Simulation GUI

Open NetSim, Go to New Simulation 🡪 LTE/LTE-A Networks

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Figure-1: NetSim Home Screen

Create Scenario

LTE comes with a palette of various devices like Wired & Wireless Nodes, L2 Switch & Access Point, EPC (Evolved Packet Core) & Router, Macro Cell eNB and UE (User Equipment).

Devices Specific to NetSim LTE Library

  • UE (LTE UE) - User Equipment

  • Macro cell eNB - Evolved NodeB

  • EPC (Evolved packet core) – Provides end to end IP connectivity between NG (New Generation) core and eNB. This is the equivalent of MME in LTE and comprises of PGW, SGW and MME. EPC can connect to Routers in NG core which in turn can connect to Switches, APs, Servers etc.

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Figure-2: LTE Device Palette in GUI

  1. Add a User Equipment (UE) – Click the UE icon on the toolbar and place the UE in the grid. The UEs are always assumed to be connected to one eNB. It can never be connected to more than one eNB, and neither can it be out-of-range of all eNBs.

  2. Add an eNB – Click the eNB icon on the toolbar and place the eNB in the grid. eNBs can also be placed inside buildings based on the network scenario created. Every eNB should be connected to at least one UE.

  3. Add an EPC – EPC is automatically placed in grid. EPC must be connected to an eNB (the connection between eNB and EPC is handled by NetSim once user drops the eNB in GUI) or to a Router. NetSim LTE Library currently supports only one EPC.

  4. Add a Router – Click the Router icon on the toolbar, Select Router and place device in the grid.

  5. Add an L2 Switch – Click the L2 Switch icon on the toolbar and place the device in the grid.

  6. Access Point – Click the Access Point icon on the toolbar and place the device in the grid.

  7. Add a Wired Node and Wireless Node – Click Wired Node icon or Wireless Node icon on the toolbar and place the devices in the grid.

  8. Configure an application as follows:

  1. Click on the Set Traffic tab in the top ribbon.

  2. Select any application from the list and configure the traffic between source and destination.

  3. Specify other application parameters per your model.

Enable Packet Trace, Event Trace(Optional)

Click the Packet Trace / Event Trace icon in the Configure Reports option and check Enable Packet Trace / Event Trace check box. For detailed help about the packet and event trace, please refer to sections 8.4 and 8.5 in the User Manual.

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Figure-3: Enable Packet Trace, Event Trace & Plots options on top ribbon

Enable protocol specific logs and plots

NetSim provides protocol-specific logs for LTE libraries, which users can enable before running a simulation. These can be enabled by clicking on configure reports in top ribbon > clicking on plots > choosing as desired, and running the simulation

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Figure-4: Enabling the Network logs in LTE

Similarly, users can enable the plots for LTE Radio Measurements.

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Figure-5: Enabling the Plots in LTE

GUI Configuration of LTE

The LTE parameters can be accessed by right clicking on eNB or UE and selecting Interface (LTE) Properties 🡪 Datalink and Physical Layers as shown Table-1.

Macro Cell eNB Properties

Interface (LTE) – Datalink Layer

Parameter

Type

Range

Description

Scheduling Type

Global

Round Robin

The scheduler serves equal portion to each queue in circular order, handling all processes without priority.

Global

Proportional Fair

Schedules proportional to the CQI of the UEs.

Global

Max Throughput

Schedules to maximize the total throughput of the network by giving scheduling priority accordingly.

EWMA Learning Rate

Local

0.00000001 to 0.1

EWMA Averaging Rate (α) determines how important the current observation is in the calculation of the EWMA.  A lower alpha discounts older data faster thereby placing greater relevance on your more recent data.

\[EWMA(t) = \left( 1 - \frac{1}{\propto} \right) \times EWMA(t - 1) + \left( \frac{1}{\propto} \right) \times r(t)\]
\[0 < \frac{1}{\propto} \leq 1\]

Measurement Interval (ms)

Local

The Range is 120 to 40960ms.

This is the time interval between two UE Measurement reports.

RRC MIB Period (ms)

Local

80

The UE needs to first decode MIB for it to receive other system information. MIB is transmitted on the DL-SCH (logical channel: BCCH) with a periodicity of 80 ms and variable transmission repetition periodicity within 80 ms.

