LTE and LTE-A

## Introduction#

NetSim’s LTE library allows for full stack, system level simulation of 4G / 4.5G LTE networks and LTE based VANETs networks. Additionally, you can connect an LTE Network with Internetwork devices and run all the protocols supported in Internetworks. The LTE library is based on 3GPP 36.xxx series.

NetSim’s protocol source C code shipped along with (standard / pro versions) is modular and customizable to help researchers to design and test their own LTE protocols.

## Simulation GUI#

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

### Create Scenario#

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

### Devices specific to NetSim LTE Library#

• UE (LTE UE) - User Equipment
• eNB (LTE eNB) - Evolved NodeB
• EPC (Evolved packet core) – Provides end to end IP connectivity between NG (New Generation) core and gNB. 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

a. Add a User Equipment (UE) – Click the UE icon on the toolbar and place the UE in the grid.
The UE’s 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.
b. Add an eNB – Click the eNB icon on the toolbar and place the eNB in the grid. gNBs can also be placed inside the building based on the network scenario created. Every eNB should be connected to at least one UE.
c. Add an EPC – EPC is automatically placed in grid. EPC must be connected to an eNB (connection between eNB and EPC is taken care by NetSim once user drops the eNB in GUI) or to a Router. NetSim LTE library currently supports only one EPC.
d. Add a Router – Click the Router icon on the toolbar, Select Router and place device in the grid.
e. Add a L2 Switch – Click the L2_Switch icon on the toolbar and place the device in the grid.
f. Access Point – Click the Access_Point icon on the toolbar and place the device in the grid.
g. Add a Wired Node and Wireless Node – Click the Node > Wired_Node icon or Node > Wireless_Node icon on the toolbar and place the device in the grid.
h. Configure an application as follows:

• Click the application icon on the top ribbon/toolbar.
• Specify the source and destination devices in the network.
• Specify other parameters as per the user requirement.

### GUI Configuration of LTE#

The LTE parameters can be accessed by right clicking on a eNB or UE and selecting Interface (LTE) Properties → Datalink and Physical Layers as shown Table 2-1

eNB Properties
Parameter Type Range Description
Scheduling Type Local Round Robin The scheduler serves equal portion to each queue in circular order, handling all processes without priority.
Local Proportional Fair Schedules in proportional to the CQI of the UEs
Local Max Throughput Schedules to maximize the total throughput of the network by giving scheduling priority accordingly
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 Link 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 tReassembly 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.
Note: For detailed information on RLC
Interface (LTE) – Physical Layer
Parameter Type Range Description
Frame Duration (ms) Frame Duration (ms) Frame Duration (ms) Frame Duration (ms)
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 (meters) Local 1 - 150 meters Height of the gNB/eNB in meters By default, 10 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 1/2/4 MIMO layer count for downlink.
RX Antenna Count Local 1/2/4 MIMO layer count for uplink.
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_NONC ONTIGUOUS_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) and inter-band
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
Note: For detailed information to Frequency Range (FR1)
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
Numerology Local µ = 0 It is the numerology value that represents the subcarrier spacing.
Channel Bandwidth (MHz) Local 5-20 MHz The frequency range 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 A 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 10 The slot within a frame is depending on the slot configuration.
Slot per Subframe Local 1 The slot within a Subframe is depending on the slot configuration.
Slot Duration (ms) Local 0.5 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 The 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 symbols per slot is 7 in the normal cyclic prefix case
Symbol Duration (ms) Local 71.43(ms) Symbol duration is depending on the subcarrier spacing.
ANTENNA
TX_Antenna_Count Local 1,2,4 The number of transmit antennas. Power is split equally among the transmit antennas.
RX_Antenna_Count Local 1,2,4 The number of receiveantennas
PDSCH CONFIG
MCS Table Local QAM64 MCS (Modulation Coding Scheme) is related to Modulation Order.
X Overhead Local XOH0 Accounts for overhead from CSI-RS, CORSET, etc. If the overhead in PDSCH-ServingCellconfig is not configured (a value from 0),N_oh^PRB the is set to 0
PUSCH CONFIG
MCS Table Local QAM64 MCS      (Modulation Coding Scheme) is related to Modulation Order.
Transform Precoding Local Enable Transform Precoding is the first step to creating a 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).
CSIREPORT CONFIG
CQI Table Local Table1 The CQI induces and their interpretations are chosen from Table 1 for reporting CQI based on 64QAM
CHANNEL MODEL
Pathloss Model Local 3GPPTR38.901-7.4.1 NONE None represents an ideal channel with no path loss. TR 38.901_Standard Table 7.4.2-1 means path loss 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 gNBs can only be outside buildings.
Local Urban Macro (UMa) Buildings can be used in the scenario. UEs can be inside/outside buildings but gNBs can only be outside buildings.
Local Urban Micro (UMi) Buildings can be used in the scenario. UEs can be inside/outside buildings but gNBs can only be outside buildings.
Building Height 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 gNB-UE communication is Line-of-sight or Non-Line-of-Sight. In case of USER_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 is set to Non-Line of-Sight. A value in between the LOS is determined probabilistically.By default, the 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.
Fading and Beamforming Local NO_Fading,RAYLEIGH_WITH_EIGEN_BEAMFORMING Referee 5G NR technology library section 3.9.
O2I_Building_Penetrat ion_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.
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 The number of transmit antennas. NetSim uses this parameter in MIMO operations.
Rx Antenna Count Local 1/2/4 The number of receiver antennas. NetSim uses this parameter in MIMO operations.

