Page 1 Planning LTE Network Deployments Introd.docx

Planning LTE Network Deployments
Introduction
LTE (Long Term Evolution) is the 4
th
Generation (4G) technology comprising of Evolved
UMTS Terrestrial Radio Access Network (E-UTRAN) and
Evolved Packet System (EPS)
components. LTE brings speeds up to 300 Mbps for roaming
users needing wireless access
Internet. LTE is the next generation technology of the popular
and widely deployed 3G
technology UMTS, and is being developed by the 3
rd
Generation Partnership Project (3GPP), a
worldwide standards body comprising of service providers,
equipment manufacturers, and

R&D institutions.
As the wireless access technology continues to evolve and
become more flexible, planning
and predicting performance of such networks becomes a
challenging task. Often claims made
in the popular media about the speed, scalability and reliability
of the LTE networks are
purely theoretical in nature, and the actual performance of these
networks depends upon a
myriad of factors. Understanding such factors and designing
network deployments to achieve
the maximal performance out of the given resources is indeed a
critical task.
In this lab exercise, we will study how OPNET Modeler/Guru
can be used as a planning tool. We will
use out-of-the-box reports, statistics, and other software tools to
understand the network
performance and how it relates to the LTE technology itself.
Using planning workflows, we
will optimize
network parameters to achieve target objectives.

The labs make use of OPNET Modeler/Guru, the Wireless
module, and the specialized
LTE model to perform this planning exercise.
Lab 1: LTE Cell Planning Study
Overview
In this lab, we will deploy an LTE cell in OPNET Modeler/Guru
and analyze how to determine
and set the cell range. You will understand how interference can
affect cell range. In the
optional lab, we will study an “efficiency-based” workflow, in
which setting certain attributes
in the simulations and running them without the physical layer
(efficiency mode) speeds up the
simulation considerably.
Methodology
• Use the wireless network wizard to deploy an LTE network
• Understand how to find and set up the range of the LTE cell
• Understand how interference affects the cell range

studies
intended for large networks (optional/take home lab)
Part I
1. Start OPNET Modeler/Guru.
a. Double-click on the OPNET Modeler/Guru icon on the
desktop.
2. You will deploy a single cell LTE network with a single end
user in this scenario using the
Wireless Deployment Wizard.
3. Deploy a simple LTE network with a single cell and a single
end user using the wizard.
a. Choose the menu option Topology > Deploy Wireless
Network. Click Continue in the
dialog box.
Page 2
b. The option “Use wizard to provide network specifications”
should already be selected.

Click Next.
c. Click on “Create network in current subnet” and change the
X coordinate to 0 as shown.
Click Next.
d. In the dialog box, select LTE from the “Choose technology”
drop-down menu, and change
the “PHY Profile” to “LTE 3 MHz FDD” as shown. Click Next.

e. Change the “Number of Cells” to 1, and the “Cell Radius
(km)” to 3.00 km as shown.
Click Next.
Page 3

f. In the next dialog box, change the UE Count per-cell to 1 and
the UE Node Name Prefix to
UE as shown. Click Next.
g. We will not deploy random mobility on the UE. In the next
dialog box, click on the cell
below Trajectory Information to highlight it. Then click on the
button Delete Row. Click
Next.
h. The summary should look like the figure below. Click
Finish. The single cell LTE network
with 1 UE will be deployed.

4. In this exercise, we will study how to find and set up the
range of the LTE cell. We will position
the UE close to the eNodeB, and then deploy a trajectory that
takes it away towards the cell edge.
We will also deploy an application on this user.
a. Right-click on UE_0_1_1 and select Edit Attributes. Click
on the box Advanced in the
bottom. Change the attribute “x position” to 100 and “y
position” to 0. Change the trajectory
attribute to tr1. Click OK to save changes.

b. Connect an external host: An external host will run FTP and
voice application services.
Click on the object palette button ( ). In the object palette
window, under the group
internet toolbox, find ppp_wkstn node model. It appears on the
right-hand pane in the
window. Click on the node to select it, and click beside the EPC
node in the project editor to
place the node. Right-click in the project editor to discontinue
any more node placements.

In the object palette window, scroll down and find the link
model PPP_DS3. Select it, and
click on node_0 and EPC_0 to connect the nodes with the link.
Right-click in the project
editor to discontinue any more actions. Click the button Close
to shut the object palette
window.
c. Deploy application profile: In the project editor window,
press Ctrl+Alt+A (or
alternatively click Protocols > Applications > Deploy Defined
Applications).
d. In the dialog box that opens, deploy the FTP and voice
applications. UE_0_1_1 will be
the source. To configure this, select UE_0_1_1 in the left, and
select the “No nodes
assigned yet” under Profile:”Cell_User” -> Source on the right.
e. Click the assignment button ( ). Both FTP and voice
services are run on node_0,

so select node_0 on the left and select first “No nodes assigned
yet” under Tier:
“Voice Destination”.
f. Click the assignment button ( ). Then, select “No nodes
assigned yet” under Tier:
‘FTP Server”. Click the assignment button ( ). The end result is
as shown in the next
figure. Click OK to close the window.
g. Enable application delay tracking (used in step 6). Right-
click on UE_0_1_1, and select Edit
Attributes. Go to Application: Supported Profiles > Cell_User