MIB packets are visible in the NetSim packet trace post simulation under Control Packet type.

RRC SIB Period (ms)

Local

160

SIB1 also contains radio resource configuration information that is common for all UEs. SIB1 is transmitted on the DL-SCH (logical channel: BCCH) with a periodicity of 80 ms and variable transmission repetition periodicity within 80 ms. SIB1 is cell-specific

SIB1 packets can be seen in the NetSim packet trace post simulation under Control Packet type.

PDCP Header Compression

Link Global

True / False

Header compression of IP data flows using the ROHC protocol, Compresses all the static and dynamic fields.

PDCP Discard Delay Timer

Link Global

50/150/300/500/750/

1500

The discard Timer expires for a PDCP SDU, or the successful delivery of a PDCP SDU is confirmed by PDCP status report, the transmitting PDCP entity shall discard the PDCP SDU along with the corresponding PDCP Data PDU.

PDCP Out of Order Delivery

Link Global

True / False

Complete PDCP PDUs can be delivered out-of-order from RLC to PDCP. RLC delivers PDCP PDUs to PDCP after the PDU reassembling.

PDCP T Reordering Timer

Link Global

0-500ms

This timer is used by the receiving side of an AM RLC entity and receiving AM RLC entity in order to detect loss of RLC PDUs at lower layer.

RLC T Status Prohibit

Global

0-2400ms

This timer is used by the receiving side of an AM RLC entity in order to prohibit transmission of a STATUS PDU.

RLC T Reassembly

Link Global

0-200ms

This timer is used by the receiving side of an AM RLC entity and receiving UM RLC entity in order to detect loss of RLC PDUs at lower layer. If t-Reassembly is running, t-Reassembly shall not be started additionally, i.e. only one t-Reassembly per RLC entity is running at a given time.

RLC T Poll Retransmit

Link Global

5-4000ms

This is used by the transmitting side of an AM RLC entity in order to retransmit a poll.

RLC Poll Byte

Link Global

1kB-40mB

This parameter is used by the transmitting side of each AM RLC entity to trigger a poll for every pollByte bytes.

RLC Poll PDU

Link Global

p4-p65536 (in multiples of 8)

This parameter is used by the transmitting side of each AM RLC entity to trigger a poll for every pollPDU PDUs.

RLC Max Retx Threshold

Link Global

t1, t2, t3, t4, t6, t8, t16, t32

This parameter is used by the transmitting side of each AM RLC entity to limit the number of retransmissions of an AMD PDU.

Handover Interruption time

Link Global

0-100ms

The handover process in NetSim is based on event A3 i.e., the target signal strength is offset (3 dB) higher than the source signal strength. Handover interruption time (HIT) is added at the time of handover command is delivered to the UE. During this time there is no data plane traffic flow to the UE from the source/target.

Handover Margin

Global

0-10dB

The handover Margin is the offset in dB that is used as part of the event A3 handover process in NetSim. Handover is triggered when the target signal strength exceeds the source signal strength by the offset than the source signal strength.

Range for Handover margin is from 0.0 to 10.0 with 3.0 as default

Time to Trigger

Global

0-5120ms

With Time-to-Trigger, the handover is initiated only if the triggering requirement is fulfilled for a time interval specified by Time-to-Trigger (ms). This parameter can decrease the number of unnecessary handovers and effectively avoid Ping-Pong effects.

3GPP defines 16 valid values for time-to-trigger (all in milliseconds):

0, 40, 64, 80, 100, 128, 160, 256, 320, 480, 512, 640, 1024, 1280, 2560, and 5120.

Users can enter any value between 0 to 5120 in milliseconds.

HARQ Mode

Local

TRUE, FALSE

Hybrid automatic repeat request (hybrid ARQ or HARQ) is a combination of re transmissions and error correction. The HARQ protocol runs in the MAC and PHY

layers. In the 5G PHY, a code block group (CBG) is transmitted over the air by the transmitter to the receiver. If the CBG is successfully received the receiver sends back an ACK, else if the CBG is received in error the receiver sends back a NACK (negative ACK).If the transmitter receives an ACK, it sends the next CBG. However, if the transmitter receives a NACK, it re transmits the previously transmitted CBG.

