What is Terahertz (THz) Communication?
The Terahertz band typically refers to frequencies between 0.1 THz and 10 THz (100 GHz to 10,000 GHz). This is the area between the uppermost microwave/mmWave frequencies and the infrared spectrum.
To have effective wireless communication, the studies are primarily aimed at:
Sub-THz: ~90 – 300 GHz is often considered the extreme mmWave or the low end of the THz band, and is the first target for 6G high-capacity links (like the D-band, 110 GHz to 170 GHz).
Low-THz: ~300 GHz – 1 THz
The ranges provide extensive contiguous bandwidth and hardware that is viable in the new semiconductor and photonic technologies. The use of THz communication is of particular significance to 6G, as the conventional microwave and mmWave bands are not able to provide the new requirements of ultra-high speeds and novel sensing abilities.
Terahertz Frequency Bands and Their Characteristics
The THz spectrum behaves differently from lower frequencies, providing unique opportunities and challenges.
1. Massive Bandwidth
THz frequencies offer enormous spectral resources — enabling multi-gigabit to terabit per second (Tbps) wireless links. This is one of the strongest motivations behind THz research for 6G.
2. High Free-Space Path Loss
Path loss increases dramatically with frequency (known as Free-Space Path Loss), meaning THz signals attenuate rapidly over distance. This requires the use of massive antenna arrays (Massive MIMO) to achieve the necessary high antenna gain and very narrow beams to maintain strong, compensated links.
3. Molecular Absorption
Water vapor and atmospheric gases absorb THz waves at specific frequencies. This creates usable “transmission windows” and high-loss regions. Key windows targeted for 6G research exist around 140 GHz, 220 GHz, and 340 GHz, which are relatively free from water vapor and oxygen absorption peaks.
4. Ultra-Short Wavelengths
The very small wavelength of THz signals enables:
- Compact high-gain antenna arrays
- Ultra-narrow beams
- Precise spatial resolution
This makes THz ideal for sensing and localization, a key area of 6G.
Read more about: Integrated Sensing and Communication (ISAC): The Key Technology for 6G Networks
Why THz Is Important for 6G
6G aims to support applications that demand extremely high capacity and low latency, including:
- Holographic communication
- Real-time digital twins
- Massive device interconnectivity
- Advanced robotics
- High-resolution wireless sensing
THz frequencies provide the only practical path to achieving Tbps-class performance while also enabling integrated sensing and communication.
Advantages of Terahertz Communication
1. Ultra-High Data Rates
THz bands support Tbps-level connectivity, ideal for:
- Wireless fiber replacement
- Data centers
- AR/VR and immersive communication
- High-speed device-to-device links
2. High Spatial Resolution
Thanks to short wavelengths, THz signals can be used for:
- Sub-centimeter positioning
- Gesture detection
- Object recognition
- Environmental mapping
This naturally aligns with 6G’s ISAC (Integrated Sensing and Communication) vision.
3. Low Interference and High Reuse
Narrow beamwidth allows highly directional links, reducing interference and enabling dense deployments in indoor and hotspot environments.
4. Compact Antennas
THz antennas can be extremely small, making it possible to integrate massive-MIMO arrays directly onto chipsets.
Limitations and Key Challenges
Despite its promise, THz communication faces several challenges:
1. Limited Range
The THz links experience high loss in free space and atmospheric absorption, making them typical of short-range line-of-sight operation.
2. Blockage Sensitivity
THz can be blocked by the human body, walls, and ordinary objects. Confidential mobility needs superior beam-tracking and multi-link connectivity.
3. Hardware Complexity and Cost
It is not easy to produce, amplify, and detect THz signals. Challenges include:
- Low transmitter power
- High device noise
- Inefficient amplifiers
- Thermal constraints
Innovations in semiconductor materials (like CMOS, SiGe, GaN, InP) and the development of photonic THz sources/detectors and hybrid electronic-photonic radios are critical to closing this power and noise gap.
4. Environmental Effects
The humidity, rain, and fog worsen THz performance even worse than lower frequency bands.
5. Regulatory Barriers
The THz spectrum is not used to capacity, and this should be co-existent with scientific services (e.g., astronomy, spectroscopy).
Real-World THz Demonstrations and Current Uses
THz technologies are not just theoretical — several real systems exist today.
1. High-Speed Wireless Backhaul
Research institutions and companies have demonstrated 100 Gbps to 1 Tbps links using 300 GHz carriers for short-distance point-to-point communication. These systems can be used for:
- Fiber extension
- Data center interconnects
- Campus networks
2. Indoor Ultra-Fast Wireless (Kiosk Links)
Short-range THz links are being tested for:
- Smartphone “data kiosks”
- Ultra-fast content downloads
- Wireless docking systems
3. Security and Imaging
THz imaging systems are already used for:
- Airport security scanners
- Non-destructive testing
- Material inspection
- Medical diagnostics
4. Industrial and Scientific Applications
THz spectroscopy is widely used for analyzing chemicals, pharmaceuticals, and biological samples due to its sensitivity to molecular vibrations.
These established practices pave the way for integrated sensing + communication capabilities in 6G.
Future Applications of THz Communications
1. Wireless Fiber Extension
Terabit-class THz links can replace or complement fiber in scenarios where physical cable deployment is difficult.
2. 6G Hotspots
Crowded venues (stadiums, airports, malls) can use THz cells to provide extreme broadband access.
3. High-Speed Device Connectivity
From AR/VR headsets to high-performance laptops, THz links can act as:
- Wireless docking stations
- Chip-to-chip wireless interconnects
- Data cable replacements
4. Integrated Sensing for Robotics and Automation
THz enables precise mapping and localization, essential for:
- Autonomous robots
- Smart factories
- Automated warehouses
5. Vehicle-to-Everything (V2X)
Future vehicles could use THz links for high-data-rate radar, sensing, and communications.
The Future of THz in 6G Networks
THz communication is expected to evolve in stages:
2025–2030: Research & Prototype Era
- Sub-THz (~140–300 GHz) becomes the first practical step
- Testbeds for backhaul, hotspots, and indoor systems mature
- Standardization discussions accelerate
2030–2035: Early 6G Deployments
- THz begins appearing in commercial 6G infrastructure
- Devices and base stations with integrated sensing become common
- hybrid electronic–photonic radios gain traction
Beyond 2035: Widespread Adoption
- low-THz (300 GHz–1 THz) expands into mainstream use
- Terabit networks support AI-driven, sensing-rich environments
- THz becomes a core part of communication-sensing unified networks
Conclusion
The most promising line of wireless technology is terahertz communication. THz frequencies will be the core of the entire 6G vision with massive bandwidth, extremely high speeds, and in-built sensing functionality.
Despite such obstacles as propagation loss, hardware constraints, and environmental sensitivity, the rapid growth of semiconductor technologies and algorithm sensing is rapidly helping to proceed with practical implementation.
With the development of 6G, THz communication will become a reality and not an isolated laboratory experiment, but it will be implemented into real-world applications and drive the next generation of applications with huge data rates and accurate sensing, and engaging digital experiences.
Source: https://www.rfpage.com/terahertz-communication/ – 16/11/25
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