and set the attribute
Application Delay Tracking to Enabled as shown below.
Page 6
h. Disable multipath from the physical layer: Right-click on
UE_0_1_1, and select Edit
Attributes. Navigate to LTE > PHY and set Multipath Channel
Model to Disabled. Click
OK to close the window.
i. Click the running man icon to run the simulation. Click the
Run button in the dialog
box.
j. When the simulation run is finished, click the Close button in
the DES execution window.
5. Analyze results.
a. There are some saved results panel templates in this
scenario. In the project editor, click the

button “Hide/Show Graph Panels”. There are seven panels. If
they are not laid out neatly
in a grid, maximize the project window, and click DES > Panel
Operations > Arrange Panels
> Tile. Finally, click DES > Panel Operations > Panel
Templates > Load With Latest
Results.
b. The range of the LTE cell: We can say that as long as the
user continues to enjoy a good
reception, the UE will be “in range”. The results should show
both voice and FTP
applications behaving well (voice MOS value is above 4, and
FTP delays are well under 1
second) even if the UE has moved away to about 5000 km,
whereas we deployed a cell with
3 km “range”.
c. Link adaptation: The LTE eNodeB performs a strategy
called link adaptation to keep the
receiver in good quality even as it is moving away. Link
adaptation is dynamic, and it basically
packs the same user data into more radio resources to improve
the quality of reception. LTE

supports 29 link adaptation values (also called Modulation and
Coding Scheme or MCS index),
with 0 being the most conservative (for the farthest users), and
28 being the most aggressive.
An aggressive MCS index indicates that there is plenty of
leeway to perform link adaptation by
reducing the MCS index of the UE.
i. Quiz: What are the MCS indexes of the UE for both the
uplink and downlink
at 5000 km from the eNodeB? uplink downlink
(Hint: The uplink MCS index is identified by
“Uplink MCS Index” and the downlink
MCS index is identified by “Best Operational Wideband MCS
Index”.)
ii. Since the MCS indexes are still high, it means that the range
perceived by the
users is much higher than the original 3 km that we intended.
d. One strategy to define the cell range as follows: If a UE has
good application performance at
a given distance from the eNodeB, and its MCS indexes achieve
a more conservative value,
then that distance shall be called the “cell range”.

e. What are the attributes to adjust the cell range? By changing
the transmission powers on the
UE and the eNodeB, we can change the LTE cell range.
f. What are the potential advantages and disadvantages of
limiting the transmission power to
define the cell range?
g. The default transmission power: In step 3, the transmission
power was left to “Cell
Size Based” in the wireless wizard. However for the single cell
scenario, we argued that
it was too high. How was the transmission power set
automatically in the first place?
i. Answer: ?

6. A deeper examination of FTP delays: LTE supports the
application delay tracking of FTP
application. Application delay tracking tracks an application
packet through the entire
network, right down to the byte range application payload. This
information can help
understand low level details that are not readily visible in DES
statistics and reports.
a. Click on DES > Results > View Application Delay Tracking
in the project
editor.
b. Click on the op_models tab in the left.
c. Choose the file 1599_lab1-single_cell_baseline-DES-1.adt,
and click on the button Open.
i. Users running the reference project should select the file
1599_lab1_ref- single_cell_baseline-DES-1.adt.
d. Examine the contents of the ADT file in the graphical
window by progressively going
into each transaction and each message of the FTP application
as shown. In particular,
examine the LTE link between the eNodeB and the UE in the

message, and click Show
more precision at the bottom. First examine transaction number
1 (the very first
transaction), message 2, and the last link between the eNodeB
and the UE as shown in
the picture.
Advantages Disadvantages
Users can conserve their battery by limiting
transmission power
Users may experience worse performance as
they move away
Less interference for neighboring cells eNodeB spends more
radio resources to
maintain an acceptable quality for the “edge
users”
Page 8

e. The higher layer application packet is chopped into smaller
segments by the LTE scheduler. f.
LTE scheduler operates every 1 ms, as seen from the results.
g. Within a single subframe, the LTE scheduler may create 1
or more packets for the same UE
and pack them into a single MAC Protocol Data Unit (MPDU),
as is evident from the results.
i. Quiz: At what time, the first message was sent by the
eNodeB and what time
the last message was sent? ,

ii. Quiz: Check the Duration column against message 2. How
much time was
spent in order to deliver this message?
in LTE?
How much of it is encountered
iii. Quiz: Check the Duration column against the entire
transaction. How much
time was spent to complete this first transaction? By looking at
the
FTP delays on the statistics, can you tell whether the delays as
shown by the
ADT look similar?
h. Now scroll down and go to the very last transaction when
the UE (transaction 584).
i. Quiz: The delay for the entire transaction is now
changed? Is this change expected?
ii. Quiz: Check the Duration for message 2. It is
the first transaction?
.