## Model Features#

### RRC#

The Radio Resource Control (RRC) protocol is used in the air Interface. The major functions of the RRC protocol include connection establishment and release functions, broadcast of system information, radio bearer establishment, reconfiguration and release, RRC connection mobility procedures, paging notification and release and outer loop power control. By means of the signaling functions, the RRC configures the user and control planes according to the network status and allows for Radio Resource Management strategies to be implemented. In NetSim RRC protocol includes the functionality related connection establishment, broadcast of system information, radio bearer establishment, reconfiguration, RRC connection mobility procedures, paging notification.

The RRC code is available in the following C files, LTENR_RRC.c, LTENR_GNBRRC.c, and LTENR_NAS.c(RRC connection mobility and Handover procedures).

A UE can move to RRC Idle mode from RRC connected/RRC Active or RRC Inactive state.

#### System information acquisition#

The system information is divided into the Master Information Block (MIB) and System Information Block 1.

##### Master Information Block (MIB)#

MIB is the broadcast information transmitted by eNodeB at periodically. UE have the information of Physical cell ID and not it can descramble the further information which Master information Block, which will provide the System bandwidth, System frame number etc.

The UE needs to first decode MIB in order 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 40 ms.

Bits and Bytes of Master information blocks:

• Logical Channel – BCCH (Broadcast common control Channel)
• Transport Channel – BCH (Broadcast Channel)
• Physical Channel – PBCH (Physical Broadcast channel)
• RLC Mode – (Transparent Mode)
##### System Information Block 1 (SIB1)#

SIB is the carries the most critical information required for the UE to access the cell e.g., random access parameters.

SIB1 includes information regarding the availability and scheduling of other SIBs e.g. mapping of SIBs to SI message, periodicity, SI-window size etc

SIB1 also indicates whether one or more SIBs are only provided on-demand, in which case, it may also provide PRACH configuration needed by the UE to request for the required SI.

SIB1 also contains radio resource configuration information that is common for all UEs and cell barring information applied to the unified access control. 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 SIB.

• Logical Channel – BCCH (Broadcast common control Channel)
• Transport Channel – BCH (Broadcast Channel)
• Physical Channel – PBCH (Physical Broadcast channel)
• RLC Mode – (Transparent Mode)

#### RRC connection establishment#

The PDCP layer receives a packet (data/control) from the upper layer, executes the PDCP functions and then transmits it to a lower layer. PDCP layer code related files LTENR_PDCP.c.

PDCP Entity: The PDCP entities are located in the PDCP sublayer. NetSim currently implements one PDCP entity per UE (users can add more by modifying the code). The same DCP entity is associated with both the control and the user plane.

The PDCP functionality supported is,

• Transmit PDCP SDU- It transmit the data between RLC and higher U-Plane interface
• Sets the PDCP Sequence Number
• Calls RLC service primitive.
• ROHC is a kind of algorithm to compress the header of various IP packets. In case of IPv4, the size of uncompressed IP header is 40 bytes.
• PDCP Association
• This call back function is invoked when the UE associates/dissociates from a eNB.
• Maintenance of PDCP sequence numbers (to know more check the PDCP entity structure)
• When the discardTimer 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.
• Discarding a PDCP SDU already associated with a PDCP SN causes a SN gap in the transmitted PDCP Data PDUs, which increases PDCP reordering delay in the receiving PDCP entity.
• PDCP maintain the sequence number, if the PDCP receives the duplicate sequence number, discard the PDCP SDU along with the corresponding PDCP Data PDU.

### RLC#

Flow of TM, UM, and AM mode between RLC upper and lower layer as shown in Figure 3-5

#### TM Mode (Transparent Mode)#

The operation being done in TM mode is a buffering operation. It keeps the input data for a certain amount of time or until next input data come in, it just discard it if it does not get transmitted within a certain time frame.

As you see in the Figure 3-6, BCCH, PCCH, CCCH goes through this type of RLC process. In WCDMA, Voice call traffic used this RLC mode as well. It means that even some type of DTCH (voice traffic) uses this mode in WCDMA. However it is technically possible to use TM mode for DTCH as well. RLC TM mode code related file LTENR_RLC.c.

#### UM Mode (Unacknowledged Mode)#

The following operation done in RLC UM transmission and reception.

RLC UM Data Flow (Transmission):

At the time of RLC UM transmission, It receives the SDU (Data) from the higher layers (PDCP or RRC) and put the SDU into the transmission buffer. When the MAC permits the transmission, it segment or concatenate the SDU into RLC PDU and add the RLC header to the RLC PDU. Then the RLC SDU sent to the next layer (MAC layer).

RLC UM Data Flow (Reception):

The MAC layer passes the received RLC PDU to the RLC layer. RLC layer removes RLC header from the RLC PDU, then the RLC layer assemble PDUs into the upper layer SDU and it passes the assembled SDUs to the higher layers (PDCP or RRC).

As you see in Figure 3-7, DTCH, MTCH. MCCH use this type of RLC process. Again, this is also a matter of choice. You can use AM or UM mode for DTCH. RLC UM mode code related file LTENR_RLC_UM.c.

#### AM Mode (Acknowledge Mode)#

The following operation done in RLC AM transmission and reception.

RLC AM Data Flow (Transmission):

At the time of RLC AM transmission, It receives the SDU (Data) from the higher layers (PDCP or RRC) and put the SDU into the transmission buffer. When the MAC permits the transmission, it segment or concatenate the SDU into RLC PDU and add the RLC header to the RLC PDU and make the copy of the transmission buffer for the possible retransmission. Then the RLC SDU sent to the next layer (MAC layer).