Large number packet errors can be observed in packet trace if HARQ is turned OFF.

HARQ Retry Limit

Local

0-4s

HARQ Retry Limit specifies the number of retransmissions attempts that will be made whenever a Code Block fails due to error.

MAX HARQ process count

Local

2,4,6,8

A HARQ entity is defined for each gNB-UE pair, separately for Uplink and Downlink and

for each component carrier. The HARQ entity handles the HARQ processes.

Max number of HARQ processes is 8 in 4G

Max number of HARQ processes is 16 in 5G

Max CBG per TB

Local

2,4,6,8

Each Transport block is split into Code blocks (CBs) and CBs are grouped into Code Block Groups (CBGs).

A Code Block group can have up to 2/4/6/8 CBs.

Interface (LTE) – Physical Layer

Parameter

Type

Range

Description

Frame Duration (ms)

Fixed

10ms

Length of the frame.

Sub Frame Duration (ms)

Fixed

1ms

Length of the Sub-frame.

Subcarrier Number Per PRB

Fixed

12

NR defines physical resource block (PRB) where the number of subcarriers per PRB is the same for all numerologies.

eNB Height (m)

Local

1 - 150 meters

Height of the base station (gNB) in meters. NetSim implements the 3GPP propagation models in which the Indoor gNB (placed within a building) range is 1 to 10 meters, while the Outdoor gNB range is 1 to 150 meters. NetSim only enforces the upper limit of 150m for both indoor and outdoor gNBs.

TX Power (dBm)

Local

-40 dbm to 100 dbm

It is the signal intensity of the transmitter. The higher the power radiated by the transmitter's antenna the greater the reliability of the communications system.

TX Antenna Count

Local

1/2/4

The number of transmit antennas. This parameter taken effect during MIMO operation; the number of MIMO layers would be Min (Nt, Nr), where Nt is the transmit antenna count at the transmitter and Nr is the receive antenna count at the receiver. The layer wise gains depends on the fading model chosen and is explained in the 5G NR manual, digital beamforming section.

RX Antenna Count

Local

1/2/4

The number of receive antennas. This parameter taken effect during MIMO operation; the number of MIMO layers would be Min (Nt, Nr), where Nt is the transmit antenna count at the transmitter and Nr is the receive antenna count at the receiver. The layer wise gains depends on the fading model chosen and is explained in the 5G NR manual, digital beamforming section.

Duplex Mode

Fixed

TDD/ FDD

In TDD, the upstream and downstream transmissions occur at different times and share the same channel.

In FDD, there are different frequency bands used uplink and downlink, The UL and DL transmission an occur simultaneously

CA Type

Local

Inter band CA

Intra band

Contiguous CA

Intra band

Non-contiguous

CA single band

Carrier Aggregation (CA) is used in LTE/5G in order to increase the bandwidth, and thereby increase the bitrate. CA options are intra-band (contiguous and non-contiguous) inter-band and single band.

LTE Single Operating Band are referred from 3GPP 36101-h60

CA Configuration

Local

Depends on CA Type | Drop down provides the various bands available for the selected CA type (Eg: n78, n258, n261 etc)

CA Count

Fixed

Depends on CA Type

Single or multiple carriers depending on the CA Type chosen

Slot Type

Local

Mixed,

Downlink,

Uplink,

Mixed supports DL and UL traffic

Downlink supports only DL traffic

Uplink supports only UL traffic

DL: UL Ratio

Local

Represents the ratio in which slots are assigned to downlink and uplink transmission

Frequency Range

Fixed

FR1

Frequency range for LTE is Frequency Range 1 (FR1) that includes sub-6 GHz, frequency bands.

Operating Band

Fixed

The LTE operates in different operating bands corresponding to CA configuration respectively

F Low (MHz)

Fixed

Lowest frequency of the Uplink/Downlink operating band.

F High (MHz)

Fixed

Highest frequency of the Uplink/Downlink operating band.

Numerology

Local

µ = 0

It is the numerology value which represents the subcarrier spacing.

Channel Bandwidth (MHz)

Local

5-20 MHz

The frequency range that constitutes the channel.

PRB Count

Local

PRB stands for physical resource block. The PRB count is determined automatically by NetSim as per the other inputs and cannot be edited in the GUI.

