Simulation GUI
Open NetSim, Go to New Simulation \(\rightarrow\) Satellite Comm. Networks
Create Scenario¶
Satellite Communication Networks palette features various devices like Wired Nodes, L2 Switch, Access Point, Wireless node, UT Router (User Terminal Router), Router, UT Node (User Terminal Node), Satellite Gateway, and Satellite.
Devices specific to NetSim Satellite Comm. Library¶
UT - User Terminal. The user terminals are part of the same communication network as the Satellite Gateway. The User Terminals in NetSim are UT Node and UT Router
UT Router - User Terminal Router. A UT Router is used when a separate communication network is required. The typical use case is where there are multiple devices downstream who seek to utilize the sat-com link. The UT Router cannot be a source of any traffic.
Satellite Gateway: Each gateway has two interfaces, a satellite interface and multiple wired interfaces. The satellite interface connects via the forward link to the satellite. The wired interface allows for connection to routers via the wired interface. When connected to a satellite, the user terminals mapped to the gateway are part of the same network. Multiple gateways can be configured per satellite, and round-robin scheduling is run (at the Network control center (NCC) which is not displayed in NetSim GUI)
Satellite: Since the satellite model is a bent pipe, the satellite does not have an IP. NetSim supports single satellite communication, and it can be connected to multiple gateways and to multiple user terminals. The satellite node cannot be the source of any traffic. The default altitude of the Satellite is 35,768,000 meters, which represents the circular geosynchronous orbit.
Coordinate System: NetSim uses a Geodetic co-ordinate system. The altitude is from Mean Sea level. The geocentric co-ordinate system uses distance from the centre of the earth.
Placement of devices on the grid environment¶
Add a User Terminal (UT) – Click the User Terminal \(>\) UT Node icon on the toolbar and place the device in the grid. UT Node must be connected to Satellite.
Add a UT Router – Click the User Terminal \(>\) UT Router icon on the toolbar and place the device in the grid. UT Router must be connected to a Node or to an L2 Switch or to a Router or to an Access_Point or Satellite.
Add a Satellite – Click the Satellite icon on the toolbar and place the Satellite in the grid. Satellite must be connected to a Satellite Gateway or to a UT Node or to a UT Router.
Add a Satellite Gateway – Click the Satellite Gateway icon on the toolbar and place the Satellite Gateway in the grid. Satellite Gateway must be connected to a Satellite or to a Router.
Add a Router – Click the Router icon on the toolbar and place the Router in the grid.
Add a Wired Node – Click the Wired Node icon on the toolbar and place the device in the grid.
Add an L2 Switch – Click the L2 Switch icon on the toolbar and place the device in the grid.
Add an Access Point – Click the Access Point icon on the toolbar and place the Access Point in the grid.
Add a Wireless Node – Click the Wireless Node icon on the toolbar and place the device in the grid.
Enable Packet Trace, Event Trace (Optional)¶
Click 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.
Enable protocol specific logs and plots¶
NetSim provides protocol-specific logs for Satellite 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.
Similarly, users can enable the plots for Satellite Radio Measurements.
GUI Configuration Parameters¶
The SATELLITE parameters can be accessed by right clicking on a Satellite, Satellite Gateway, UT Router or UT and selecting Interface (SATELLITE) Properties \(\rightarrow\) Datalink and Physical Layers.
| Parameter | Type | Range | Description |
|---|---|---|---|
| Link Model | Local | Satellite Link, Abstract Link | The Satellite Link implements a detailed
physical layer model that captures RF propagation characteristics such
as free-space pathloss, antenna gain, EIRP, additional losses, noise
figure, interference (CIR), exact geometric and SNR/SINR-based adaptive
and fixed modulation and coding. The Abstract Link represents an idealized communication channel model implemented under the Physical Layer. |
| Noise Figure (dB) | Local | –12 | Represents the receiver’s internal noise contribution. A lower noise figure indicates that the receiver is more sensitive and capable of detecting weaker signals. |
| Carrier to Interference Ratio (dB) | Local | \(-20\) to \(+20\) | Measures the strength of the desired signal compared to the interference power in the channel. |
| Exact Geometric Interference (dB) | Local | Geometric interference arises when multiple beams sharing the same channel ID overlap, leading to co-channel interference at user terminals. | |
| Antenna aperture Radius (m) | Local | – 5 | This parameter defines the antenna’s aperture radius. Used for antenna gain calculations. |
| Frequency reuse factor | Local | FR1, FR2, FR3, FR4 | Represents the number of channels allocated per beam configuration. FR1 indicates full frequency reuse across all beams, while FR3 reduces inter-beam interference by using three distinct frequency groups. |
| Beam radius (km) | Local | Based on band it varies | The beam radius is calculated based on the frequency band, satellite altitude, and antenna aperture radius for the selected scenario. It is defined at the point where the beam power drops to half of its maximum value (3 dB beamwidth). |