RLC AM Data Flow (Reception):

The MAC layer passes the received RLC PDU to the RLC layer. RLC layer removes RLC header from the RLC PDU. If the received RLC PDU does not have any problem, mark it as positive ACK. Then the RLC layer assemble PDUs into the upper layer SDU and it passes the assembled SDUs to the higher layers (PDCP or RRC). RLC AM mode code related file LTENR_RLC_AM.c.

### MAC Scheduler#

At each eNB the MAC Scheduler decides the PRB allocation, in a slot, for each carrier. The max schedulers work as follows:

• Round Robin - It divides the available PRBs among the active flows, i.e., those logical channels which have a non-empty RLC queue. The MCS for each user is calculated according to the received CQIs.
• Proportional fair - It allocates PRBs in proportion to the channel quality in the active flows.
• Max throughput - It allocates PRBs to the active flow(s) to maximize the achievable rate.
• Fair Scheduler - It ensures equal throughputs for all active flows.

Note that these are MAC scheduling algorithms, and they aren't based on the QoS set in the Application.

### PHY Layer#

#### Physical Speed of the LTE Air Interface#

One Resource Block (RB) in LTE has 12 carriers (each carrier is 15 KHz) in frequency domain and 0.5 milliseconds (7 symbols) in time domain.

$$𝑺𝒐, \ 𝒕𝒉𝒆 \ 𝒕𝒐𝒕𝒂𝒍 \ 𝒏𝒖𝒎𝒃𝒆𝒓 \ 𝒐𝒇 \ 𝒔𝒚𝒎𝒃𝒐𝒍𝒔 \ 𝒊𝒏 \ 𝒂 \ 𝑹𝒆𝒔𝒐𝒖𝒓𝒄𝒆 \ 𝒃𝒍𝒐𝒄𝒌 \ = 𝟏𝟐 \times 𝟕 = 𝟖𝟒$$

A symbol accommodates a specific number of bits depending on the modulation scheme. The following table lists the number of bits for different modulation schemes as shown Table 3-1.

Modulation scheme # of bits per symbol
QPSK 2
16-QAM 4
64-QAM 6

The following table lists the number of Resource blocks, carriers, and the bandwidth available for different LTE channel bandwidths as shown Table 3-2.

Channel bandwidth (MHz) 5 10 15 20
Resource blocks 25 50 75 100
Number of carriers 300 600 900 1200
Occupied bandwidth (MHz) 4.5 9 13.5 18

Note: In an LTE or LTE-A network, 10% of total bandwidth is used for the guard band. For example, if the channel bandwidth is 20 MHz, then 2 MHz is used for the guard band. So, if 180 KHz has 1 RB, 18 MHz has 100 RBs.

#### LTE and LTE-A Operating Bands#

The following table lists the details of the LTE and LTE-A frequency bands defined by 3GPP. NetSim uses these bands to let you simulate LTE-A networks.

Note: NetSim supports both TDD and FDD.

LTE band # Uplink (MHz) Downlink (MHz) Width (MHz) Duplex spacing(MHz) Band gap (MHz)
1 1920 – 1980 2110 – 2170 60 190 130
2 1850 – 1910 1930 – 1990 60 80 20
3 1710 – 1785 1805 -1880 75 95 20
4 1710 – 1755 2110 – 2155 45 400 355
5 824 – 849 869 – 894 25 45 20
7 2500 – 2570 2620 – 2690 70 120 50
8 880 – 915 925 – 960 35 45 10
11 1427.9 - 1447.9 1475.9 - 1495.9 20 48 28
12 699 – 716 729 – 746 18 30 12
13 777 – 787 746 – 756 10 -31 41
17 704 – 716 734 – 746 12 30 18
18 815 – 830 860 – 875 15 45 30
19 830 – 845 875 – 890 15 45 30
20 832 – 862 791 – 821 30 -41 71
21 1447.9 - 1462.9 1495.9 - 1510.9 15 48 33
23 2000 – 2020 2180 – 2200 20 180 160
25 1850 – 1915 1930 – 1995 65 80 15
26 814 – 849 859 – 894 30 / 40 10
27 807 – 824 852 – 869 17 45 28
28 703 – 748 758 – 803 45 55 10

#### LTE and LTE-A Transmission Modes#

NetSim supports the following LTE Transmission modes:

• Transmission Mode 1 – SISO, by using of a single antenna at eNodeB. Because of Round-robin scheduling, all applications see equal throughput
• Transmission Mode 2 – MIMO and Transmit Diversity (TxD). Sends copies of same information via multiple antennas. This leads to higher reliability, but the throughput remains the same as Mode 1 .
• Transmission Mode 3, SU – MIMO Spatial Multiplexity, Open Loop. This is used to achieve high data rates. The data is divided and sent via various antennas. The throughput increases.
• Transmission Mode 4, MU-MIMO Spatial Multiplexing, Per the LTE standard. With a multi-user setup, multiple antennas are used to send and receive data. The data throughput further increases.
• Transmission mode 5 – MU-MIMO, where the number of receive antennas is fixed to 2.

#### LTE and LTE-A PHY Layer Parameters#

The following table lists the details of the parameters of the PHY layer in LTE as shown Table 3-4.

Channel bandwidth (MHz) 1.4 3 5 10 15 20
Number of Resource blocks (NRB) 6 15 25 50 75 100
Number of occupied carriers 73 181 301 601 901 1201
IFFT(Tx) /FFT size (Rx) 128 256 512 1024 1536 2048
Sampling frequency (Sampling rate) 1.92 3.84 7.68 15.36 23.04 30.72
Samples per slot 960 1920 3840 7680 11520 15360

IFFT = Inverse Fast Fourier Transform and FFT = Fast Fourier Transform

#### PHY measurements#

All PHY measurements, downlink and uplink, are done on the actual transmitted data on the data channel. The measurements are not done using control the control channels.