Guard Band (KHz)

Local

Guard band is the unused part of the radio spectrum between radio bands, for the purpose of preventing interference.

Subcarrier Spacing

Local

15 kHz

The LTE radio link is divided into three dimensions: frequency, time and space. The frequency dimension is divided into subcarriers with 15 kHz spacing in normal operation

Bandwidth PRB

Local

180 KHz

Physical Resource Block Bandwidth is a range of frequencies occupied by the radio communication signal to carry most of PRB energy.

Slot per Frame

Local

20

Slot within a frame is depending on the slot configuration.

Slot per Subframe

Local

2

Slot within a Subframe is depending on the slot configuration.

Slot Duration (us)

Local

500

Slot duration gets different depending on numerology. The general tendency is that slot duration gets shorter as subcarrier spacing gets wider.

Cyclic Prefix

Local

Normal

Cyclic prefix is used to reduce ISI(Inter Symbol Interference), If you completely turn off the signal during the gap, it would cause issues for an amplifier. To reduce this issue, we copy a part of a signal from the end and paste it into this gap. This copied portion prepended at the beginning is called 'Cyclic Prefix'.

Symbol per Slot

Local

7

The number of OFDM symbol per slot is 7 in normal cyclic prefix case

Symbol Duration (ms)

Local

71.43(ms)

Symbol duration is depending on the subcarrier spacing.

BWP

Local

Disable

A Bandwidth Part (BWP) is a contiguous set of physical resource blocks (PRBs) on a given carrier. These PRBs are selected from a contiguous subset of the common resource blocks for given numerology (u). This parameter was included in NetSim v13.1, as is reserved for future use. It therefore currently always set as disabled.

Overhead (%) per DL slot

Local

0.01-0.99,

Default – 0.25

This represents the fraction of symbols in a slot used for control signaling. The remaining fraction is used for data transmission. In NetSim calculations are done over aggregated PRBs per the formula given below

\[Data\ PRB\ available = Total\ PRB\ available - Ceil(Total\ PRB\ available \times Overhead\ Fraction)\]

Overhead (%) per UL slot

Local

0.01-0.99,

Default – 0.25

This represents the fraction of symbols in a slot used for control signaling. The remaining fraction is used for data transmission. In NetSim calculations are done over aggregated PRBs per the formula given below

\[Data\ PRB\ available = Total\ PRB\ available - Ceil(Total\ PRB\ available \times Overhead\ Fraction)\]

ANTENNA

RX Antenna Count

Local

1,2,4

The number of receive antennas

TX Antenna Count

Local

1, 2, 4, 8, 16, 32, 64, 128 in gNB

(1, 2, 4, 8, 16 in UE)

The number of transmit antennas. Power is split equally among the transmit antennas.

PDSCH CONFIG

MCS Table

Local

QAM64LOWSE,

QAM64,

QAM256

MCS (Modulation Coding Scheme) is related to Modulation Order.

X Overhead

Local

XOH0

Accounts for overhead from CSI-RS, CORESET, etc. If the xOverhead in PDSCH-ServingCellconfig is not configured (a value from 0), N_oh^PRB the is set to 0

PUSCH CONFIG

Transform Precoding

Local

Enable

Transform Precoding is the first step to create DFT-s-OFDM waveform. Transform Precoding is to spread UL data in a special way to reduce PAPR(Peak-to-Average Power Ratio) of the waveform. In terms of mathematics, Transform Precoding is just a form of DFT(Digital Fourier Transform).

MCS Table

Local

QAM64LOWSE,

QAM64,

QAM256

MCS (Modulation Coding Scheme) is related to Modulation Order. This is based on 3GPP 38.214-Table 5.1.3.1-1, 5.1.3.1-2 and 5.1.3.1-3

Users must set the MCS and CQI tables in the following combination

QAM64: CQI Table 1

QAM 256: CQI Table 2

QAM 64 LOWSE: CQI Table 3

CSIREPORT CONFIG

MCS Table

Local

QAM64LOWSE,

QAM64,

QAM256

MCS (Modulation Coding Scheme) is related to Modulation Order. This is based on 3GPP 38.214-Table 5.1.3.1-1, 5.1.3.1-2 and 5.1.3.1-3

Users must set the MCS and CQI tables in the following combination

QAM64: CQI Table 1

QAM 256: CQI Table 2

QAM 64 LOWSE: CQI Table 3

CHANNEL MODEL

Pathloss Model

Local

3GPPTR38.901-7.4.1

LOG DISTANCE

NONE

None represents an ideal channel with no pathloss.