Quiz: Dig into the last LTE link of the message 2 of this
transaction. There are
2 entries as shown in the picture below. What are the dropped
packets?
Answer: ?
iv. Quiz: How did the dropped packets get retransmitted and
when?
. How have the delays . How has it changed since
i. Answer: ?
1. Answer: ?

v. Quiz: Compared to the very first transaction, how have the
number of
segments changed?
1. Answer: ?
i. You may browse into this file more. When done, click the
button Close.
Setting the eNodeB and UE Transmission Powers for a 3 Km
cell Range
We will now adjust the transmission powers at the UE and the
eNodeB, and then select an

appropriate value that corresponds to a 3 Km cell range. Switch
to scenario
single_cell_reduced_power. If you choose to follow the
reference project then go to step 8.
7. Creating a parametric run: We will run multiple simulations
by changing the transmission power
attribute of the eNodeB and the UE.
a. Right-click on the UE_0_1_1 node and select Edit
Attributes. If the UE icon is too small,
click View > Show Network Browser, and find the UE_0_1_1
node on the left hand side.
Right-click on the node there.
b. Right-click against the value cell of LTE>PHY>Maximum
Transmission Power (W) and
select Promote Attribute To Higher Level. Click OK to close the
window.
Page 10

c. Repeat steps a and b for eNodeB_1.
d. Click on the running man icon and navigate to
Inputs/Object Attributes.
e. Click in the first row beneath the column Attribute. In the
window that opens, the
second row is the attribute for Maximum Transmission Power
(W) of all nodes. Add it
as shown. Click OK to close the attribute add window.
f. In the original DES execution window, click in the cell
below the Value column and
click the button Enter Multiple Values… Enter the following
values as shown.

i. Quiz: The transmission power is reduced from mW to
mW. Click OK to close the window. Click Run in the original
DES execution window
to run the
simulation. 6 DES simulations should be executed.
8. Analyze Results:
a. Click Close to shut the execution manager window. Click
the button “Hide/Show
Graph Panels” and click DES > Panel Operations > Panel
Templates > Load
With Latest Results.
b. Use the time controller feature to find the UE’s application
performance at the edge of the
cell (3 Km). Move the panels around so that the menu bar and
the LTE network are visible
in the project editor. Click View > Show Time Controller. Click
on the button Configure
and uncheck Start modeling at time, if it is checked. Click OK
to close the configuration
window. Move the sliding window using your mouse, and stop
when the UE is at

approximately 3 Km. Check the position of the thick green lines
on the results.
Page 11
Answer: Include the results from OPNET here
c. FTP delays are still sub-second, and MOS values for the
voice are still above 4.0 for all
values of transmission powers. For the last value (0.5 mW), we
can observe that MOS
values are very close to being going under 4.0, and any further
reduction in transmission

power would have that effect on the cell edge.
d. MCS indexes: For the last transmission power value (0.5
mW), the uplink MCS index is
13, and the downlink MCS index is 12. These values are
acceptable at the cell edge.
e. Quiz: For a 3 Km cell range, can we reduce the transmission
power to 0.5 mW?
Answer: ?.
Studying the Effects of Inter-cell Interference on Application
Performance
9. Switch to scenario multi_cell_interference. In this scenario,
there are three cells and one UE per
cell. In Cell 1, Mobile_0_1_1 is running both FTP and Voice
applications. Mobile_0_1_1 is
located nearby eNodeB_1 but it is also assigned a trajectory.
The trajectory is set such that

Mobile_0_1_1 will be moving away from eNodeB_1 towards the
cell boundary between
eNodeB_1 and eNodeB_2. In this part of the lab, we want to
study the effects of inter-cell
interference. Therefore the UEs in other cells are assigned both
uplink and downlink IP traffic
flows so that they can act as interferers. The IP traffic flows are
scalable. We will scale up the IP
traffic in each run to see the effect of increasing interference. In
each simulation run, the
interference will also increase as Mobile_0_1_1 moves away
from eNodeB_1.
Page 12
10. The network model is completely setup. We only need to
enter how we want to scale up the IP
traffic flows.
a. Click on the running man icon and navigate to Inputs >
Global Attributes.
b. On the right, select the global attribute Traffic >Traffic
Scaling Factor, and click on Enter

Multiple Values. Enter 4 values in this order: 1, 4, 10 and 50
(The base traffic is 10 Kbps).
c. Click OK to confirm. Make sure the settings look as shown
below:
d. Click Run in the Configure/Run DES execution window to
run the simulations. Four
simulations should be executed.
11. Analyze Results:
the button “Hide/Show Graph
Panels” and choose DES > Panel Operations > Panel Templates
> Load With Latest
Results.
Answer: Include the results from OPNET here.
b. Notice that as interference traffic scales up, application
performance degrades and the UE’s
MCS index becomes worse with increasing traffic. Thus in the
presence of interfering sources,
single cell based cell planning studies need to be modified. In
the present scenario, the cell

radius estimate needs to be adjusted and the transmission power
needs to be scaled up
appropriately to account for the interfering traffic.
c. The FTP performance is acceptable for the first 3 values of
traffic but degrades very quickly
for the last value. What can be done to make things better?
i. Take home exercise: First increase the power of
Mobile_0_1_1 to its default
value of 0.0152 W. Then increase the power of eNodeB_1 to its
default value
of 0.0334. Increasing the power in the serving cell to combat
interference
makes the application performance better. Similar to how it was
done in the
second part, conduct a parametric study to find the optimal
power setting in
this scenario.
Page 13