The measurements are wideband i.e., a single value of channel state that is deemed representative of all RBs in use. This assumes that the PHY layer that the channel is flat across all the RBs. Such an assumption ensures acceptable accuracy for a system level simulation while keeping the computational complexity manageable.

The SNR in downlink (received by a UE from a eNB/gNB) and in the uplink (received by an eNB/gNB from a UE). The SNR is calculated at every slot and thereafter the SNR gets averaged after every "Average_SNR_Window" time frame to go forward and compute the AMC (Modulation & coding) information, and for each carrier as:

• SNR = Received power / Thermal Noise.
• Interference from other UEs / eNBs / gNBs are not considered.
• The received power is transmit power less propagation loss.
• The MCS values are chosen based on the received SNR.

#### Carrier Aggregation#

Carrier aggregation is a feature that LTE-A uses to increase the bandwidth, and the bitrate. An aggregated carrier is known as a component carrier (CC). The component carrier can have a bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz and a maximum of five component carriers can be aggregated. So, the maximum aggregated bandwidth is 100 MHz.

Carrier aggregation can be used: Frequency Division Duplex (FDD) and Time Division Duplex (TDD). The following figure illustrates the use of FDD.

FDD can use different number of component carriers in the Downlink (DL) and Uplink (UL). But, the number of UL component carriers must always be equal to or lower than the number of DL component carriers. Also, the individual component carriers can use different bandwidths.

TDD uses the same number of component carriers with identical bandwidths for DL and UL

##### CA Configurations#

CA can be configured as into intra-band (contiguous and non-contiguous) and inter-band non-contiguous. Intra-band contiguous and inter-band combinations, that aggregate two Component Carriers (CCs) in downlink, are specified from Release 10.

The Intra-band contiguous CA configuration refers to contiguous carriers aggregated in the same operating band.

The Intra-band non-contiguous CA configuration refers to non-contiguous carriers aggregated in the same operating band.

The Inter-band CA configuration refers to aggregation of component carriers in different operating bands, where the carriers aggregated in each band can be contiguous or non-contiguous.

The following figure illustrates the CA configurations.

##### CA Bandwidth Classes#

The following table lists the details of the Carrier Aggregation Bandwidth classes in terms of the total number of Resource blocks used by the CC.

For example, the Bandwidth class A specifies N_RB,agg <= 100. This means that the Number of the aggregated RBs within the fully allocated Aggregated Channel bandwidth (NRB,agg) should be less than 100 and the aggregated Tx Bandwidth for class A cannot exceed 20 MHz, and limits to 1 CC in the band.

Note: NetSim currently supports CA Bandwidth classes A, B and C only.

Class Aggregated Transmission Bandwidth Configuration (ATBC) Maximum # of CC
NRB,agg Maximum Tx bandwidth
A N <= 100 20 1
B 25 < N <= 100 20 2
C 100 < N <= 200 40 2
D 200 < N <= 300 60 3
E 300 < N <= 400 80 4
F 400 < N <= 500 100 5
I 700 < N <= 800 160 8
##### CA Configuration Naming Conventions#

To understand the naming conventions in a CA configuration and the bandwidth combination set usage, let us see the CA_1C configuration. This CA configuration states that the UE can operate on Band 1, with two continuous CCs and with a maximum of 200 RBs. The bandwidth combination set states that the allocation of those 200 RBs can be either 75 RBs on both CCs or 100RBs on both CCs.

https://www.3gpp.org/technologies/keywords-acronyms/101-carrier-aggregation-explained

##### CA Configuration Table (based on TR 36 716 01-01)#

Carrier aggregation can be configured in the eNB's Physical layer properties. Following are the various configuration options that are available as shown Table 3-5 and Table 3-6.

FDD Bands:

CA Configuration Table
INTER_BAND_CA
CA_1A_3A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1920,1710 1980,1785, 2110,1805 2170,1880
CA_3A_7A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,2500 1785,2570 1805,2620 1880,2690
CA_3A_20A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,832 1785,862 1805,791 1880,821
CA_3A_28A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,703 1785,748 1805,758 1880,803
CA_3A_8A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,880 1785,915 1805,925 1880,960
CA_7A_20A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 2500,832 2570,862 2620,791 2690,821
CA_7A_28A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 2500,703 2570,748 2620,758 2690,803
CA_28A_32A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 703, 1452 748, 1496 758, 1452 803, 1496
CA_1A_3A_7A 3 CA1_UL,CA1_DL,CA2_UL,CA2_DL,CA3_UL,CA3_DL FR1 1920,1710,2500 1980,1785,2570 2110,1805,2620 2170,1880,2690
CA_3A_7A_20A 3 CA1_UL,CA1_DL,CA2_UL,CA2_DL,CA3_UL,CA3_DL FR1 1710,2500,832 1785,2570,862 1805,2620,791 1880,2690,821
INTRA_BAND_CONTIGUOUS_CA
CA_1C 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1920,1920 1980,1980 2110,2110 2170,2170
CA_2C 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1850,1850 1910,1910 1930,1930 1990,1990
CA_3B 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,1710 1785,1785 1805,1805 1880,1880
CA_3C 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,1710 1785,1785 1805,1805 1880,1880
CA_5B 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 824,824 849,849 869,869 894,894
CA_7B 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 2500,2500 2570,2570 2620,2620 2690,2690
CA_7C 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 2500,2500 2570,2570 2620,2620 2690,2690
CA_8B 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 880,880 915,915 925,925 960,960
CA_12B 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 699,699 716,716 729,729 746,746
INTRA_BAND_NONCONTIGUOUS_CA
CA_1A_1A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1920,1920 1980,1980 2110,2110 2170,2170
CA_2A_2A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1850,1850 1910,1910 1930,1930 1990,1990
CA_3A_3A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,1710 1785,1785 1805,1805 1880,1880
CA_4A_4A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,1710 1755,1755 2110,2110 2155,2155
CA_5A_5A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 824,824 849,849 869,869 894,894
CA_7A_7A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 2500,2500 2570,2570 2620,2620 2690,2690
CA_12A_12A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 699,699 716,716 729,729 746,746
CA_23A_23A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 2000,2000 2020,2020 2180,2180 2200,2200
CA_25A_25A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1850,1850 1915,1915 1930,1930 1995,1995
CA_66A_66A 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,1710 1780,1780 2110,2110 2200,2200
CA_66A_66B 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,1710 1780,1780 2110,2110 2200,2200
CA_66A_66C 2 CA1_UL,CA1_DL,CA2_UL,CA2_DL FR1 1710,1710 1780,1780 2110,2110 2200,2200
CA_25A_25A_25A 3 CA1_UL,CA1_DL,CA2_UL,CA2_DL,CA3_UL,CA3_DL FR1 1850,1850,1850 1915,1915,1915 1930,1930,1930 1995,1995,1995
CA_66A_66A_66A 3 CA1_UL,CA1_DL,CA2_UL,CA2_DL,CA3_UL,CA3_DL FR1 1710,1710,1710 1780,1780,1780 2110,2110,2110 2200,2200,2200