TR 38.901_Standard Table 7.4.2-1 means pathloss will be calculated per the formulas in this standard

Outdoor Scenario

Local

Rural Macro (RMa)

For RMa, we need to specify the Building Height and Street Width.

Buildings can be used in the scenario. UEs can be inside/outside buildings but eNBs can only be outside buildings.

Outdoor Scenario

Building Height

Local

Urban Macro (UMa)

Buildings can be used in the scenario. UEs can be inside/outside buildings but eNBs can only be outside buildings.

Local

Urban Micro (UMi)

Buildings can be used in the scenario. UEs can be inside/outside buildings but eNBs can only be outside buildings.

Local

5-50m

It is the height of the building in meters.

Street Width

Local

5-50m

It is the width of the street in meters.

Indoor Scenario

Fixed

Indoor Office

Automatically chosen by NetSim in case the UE is within an indoor building.

Indoor Office Type

Local

Mixed-Office

Open- Office

The pathloss will be per the chosen option when the UE is within a building

LOS_NLOS Selection

Fixed

3GPPTR38.901-Table 7.4.2-1

USER DEFINED

This choice determines how NetSim decides if the eNB-UE communication is Line-of-sight or Non-Line-of-Sight. In case of USE_DEFINED the LOS probability is user defined. Else it is standards defined.

LOS Probability

Local

0 to 1

If LOS Probability =1, the LOS mode is set to Line-of-Sight and if the LOS Probability =0, the LOS mode as set to Non-Line-of-Sight. For a value in between the LOS is determined probabilistically.

By default, value is set to 1.

Shadow Fading Model

Local

NONE

LOG NORMAL

Select NONE to Disable Shadowing Select LOG_NORMAL to Enable Shadowing Model, and the Std dev would be per 3GPP TR38.901-Table 7.4.1-1

Fading and Beamforming

Local

No Fading MIMO unit gain,

No fading MIMO array gain,

Rayleigh with Eigen beamforming

Rician with Eigen beamforming

RAYLEIGH WITH EIGEN BEAMFORMING: When fading and beamforming is enabled, NetSim uses the rich scattering in the channel to form spatial channels. The number of spatial channels is equal to the number of layers (in turn equal to Min (\(Nt,\ Nr\))). The beamforming gains in the spatial channel is equal to the eigenvalues of the channel covariance (Wishart) matrix. When running in SISO (\(N_{t} = N_{r} = 1)\) this simply simulates Rayleigh fading.

No fading MIMO unit gain: No fading with gain equal to unity (0 dB)

No fading MIMO array gain: No fading but gain equals \(Min\ (N_{t},\ N_{r})\)

RICIAN WITH EIGEN BEAMFORMING: In Rician fading, the channel combines a dominant Line-of-Sight (LoS) component with scattered (Rayleigh) components. NetSim forms spatial channels equal to Min (N_t , N_r ) layers, with beamforming gains set by the eigenvalues of the Rician channel covariance matrix. The dominant eigenvalue (strongest layer) is boosted by the LoS path, delivering higher gains than Rayleigh fading, particularly in strong LoS scenarios. For SISO (N_t =N_r =1), this reduces to Rician fading with a defined K-factor (LoS-to-scattered power ratio).

O2I Building Penetration Model

Local

None,

Low Loss Model,

High Loss Model,

The composition of low and high loss is a simulation parameter that should be determined by the user of the channel models and is dependent on the buildings and the deployment scenarios.

None to disable O2I Loss.

Low-loss model is applicable to RMa.

High-loss model is applicable to UMa and UMi.

Additional Loss Model

Local

NONE,

MATLAB

Additional Loss model can be set to None or MATLAB, if set to MATLAB then MATLAB will be automatically called by NetSim during execution.

Path Loss Exponent (n)

Local

2 to 5

Path loss exponent indicates the rate at which the path loss increases with distance. The value depends on the specific propagation environment.