Using the Efficiency Mode to Speed Up Simulations (Take
Home/Optional)
Running simulations that consider the entire physical layer
effects can be intensive with respect to
simulation speed and memory. There is an alternative way to
run simulations in LTE – called
Efficiency Mode. In the efficiency mode, random packet drop
probability can be pre-configured.
The strategy for using efficiency mode for LTE simulations is
as follows: a) Configure an
appropriate packet drop probability, and b) configure
appropriate MCS indexes on the UEs. The link
adaptation procedure in the physical layer can compute MCS
indexes automatically, but for the
efficiency mode, they should be pre-configured.
Efficiency based simulations can be the logical next step after
the cell planning exercise. Once you
plan the cell and, through statistics, understand how an “average
UE” behaves, it is possible to
parameterize this average behavior as efficiency mode inputs
and run the simulations much faster

while maintaining accuracy at the cell level.
12. Switch to scenario multi_cell_phy, using a scenario with
physical layer effects.
a. In this scenario, there are seven cells and five UEs per cell.
The UEs run a mixture of
voice and FTP applications. This scenario has already been
executed and the panels have
been saved.
b. Click the Hide > Show Graph Panels button to activate the
panels. Uplink and
Downlink BLER statistics have been collected for the center
cell, and they both
converge to about 0.4 as shown in the panels.
Also, the MCS index statistics are collected for the UEs in the
center cell for both uplink
and downlink.

As shown, the node UE_0_1_1 achieves a high MCS index of
28, since it is close to the
eNodeB. The remaining UEs achieve an MCS index of around
10 on the downlink and 16 on
the uplink.
Finally, we collect the load and throughput as well as utilization
statistics at eNodeB_1.
The throughout (traffic received on the uplink) is around 200
Kbps, while the load is around 1.2
Mbps on average. Correspondingly, the PUSCH utilization is
about 20% and the PDSCH utilization
is around 60%.
13. In the DES log, find out the number of events and the total
time it took to run this simulation.
Choose DES > Open DES Log and scroll to the right. Click in
the last row under the Message
column to open the DES log as shown.

The simulation executed 124.2 million events and took 6
minutes 40 seconds for simulation time
of 150 seconds. The memory consumed was 71.6 MB.
Note: The time it takes on your machine may be different
depending upon the speed and set up
of your machine.
14. Switch to scenario multi_cell_eff. We will configure this
scenario with appropriate input
parameters so it gives us a similar performance. We will only
focus upon the center cell.
a. First, configure the simulation to run in the efficiency mode

and appropriate packet drop
statistics. Right-click on the LTE configuration node, and select
Edit Attributes. Expand
Efficiency Attributes, and set the Mode to PHY Disabled. Set
the Initial MPDU Drop
Probability to 0.4.
i. Because subsequent HARQ retransmissions increase the
probability of
detection of a packet, we model this behavior by a parameter
called
Retransmission Improvement Factor (r). Then, the probability of
MPDU drop
of the nth retransmission (where n is an integer) is:
p = P × (
1
)
n
i
r

b. Now we will configure the UEs with static MCS indexes

that are the approximate averaged
values of uplink and downlink MCS index found in the previous
scenario.
, where Pi is the initial MPDU drop probability.
.
i. Double-click on Campus Network, and then double-click on
Wireless
Subnet_0.
ii. Right-click on UE_0_1_1 and go to LTE > PHY >
Modulation and Coding
Scheme Index. Set it to 28. Click OK to save changes. (If the
node is not
visible due to its proximity to eNodeB, click View > Show
Network Browser
and find it in the browser on the left).
iii. Similarly, select UE_0_1_2, UE_0_1_3, UE_0_1_4 and
UE_0_1_5 and set
the attribute LTE > PHY > Modulation and Coding Scheme
Index to 12 for
all those UEs.

c. Click on the running man icon and execute the simulation.
When done, click on Hide >
Show Graph Panels and click DES > Panel Operations > Panel
Templates > Load With
Latest Results. The channel utilization statistics are similar
(since we specified a single MCS
index instead of 2 separate MCS indexes for the uplink and
downlink, there are some
differences).
The load throughput statistics for the eNodeB_1 are also
similar.
Finally, the cell delays are also similar.
d. Thus, the overall performance is similar to what it was for

the physical layer enabled case.
Now open the DES log by clicking DES > Open DES Log, and
again click in the row
under Message, as shown, by scrolling to the right.
Compared to the physical layer, how does the speed and
memory behave for the
efficiency level case?
Total events Total time Memory
Physical layer 124.2 Million 71.6 MB
No physical layer 10.3 Million 62.8 MB
Due to the higher order scale of a simulation running the
physical layer, the gap
between efficiency case and physical layer case will increase
with larger scenarios.
Conclusion
It is possible to rapidly deploy and analyze LTE networks in
OPNET Modeler/Guru.

