are allowed to use the
femtocell resources.
16


CSG indication: To indicate
whether this cell is CSG cell or
not. If it is CSG cell, then CSG
identity stored in the UE
should match with CSG id of
the cell

Part of
SIB 1

A femtocell can be also configured in Open Access mode, in which any
user is allowed access to the femtocell
17


USIM
contains any
closed
subscriber
groups,

CSG entries on the USIM consist of:
• PLMN Identifier
• CSG Identifier
• Home eNodeB Name
• CSG Type
Home eNodeB

SIB 9
SIB9: Home eNB name
contains a home eNB name (HeNB Name)
CSG Type
• Closed access (residential deployment):
Access is only allowed for the subscribed user.
• Open access
All users are allowed access to the HeNB and receive the offered services.
18


Indoor coverage
• Indoor coverage can be badly degraded by penetration losses
through the walls of buildings.
• If the base station is outdoors but the mobile is indoors, then
penetration losses typically reduce the received signal power by
10 to 20 decibels, which can greatly reduce the indoor coverage
area.
• This is one of the motivations behind the progressive
introduction of femtocells.

19


Increasing coverage using Repeaters
3GPP Release 8
Introduction of LTE
Repeaters
Home eNode B
Inter Cell Interference Coordination
(ICIC)
SON – Self Establishment of eNode B
SON – Automatic Neighbour Releations

Repeater receives
• downlink signal from donor cell
before amplifying and
transmitting to UE
• uplink signal from UE before
amplifying and transmitting to
donor cell
•

Repeaters and relays are devices that
extend the coverage area of a cell.

•

Macrocells

They can also increase the data rate at the
edge of a cell, by improving the signal to
interference plus noise ratio there.

Repeater

20


Relays-3GPP Release 10

wired backhaul

MIMO-OFDM concepts to deliver high data
rate over small cells
Limitation of cell size is mainly because:
• path loss
• down-tilting angle
• Other cell Interference
• Parameters
Limitation of LTE roll out mainly due to:
• wired backhaul

EPC

MIMO Setting

Data
Efficiency
(bit/s/Hz)

Sectors

Total
Bandwidth
(Mbps)

LTE
1x2

5

1.7

3

25

LTE
2x2

5

3.4

3

50

LTE
2x2

10

3.4

3

102

LTE
4x4
21

Data
Spectrum
(MHz)

20

6.8

3

408

Bandwidth

REL’8
20MHz

The amount of bandwidth on a wireless network is ultimately
constrained by two factors:
1. amount of licensed spectrum a carrier owns.
2. the spectral efficiency of the wireless interface

15MHz
10MHz
5MHz
3MHz
1.4MHz

Application
overhead

TCP/UDP

TCP/UDP

overhead

Application

Application Rate

IP
Relay

IP

PDCP

PDCP

GTP-U

overhead

RLC

RLC

UDP

overhead

MAC

MAC

IP

L1

L1/L2

overhead

Physical Rate

L1
UE
22

AirInterface

eNode B

Data Rate
In/out of core

CORE
NETWORK
(EPC)

L1/L2

Server

Relays-3GPP Release 10
•LTE relaying is different to the use of a repeater which re-broadcasts the
signal.
•A relay will actually receive, demodulates and decodes the data, apply any
error correction, etc to it and then re-transmitting a new signal.
• In this way, the signal quality is enhanced with an LTE relay, rather than
suffering degradation from a reduced signal to noise ratio when using a
repeater
wired backhaul
Relay Node (RN)
Uu

donor cell (eNodeB)

Un
EPC
physical cell ID

23


Coverage depends on carrier frequency
Coverage depends on carrier frequency: low carrier frequencies
such as 800MHz are associated with a high coverage, while at
high carrier frequencies such as 2600 MHz, the coverage is less.
E-UTRA
Band

Bandwidth
UL (MHz)

Bandwidth
DL (MHz)