Set any value between 2 to 5.

Shadowing Model

Local

Constant

Log Normal

Constant: A shadowing model is used to represent the signal attenuation caused by obstructions along the propagation path. The constant shadowing model is suitable for the scenarios without mobility where the obstructions along the propagation paths remain unchanged.

Log Normal: The lognormal shadowing model is suitable for a scenario with mobility and obstructions within the propagation environment. In this model, the shadowing value follows a log-normal distribution with a user specified standard deviation. In general, this value should be in the range of 5 to 12 dB depending on the density of obstructions within the propagation environment.

Standard Deviation (dB)

Local

5 to 12 dB

Shadowing is caused mainly by terrain features of the radio propagation environment. The mathematical model for shadowing is a log-normal distribution with standard deviation of 5 to 12 dB.

Set any value between 5 to 12 dB.

INTERFERENCE MODEL

Downlink Interference Model

Global

NO INTERFERENCE, GRADED DISTANCE BASED WYNER MODEL, EXACT GEOMETRIC MODEL

DL interference options are No interference, Graded Distance based Wyner model and Exact geometric models. If no interference is chosen then in the SINR calculations, the values of I is set to zero. Wyner and geometric models compute interference. Wyner is an approximate model used by the research community while the geometric model is exact. Technical details of the two models are provided in the 5G/LTE NR manual.

Uplink Interference Model

Global

NO INTERFERENCE, INTERFERNEC OVER THERMAL

NetSim uses Interference-over-thermal (IoT), to model co-channel uplink interference.

IoT value (dB)

Global

0 to 20

The Uplink IoT (dB) value is used to compute the SINR, and Interference power based on the following equations:

𝑆𝐼𝑁𝑅 (𝑑𝐵) = 𝑆𝑁𝑅(𝑑𝐵) − 𝐼𝑜𝑇(𝑑𝐵)

The interference power (dBm units), logged in the radio measurements file will be given as

I (dBm) = 10 * log_10 ((N * (10^(IOT (dB)-1))

where N is thermal noise and is equal to k*T*B.

ERROR MODEL AND MCS SELECTION

MCS Selection Model

Global

IDEAL SHANNON THEOREM BASED RATE, SHANNON RATE WITH ATTENUATION FACTOR

MCS Selection Model determines how modulation and coding scheme is determined in 5G and LTE.

The following Models are supported:

Ideal Shannon Theorem-Based Rate: Spectral Efficiency is computed as

SpectralEfficiency = log(1+SINR)

Shannon Rate with Attenuation Factor (α): Spectral Efficiency is computed as

SpectralEfficiency = α x log(1+SINR)

Spectral Efficiency - MCS Table is looked up to select the MCS.

Attenuation Factor

Global

0.5-1

Attenuation factor (α) takes value between 0.5 and 1 with the default value of 0.75.

BLER Model

Global

ZERO BLER

BLER ENABLE

Block Error Rate Model (BLER) is used to decide code block and transport block error in 5G and LTE.

Outer loop link adaption

Global

TRUE

FALSE

The Outer Loop Link Adaptation (OLLA) technique, if enabled can improve the channel quality estimation by adjusting the value of SINR by an offset dependent on whether previous transmissions were decoded successfully or not, as captured by Hybrid Automatic Repeat Request (HARQ) feedback

Target BLER

Global

0-1

Target BLER plays an important role in 5G link adaptation. The BLER target is usually around 10% based on specifications but it can be varied depending on the characteristics of the cell.

Range: 0 to 1

UE Properties

Interface 1 (LTE) – Physical Layer

Parameter

Type

Range

Description

UE Height (meters)

Local

1 to 22.5

Height of the UE in meters

TX Power (dBM)

Local

-40dBM to 50dBM

It is the signal intensity of the transmitter. The higher the power radiated by the transmitter's antenna the greater the reliability of the communications system.

Tx Antenna Count

Local

1/2

Number of transmit antennas. NetSim uses this parameter in MIMO operations.

Rx Antenna Count

Local

1/2/4

Number of receive antennas. NetSim uses this parameter in MIMO operations.

Table-1: Datalink layer and Physical properties for eNB and UE