Answer: Include your conclusions about this lab here. Submit a
complete report including all results.
Page 1
Planning LTE Network Deployments
Introduction
LTE (Long Term Evolution) is the 4
th
Generation (4G) technology comprising of Evolved
UMTS Terrestrial Radio Access Network (E-UTRAN) and
Evolved Packet System (EPS)
components. LTE brings speeds up to 300 Mbps for roaming
users needing wireless access
Internet. LTE is the next generation technology of the popular
and widely deployed 3G
technology UMTS, and is being developed by the 3

rd
Generation Partnership Project (3GPP), a
worldwide standards body comprising of service providers,
equipment manufacturers, and
R&D institutions.
As the wireless access technology continues to evolve and
become more flexible, planning
and predicting performance of such networks becomes a
challenging task. Often claims made
in the popular media about the speed, scalability and reliability
of the LTE networks are
purely theoretical in nature, and the actual performance of these
networks depends upon a
myriad of factors. Understanding such factors and designing
network deployments to achieve
the maximal performance out of the given resources is indeed a
critical task.
In this lab exercise, we will study how OPNET Modeler/Guru
can be used as a planning tool. We will
use out-of-the-box reports, statistics, and other software tools to
understand the network

performance and how it relates to the LTE technology itself.
Using planning workflows, we
will optimize
network parameters to achieve target objectives.
The labs make use of OPNET Modeler/Guru, the Wireless
module, and the specialized
LTE model to perform this planning exercise.
Lab 1: LTE Cell Planning Study
Overview
In this lab, we will deploy an LTE cell in OPNET Modeler/Guru
and analyze how to determine
and set the cell range. You will understand how interference can
affect cell range. In the
optional lab, we will study an “efficiency-based” workflow, in
which setting certain attributes
in the simulations and running them without the physical layer
(efficiency mode) speeds up the
simulation considerably.
Methodology

• Use the wireless network wizard to deploy an LTE network
• Understand how to find and set up the range of the LTE cell
• Understand how interference affects the cell range
studies
intended for large networks (optional/take home lab)
Part I
1. Start OPNET Modeler/Guru.
a. Double-click on the OPNET Modeler/Guru icon on the
desktop.
2. You will deploy a single cell LTE network with a single end
user in this scenario using the
Wireless Deployment Wizard.
3. Deploy a simple LTE network with a single cell and a single
end user using the wizard.
a. Choose the menu option Topology > Deploy Wireless
Network. Click Continue in the
dialog box.

b. The option “Use wizard to provide network specifications”
should already be selected.
Click Next.
c. Click on “Create network in current subnet” and change the
X coordinate to 0 as shown.
Click Next.
d. In the dialog box, select LTE from the “Choose technology”
drop-down menu, and change
the “PHY Profile” to “LTE 3 MHz FDD” as shown. Click Next.

e. Change the “Number of Cells” to 1, and the “Cell Radius
(km)” to 3.00 km as shown.
Click Next.

f. In the next dialog box, change the UE Count per-cell to 1 and
the UE Node Name Prefix to
UE as shown. Click Next.
g. We will not deploy random mobility on the UE. In the next
dialog box, click on the cell
below Trajectory Information to highlight it. Then click on the
button Delete Row. Click
Next.

h. The summary should look like the figure below. Click
Finish. The single cell LTE network
with 1 UE will be deployed.
Page 4
4. In this exercise, we will study how to find and set up the
range of the LTE cell. We will position
the UE close to the eNodeB, and then deploy a trajectory that
takes it away towards the cell edge.
We will also deploy an application on this user.
a. Right-click on UE_0_1_1 and select Edit Attributes. Click

on the box Advanced in the
bottom. Change the attribute “x position” to 100 and “y
position” to 0. Change the trajectory
attribute to tr1. Click OK to save changes.
b. Connect an external host: An external host will run FTP and
voice application services.
Click on the object palette button ( ). In the object palette
window, under the group
internet toolbox, find ppp_wkstn node model. It appears on the
right-hand pane in the
window. Click on the node to select it, and click beside the EPC

node in the project editor to
place the node. Right-click in the project editor to discontinue
any more node placements.
Page 5
In the object palette window, scroll down and find the link
model PPP_DS3. Select it, and
click on node_0 and EPC_0 to connect the nodes with the link.
Right-click in the project
editor to discontinue any more actions. Click the button Close
to shut the object palette
window.
c. Deploy application profile: In the project editor window,
press Ctrl+Alt+A (or
alternatively click Protocols > Applications > Deploy Defined
Applications).
d. In the dialog box that opens, deploy the FTP and voice
applications. UE_0_1_1 will be
the source. To configure this, select UE_0_1_1 in the left, and
select the “No nodes

assigned yet” under Profile:”Cell_User” -> Source on the right.
e. Click the assignment button ( ). Both FTP and voice
services are run on node_0,
so select node_0 on the left and select first “No nodes assigned
yet” under Tier:
“Voice Destination”.
f. Click the assignment button ( ). Then, select “No nodes
assigned yet” under Tier:
‘FTP Server”. Click the assignment button ( ). The end result is
as shown in the next
figure. Click OK to close the window.

g. Enable application delay tracking (used in step 6). Right-
click on UE_0_1_1, and select Edit
Attributes. Go to Application: Supported Profiles > Cell_User
and set the attribute
Application Delay Tracking to Enabled as shown below.
Page 6
h. Disable multipath from the physical layer: Right-click on
UE_0_1_1, and select Edit
Attributes. Navigate to LTE > PHY and set Multipath Channel
Model to Disabled. Click
OK to close the window.
i. Click the running man icon to run the simulation. Click the
Run button in the dialog
box.
j. When the simulation run is finished, click the Close button in
the DES execution window.

