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AIRCOM LTE Webinar 4 - LTE Coverage
- 1. The webinar will start shortly.
AIRCOM LTE Webinar Series:
Basic overview of LTE radio Coverage
© 2013 AIRCOM International Ltd
- 2. AIRCOM LTE Webinar Series:
Basic overview of LTE radio Coverage
© 2013 AIRCOM International Ltd
- 3. 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
© 2013 AIRCOM International Ltd
- 4. About AIRCOM
AIRCOM is the leading provider of mobile network planning,
optimisation and management software and consultancy services.
Advise
Manage
Audit
Network
Optimise
4
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
Plan
TEOCO offer very complimentary assurance an optimisation solutions as
well as an excellent analytics portfolio.
Significantly stronger combined offering for customers
Find out more at www.aircominternational.com
© 2013 AIRCOM International Ltd
- 6. 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
© 2013 AIRCOM International Ltd
- 7. 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
© 2013 AIRCOM International Ltd
- 8. 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
© 2013 AIRCOM International Ltd
- 9. 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
© 2013 AIRCOM International Ltd
- 10. Single radio voice call continuity
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
© 2013 AIRCOM International Ltd
- 11. Single radio voice call continuity
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
© 2013 AIRCOM International Ltd
- 12. 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
© 2013 AIRCOM International Ltd
- 13. 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
© 2013 AIRCOM International Ltd
- 14. 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
© 2013 AIRCOM International Ltd
- 15. 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
© 2013 AIRCOM International Ltd
- 16. 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
© 2013 AIRCOM International Ltd
- 17. Closed Subscriber Group Selection
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
© 2013 AIRCOM International Ltd
- 18. Closed Subscriber Group Selection
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
© 2013 AIRCOM International Ltd
- 19. 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
© 2013 AIRCOM International Ltd
- 20. 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
© 2013 AIRCOM International Ltd
- 21. 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
© 2013 AIRCOM International Ltd
- 22. 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
© 2013 AIRCOM International Ltd
- 23. 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
© 2013 AIRCOM International Ltd
- 24. 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.
© 2013 AIRCOM International Ltd
- 25. 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
Physical Rate 6bits/Hz
GTP-U
RLC
UDP
Evolved
Node B
IP
(eNB)
L1
Physical Rate 2bits/Hz
PDCP
MAC
modulation and coding scheme
L1/L2
eNode B
Physical Rate
25
© 2013 AIRCOM International Ltd
- 26. 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
modulation and coding scheme
L1/L2
eNode B
Physical Rate
VoIP Service- GBR
26
© 2013 AIRCOM International Ltd
- 27. 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
modulation and coding scheme
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
© 2013 AIRCOM International Ltd
- 28. 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
© 2013 AIRCOM International Ltd
- 29. 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
© 2013 AIRCOM International Ltd
- 30. 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
© 2013 AIRCOM International Ltd
- 31. Coverage depends MIMO setting
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
© 2013 AIRCOM International Ltd
- 32. Coverage depends MIMO setting
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
© 2013 AIRCOM International Ltd
- 33. Coverage depends MIMO setting
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
© 2013 AIRCOM International Ltd
- 34. 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
© 2013 AIRCOM International Ltd
- 35. 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
© 2013 AIRCOM International Ltd
- 36. Coverage depends
50% Loaded Network without MIMO
50% Loaded Network with SU-MIMO (Diversity
and Spatial Multiplexing in Adaptive Switching
Adaptive Switching
36
© 2013 AIRCOM International Ltd
- 37. 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
© 2013 AIRCOM International Ltd
- 38. Coverage depends on traffic SINR
Methods
•Tilt Adjustment
•Azimuth Adjustment
•Power Adjustment
• Antenna Height
38
© 2013 AIRCOM International Ltd
- 39. Coverage depends on link budget
Ref Sens = KTB + NF + SINR + IM
Path Loss = Tx – REF sens
TX Power
Lpmax_UL
TX Power
Path Loss = Tx – REF sens
Ref Sens = KTB + NF + SINR + IM
39
© 2013 AIRCOM International Ltd
- 40. 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
© 2013 AIRCOM International Ltd
- 41. 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
© 2013 AIRCOM International Ltd
- 42. 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
© 2013 AIRCOM International Ltd
- 43. 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
© 2013 AIRCOM International Ltd
- 44. 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
© 2013 AIRCOM International Ltd
- 45. 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
© 2013 AIRCOM International Ltd
- 46. 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
•Azimuth Adjustment
•Power Adjustment
© 2013 AIRCOM International Ltd
- 47. 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
© 2013 AIRCOM International Ltd
- 48. 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
© 2013 AIRCOM International Ltd