| Beam count | Local | , 7, 19 | This parameter defines the number of beams formed in the coverage area. A value of 1 corresponds to a single central beam. The 7-beam configuration consists of one central beam surrounded by a single hexagonal ring, while the 19-beam configuration consists of the central beam with two hexagonal layers of surrounding beams. |
| G/T (dBK) | Local | Manual | Antenna gain-to-noise-temperature (G/T) where G is the antenna gain in decibels at the receive frequency, and T is the equivalent noise temperature of the receiving system in kelvins. |
| G/T (dBK) | Auto | Computed using the noise figure and the RX gain | |
| Antenna model | Local | TR 38.811 S.6.4.1, ITU-R S.672-4 | TR 38.811 S.6.4.1: The normalized antenna
gain pattern, corresponding to a typical reflector antenna with a
circular aperture, is considered. ITU-R S.672-4: To model the off-axis behavior of satellite antennas, the ITU-R S.672 recommendation specifies that, for single-feed circular or elliptical beam spacecraft antennas operating in the fixed-satellite service (FSS). |
| LN Value (dB) | Local | \(-25\), \(-20\) | LN is near-in-side-lobe level in dB relative to the peak gain required by the system design. |
| LF Value (dB) | Local | \(-100\) to \(10\) | LF represents the minimum gain level (in dB) beyond which the antenna pattern does not decrease further. |
| \(a\), \(b\), \(\alpha\) | Local | Values are updated based on the LN selection as per ITU-R specification. | |
| \(z\) | Local | (major axis/minor axis) for the radiated beam. | |
| LB (dB) | Local | \(LB = 15 + LN + 0.25\,G_m + 5\,\log z\) dBi or 0 dBi whichever is higher. | LB is the back lobe gain level used in the antenna pattern |
| Theta HPBW (\(^{\circ}\)) | Local | –10 | One-half the 3 dB beamwidth in the plane of interest (3 dB below Gm) (degrees) |
| Access Protocol | Fixed | TDMA | TDMA allows a number of clients to access a single radio-frequency channel without interference by allocating unique time slots to each user within each channel, reducing the loss of packets and improving the data rate thereby delivering QoS to the clients. |
| Access Protocol | Fixed | MF-TDMA | Multi-frequency time-division multiple access is a technology for dynamically sharing bandwidth resources in an over-the-air two-way communications network. |
| Base Frequency (GHz) | Local | Ku-band: 12–18 GHz, Ka-band: 26–40 GHz | The “band” in use refers to the radio frequencies used to and from the satellite. Ku-band services use the 12–18 GHz, and Ka-band services use the 26–40 GHz segment of the electromagnetic spectrum. |
| Band | Fixed | KU | Microwave frequency band used for satellite communication and broadcasting, using frequencies in the range of 12–18 GHz |
| Band | Fixed | KA | Microwave frequency band used for satellite communication and broadcasting, using frequencies in the range of 26–40 GHz |
| Rolloff Factor | Local | –1 | In NetSim, Symbol Rate = BW / (1+Roll off factor) and Bit Rate = Symbol rate \(\times\) Modulation order \(\times\) CodeRate |
| Spacing Factor | Local | –1 | In NetSim EffectiveBandwidth (Hz) = AllocatedBandwidth (Hz) / ((RollOffFactor + 1.0) \(\times\) (SpacingFactor + 1.0)); Spacing factor should be in the range of [0,1] |
| Carrier Bandwidth (Hz) | Local | –1000000 Hz | Bandwidth of the carrier in Hz |
| Frame count in Superframe | Local | –1000000 | Number of frames present in a superframe. |
| MCS Selection | Local | Fixed MCS, Adaptive MCS | Fixed MCS: The modulation and coding rate remain constant throughout the simulation. Adaptive MCS mode: The physical layer dynamically adjusts the modulation and coding rate based on the Signal-to-Noise Ratio (SNR) calculated from the link-budget model. |
| MCS Index table | Local | Index, Modulation, Coding rate, Spectral efficiency | The MCS Index Table defines the mapping between modulation and coding schemes used for data transmission. |
| Frame Usage Mode | Local | NORMAL, SHORT | Baseband frame usage modes. |
| Modulation | Local | QPSK, 8PSK, 16APSK, 16QAM, 32APSK | Modulation is the process of varying one waveform in relation to another waveform. It is used to transfer data over an analog channel. |
| Coding Rate | Local | /3, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, 9/10 | It states what portion of the total amount of information that is useful (non-redundant). This code rate is typically a fractional number. |
| BER Model | Local | Fixed | BER value is based on the user input and is independent of the received SINR. |
| BER Model | Local | FILE BASED | File Based is a feature in NetSim with which users can define the BER. Users will have to provide a BER_FILE.txt file as input to NetSim by clicking on the Open file link the Physical Layer-Properties of the device. |
| BER Model | Local | MODEL BASED | BER is computed using the SINR-BER formula for the chosen Modulation and coding. The pathloss and fading models are used in the SINR calculation. |
| BER | Local | –1 | This parameter is shown if the Fixed option is chosen for the BER model parameter. Users can set the Bit Error Rate (BER) in the range shown. |
| Additional loss (dB) | Local | \(-20\) to \(+20\) | Represents attenuation in the signal path due to imperfections |
| EIRP Density (dBW/MHz) | Local | –70 | This parameter defines the effective isotropic radiated power per unit bandwidth. |