5. Analyze results.
a. There are some saved results panel templates in this
scenario. In the project editor, click the
button “Hide/Show Graph Panels”. There are seven panels. If
they are not laid out neatly
in a grid, maximize the project window, and click DES > Panel
Operations > Arrange Panels
> Tile. Finally, click DES > Panel Operations > Panel
Templates > Load With Latest
Results.
b. The range of the LTE cell: We can say that as long as the
user continues to enjoy a good
reception, the UE will be “in range”. The results should show
both voice and FTP
applications behaving well (voice MOS value is above 4, and
FTP delays are well under 1
second) even if the UE has moved away to about 5000 km,
whereas we deployed a cell with
3 km “range”.
c. Link adaptation: The LTE eNodeB performs a strategy
called link adaptation to keep the

receiver in good quality even as it is moving away. Link
adaptation is dynamic, and it basically
packs the same user data into more radio resources to improve
the quality of reception. LTE
supports 29 link adaptation values (also called Modulation and
Coding Scheme or MCS index),
with 0 being the most conservative (for the farthest users), and
28 being the most aggressive.
An aggressive MCS index indicates that there is plenty of
leeway to perform link adaptation by
reducing the MCS index of the UE.
i. Quiz: What are the MCS indexes of the UE for both the
uplink and downlink
at 5000 km from the eNodeB? uplink downlink
(Hint: The uplink MCS index is identified by
“Uplink MCS Index” and the downlink
MCS index is identified by “Best Operational Wideband MCS
Index”.)
ii. Since the MCS indexes are still high, it means that the range
perceived by the
users is much higher than the original 3 km that we intended.

d. One strategy to define the cell range as follows: If a UE has
good application performance at
a given distance from the eNodeB, and its MCS indexes achieve
a more conservative value,
then that distance shall be called the “cell range”.
Page 7
e. What are the attributes to adjust the cell range? By changing
the transmission powers on the
UE and the eNodeB, we can change the LTE cell range.
f. What are the potential advantages and disadvantages of
limiting the transmission power to
define the cell range?

i. Answer: ?
6. A deeper examination of FTP delays: LTE supports the
application delay tracking of FTP
application. Application delay tracking tracks an application
packet through the entire
network, right down to the byte range application payload. This
information can help
understand low level details that are not readily visible in DES
statistics and reports.
a. Click on DES > Results > View Application Delay Tracking
in the project
editor.
b. Click on the op_models tab in the left.
c. Choose the file 1599_lab1-single_cell_baseline-DES-1.adt,
and click on the button Open.
i. Users running the reference project should select the file
1599_lab1_ref- single_cell_baseline-DES-1.adt.

d. Examine the contents of the ADT file in the graphical
window by progressively going
into each transaction and each message of the FTP application
as shown. In particular,
examine the LTE link between the eNodeB and the UE in the
message, and click Show
more precision at the bottom. First examine transaction number
1 (the very first
transaction), message 2, and the last link between the eNodeB
and the UE as shown in
the picture.
Advantages Disadvantages
Users can conserve their battery by limiting
transmission power
Users may experience worse performance as
they move away
Less interference for neighboring cells eNodeB spends more
radio resources to
maintain an acceptable quality for the “edge
users”

e. The higher layer application packet is chopped into smaller
segments by the LTE scheduler. f.
LTE scheduler operates every 1 ms, as seen from the results.
g. Within a single subframe, the LTE scheduler may create 1
or more packets for the same UE
and pack them into a single MAC Protocol Data Unit (MPDU),
as is evident from the results.

i. Quiz: At what time, the first message was sent by the
eNodeB and what time
the last message was sent? ,
ii. Quiz: Check the Duration column against message 2. How
much time was
spent in order to deliver this message?
in LTE?
How much of it is encountered
iii. Quiz: Check the Duration column against the entire
transaction. How much
time was spent to complete this first transaction? By looking at
the
FTP delays on the statistics, can you tell whether the delays as
shown by the
ADT look similar?
h. Now scroll down and go to the very last transaction when
the UE (transaction 584).
i. Quiz: The delay for the entire transaction is now
changed? Is this change expected?

ii. Quiz: Check the Duration for message 2. It is
the first transaction?
.
Page 9
Quiz: Dig into the last LTE link of the message 2 of this
transaction. There are
2 entries as shown in the picture below. What are the dropped
packets?
Answer: ?
iv. Quiz: How did the dropped packets get retransmitted and
when?
. How have the delays . How has it changed since

i. Answer: ?
1. Answer: ?
v. Quiz: Compared to the very first transaction, how have the
number of
segments changed?
1. Answer: ?
i. You may browse into this file more. When done, click the
button Close.