TDD Bands

CA Configuration CA Count CA Type Frequency Range Uplink Low (MHz) UplinkHigh(MHz)
INTER_BAND_CA
DL_2A-48A_UL_2A-48A_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
DL_2A-48A-48A_UL_2A-48A_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
DL_2A-48A-48C_UL_2A-48A_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
DL_2A-48C_UL_2A-48A_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
DL_2A-48D_UL_2A-48A_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
DL_2A-48A-48D_UL_2A-48A_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
DL_2A-48E_UL_2A-48A_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
DL_2A-48A-48E_UL_2A-48A_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
INTRA_BAND_CONTIGUOUS_CA
CA_3DL_41D_3UL_41D_BCS0 3 CA1, CA2, CA3 FR1 2496,2496,2496 2690,2690,2690
CA_4DL_41E_3UL_41D_BCS0 4 CA1, CA2, CA3, CA4 FR1 2496,2496,2496,2496 2690,2690,2690,2690
CA_5DL_41F_3UL_41D_BCS0 5 CA1, CA2,CA3, CA4,CA5 FR1 2496,2496,2496,2496,2496 2690,2690,2690,2690,2690
2DL_48C_2UL_48C_BCS0 2 CA1, CA2 FR1 3550,3550 3700,3700
3DL_48D_2UL_48C_BCS0 3 CA1, CA2, CA3 FR1 3550,3550,3550 3700,3700,3700
4DL_48E_2UL_48C_BCS0 4 CA1, CA2, CA3, CA4 FR1 3550,3550,3550,3550 3700,3700,3700,3700
CA_48A_48B 2 CA1, CA2 FR1 3550,3550 3700,3700
CA_48B_48B 2 CA1, CA2 FR1 3550,3550 3700,3700
CA_48B_48C 2 CA1, CA2 FR1 3550,3550 3700,3700
CA_48B_48D 2 CA1, CA2 FR1 3550,3550 3700,3700
CA_48B_48E 2 CA1, CA2 FR1 3550,3550 3700,3700
INTRA_BAND_NONCONTIGUOUS_CA
CA_2DL_42A-42A_1UL_BCS1 2 CA1, CA2 FR1 3400,3400 3600,3600
CA_3DL_42A-42C_2UL_42C_BCS1 3 CA1, CA2, CA3 FR1 3400,3400,3400 3600,3600,3600
CA_4DL_42C-42C_2UL_42C_BCS1 4 CA1, CA2, CA3, CA4 FR1 3400,3400,3400,3400 3600,3600,3600,3600
3DL_48A-48C_2UL_48C_BCS0 3 CA1, CA2, CA3 FR1 3550,3550,3550 3700,3700,3700
4DL_48C-48C_2UL_48C_BCS0 4 CA1, CA2, CA3, CA4 FR1 3550,3550,3550,3550 3700,3700,3700,3700
##### Configuration#

Downlink Interference Model can be configured in the eNB’s LTE interface properties under channel models section of Physical Layer as shown below:

Downlink Interference Model is set to NO_INTERFERENCE by default.

The Wyner model is widely used to model and analyze cellular networks due to its simplicity and analytical tractability. In this model:

• Only interference from (two) adjacent cells is considered
• Random user locations and path loss variations are ignored, and
• The interference intensity from each neighboring base station (BS) is characterized by a single fixed parameter 0 ≤ $\alpha$ ≤ 1). The channel gain between BS and its home user is 1 and the intercell interference intensity is $\alpha$. Thus, a user sees a constant interference irrespective of its location.