Duplex
Mode

1

1920-1980

2110-2170

FDD

2

1850-1910

1930-1990

FDD

3

1710-1785

1805-1880

FDD

4

1710-1755

2110-2155

FDD

5

824-849

869-894

FDD

6

830-840

875-885

FDD

7

2500-2570

2620-2690

FDD

8

880-915

925-960

FDD

9

1749.9-1784.9

1844.9-1879.9

FDD

10

1710-1770

2110-2170

FDD

11

1427.9-1452.9

1475.9-1500.9

FDD

12

698-716

728-746

FDD

13

77-787

746-756

FDD

14

788-798

758-768

FDD

24

Europe:
Band 7: The 2.6 GHz auctions have been
running in a few countries
Band 8:is currently used mostly by GSM. The
band is attractive from a coverage point of
view due to the lower propagation losses.


Coverage depends on data rate
A high data rate requires a fast modulation scheme, a high coding rate and possibly
the use of spatial multiplexing, all of which increase the receiver’s susceptibility to
noise and interference.

Modulation and coding scheme
QPSK
2bits/Hz
SINR

SINR

SINR

16QAM
4bits/Hz
SINR

SINR

SINR

64QAM
6bits/Hz
SINR

SINR

SINR
Relay

Physical Rate 4bits/Hz


GTP-U

RLC

UDP

Evolved
Node B

IP

(eNB)

L1


PDCP

MAC


L1/L2

eNode B

Physical Rate

25


Coverage depends SINR for Service
A high data rate requires a fast modulation scheme, a high coding rate and possibly
the use of spatial multiplexing, all of which increase the receiver’s susceptibility to
noise and interference.

Modulation and coding scheme
QPSK
2bits/Hz
SINR

SINR

SINR

16QAM
4bits/Hz
SINR

SINR

SINR

64QAM
6bits/Hz
SINR

SINR

SINR
Relay
GTP-U

RLC

UDP

Evolved
Node B

IP

(eNB)

L1

Web browsing

PDCP

MAC


L1/L2

eNode B

Physical Rate
VoIP Service- GBR

26


Improving SINR will improve coverage
Evolved
Node B
(eNB)

SINR -4

QPSK
2bits/Hz

SINR -4
SINR

SINR

SINR

16QAM
4bits/Hz
SINR

SINR

64QAM
6bits/Hz
SINR

SINR

SINR

Improving SINR

Relay


PDCP

GTP-U

RLC

UDP

MAC

IP

L1

L1/L2

eNode B

SINR ave = S
I+N

The average interference power can be
further decomposed as
I = Iown + Iother ,

Inter Cell Interference Coordination (ICIC), Frequency Selective scheduling etc
27


Poll
What best describes the term Single radio voice call continuity?
1. SRVCC is a technology whereby voice and SMS services are delivered
to LTE devices through the use of GSM/UMTS
2. SRVCC is needed because LTE is a packet-based all-IP network that
cannot support circuit-switched calls.
3. SRVCC is often seen as an interim solution for LTE operators.

4. SRVCC is an LTE functionality that allows a VoIP/IMS call in the LTE
packet domain to be moved to a (GSM/UMTS or CDMA)

28


Poll- answers
1. Circuit Switched FallBack (CSFB) is a technology whereby voice and SMS services
are delivered to LTE devices through the use of GSM or another circuit-switched
network.

2. Circuit Switched FallBack is needed because LTE is a packet-based all-IP network
that cannot support circuit-switched calls. When an LTE device is used to make or
receive a voice call or SMS, the device "falls back" to the 3G or 2G network to
complete the call or to deliver the SMS text message.
3. CSFB is often seen as an interim solution for LTE operators. Voice over LTE
(VoLTE) is considered to be the long-term goal for the delivery of voice services
on LTE networks.
4. SRVCC is an LTE functionality that allows a VoIP/IMS call in the LTE packet
domain to be moved to a legacy voice domain (GSM/UMTS or CDMA)

29


Coverage depends MIMO setting
Spatial multiplexing is often described as the use of multiple input multiple output
(MIMO) antennas.
This name is derived from the inputs and outputs to the air interface,
so that ‘multiple input’ refers to the transmitter and ‘multiple output’ to the
receiver.

