THz system module is a software architecture for simulating configurable Terahertz(THz)-band (0.1-10 THz) communication networks. This module takes into account both the nanoscale scenario (transmission distance less than one meter) and the macroscale scenario (transmission distance larger than several meters) of THz-band communication. The THz module consists of the protocol stack layer design from THzChannel to THzPhy(Nano/Macro) up until the THzMac(Nano/Macro). It also includes the supporting modules such as THzDirectionalAntenna and THzEnergyHarvestor to achieve the scenario specific functionalities. Other supporting modules that help modeling the THz channel peculiarities, such as THzSpectrumValueFactory and THzSpectrumPropagationLoss, are also included in the system module. The THz system module provides a comprehensive THz-band communication networks simulator that is expected to help the research community to test THz networking protocols without having to delve into the channel and physical layers.

In this module, it tests the link-layer transmission performance of the nanoscale scenario with an adhoc network architecture and the macroscale scenario with a centralized network architecture. The following handshake protocols are implemented:

• Nanoscale scenario: 0-way (ALOHA) and 2-way (CSMA)
• Macroscale scenario: 0-way (ALOHA), 1-way (ADAPT-1), 2-way (CSMA) and 3-way (ADAPT-3)

Model Description

The source code for the new module lives in the directory thz/. This directory is typically placed in the contrib/ directory of ns-3.

• The frequency database file (data_frequency.txt) and the corresponding molecular absorption coefficient database file (data_AbsCoe.txt) are located inside /thz/model.

Design

• THzNetDevice: derived from the ns-3 NetDevice class and used for creating new MAC protocols. It performs as the joint point which connects the THzChannel module, THzPhy module and the assistant modules.
• THzChannel: provides a general THz band channel that can be used by any upper layer design.
• THzSpectrumValueFactory: is derived from ns-3 SpectrumModel class, it creates a frequency dependent THz-band based on the HITRAN (HIgh resolution TRANsmission molecular absorption) database and masks the transmit power to user defined bandwidth.
• THzSpectrumPropagationLoss: Creates the frequency and transmission distance dependent propagation loss module based on the peculiarities of THz-band communication.
• THzPhyNano: models the hundred-femto-second pulse based physical layer with pulse interleaving and calculates the SINR (Signal to Noise plus Interference Ratio).
• THzMacNano: models slightly modified version of two classical MAC layer protocol tailored to nanodevice energy harvesting.
• THzEnergyModel: models the energy harvesting and energy consumption process of a node in nanonetworks.
• THzPhyMacro: mainly considers the time duration of a frame being propagated in the THz channel and check if the receiver is able to receive the signal with enough power strength by comparing with the SINR threshold.
• THzMacMacro: implements the 0-way handshake and 2-way handshake protocols, a NAV mechanism is applied in this module.
• THzMacMacroAP: implements the 1-way and 3-way ADAPT protocols for the AP end.
• THzMacMacroClient: implements the 1-way and 3-way ADAPT protocols for the client node end.
• THzDirectionalAntenna: is derived from ns-3 CosineAntennaModule class. The main extention in THzDirectional Antenna is enabling the turning ability.

Scope and Limitations

• In its current state, the THz system module is tested against the latest ns-3 version (ns-3.38) and should be kept aligned with ns-3-dev.
• As of now, the ns-3 interface to THz is IPv4 only.

References

• Z. Hossain, Q. Xia, and J. M. Jornet, TeraSim: An ns-3 extension to simulate Terahertz-band communication networks
• D. Morales, J. M. Jornet, ADAPT: An Adaptive Directional Antenna Protocol for medium access control in Terahertz communication networks

Usage

Helpers

All the helper files can be found in /thz/helper/:

• THzHelper: helps to create THzNetDevice objects:
• THzMacHelper: create THz MAC layers for THzNetDevice
• THzPhyHelper: create THz PHY layers for THzNetDevice
• THzDirAntennaHelper: create THz directional antenna implementation for THzNetDevice
• THzEnergyModelHelper: installs THzEnergyModel to the nodes.