These three simplifications lose a lot of information. We alter the Wyner model to address these flaws by:

• Considering interference from arbitrary number of BSs
• Factoring in the user location. The UEs distance from the interfering BS is an obvious factor that determines the interference intensity since the amount of interference caused depends on the signal attenuation with distance, the path loss law. Since the Wyner model uses relative interference, the ratio of a UEs distance from serving and interfering BSs is used as one of the interference parameters.
• Using a graded interference intensity model, whereby a UE will see a different value of $\alpha$ at different locations, thereby modelling the effect of interference more accurately.
###### Technical description#
• We model DL interference from any number of interfering BSs. Let $𝐵𝑆_𝑖$ be the serving BS to $𝑈𝐸_𝑘$. Let $𝐵𝑆_𝑗$ be any other BS $(𝑗 \not ={i})$. Then the distance between $𝑈𝐸_𝑘$ and $BS_i$ is denoted as $D^{BS_i}_{UE_k}$

• A UE sees interference if $\frac{(D^{BS_j}_{{UE_k}}- {D^{BS_i}_{UE_k}})}{D^{BS_j}_{UE_k}}$ s within a user defined threshold (for example, 20%). This ratio is also equal to $1 − \frac{D^{BS_i}_{UE_k}}{D^{BS_j}_{UE_k}}$ When $D^{BS_i}_{UE_K} \leq \ D^{BS_j}_{UE_K}$ we see that $0 \leq \ \frac{(D^{BS_j}_{{UE_k}}-D^{BS_i}_{UE_k})}{D^{BS_j}_{UE_k}} \leq 1$ the ratio is 0 when $D^{BS_i}_{UE_k} = D^{BS_j}_{UE_k}$ and is 1 when $D^{BS_i}_{UE_k} = 0$ when $D^{BS_i}_{UE_k} = D^{BS_j}_{UE_k}$ the UE is equidistant from both BS i.e., at the cell edge. When $D^{BS_i}_{UE_k} = 0$, the UE is at the center of the serving BS, $BS_i$

• Users at the cell-edge will see out of cell interference; as the user moves closer to the cell centre, it sees lesser interference.

• We call this user defined threshold as differential distance ratio threshold and denote it by $𝐷𝐷𝑅_{𝑡ℎ}$. The DDR threshold is used to define 𝐾 thresholds, which are in turn used to determine the out of cell interference experienced by $𝑈𝐸_𝑘$, as explained below. First, we bin the $𝐷𝐷𝑅_{𝑡ℎ}$, conditional on $D^{BS_i}_{UE_k} \leq D^{BS_j}_{UE_k}$, into K steps,as follows: $$0 \leq \frac{(D^{BS_j}_{UE_k}- D^{BS_i}_{UE_k})}{D^{BS_j}_{UE_k}} < \bigg(\frac{DDR_{th}}{k}\bigg) \times 1$$ $$\bigg(\frac{DDR_{th}}{k}\bigg) \times 1 \leq \frac{(D^{BS_j}_{UE_k}- D^{BS_i}_{UE_k})}{D^{BS_j}_{UE_k}} < \bigg(\frac{DDR_{th}}{k}\bigg) \times 2$$ $$....$$ $$....$$ $$\bigg(\frac{DDR_{th}}{k}\bigg) \times (k-1) \leq \frac{(D^{BS_j}_{UE_k}- D^{BS_i}_{UE_k})}{D^{BS_j}_{UE_k}} < \bigg(\frac{DDR_{th}}{k}\bigg) \times k$$ $$\bigg(\frac{DDR_{th}}{k}\bigg) \times k \leq \frac{(D^{BS_j}_{UE_k}- D^{BS_i}_{UE_k})}{D^{BS_j}_{UE_k}}$$

Where $𝐷𝐷𝑅_{th}$, is a user input varying from 0.00 to 1.00 (default is 0.1 or 10%), and K, the number of steps, is a user input varying from 1 to 4 (default is 1).

• The relative interference for each of these steps would be 𝐼𝑛 (0 ≤ 𝑛 ≤ 𝐾) where 𝐾 is the number of steps and 𝑛 represents each individual step (𝑛 = 𝑝 if the $𝑝^{th}$ inequality in the above is satisfied, counting the first inequality as the zeroth inequality).
• We specify the interference power relative to the power received from $𝐵𝑆_{i}$ . Therefore, given the value of $l_{n}$, interference power is calculated as the received power from 𝐵𝑆𝑖(excluding beamforming gain) less $𝐼_{n}$. Thus $$𝐼𝑛𝑡𝑒𝑟𝑓𝑒𝑟𝑒𝑛𝑒 \ 𝑃𝑜𝑤𝑒𝑟𝑓𝑟𝑜𝑚𝐵𝑆_{j}(𝑑𝐵) = 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑑𝑃𝑜𝑤e𝑟𝑓𝑟𝑜𝑚𝐵𝑆_{i} (𝑑𝐵𝑚) − 𝐼^{j}_{n}(𝑑𝐵)$$ Therefore, we have $𝐼^i_n (𝑑𝐵) = 𝑃^{BS}_{𝑠𝑒𝑟𝑣𝑖𝑛𝑔}(𝑑𝐵𝑚)−𝑃^{BS}_{𝐼𝑛𝑡𝑒𝑟𝑓𝑒𝑟𝑖𝑛𝑔}(𝑑𝐵𝑚)$.This is equivalent to the Wyner model with $\alpha = \frac{P^{BS}_{interfering}}{p^{BS}_{serving}}$ in the linear scale; however, note that in our interference model, $\alpha$ depends on the UE’s location, because $l_n$ depends on the distance.
• This interference powers (linear) from all interfering BSs are added to the noise power (in linear scale) and then $$𝑆𝐼𝑁𝑅 = \frac{𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑑 𝑝𝑜𝑤𝑒𝑟 𝑓𝑟𝑜𝑚 𝐵𝑆𝑖 + 𝐵𝑒𝑎𝑚𝐹𝑜𝑟𝑚𝑖𝑛𝑔𝐺𝑎𝑖𝑛}{𝑁𝑜𝑖𝑠𝑒𝑃𝑜𝑤𝑒𝑟 + \sum 𝐼𝑛𝑡𝑒𝑟𝑓𝑒𝑟𝑒𝑛𝑐𝑒𝑃𝑜𝑤𝑒𝑟}$$
• Each 𝐼𝑛 is a user input. It is subject to the limits 0 ≤ 𝐼𝑛 ≤ 20 𝑑𝐵. NetSim will enforce the sanity check 20 $\geq$ 𝐼𝐾 $\geq$ 𝐼𝐾−1 $\geq$ … $\geq$ 𝐼0 $\geq$ 0. Here $I_K$ is the relative interference seen when the UE is near 𝐵𝑆𝑖 and $I_0$ is the relative interference seen when the UE is nearly equidistant from its two nearest BSs (and hence far from 𝐵𝑆𝑖 ).
• In an ideal case, when the user is at the cell edge, the received power from $𝐵𝑆_{i}$ will be roughly equal to the received power from $BS_j$(since it is equidistant from the two BSs), and so $𝑆𝐼𝑁𝑅_{𝐶𝑒𝑙𝑙𝐸𝑑𝑔𝑒}$ will necessarily be less than 0 dB.
• As the UE moves away from the cell edge and towards 𝐵𝑆𝑖 , the received power from $𝐵𝑆_{i}$ increases and that from $BS_{j}$ decreases, and so the SINR improves. For this reason, we have the limits on 𝐼𝑛 as 0 𝑑𝐵 $\leq$ 𝐼𝑛 $\leq$ 20 𝑑𝐵. If the user sets 𝐼𝑛 to a large value, it will be equivalent to having no inter-cell interference