Setting the eNodeB and UE Transmission Powers for a 3 Km
cell Range
We will now adjust the transmission powers at the UE and the
eNodeB, and then select an
appropriate value that corresponds to a 3 Km cell range. Switch
to scenario
single_cell_reduced_power. If you choose to follow the
reference project then go to step 8.
7. Creating a parametric run: We will run multiple simulations
by changing the transmission power
attribute of the eNodeB and the UE.
a. Right-click on the UE_0_1_1 node and select Edit
Attributes. If the UE icon is too small,
click View > Show Network Browser, and find the UE_0_1_1
node on the left hand side.
Right-click on the node there.
b. Right-click against the value cell of LTE>PHY>Maximum
Transmission Power (W) and
select Promote Attribute To Higher Level. Click OK to close the
window.

c. Repeat steps a and b for eNodeB_1.
d. Click on the running man icon and navigate to
Inputs/Object Attributes.
e. Click in the first row beneath the column Attribute. In the
window that opens, the
second row is the attribute for Maximum Transmission Power
(W) of all nodes. Add it
as shown. Click OK to close the attribute add window.
f. In the original DES execution window, click in the cell

below the Value column and
click the button Enter Multiple Values… Enter the following
values as shown.
i. Quiz: The transmission power is reduced from mW to
mW. Click OK to close the window. Click Run in the original
DES execution window
to run the
simulation. 6 DES simulations should be executed.
8. Analyze Results:
the button “Hide/Show
Graph Panels” and click DES > Panel Operations > Panel
Templates > Load
With Latest Results.
b. Use the time controller feature to find the UE’s application
performance at the edge of the
cell (3 Km). Move the panels around so that the menu bar and
the LTE network are visible
in the project editor. Click View > Show Time Controller. Click

on the button Configure
and uncheck Start modeling at time, if it is checked. Click OK
to close the configuration
window. Move the sliding window using your mouse, and stop
when the UE is at
approximately 3 Km. Check the position of the thick green lines
on the results.
Page 11
c. FTP delays are still sub-second, and MOS values for the

voice are still above 4.0 for all
values of transmission powers. For the last value (0.5 mW), we
can observe that MOS
values are very close to being going under 4.0, and any further
reduction in transmission
power would have that effect on the cell edge.
d. MCS indexes: For the last transmission power value (0.5
mW), the uplink MCS index is
13, and the downlink MCS index is 12. These values are
acceptable at the cell edge.
e. Quiz: For a 3 Km cell range, can we reduce the transmission
power to 0.5 mW?
Answer: ?.
Studying the Effects of Inter-cell Interference on Application
Performance
9. Switch to scenario multi_cell_interference. In this scenario,
there are three cells and one UE per

cell. In Cell 1, Mobile_0_1_1 is running both FTP and Voice
applications. Mobile_0_1_1 is
located nearby eNodeB_1 but it is also assigned a trajectory.
The trajectory is set such that
Mobile_0_1_1 will be moving away from eNodeB_1 towards the
cell boundary between
eNodeB_1 and eNodeB_2. In this part of the lab, we want to
study the effects of inter-cell
interference. Therefore the UEs in other cells are assigned both
uplink and downlink IP traffic
flows so that they can act as interferers. The IP traffic flows are
scalable. We will scale up the IP
traffic in each run to see the effect of increasing interference. In
each simulation run, the
interference will also increase as Mobile_0_1_1 moves away
from eNodeB_1.
Page 12
10. The network model is completely setup. We only need to
enter how we want to scale up the IP
traffic flows.

a. Click on the running man icon and navigate to Inputs >
Global Attributes.
b. On the right, select the global attribute Traffic >Traffic
Scaling Factor, and click on Enter
Multiple Values. Enter 4 values in this order: 1, 4, 10 and 50
(The base traffic is 10 Kbps).
c. Click OK to confirm. Make sure the settings look as shown
below:
d. Click Run in the Configure/Run DES execution window to
run the simulations. Four
simulations should be executed.
11. Analyze Results:
the button “Hide/Show Graph
Panels” and choose DES > Panel Operations > Panel Templates
> Load With Latest
Results.
b. Notice that as interference traffic scales up, application

performance degrades and the UE’s
MCS index becomes worse with increasing traffic. Thus in the
presence of interfering sources,
single cell based cell planning studies need to be modified. In
the present scenario, the cell
radius estimate needs to be adjusted and the transmission power
needs to be scaled up
appropriately to account for the interfering traffic.
c. The FTP performance is acceptable for the first 3 values of
traffic but degrades very quickly
for the last value. What can be done to make things better?
i. Take home exercise: First increase the power of
Mobile_0_1_1 to its default
value of 0.0152 W. Then increase the power of eNodeB_1 to its
default value
of 0.0334. Increasing the power in the serving cell to combat
interference
makes the application performance better. Similar to how it was
done in the
second part, conduct a parametric study to find the optimal
power setting in
this scenario.