Attributes

Basically every THz-class in THz module holds attributs. Some key attributes from different classes are summarized as follows:

• THzNetDevice:
  • Channel: The channel attached to this device
  • DirAntenna: The Directional Antenna attached to this device
  • Phy: The PHY layer attached to this device
  • Mac: The MAC layer attached to this device
• THzChannel:
  • NoiseFloor: Noise Floor (dBm)
• THzSpectrumValueFactory:
  • NumSubBand: The number of sub-bands containing in the selected 3dB frequency window
  • SubBandWidth: The bandwidth of each sub-band
  • TotalBandWidth: The total bandwidth of the selected 3dB frequency window
  • CentralFrequency: The central frequency of the selected 3dB frequency window
  • NumSample: The number of sample bands of the selected 3dB frequency window
• THzPhyNano:
  • SinrTh: SINR Threshold (dB)
  • TxPower: Transmission Power (dBm)
  • PulseDuration: Duration of a short pulse
  • Beta: Ratio of symbol duratio to pulse duration
• THzMacNano:
  • EnableRts: If true, RTS is enabled
  • DataRetryLimit: Maximum Limit for Data Retransmission
  • FrameLength: Actual packet length at the MAC layer
• THzEnergyModel:
  • EnergyHarvestingAmount: Amount of Energy Harvested in each time
  • PeriodicEnergyUpdateInterval: Time between two consecutive periodic energy updates
  • EnergyConsumptionPulseTx: Energy consumption for the transmission of a pulse
• THzPhyMacro:
  • SinrTh: SINR Threshold (dB)
  • TxPower: Transmission Power (dBm)
  • BasicRate: Transmission Rate (bps) for Control Packets
  • DataRate: Transmission Rate (bps) for Data Packets
• THzMacMacro:
  • EnableRts: If true, RTS is enabled
  • DataRetryLimit: Maximum Limit for Data Retransmission
• THzMacMacroAP/Client:
  • HandshakeWays: Select 1-way or 3-way handshake
  • PacketSize: Size of payload used
  • UseWhiteList: activate or deactivate the use of a white list for the sectors
  • UseAdaptMCS: activate or deactivate the use of an adaptive MCS depending on Rx power
• THzDirectionalAntenna:
  • TuneRxTxMode: If 0, device is a Directional Transmitter; 1, Directional Receiver; 2, Omni-directional Tranceiver
  • BeamWidth: The 3dB beamwidth (degrees)
  • MaxGain: The gain (dB) at the antenna boresight (the direction of maximum gain)
  • TurningSpeed: The turning speed of the Rx antenna unit in circles per second

Output

The link layer performance in terms of the throughput and the discarding probability of DATA packets on each node will be output as the result. Besides, the perfermance of each layer in the protocol stack can be enabled by using LogComponentEnable function in the main function i.e.,:

$ LogComponentEnable("THzChannel", LOG_LEVEL_ALL);

In the case of macroscale scenario with the ADAPT procotol, the output is a TXT file with an entry for each packet with the format (client_id, packet_size, packet_delay, success, discard). This can be then postprocessed to obtain the desired metrics, such as throughput or discard rate, both overall and per node. A MATALB script is provided in /thz/macro_postprocessing/compute_metrics.m.

Examples

The following examples have been written, which can be found in /thz/examples/:

• nano-adhoc.cc: This example file is for the nanoscale scenario of the THz-band communication networks, i.e., with transmission distance below one meter. It outputs the link layer performance mainly in terms of the throughput and the discarding probability of the DATA packets. In this example, an adhoc network architecture is implemented. User can set network topology in this file. The nodes in the nanonetwork are equipped with the energy module we developed. The basic parameters of the energy model can be set in this file. User can also set the number of samples of the TSOOK pulse within frequency range 0.9-4 THz window in this file. User can select one of the two MAC protocols that include a 0-way and a 2-way handshake protocols. 0-way starts the link layer transmission with a DATA frame and 2-way with an RTS frame. The selection can be done by setting the attribute value of EnableRts in THzMacNano. In the end, the user can also set the generated packet size and the mean value of the packet generation interval in this file.

• macro-central.cc: This example file is for the macroscale scenario of the THz-band communication networks, i.e., with transmission distance larger than several meters. A centralized network architecture is implemented. A high speed turning directional antenna is used in the base station (Servernodes), while all clients (Clientnodes) point the directional antennas towards the receiver. Important parameters:

  • configuration: sets the frequency window used, the number of sectors and modulation used.
  • handshake_ways: use a 0-, 1-, 2- or 3-way handshake. (0: CSMA, 1: ADAPT-1, 2: CSMA/CA, 3: ADAPT-3)
  • nodeNum: number of client nodes
  • interArrivalTime: average time between two packets arriving at client's queue

Validation

This model has been tested validated by the results generated from the following test files, which can be found in /thz/test:

• The test files test-thz-psd-macro.cc and test-thz-psd-nano.cc are used to plot the power spectral densities of the generated waveform by the physical layer and the received signal at certain distance for macroscale scenario and nanoscale scenario respectively.
• The test file test-directional-antenna.cc plots the antenna radiation pattern of the directional antenna.
• The test file test-thz-path-loss.cc plots the path loss as a function of distance.

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