therefore the equations where $\frac{(D^{BS_j}_{UE_k}- D^{BS_i}_{UE_k})}{D^{BS_j}_{UE_k}}$ is equal to $\frac{k}{4} = 0.1\ , \frac{2k}{4} = 0.2 \ , \frac{3k}{4} = 0.3$ and $\frac{4k}{4} = 0.4$The handover interference region is also shown.

• In case $\frac{(D^{BS_j}_{UE_k}- D^{BS_i}_{UE_k})}{D^{BS_j}_{UE_k}} > DDR_{th}$,the out of cell interference seen at the UE is set to $I_K$. The default value of 𝐼𝐾 is 0, i.e., cell centre users do not see any out of cell interference. The default values of $I_K$ for 𝑘 = 1, 2, … ,𝐾 − 1 is 10 dB.
• In NetSim, handover is triggered when the signal strength from $BS_j$ is offset (3dB by default) higher than signal strength from $BS_j$. A handover is not triggered when $UE_K$ is equidistant from both BSs but only when it is slightly nearer to $BS_j$.Therefore, the short time when $𝐷^{BS_i}_{𝑈𝐸_𝐾} \geq D^{BS_j}_{UE_k}$ is a special case requiring a different interference power. We term this interference as “Handover interference” and is a separate user input. Handover interference is denoted as 𝐼−1 and −3𝑑𝐵 $\leq$ 𝐼−1 $\leq$ 0 𝑑𝐵.
##### Exact Geometric Model#

NetSim supports various 3GPP propagation models. These models are used to calculate the pathloss between every BS (gNB) and UE. One the parameters in the pathloss equations is the distance between the BS and the UE. Some of the other user settable parameters used in the 3GPP models are (i) Centre frequency (chosen from the band selected) (ii) Rural or Urban environments (iii) UE-BS channel is in LOS or NLOS (iv) Shadow-fading in the UE-BS channel (v) Indoor or outdoor UE location, etc., are also supported in NetSim.

Let $BS_i$ be the serving BS to $UE_k$. Let $BS_j$ be any other $BS (𝑗 ≠ 𝑖).𝑈𝐸_k$communicates with $BS_i$ while all other $BSs (𝑗 ≠ 𝑖)$ act as interferers. The distance between $𝑈𝐸_𝑘$ and $BS_i$ is denoted as $𝐷^{BS_i}_{𝑈𝐸_𝑘}$, while the distance between UE and $BS_j$ is denoted as $𝐷^{BS_j}_{𝑈𝐸_𝑘}$.The power of the interfering signal from any $BS_j$ at any $UE_k$ depends on (i) the transmit power of the interfering BS and (ii) pathloss between the interfering BS and the UE. It can therefore be expressed as $$I^{BS_j}_{UE_k} = P^{BS_j} - PL^{BS_j}_{UE_k}$$ where $𝑃^{𝐵𝑆_𝑗}$ is the transmit power of $𝐵𝑆_𝑗$,$𝑃𝐿^{BS_j}_{𝑈𝐸_𝑘}$ represents the 3GPP model based pathloss between $𝐵𝑆_j$ and $𝑈𝐸_k$. This pathloss is dependent on $𝐷^{BS_j}_{𝑈𝐸_𝑘}$ and the channel between $𝐵𝑆_𝑗$ and $𝑈𝐸_𝑘$. The interference powers (linear) from all interfering BSs (i.e., apart from the serving BS) are added to the noise power (in linear scale) and we get the expression $$SINR_{UE_k} = \frac{𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑑 \ 𝑝𝑜𝑤𝑒𝑟 \ 𝑓𝑟𝑜𝑚 BS_i + 𝐵𝑒𝑎𝑚𝐹𝑜𝑟𝑚𝑖𝑛𝑔𝐺𝑎𝑖n}{𝑁𝑜𝑖𝑠𝑒𝑃𝑜𝑤𝑒r + \sum_{j} I^{BS_j}_{UE_k} }$$ The Wyner model is approximate but is computationally faster; the geometric model is precise but computationally slower due to the calculations involved.