| Link speed (Mbps) | Local | –100 | Defines the constant data rate available on the link and is used to compute the packet transmission time. |
| Propagation delay (ms) | Local | Auto computed, Fixed (1–100) | Auto computed: Calculated automatically based on device distance and the speed of light. Fixed: A constant delay value entered by the user. |
| Rx Antenna Gain (dB) | Local | –1000000 dB | A relative measure of an antenna’s ability to receive radio frequency energy in a particular direction or pattern at the receiver side. |
| Parameter | Type | Range | Description |
|---|---|---|---|
| Propagation Medium | Link | Air | Medium of propagation in NetSim would be Air for RF waves. |
| Channel Characteristics | Fixed | Pathloss and Fading and Shadowing | Path loss and fading and shadowing: In pathloss models, for a fixed distance between source and destination, path loss is the same. We get varied path loss for the same distance between source and destination in shadowing, and fading is the variation of the attenuation of a signal with various variables. These variables include time, geographical position, and radio frequency. |
| Shadowing Model | Fixed | NONE | |
| Pathloss Model | Link | Friis Free Space | Used to model the LOS path loss incurred in the channel. The Friis Free space model is restricted to unobstructed clear path between the transmitter and the receiver. |
| Pathloss Exponent (\(\eta\)) | Fixed | Path loss exponent indicates the rate at which the path loss increases with distance. The value depends on the specific propagation environment. | |
| Fading Model | Fixed | Markov Loo | Each state of the three-state Markov channel models obeys the Loo distribution with different parameters; while the state transition is modeled as a first-order Markov random process. |
| Direct Signal Mean (dB) | Link | \(-\infty\) to \(\infty\) | Mean value of the direct signal, value can be differentiated according to the state. |
| Direct Signal Standard Dev (dB) | Link | to \(\infty\) | Standard Deviation of the direct signal value can be differentiated according to the state. |
| RMS Multipath Power (dB) | Link | \(-\infty\) to \(\infty\) | RMS squared multipath power in dB |
| Number of Direct Signal Oscillators | Link | to \(\infty\) | Number of direct signal oscillators is used for frequency conversion process in superheterodyne receiver. |
| Number of Multipath Oscillators | Link | to \(\infty\) | Number of multipath oscillators is used to generate higher oscillation frequencies. |
| Direct Signal Doppler (Hz) | Link | to \(\infty\) | |
| Multipath Doppler (Hz) | Link | to \(\infty\) | The normalized PSD (its integral in the whole frequency range equals to one) constitutes the PDF for the Doppler frequencies, arising from the different angles of arrival the multipath components have with respect to the receiver’s motion. |
| Initial Probability | Link | to 1 | An initial probability distribution, defined on S, specifies the starting state. Usually this is done by specifying a particular state as the starting state. |
Mapping of User Terminal (UT Node / UT Router) to Satellite Gateway¶
Each satellite can be connected to multiple Satellite Gateways and to Multiple User Terminals. The following screen shot shows how to map the User Terminal to Satellite Gateway as shown in Figure 1.
In order to Map User Terminal (UT Node / UT Router) to Satellite Gateway right click go to the properties of UT Node/UT Router \(\rightarrow\) INTERFACE1 (SATELLITE) \(\rightarrow\) DATALINK LAYER \(\rightarrow\) Gateway user can map the Satellite Gateway with UT Node / UT Router accordingly.
Additionally, in the UT Router/UT Node \(\rightarrow\) Interface Satellite the default gateway IP should be set as the IP of the connected Satellite Gateway.
Incorrect mapping of the Satellite Gateway and/or the default Gateway IP address, in the properties of the UT Node / UT Router could lead to application crash or NIL application throughputs.
Configuring Static Routes¶
After mapping the UT Router/UT Node to a Satellite Gateway, static routes need to be configured in the devices to forward traffic. Let us consider the following network scenario as shown in Figure 2.
In this network scenario, for UDP traffic to be sent from UT Node 3 to UT Node 4, static routes need to be set in UT Node 3 and in the Satellite Gateway 2.
If TCP traffic needs to be sent from UT Node 3 to UT Node 4, then static routes need to be set in UT Node 4 as well. This is essential for connection establishment and sending acknowledgements.
Refer to the featured example on Configuring applications from UT Node to UT Node for detailed information on static route configuration.
Mobility model in Satellite¶
Satellite and UT devices support file-based mobility in Satellite.
In the File Based Mobility model, users can write their own custom mobility models and define the movement of the mobile users. The content should be per the NetSim Mobility File Format explained below. Users can also generate the mobility files using external tools like SUMO (Simulation of Urban Mobility), etc.
The NetSim Mobility File setting and format is explained below:
Step 1: Right click to open Properties as a new window of Satellite or UT. Then properties \(>\) Position Properties \(>\) Mobility model as File Based Mobility and click on Open Mobility file.
Step 2: Open the csv file and write the node mobility in the format shown below.
<TIME IN SECONDS>,<DEVICE ID>Lat(°),Lon(°),Alt(m)