30


3GPP Release 8
4x4 MIMO in the Downlink
1x1 MIMO in the Uplink
Repeaters
Home eNode B

The eNode B instructs the UE to use a
specific antenna solution via:
• RRC signalling
• Downlink Control Information
(DCI) on the PDCCH

3GPP Release 10
Carrier Aggregation
8x8 MIMO in the Downlink
4x4 MIMO in the Uplink
Relays

Relay
GTP-U

RLC

UDP

Evolved
Node B

MAC

IP

(eNB)

L1

1. Single-Antenna transmission, no MIMO
2. Transmit diversity
3. Open-loop spatial multiplexing, no UE feedback required
4. Closed-loop spatial multiplexing, UE feedback required
5. Multi-user MIMO (more than one UE is assigned to the same
resource block)
6. Closed-loop precoding for rank=1 (i.e. no spatial multiplexing, but
precoding is used)
7. Beamforming
31

PDCP

L1/L2

eNode B


SINR

SINR

Transmit
Diversity

Spatial Multiplexing (SM) targets increasing
users’ throughput
BEARER 1110
BEARER 0101

INCREASING
COVERAGE

Relay

PDCP

Adaptive Switching

BEARER 1110 SAME DATA
BEARER 1110-SAME DATA

32

GTP-U

RLC

UDP

Evolved
Node B

MAC

IP

(eNB)

L1

L1/L2

eNode B

SU-MIMO
2x2 Doubles peak rate
compared to 1x1


MU_MIMO
BEARER 1110
BEARER 0101
Relay
PDCP

GTP-U

RLC

UDP

Evolved
Node B

MAC

IP

(eNB)

L1

L1/L2

eNode B

MU-MIMO
2x2 Doubles capacity
compared to 1x1

33


Closed Loop Transmit Diversity
Here, the transmitter sends two copies of the signal in the expected way, but it also
applies a phase shift to one or both signals before transmission.
By doing this, it can ensure that the two signals reach the receiver in phase, without
any risk of destructive interference.
two signals reach the receiver in phase
BEARER 1110 SAME DATA
You also have
Receive diversity

BEARER 1110-SAME DATA
Relay

Closed Loop Transmit Diversity

GTP-U

RLC

UDP

Evolved
Node B

MAC

PMI

PDCP

IP

(eNB)

L1

L1/L2

eNode B

The phase shift is determined by a precoding matrix indicator (PMI), which
is calculated by the receiver and fed back to the transmitter.
34


SM close to the eNodeBs
to increase data rates
switches to Diversity
Transmit Diversity increases
coverage

MU-MIMO for heavily
loaded cells switches to
Diversity
35


Coverage depends
50% Loaded Network without MIMO

50% Loaded Network with SU-MIMO (Diversity
and Spatial Multiplexing in Adaptive Switching

Adaptive Switching
36


Coverage depends
Small tilt usually 5-10 degrees. This would
reduce the cell radius but allow for a more
uniform distribution of energy within the cell.

Methods
•Tilt Adjustment
•Azimuth Adjustment
•Power Adjustment
• Antenna Height

Antenna Tilt of 10 Degrees
In signal from the main beam and side lobes
would bounce off the ground and buildings
around the cell site and spread the signal
around the cell
37


Coverage depends on traffic SINR
Methods
•Tilt Adjustment
•Power Adjustment
• Antenna Height

38


Coverage depends on link budget

Path Loss = Tx – REF sens

TX Power

Lpmax_UL

TX Power

Path Loss = Tx – REF sens

39


link budget
Comparing systems with the same data rate, carrier frequency, then we find that the
maximum ranges of LTE and 3G systems are actually very similar.