##### Interference modeling in OFDM in NetSim#

NetSim doesn’t model the allocation of specific subcarriers to individual users. The aggregate resources are divided amongst the UEs per UEs’ requirements and the scheduling algorithm.

• The received power at $𝑈𝐸_𝑘$ from $BS_i$ , with transmit power $𝑃_𝑖$ is given (in the linear scale) as $$p^{BS_i}_{UE_k} = \bigg(\frac{p_i}{PL^{BS_i}_{UE_k}}\bigg)$$
• $𝐼^j_{ik}$ or the interference in linear scale at a $𝑈𝐸_𝑘$ (associated with $𝐵𝑆_𝑖$) from $𝐵𝑆_𝑗$
• To normalize the power should we further multiply by the ratio given below $$I_{ik} = \sum_j I^j_{ik}\bigg(\frac{p_i}{PL^{BS_i}_{UE_k}}\bigg)$$
• Assumptions:
• A1.The above formula assumes the interference seen by $𝑈𝐸_𝑘$ is proportional to the number of RBs allotted to $𝑈𝐸_𝑘$
• A2.Fast fading is not accounted for in the interference calculations since it would require too much computational time, given that it needs to be re-calculated every coherence time.
• The total noise seen will be $$K \times T \times RB^{slot}_{UE_k}$$
• The signal power $𝑃^{BS_i}_{𝑈𝐸_𝑘}\times \bigg(\frac{RB^{slot}_{UE_k}}{RB^{slot}_{total}}\bigg)$
Therefore, $$SINR = \frac{P^{BS_i}_{UE_k}\times\bigg(\frac{RB^{slot}_{UE_k}}{B^{slot}_{total}}\bigg)}{k\times T \times RB^{slot}_{UE_k}} = \frac{P^{BS_i}_{UE_k}}{k \times T \times RB^{slot}_{total} + \sum_j I^j_{ik}}$$
###### Interference in MIMO#
• If $𝑈𝐸_𝑘$ is receiving from $𝐵𝑆_𝑖$ in multiple layers, the interference power $𝐼^j_{ik}$ is the same for all layers. $$SINR_L = \frac{P^{BS_i}_{UE_k} \times \lambda_L}{k \times T \times RB^{slot}_{total} + \sum_j I^j_{ik}}$$ Where 𝐿 represents a MIMO layer
• Note that neither the noise nor the interference is divided by the layer count, because the combining vector has unit norm
###### Limitations#
• In the above interference formula NetSim assumes that all interfering BSs transmit data in that slot.
• The calculations need to be done for each slot. Enabling interference in the UI will slow down the simulation.

### Data rate calculation#

For NR, the approximate data rate for a given number of aggregated carriers in a band or band combination is computed as follows.

$$Data \ rate(in \ Mbps) = 10^{-6} \sum_{j=1}^j\Bigg(v^{(j)}{layers}.Q^{(j)}_{m}.R_{max}. \frac{N^{BW(j).\mu}.12}{T^{\mu}_s}.(1-OH^{(j)}\Bigg)$$ where in
J is the number of aggregated component carriers in a band or band combination. $R$ = 948/1024 For the j-th CC,

$v^{(j)}_{Layers}$ is the maximum number of supported layers given by higher layer parameter maxNumberMIMO-LayersPDSCH for downlink and maximum of higher layer parameters maxNumberMIMO-LayersCB-PUSCH and maxNumberMIMO-LayersNonCB-PUSCH for uplink.

$Q^{(j)}_m$ is the maximum supported modulation order given by higher layer parameter supportedModulationOrderDL for downlink and higher layer parameter supportedModulationOrderUL for uplink.

$f^{(j)}$ is the scaling factor given by higher layer parameter scalingFactor and can take the values 1.

$\mu$ is the numerology (value is always 0)

$T^\mu_s$ is the average OFDM symbol duration in a subframe for numerology $\mu$, i.e.$T^\mu_s = \frac{10^{-3}}{14 \times 2^\mu}$

Note that normal cyclic prefix is assumed.

$N^{BW(j).\mu}_{PRB}$ is the maximum RB allocation in bandwidth $𝐵𝑊^{(𝑗)}$ with numerology $\mu$

$OH^{(j)}$ is the overhead and takes the following values.

0.14, for frequency range for DL
0.08, for frequency range for UL

NOTE: Only one of the UL or SUL carriers (the one with the higher data rate) is counted for a cell operating SUL.

### LTE Metrics#

#### LTE Packet trace#

The LTE packet trace file has in its column the field CNTROL_PACKET_TYPE. This field has control and data packets information, this field contains control packets related RRC connection (RRC_MIB, RRC_SIB1, RRC_SETUP_REQUEST, RRC_SETUP_COMPLETE, RRC_SETUP), UE_MEASUREMENT_REPORT, and STATUSPDU.

#### Limitations#

NetSim’s LTE module has been developed a special case of the 5G NR library operating in the FR1 band with $\mu$ = 0. Hence some output metrics of 5G NR such as the SDAP metrics would appear in the LTE results. These can be ignored

NetSim contains some example configuration files to simulate and understand how LTE and LTE-A work.

To simulate these examples, click Examples > LTE-and-LTE-A in the NetSim Home Screen.

You can change the default values of the parameters in these examples and see how they impact the LTE and LTE-A network.

## Reference Documents#

3GPP 36 series specifications for Long Term Evolution Networks.
3GPP TS 36.300 (Rel 10) Section 19.2.2.5

## Latest FAQs#

You can refer to the up-to-date FAQs about NetSim’s LTE library at
https://tetcos.freshdesk.com/support/solutions/folders/14000107855