Using the Efficiency Mode to Speed Up Simulations (Take
Home/Optional)
Running simulations that consider the entire physical layer
effects can be intensive with respect to
simulation speed and memory. There is an alternative way to
run simulations in LTE – called
Efficiency Mode. In the efficiency mode, random packet drop
probability can be pre-configured.
The strategy for using efficiency mode for LTE simulations is
as follows: a) Configure an
appropriate packet drop probability, and b) configure
appropriate MCS indexes on the UEs. The link
adaptation procedure in the physical layer can compute MCS
indexes automatically, but for the
efficiency mode, they should be pre-configured.
Efficiency based simulations can be the logical next step after
the cell planning exercise. Once you

plan the cell and, through statistics, understand how an “average
UE” behaves, it is possible to
parameterize this average behavior as efficiency mode inputs
and run the simulations much faster
while maintaining accuracy at the cell level.
12. Switch to scenario multi_cell_phy, using a scenario with
physical layer effects.
a. In this scenario, there are seven cells and five UEs per cell.
The UEs run a mixture of
voice and FTP applications. This scenario has already been
executed and the panels have
been saved.
b. Click the Hide > Show Graph Panels button to activate the
panels. Uplink and
Downlink BLER statistics have been collected for the center
cell, and they both
converge to about 0.4 as shown in the panels.

Also, the MCS index statistics are collected for the UEs in the
center cell for both uplink
and downlink.
As shown, the node UE_0_1_1 achieves a high MCS index of
28, since it is close to the
eNodeB. The remaining UEs achieve an MCS index of around
10 on the downlink and 16 on
the uplink.
Finally, we collect the load and throughput as well as utilization
statistics at eNodeB_1.
The throughout (traffic received on the uplink) is around 200
Kbps, while the load is around 1.2
Mbps on average. Correspondingly, the PUSCH utilization is
about 20% and the PDSCH utilization
is around 60%.
13. In the DES log, find out the number of events and the total

time it took to run this simulation.
Choose DES > Open DES Log and scroll to the right. Click in
the last row under the Message
column to open the DES log as shown.
Page 14
The simulation executed 124.2 million events and took 6
minutes 40 seconds for simulation time
of 150 seconds. The memory consumed was 71.6 MB.
Note: The time it takes on your machine may be different
depending upon the speed and set up
of your machine.

14. Switch to scenario multi_cell_eff. We will configure this
scenario with appropriate input
parameters so it gives us a similar performance. We will only
focus upon the center cell.
a. First, configure the simulation to run in the efficiency mode
and appropriate packet drop
statistics. Right-click on the LTE configuration node, and select
Edit Attributes. Expand
Efficiency Attributes, and set the Mode to PHY Disabled. Set
the Initial MPDU Drop
Probability to 0.4.
i. Because subsequent HARQ retransmissions increase the
probability of
detection of a packet, we model this behavior by a parameter
called
Retransmission Improvement Factor (r). Then, the probability of
MPDU drop
of the nth retransmission (where n is an integer) is:
p = P × (
1
)
n

i
r

b. Now we will configure the UEs with static MCS indexes
that are the approximate averaged
values of uplink and downlink MCS index found in the previous
scenario.
, where Pi is the initial MPDU drop probability.
.
i. Double-click on Campus Network, and then double-click on
Wireless
Subnet_0.
ii. Right-click on UE_0_1_1 and go to LTE > PHY >
Modulation and Coding
Scheme Index. Set it to 28. Click OK to save changes. (If the
node is not
visible due to its proximity to eNodeB, click View > Show
Network Browser
and find it in the browser on the left).

iii. Similarly, select UE_0_1_2, UE_0_1_3, UE_0_1_4 and
UE_0_1_5 and set
the attribute LTE > PHY > Modulation and Coding Scheme
Index to 12 for
all those UEs.
Page 15
c. Click on the running man icon and execute the simulation.
When done, click on Hide >
Show Graph Panels and click DES > Panel Operations > Panel
Templates > Load With
Latest Results. The channel utilization statistics are similar
(since we specified a single MCS
index instead of 2 separate MCS indexes for the uplink and
downlink, there are some
differences).
The load throughput statistics for the eNodeB_1 are also
similar.

Finally, the cell delays are also similar.
d. Thus, the overall performance is similar to what it was for
the physical layer enabled case.
Now open the DES log by clicking DES > Open DES Log, and
again click in the row
under Message, as shown, by scrolling to the right.
Compared to the physical layer, how does the speed and
memory behave for the
efficiency level case?
Total events Total time Memory
Physical layer 124.2 Million 71.6 MB
No physical layer 10.3 Million 62.8 MB
Due to the higher order scale of a simulation running the
physical layer, the gap
between efficiency case and physical layer case will increase
with larger scenarios.

Conclusion
It is possible to rapidly deploy and analyze LTE networks in
OPNET Modeler/Guru.
Answer: Include your conclusions about this lab here. Submit a
complete report including all results.

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