40


Propagation models
Propagation models relate the propagation loss to the distance between the
transmitter and the receiver.
Frequency

Base Station
Antenna
height

Propagation loss to Distance (Km)
Relay
PDCP

Mobile Station
Antenna
height.

Path Loss in dB

GTP-U

RLC

UDP

Evolved
Node B

MAC

IP

(eNB)

L1

L1/L2

eNode B

Several propagation models exist and vary greatly in their complexity.
A simple and frequently used example is the Okumura-Hata model, which predicts
the coverage of macrocells in the frequency range 150 to 1500MHz

41


Propagation models-COST Hata model
Coverage
Frequency: 1500 MHz to 2000 MHz
Mobile Station Antenna :Height: 1 up to 10m
Base station Antenna Height: 30m to 200m
Link Distance: 1 up to 20 km

L = path loss. Unit: Decibel (dB)

f = Frequency of Transmission.
(MHz)

C= 0dB for medium sized city and
suburban areas
C=3 dB for metropolitan centers

hB = Base Station Antenna
height. Unit: Meter (m)

d = Link distance. Kilometer (km)

hR = Mobile Station Antenna
height.
42

This model requires that the base
station antenna is higher than all
adjacent rooftops

Coverage depends timing advance
• The signals from different mobiles have to reach the base station at
roughly the same time, to prevent any risk of inter-symbol interference
between them.

• To enforce this requirement, distant mobiles have to start transmitting
slightly earlier than they otherwise would.

Frequency

inter-symbol interference

Relay
PDCP

GTP-U

RLC

UDP

Evolved
Node B

MAC

IP

(eNB)

L1

L1/L2

eNode B

43


Coverage depends timing advance
Because the uplink transmission time is based on the downlink arrival time,
the timing advance has to compensate for the round-trip travel time
between the base station and the mobile:

D is the distance between the mobile and the base station, and v is the
speed of light. The timing advance does not have to be completely accurate,
as the cyclic prefix can handle any remaining errors.
LTE is required to support cell
ranges up to 100 km, which
translates to 667 μs two-way
propagation delay
= 200 Km/300000= 667uS

Distance (D)
Relay
PDCP
RLC

Round trip distance
44

GTP-U
UDP

MAC

IP

L1

L1/L2

eNode B

V = 300,000,000 meters per
second OR
300,000 km per second

Coverage depends Parameters
There are some parameters which also effect coverage one
of these are the PRACH parameters:

PRACH parameters
SIB

There are 5 PRACH preamble formats
formats 0 to 3 applicable to FDD and TDD
format 4 is only applicable to TDD (short preamble )

45

Timing
advance


Summary
Coverage depends on:
• SINR
• GBR of services
• MIMO setting
• Parameters for cell
selection
• Parameters for PRACH
• Timing Advance
• Frequency
• Base Station Antenna
height
• Mobile Station Antenna
height
• Path Loss
• Environment
46

Some items for increasing
coverage:
• GSM refarming (lower
frequency)
• Adaptive Switching
• Repeaters/Relays
Improving SINR so increasing
coverage:
• Inter Cell Interference
Coordination (ICIC)
• Frequency Selective
scheduling
•Tilt Adjustment
•Power Adjustment

Next Topic
Cell Selection Part2

System Information (SIB’s)
Cell Selection Part1

Handover Part2
Handover Part1

Comparison between GSM, UMTS & LTE
PDCCH &DCI Formats

PCI Planning

What effects LTE capacity

Comparison of LTE Release 8, 9 &10

Increasing coverage &
Capacity in LTE

RRC Signalling

UE measurement reports

Attach Procedure

NAS Signalling

Resource Allocation
Type

LTE Protocols – UE & eNode B

LTE Parameters
Designing High
capacity cells

47


In Closing
 Thank you for attending
 Webinars webpage – keep up to date and
register to receive email alerts on new
webinars
http://www.aircominternational.com/Web
inars.aspx

48


AIRCOM LTE Webinar 4 - LTE Coverage

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